OPS335W11

OPS335

ubuntu apt-getn install apache
info

sudo apt-get install bind


samaba 3 ways to act as a client

1. you can use a file/web browser that understands the smb protocol


Konquere understands the ftp http and smb protocols

2. command : smbclient
get
put

3. As root do the mount

mount -t cifs //matrix/john.selmys /mnt/banana



cifs driver uses encryption for the password, matrix samba server only accepts passwords in plain text



Assignment 3 (bonus)10%


Write up a document how you will set up a backup/restore system for a client



DNS

1978-79 tcp/ip started

two universities a line between the two, for U1 and U2

then came U3 and came online paying full price

/etc/hosts
each had a host file, information matches forward and reverse mapping, '
registered


1984 - DNS

root servers = 13



Too many request is a DOS denial of service


Vince Surf

Lab 9 Install Bind

DCN386 Frame Relay

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/frame.htm

What does Frame Relay do and how does it work?


Frame Relay - is a modern datacom protocol,
-created to handel a specific job
all protocols specific job
X.25 - Users for small amounts of data infrequently


However
Introduction to LAN 1990
-Require emerged, link Remote area networks together

- LAN 100mil bps

How can you connect this to connect two offices together?

X.25 - top speed in canada 64K----around----not sure-----

Frame Relay, equipment such as routers,
-Have serial ports
-Routers send data using HDLC, ciscos default

HDLC is a module, if you want FameRelay you get cisco to get you the Frame Relay Module

First out of the five.

-Frame Relay perfect protocol for intercommunication for LAN
-its good cause its incredibly fast

Why is frame relay fast?
-It doesnt do anything except transmit data
-Does do error checking, but if their is an error it dumps the frame
-The point is speed



-----------
X.25 do 20 seperate operations, so the packet is preserved and protects
-----------

Frame Relay devices do two things with every frame
-Validate it, error checking, dumps packet if error
-Validate the destination address, dumps it if it dont know it
-It makes sure every frame ZIPS through the network

--We let the end connections worry about the frames.

Where did Frame Relay come from?

A small part of a big initiative put by the ITU
In the future full digital everything
----------
Build the international digital service known as
ISDN
Essentially it failed

ISDN puzzle was examined by 4 companies and saw value in a little piece
Novel Telecome
Cisco
....


They developed the little piece called FrameRelay
-----------------------
Started an organization called FrameRelay Forum,
www.frforum.com
-----------------------
How does it work?

-First confusing thing
-Frame Relay is a DataLink Layer Protocol

----------------------
Phone companies have pre-build Frame Relay networks
ex: every bell office has routers that can handel FR
Idea customers can call bell and attach them into the FR cloud
---------------------
If you have a router of ur own u can take out the HDLC module and put in a FR modeuls
--------------------
Most orginations use the shared FR bell network
--------------------
Bell uses HIgh speed FIbre-optics
--------------------


Frame Relay Format:

f | Control | f

Flags are used when the amount of data is variable
-No specification of data unit

Because their is no knowledge of the variable it puts Flags around the data.

------------------------
Ethernet does 1500bytes
-----------------------

Frame Relay - Combines the address and control field, for the test call it Control

Control Field --- 2 3 or 4 bytes long
^ is known to use

Remember to understand a protocol look at the control field

2 bytes - 16 bits

first 6 bits
- Part of the protocols addressing scheme
second 4 bits
- Also part of frame relay addressing scheme

They are called the DLCI
Data-Link Control Id

| DLCI | DLCI |

In byte one its called the command response bits,
-useless no function


Last bit in byte one is the Extended address
-simply means their another byte incolved
In byte 2 theirs an extended address
- if the EA is a 1 theirs no more addressing

3 bits unaccounted for

BECN -Back Explicit COngestion Notification
FECN -Forward Explicit congestion Notification
DE -Disguard Eligibility

DE - is a key feature

-----------------------------------
Two organization

Have offices Vancouver and Toronto
Happy NEtworking People
-Want to use Bell Canada Frame Relay Network
-Big expensive Routers with FrameRelay Modules
-Bell network Extremely Fast Fibre Optic Cables
TD gets the Routers to the network
Scotia GIrl gets her Router to the network

How will bell build this network
-Bell Canada has a special device at the boundry called a FRAD
FRAD - Frame Relay Assembler Disasembler

Its at the parameters of the cloud not inside the cloud, thats how they attach themselves
to the cloud

SB and TD different data-
How does bell invoice?
-When you phone bell he asks how much data u going to send into the network
-Frame Relay was designed to handel bursts of data
-Designed to connect LANs
20% locally 70% lan
Want to know how big the bursts is going to be,

Range from 64K bps
128k BPS
etc...
Networker, does analysis how much data is going to be tranmitted
and a conclusion to how much data going to be sent and received
Bell bills towards the K
--------------------------------

Frame Relay simply moves the data to the next router, quickly as possible

--------------------------------

FRAD -- Bell canada programs the FRADS


How will bell build this network
-Bell Canada has a special device at the boundry called a FRAD
FRAD - Frame Relay Assembler Disasembler

Its at the parameters of the cloud not inside the cloud, thats how they attach themselves
to the cloud

--------------------------------

DiscardEgibility - gets turned on when you send bursts of data

Bell canda calls bursts of data CIR - COmmunited Information Rate

-------------------------------

Frame Relay has one trick, if it becomes congested, will drop the frame.

-----------------
Getting customers to commit to the FRAD rate if you congest(go over the) CIR rate.
-----------------

BECN -Back Explicit COngestion Notification
FECN -Forward Explicit congestion Notification

When a device gets congestions it turns on BECN and FECN,
Whole idea - intended by frame relay forum, user device would notice
frames will arrive, it was hoped somebody develop a
program to have their own flow control to control the data coming in
Everyone ignored these bits.
----------------



Subnetting:

11.0.0.0

Require 5000 Subnets




00000000.00000|000.00000000

10.0.0.0 internal address

Classless /26

OPS335W10

whereis ls


/usr/share/man

manare like ls, echo, cat, mv all of these are in volume 1

all the manupages are compressed in gz, its easier to read a small file rather then
a big file to memory to read it,

ls.1.gz

all system administration commands are going to be .8


rezise2fs - volume 8

copy the ls command to your home directory so you have something to work with,
gzip-d ls.1.gz

ls -l
ls.1

now its in a language groff
groff - is a precurses to html

If you look at the html, from html you have xhtml, xml, all of these are markup languages,
before this if you go to 1960, IBM made up GML, they are nothing new they are just
derivatives, some where you will see roff, which is a form, then

groff(GNU free version)

MKGW 8 NOve 2007 mkgw.8 admin commands

mkgw \- Configure a linux host as a network gateway

groff -Tascii -man mkgw.8 |more <---intrepret what it looks like,

gzip mkgw.8

be root and copy it to volume 8 be sure its zipped /usr/share/man8/


On our floppy, we should have mkgw, mkgw.8.gz


show mkgw groff, listing of all the groff listeing and we should also show the man page
bash program as well

chmod 644 <----man page
-----------------------------------------
---------------------------------------
------------------------------------
----------------------------------
Distributed File Systems

All about file sharing, share files between two Dos Machines


The idea is:


Server Client
/
| | | | | |
home home
| |
| |
frank joker
| |
| |
stuff---------------------junk

Make a directory under junk

Connect stuff to junk
Make a file under junk "ABC" as the Server

Alot of things ot be set up to make this work

you have to know the IP address of both machines

1. IP of each machine
"FQDN"
2. Server needs a file sharing program
and-configured to allow the client to read or write or r/w
the stuff directory.
File sharing deamon or file sharing server
It will allow the client to read the directory

Withing our Server we have a file sharing program to allow the client to use this program

3. The client needs a program or software, to attach and use stuff(dir) from the server


^^^^^^^^^^Basic idea od DFS(Distributed File Systems)

The two systems we look at are

NFS - method of sharing files
SAMBA - method of sharing files

Network File System

-Developed by Sun Microsystems 1984

When did the first pc come out 1988,
versions for Dos and Windows,

-important to note,
b/c it was written so long ago it uses ports in a different way

Web Server
-Running Apache
-Port 80 (waiting for connections)-------1024---IE6 (WINXP)
|_1026___Firefox (FEdora7)
|_1024___Safari (MAC OSX)
In 1984 Sun did not use port numbers
-used sun numbers,
ex: SUN NFS Server Sun Client
\(directories)--8----------------8----\(directories)
-The numbers used have nothing to do with ports ^^

This is where
-Remote Procedure Call (RPC)


--We still use the sun numbers but software converst it to ports

When you jrun the server you have to run another program
that changes the number to ports.

man exports ----its in /etc/exports
- on the server side this file tells what directories are avaliable
to which clients & in what mode, read or write mode
Their is an example in the man page
id frank

----------------------

NFS SErver NFS Client(Fedora 7 Client)

-host abc joker on xyz
/home xyz (r,w) $su -
/etc/exports #mount -t nfs abc:/home /mnt
|_usually an empty dir used for mounting
|
# | |
joker clown
#cd /mnt/joker
#rm *
This wi9ll alow the person to do w.e.

If you put xyz (r,w) root_squash
so the rm will fail

or no_root_squash

Setting NFS
1. install NFS-server
2. edit /etc/exports
3. start nfs server

4. you change /etc/exports

5. Choice
- Stop & stop the NFS server
OR
#exportfs -a
-reread the exports file without restarting



READ bout NFS



Samba is different
- Andrew Tridgell -wrote Samba-1995 Microsoft - SMB (used for fily sharing -OLD)
-idea to work in a microsoft enviroment -CIFS (Common internet file system) *newer*
-use windows as a client
- use the share
- can become a client on linux and become a user share
-he also wanted linux with its own share and have
win1 win2 win3 machines just as though linux was windows box
Basically Samaba - A client and a Server, a client for windows shares and a server for windows shares


using smb protocol to see the files in their
konquer - shows file systems and a webbrowser

seneca subnet 142.204
LEARN NFS and
export, exportfs, NFSDEAMON, know how to config the files


Lab 8 is three parts,

Connectings to a Samba server- file sharing server using
cifs - file samaba system
Part One - Client
Part Two - Own Samaba server

testparm - check if syntax is correct

DCN386W10

Alot of subnet questions in test 2

10.0.0.0
255.255.192.0

Question 2 Test2?

What is X.25 and how does it work?


X.25 when you see a letter then a number you know you are dealing with a protocol or equipement
ITU V.90

SDLC HDLC was last week, in PPP,

but their are different applications in this world,



Example.

A central computer, build a network for lottery ticket machines

X.25 solves specific application issue, if you have an application that sends data
infrequently you need X.25, lottery ticket, its a

Network Layer protocol, packet-switched network.

DCN386 only two network layer protocols, IP and X.25.

X.25 Network Packet Devices


X.25 designed to be a sutible protocol for people who want to send small amounts of data
infrequently.

All the telephone companies have all pre built x.25 network

Bell installed X.25 switched devices that spand all of canada

Easy to install and immediate benefit

Packet switching is already their and ready to be used. X.25.


Tip Top Tailers

because their all using the service is also shared, the second major benefit

It is extremely cost effecient. Pay for the service how much you use the network.

Based on a number of packets ur company of information

Packet is data send through a network layer protocol, IP and X.25 does this.

X.25 will take data and break it into a piece and will be a fixed lengthed, in Canada
Bell canada offeres serveral flavours, 90% of companies, of a basic frame size of 128bytes
this device will build you a packet and the max size is 128bytes.

Theory take user data, break it into pieces and sending it through the cloud.

How does the customer get the data into the cloud,

How does this work?

Simple their are 2 addresses involved,
1. is a real physical address
X121 - internation addressing scheme
-works and acts exactly like a phone number
-14byte address scheme
ha ha ha ha

Number can be up to 14 digits ex: 123-456-789-111

One of are job for us:
Supply the number of the cash register to dial into

The start of the day:

To set up the X.25, he(Manager) will send a packet from the tip top register called
-CALL REQUEST
-sent into the cloud
-goes to the switch, looks at the area local codes
-switch will select a route(path) through the network

The reciever will send a
-CALL ACCEPT

You now have a path way through a cloud,
-PathWay = Virtual Circuit

At the end of the day the guy turns the machine off, a last packet will be sent
-CALL CLEAR
No Longer a Virtual Circuit it is shut down

Another Day:
-CALL REQUEST
A Different Route is taken
-CALL ACCEPT
A Different Virtual Circuit

-------------
The X.25 machines are computer specialized in packet switching
-Lots of memory
Holding-Tables how to get to the Destination
--------------
First address is used in the CALL REQUEST

Once set up a second Address called:
-Virtual Circuit Address
-12 bits ~4096
---------------
VC-ID is sent = virutal circuit 1 - ALWAYS
-talking to 1 computer
---------------
Head office computers talk to Numerous Devices, thousands of lottery ticket machines-
-Identifying 4096 cicuits per physical line
---------------
X.25 Low Grade Low Speed Telecommunications Copper Wire ARgh!
---------------
When you phone bell and ask for an X.25 circuit, how many virtual curcuits on this physical line?
Pick a number -a number 0-4096

Never install more than
-32 virtual curcits in one physical line
----------------Rule of Thumb----------------------------
Cheap phone line!
------------------------------

Confusing Part:

Second thing that we will be asked when asking for the cuircut,

Do you want a private, switched or a combination of virtual circuit
-------------------
Two types of Virtual Circuits
-PVC (Private Virtual Circuit)
-SVH (Switched Virtual Circuits)

Depends on the packet a month you pay for it
--------------------
Another Cost a number of virtual circuits for a physical line

You want all permanent circuits, Bell will install a permanent route through the cloud
--------------------
Why would we used Switched hmmmm yea sooo
Three offices
Three networks
| | |




Every night the offices download the daily sales,
How many Virutal Circuits will i need on this line, One
All the networks in different locations and times will switch it,
-------------------
What if its modern and u want to install on real time, you would need three virtual circuits
and make them PVC


------------------------------------
-----------------------------------
---------------------------------
X.25 most endeering
Most Reliable protocol ever developed
-Error Handeling
-Flow Control Mechanisms
-----------------------------------
---------------------------------
-------------------------------
-Error Handeling (CRC)
------------------------------
-Max 128 bits
-Closest Circuit does error checking
-EVERY PORT IT'EL DO ERROR CHECKING
------------------------------------
------------------------------------
-FLOW CONTROL
- Any activity that prevents the loss of data
------------------------------------
------------------------------------
X.25 does not drop packets
-flow control mechnisms to stop sending data
--------------------------------------------
Because of speed its not used, ^ the things it does
--------------------------------------------

X.25 perfect for customers Infrequently
X.25 people looking over it!
X.25 1 component of a huge body of work
X.25 RULES PAD EQUIMENT TO ACCESS THE CLOUD
X.25 - small amounts data every so often ==== PERFECT ====

Once in the clout Dozen of protocols you can use

You can attached ur PC to Bells X.25 Network,

Phone connectiong, Packet Sender and Disembler (PAD)100$

--------------------------

X.3 - sepcification for what PADS do
X.75 - International speicification

--------------------------
X.25 is the slang to get into the cloud,
--------------------------


WEEK 13 TEST 2, IN THE LAB we are going to go the quiz, worth 10 %,

2 hours of subnetting

and Access Lists. ACL

GROOVEY LIKE GRAVEY

--------------------------

A packet arrives in a router, and the packet has the address 10.1.240.14, router does not revognize
the address and has the folling mask 255.255.240.0 , company network mask.


Class a 10.1.240.14

00000000.0000|0000.00000000

alL U HAVE TO do to see what subnet it belongs to?
00000001.1111|0000.00000000
subnet 31

OPS435W9

We are going to be covering stuff that is more difficult that what we have done so far,
regular expression, awk, sed language.

Looking at Assignment #2:

A program what makes exchange rate do, take any currency of any country and your program will exchange it to anyother country
from the exchange rate.


Done in 2 stages,

Stage 1, evalaluation varification of input, Nov 16
Stage 2, 2 weeks later

Being Partnersz we are going to use the RCS system

Between the two partners who accounts to use

In that persons home directory ~/asgm2/***/exchange.bash & RCS

710/ 710 / 770/ 770 / 770 /



#GroupMember:
#GroupMember:

The rates are freezed as of today and put on a table on the site

convert.table will reflect the data in that file

cad
CAD
Cad



2arg cad us


Oc can do anything mathimatics


sed -nl | file

We are going to use regular expressions, subject of our lecture today

What are they used for?
To match patterns in data


You can use similar special chars to search for patters in data, called regular expression.


grep 'patt' f1

FNE * - zero or more
RE * - Zero or more of the previous char

FNE . - is dot
RE . - any single char

FNE ? -any single char
RXE ? - is a ? extended regular expression -egrep -awk - zero or one of the previous char


FNE - [!dfds]
RE - [^Fdsa]

RE - ^a[^fds]d - specifies the begining of the line because the other one does any pattern within the line
$ - its the end of the line, this belongs at the end of ^^ that line

.* - zero or more any character, combine those two<---

RE - a\{3\}b - a repeater refereing to the previous char which is a, how many a's their are, 3 a's followed by a b = aaab.
,5 - min 3 max 5, longest pattern first then the shortest

RXE - a+b - extended regular expression - one or more of the previous char. shortest patt ab.

RE - a+b|c?d - the pipe is a or

grep - can use RE - single pattern
egrep - can use RXE - multiple pattern by using the or which is the |


grep 'a+b|c?d' f1 - none are special chars to grep
egrep 'a+b|c?d' f1 - 1 or more a's followed by a b OR zero or 1 c's followed by a d


echo $1|grep '^[0-9]\{8\}$'

(( *sum *= *$?AA *+ *$?BB *))

sed

:S,$ s/exchange/convert/g - in vi

g = globably
no g only first match each line

sed - stream line editor, tell sed what to make to data

sed -op 'address sub-comm/searchpattern/replacepatt/tag' data

some options:

-n
-f
-e

address :

2,10 - only lines through 2 to 10 do the stuff
can also use RE
2,/dog.s/ - start at line 2 next line must have dogs or dogs
/dog.s/,15
1,$ - line 1 to the end of the file
subcommands cover:
s - search
i
a
c

Search pattern:
-RE - here

replacement pattern:
does not use RE

tags:
g - global
d - delete
p


How sed actually really works

has a pattern space buffer,
opens the file takes line number 1 first thing it does check the line number, automatically line 1 goes to STNOUT
Next line comes in #2, address match yes then continue with the rest, if we say s subtitute search for a pattern it will
replace it with that pattern.

sed '/^$/d' f1 - delete blank lines

DCN386 Introduction To SDLC

SDLC Intro-Continue
P=Primary Unit
S=Secondary Unit

-SDLC is a primary Systems Network Architechture (SNA) link layer protocol for WAN links

-Used with PPP & multipoint links bounded & unbounded media, half & full duplex transmission, transmission facilities, and circuit switched and packet switched networks.

- Network nodes: primary and secondary

Primary - control the operation of other station called, secondaries.

P & S connected by four basic configs-

Point-to-Point - two nodes 1P & 1S
Multipoint - 1P 2xS
Loop - topology P = First & Last S (connected to first and last S)
Hub go-ahead - In bound/outbound channel
P-outb-S S-inb-P
In bound daisy-chained back to the P through each S
--------------------------------------------------------------------------------
Derivative Protocols
- IEE 802.2 LLC is a modification of HDLC for LAN enviroments

-HDLC is a compatible super set of SDLC

-Qualified logical link control is a link layer protocol defined by IBM that allows SNA to be transported across X.25 networks.

-----------------------------------------------------------------------------------
High-Level Data Link Control (HDLC)
-HDLC supports sync, full-duplex operation

-HDLC 32-bit checksum, does not support the loop or hub go-ahead configs

SDLC 1 transfer mode
HDLC Supports THREE:

Normal Response Mode (NRM) - Used by SDLC. S cannot communicate with a P until P gives permission

Asynchronous Response Mode (ARM) - S to intiate comm w/ a P unitil P have given permission

Asynchronous balanced Mode (ABM) - Combined mode ABM - act as a P or S depending on the situation - Occurs through multiple combined nodes - No permission required-

----------------------------------------------------------------------------------
Link Access Procedure Balance
- in X.25 protocol stack
- shares same frame types, and field functions as SDLC & HDLC
- Restricted to ABM
- Can be established through DTE & DCE
- Intiate call P responding S
- LAPB use of the P/F bit is different from that of other protocols
-------------------------------------------------------------------------------------
IEEE 802.2
Three types of service
T1- procides unack connectionless service
-TCP/IP componsate for this
-commonly used

T2 -connection oriented
-ack data upon receipt
-used in IBM communication

T3 -ACK service
-Factory automated enviroments
-where eroor detection is important

Upper-layer proccess use IEEE 802.2 services through service access points.

------------------------------------------------------------------------------
802.2 header DSAP - Destination service acc point
- identifies the receiving upper-layer proccesses
------------------------------------------------------------------------------

OPS335W9

OPS335

Lab #7 setting up web server using apache,
Assignment 2 posted


Intresting networking type commands:

netstat -an |grep :80|wc -l - how many connections you have to your apache web server

/sbin/ifconfig - to configure an interface, bring it down or up

Commands located in for:
/sbin - administrators
/bin - regular uses

arp - find out MAC address

hostname - tell you host name or change your host name

host yahoo.com - does a dns query which are handeled on port 53, you can also to ip to hostname

ssh username@hotname - its encrypted

scp - remote:/home/me/junk/* . [from] [to]


rsync - sync two directories, if you have host a and host b with 2 harddrive the firstname you do rsync the two harddrives
because identical to the other harddrive.The second time you do it it copies the files that were updates.

tcpdump - print all traffic in the network - nice to monitor what is going on.

nmap [website] - used for port scan - 65000 on Unix -

wget [website] - retrive website information -r whole website tree

Apache Shell commands

httpd - its a deamon

service httpd restart

The very first webserver was called MOSAIC by NSC government computer before IE before Mozilla.

Apache, pached mosaic, Microsoft Webserver is called IIS

50% =====apache
40% =====IIS

/etc/resolv.conf ----short form of resolver---take a domain name and convert it to an ip number

/etc/hosts - names and ip numbers for the local

/etc/nsswitch.conf - order where to look first

/var/log - contains all logging information, want to know what happen to the system \

rootkit hunter- malacious attack suspected

Assignment

A Man page, and a bash script

mkgw

interneral, masquerading

serveral designes


mkgw.8
volume 8 - fdisk

volume 1 - cat, ls

man man ^^

DCN386 SDLC RIPv1 compile

SDLC - HDLC - FrameRelay - PPP

SDLC - Synchronous Data Link Control

SDLC - Datalink Protocol which are Point to Point protocols

The Bank and customer start a PPP so their is no Network Layer Involved

Website for SDLC frame and ALL information:

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/sdlcetc.htm

Below will Summerize what was talked about in class:

SDLC + HDLC + PPP have one thing in common

Variable Datasize
- the protocol does not specify the maximum data unit

SDLC Fields

Flag |- 8 bits of information - 01111110 -|

The first zero start bit last zero end bit.

Why? - To know when the message is over because its variable datasize

Start and End bits - Marks between data.

To ward off mixed data when the bits have a consecutive 6 1bits SDLC will put an artificial 0 at the end aka bitstuffing.
---------------------------------------------------
Control Field |- 8 bits of informaiton -|

A three bit frame format field: Info Frame, Supervisory Frame, Unnumbered Frame

Info Frame
0 - in the control field, means information is being transmitted
Supervisory Frame
1 - Supervisory frame
- positive ack
- Negative ack
- Flow control Feature
Unnumbered - Used For Network Management Functions
- Shut down & restart "Banke Machines...."
--------------------------------------------------------------------
Still in the control field
|Sequence Number| - 3 bits - Can send 7 frames before an ack is demanaded
000 - Received SN
000 - Send SN
Error checking is done for the seven frames

If they are all correct their will be a supervisory frame of 111 for completeness

----------------------------------------------------------------------
Supervisory Frame
|Function Code| - 00 = means no errors
01 = errors
11 = stop sending data
----------------------------------------------------------------------
Unnumbered Frame - 5 bits -
| function code |
- Bring up down reset
- Done by a Network Manager Person
- Preforms network management functions
----------------------------------------------------------------------
Info | Supervisory | Unnumbered
| Poll Final |
- 1 bit 2 functions
- Depends on direction
We call computers usings these protocols
Central Units & Primary Units

Primary unit - control the ordered delivery of data

Polling will ask each primary unit if it has data

- When it is coming from the final primary unit a final bit is indicated
------------------------------------------------------------------------

Thats it for SDLC at this time.

-------------------------------------------------------------------------

RIPv1 - Request Ip address | Hop Count | Interface ...depending on the Hop count it will choose the lowest one as its main route to destination
- Every 20 seconds a request is made
- Does not address Subnets
-------------------------------------------------------------------------

DCN386W9 - SDL HDLC FRAMERELAY RIPv1

Question 1 Test 2

Test 2 in week 13

Scummed the test AAAAAAAAAHHHHHHHHHHHHHHHRRRRRRRRHHHHHHHHHH!


In the course outline
2test each worth 25%,
1Q 10%
FE 40%

Test 1 20%


60/3




Question 1

It’s a protocol

SDLC- Synchronous Data link Control Protocol

For the 100$ coming out of your bank accounts, you use SDLC

IBM’s protocol very expensive

OSI changed SDCL to –HDLC-

HDLC is ciscos default datalink protocol, if you understand SDLC you will understand HDLC

This is a data link layer protocol
IETF renamed it to PPP, is a derivative of HDLC which is the DERATIVE of SDLC

SDLC insights to half a dozen other modern protocols, SDLC and HDLC and PPP and FrameRelay are lay DATALINK layer protocols,

How do you catergorize it, datalink protocols are PPP protocols

What does this mean exactly,


You and to the bank is PPP no Network Layer Involved, by week 14 why is is not a good idea to put a bank machine on the Internet.

You don’t have to worry about Ordered Delivery theirs only one route

It is stressed it is a Data link protocol,

When you want to learn about protocol you look at the control information that is infront TCP/IP 20 bytes of information in front of every protocol.

He will send us a website with the information to the diagram from this lecture

SDLC + HDLC + PPP and all the things have a
Variable data size – the protocol does not specify the maximum data unit

Ethernet is also a data link protocol it has a maximum variable data size.

If you worked at Scotia bank you would pick the maximum data size, it has versatility you can do what you want with the variable size.

U would say if setting up a bank application down at the bottom of the script would be
MAXDATA : 100

The address 8 bits, 2 bytes long

Lets go through this you ask for 100 bucks from a bank machine it will put the information into the data field, the bank machines surrounds your data with this extra information, a 1 byte
FLAG – 8 bit of information - 01111110
Frame Relay same information it starts with a flag

Why do we need flags, know when we know the message is over.

The reason you need a flag cause SDLC does not have a fixed data size,

Ex: what happends a receiving machines gets a start flag it reads data, onlt when it sees an end flag it knows it has received a complete message.

Start flag and end flag are like book marks between the data.

SDLC will guard against theirs another 6 bits that our not ours, when they all want to send a message the protocols will examines the data, looking for an occurrence of six consecutive ones

While building a frame the data is examined if the software (HDLC) if it ever finds 5 consecutive 1 bits it will stick an artificial zero at the end it will say AH I have a astart frame the computer will then remove the artificial bit and restore the bit, this is called BIT stuffing after 5 consecutive 1’s.

The 1’s are used cause we don’t know the size of the data field

The address is manually applied, one thing to consider, a 1 byte control field,

TCP/IP had 20 bytes of control information, very very inefficient, SDLC 8 bits of control information these 8 bits DETERMINE how SDLC operates, To control 8 bits wonderfully efficiently.


All the protocols we we are going to look at have
THREE FRAME formats its determined by the CONTROL FIELD


This is the first format, theirs a 0 in the control field that means an

information frame is being transmitted, however if if its 1 then a 0 then we are dealing with a

supervisory frame – positive ack, neg ack, and flow control feature

We are doing this with 8 bits instead of 20 bytes like TCP

So we got sending data, error handeling done by the supervisory frame,

A THIRD FRAME

Unnumbered – Used for Network Management Functions

its specially special, Network Management software, theirs number frames with 1 command u can take down and put up

SDLC uses what is called a SLIDING WINDOW (this is the window size), they call this a

Sequence Number
000 – Received Sequence Number
000- Send Sequence Numbers

SDLC can send 7 frames before an acknowledgement is demanded
Totally Reliable, it’s a VERY VERY.

Why 7 frames?

001
010
011
It will senevn frames cause the SN only has 7 frames cause it only has 3 bits,
The seven frames will go out into the internet and the deatination computer will get the 7 frames and then it will do
Error Checking
Under 7 frames CRC on each and every frames
If they are all correct the receiving computer will build a supervisory frame in the reciving computer it will put receive data
111

Function Code
00 means no errors
Supervisors address control and flags

The sending machine sends the other information, once it gets to 7 gets back to zero then starts again

What if their was an error in frame 6, it does CRC error checking.

The receiving computer sends a supervisory frame of a function code of 01 indicating their has been an error, 110.


Supervisory from 11 means stop sending data

Supervisory three things, pos ack, neg ack , and flow control

Whether its an information , supervisory and unnumbered frame, why is it unnumbered, cause they have received sequence number
Information have reveinumber send number

Unnumbered have 5 bits of function code, bring a network down up , reset the machine, 5 bits has 32 different functions, Network Manage Person can do function

Understand unnumbered frams perform network management functions.

Supervisory frames never send data, address control and end flag,

You can send data unnumbered frames, buy your RRSP the NMPerson, here’s a little

The final bit

Pull Final – 1 bit has 2 jobs, depends on which direction the message is moving, with SDLC central computer are called primary units and others primary units, primary units are computers that control the ordered delivery of data

Their can be no collisions in SDLC, think about it,

There is two people and they are side by side and they both ask for $100 and press enter at exactly the same time what will happen

POLLING is used for flow control, hence the name POLL, the bank machine handling SDLC each circuit SDLC will send a POLLING message is a supervisory frame with no data the bit in the middle will be turned on,

It will send it to the new frame ask if it has data pull back and see if it needs pulls the data then it goes to the next machine,

POLLING to each machine, pul indicator primary to secondary

Different if its coming from the secondary unit to the primary unit its called a final indicator bit.

Final frame it know it has received 1 2 3 and there is no more frames, 1 bit with 2 jobs.




Next 5 weeks:

WAN protocol, and Internet protocol, Test 2 WAN protocol questions and Internet specific questions

When you typed router rip
Router RIP- To build something called a Routing Information Table

Two flavours of routing information protocols RIP is the oldest.
RIP V2

Configuring router 1, R1 knows two things, R1 knows about subnet 1 and subnet 2,
R2 knows about S2 S3, R3 S3 S4.

RIP starts up in your router, does something intresting, will send out ever interface it knows and every serial it knows


RIP REQUEST – frame of data – 2 pieces of information, it knows about S1 and S2 and will send it to its neighbour, when R2 gets the rip request will send a rip request, it will say it knows about Subnet3 and Router 3
R1
IP address | Hop Count | Interface
S3 1 S0
*Add*
S4 2 S0

Now R1 knows that R1 is associated with R2 subnet 3

R2
IP address | Hop Count | Interface
S1 1 S1
S4 1 S0



Every 20 seconds when started, biggest problem, every 20 seconds on average it sends a RIP request to its Neighbours.

Another 20 seconds pass so R2 will send everything it knows ^^Addings to RIP: router 1 will *Add*

Second Major problem

IETF webpage, - Specification for maximum Hop count of 15

If you connect 2 routers together it will see that it will be 1hop count, rip will always send it out the fasts, the minimum HOP count.

Next week A FAR BETTAH routing PROTOCOL HA HA HA AHHHHH!

OPEN SORTING PATH is by far a superior protocol, far more complex protocol.

When you type in router RIP its rip version rip, the third crucial failure it cannot understand subnets. RIPv2 does address subnets

OPS435W9

No double quotes the shell will automatically go into file name expansion, this was one problem with the assignment.
An example with this
Echo $bs|grep [^0-9]

New stuff

RCS

Revision Control System

What is RCS?
What is it used for?

What is the revision number of the current Linux kernel 2.6.28….the second number if its odd its development if its 6 it’s a working version.

What does the 28 mean, it tells you the 2.6 version has been 28 times since its release.
Bugs or any functionality that needs to be upgraded.

^^this is what its all about,

These numbers are not being tracked its being done by the RCS system, lets look at how it works,

We are going to be using this for our next assignment 2, this system will keep track of the changes you make all long, this will keep track with revision numbers like the kernel numbers in Linux, this is used when you graduate when you get a job you will work in groups and your working on a utility of some sort this system has to keep track of all the ongoings, and has to allow each member of the group to develop and making changes, and also prevent people outside of the group to not come in and make changes.

Version Management
You can use this program to keep track of data files or anything, all versions are stored as a single file, for instance when you have revisions there is only ONE file, you can have multiple revision in a single file, with RCS you can keep track of it, or you can ask it to what ever revision you want to work with, the system will go back and undo the changes you have done to work with.

Some commands

-rcs
-ci
-co

To initialize rcs you use rcs –i filename
RCS needs a unique director so we have created a directory called RCS
When you initiate files, the rcs will ask you to give a description what the files about the comma v is added to any file that is created in any RCS system this is created to say it’s a RCS file not a regular file, the file we have initiated it does contain the file of the original file, it has created a RCS shell around it

My New Prompt $RCS
-bash: RCS: command not found
My New Prompt $ls RCS/
age,v
My New Prompt $cat RCS/age,v
head ; version number
access; who has access to the file
symbols;
locks; strict;
comment @# @;



desc
@this is my assignment 1 file from OPS435
@

When you do assignment #2 you will have to give ur partner cause we will be only using 2 accounts, once you make this decision the other person will have to have access to the file,

You have to use the check commands to play with the file, you have to check the file in or check the file out, when someone is on it you cant use it.

Ci jj

This checks it into the RCS directory you never go into the jj,v you have to check it out, you can use
Co –l jj

You want to use co –l because then it will be locked, so no one else can use it and only you,

Ci jj

RCS –a command, to give access to the person, you add the name of the user with no space
Rcs –afcrusso age,v

Rlog to see the history of this file

Ex: rlog jj


My New Prompt $RCS
-bash: RCS: command not found
My New Prompt $ls RCS/
age,v
My New Prompt $cat RCS/age,v
head ;
access;
symbols;
locks; strict;
comment @# @;



desc
@this is my assignment 1 file from OPS435
@

You can branch off to different branches, the particular item will tell you which branch the tree is in.

Make more changes
Co –l age.v


There are a number of commands parted of the RCS system

.rlog – history of the command

Not using this semester

.ident – certain keywords
.rcsdiff – different of versions
.rcsmerge – merge files
.rcsclean – get rid of duplicate copies

Another system CBS and has many more functionalities.


And that’s our RCS.

On warning, if you initialize a file with the rcs –I as you know that’s just a shell does not contain the data of the file, if you were to check out the file, because the file does not contain data it will wipe out ur original file if you continue if will put nothing in your original file, do a check in before you do a check out.

When you encounter during the test some of the simple things, one thing that was expected the bonus question
Regular expressions
Find if $1 is an integer
Echo $1 | grep ‘[^0-9]’ || \$1
[ $1 –ge 0 ] 2> /dev/null
Expr $1 / 1

Thedate:

Cal|tail +3|wc –w
Cal|grep –v ‘[a-z]’

DCN 286 - Information on Ethernet...MORE INFO!

DCN January 26. 2007


Trying to understand how Ethernet work? What is Ethernet?
Go back in history, the island of Hawaii in the Pacific, in the late 60’s the university of Hawaii had a very clever thought, they had some offices on one side of the island and on the other side, they wanted to communicate between these offices, and their was no way for them to do this, they invented a method, which was satellite service, they developed their own little protocol to send messages to each other, they sent the messages to the satellite and it was a source address and a destination address and of course data, if add wanted to send to add four, the messages would be sent to the satellite and rebound it to the computer. Lets say SA = 1 DA=4, Three would receive the message and ignore it and would only go to its destination. Primitive and it worked. This was called Aloha net. They thought to themselves to send a single down through copper wire. There was a group in the 60’s that developed things like mice, but the most important was Ethernet, and the most was Zerox. ThreeCOM manufacturing Ethernet cards, at the same time IBM was inventing token ring, yet today token ring is gone, Ethernet survived and Ethernet is thriving, December of last year Ethernet people put the standards at running Ethernet at 10 billion bits per second, Then the standardized of 100 billion bits per second. Macaffe invented Etherenet, they put in strands of coaxial cable, DataCom cables coaxial and twisted pair cables, Coax has a thick piece of copper surrounded by a insulated matieral (plastic), surround by a weave, amazing thing about coax the copper is thick and can transfer a lot of Hrz, (hrz dead German guy, working in the 18’s with electricity), the number of wave cycles per second is called one Hrz(hertez), a million Hrz means 100 hrz per second, coax cable b.c its nice and thick can theoretical can handle 100, mill hrz. The coax in the tv can handle 600 mil hrtz, Each station takes 600mil hrtz, Back to MacAfee, we invent a little plug that attaches in the coax, in every comp a special hard that will sit in the expansion slot in each computer (THE NIC) the Network Interface Card has logic, try in to visualize the NIC is a separate device, and has simple logic burned into it, and works with your computer, The idea about the cable was SPEED, A NIC using Ethernet would take data, Operating software uses the inturp and inturrpts the cpu and sends the data, INT52 is a well known interrupt and goes through a specific area in ram grabs the data and moves it to a NIC, The Ethernet guys MacAfee used the follow rules: First the Maximum Transition Unit (MTU), 100 protocols Each has a MTU, All protocols take data, and break it in to pieces the maximum transition unit size is going to be 1500bytes, if you wanted to send 1501 bytes, it would resolve in two transmissions, that is just Ethernet, remember this and remember it NEXT SEMISTER. As the same time in the Ethernet guys IBM was inventing token ring, TOKEN RING when they designed it could send 64,000bytes (huge packets of information), we are going to figure out why the groups made these bye decision Ethernet primitive simple protocol survived, and Token ring survived. When ever a int was sent the NIC would build a frame of data, and infront of it there is a Header, Ethernet header very simple while the TCPIP complicated, HDR has DA SA TL Destination Address, Source Address, A one byte fule called either TYPE or LENGTH. Ethernet uses MAC address, All LAN addresses is how many bytes 4 bytes ip and MAC address is 6 bytes, trillion of address, IMPORTANT’ the MAC address is made up of TWO components, NO two MAC address can be the same, Network standards, the IEEE group Institute of Electronic Engineering (A GROUP), OKAY you are company 999, the first three bytes of the 6 byte address is Manufacture ID, They are identical to AHOLA net, Workstation one wants to send data to Workstation three, the NIC would build the bytes and send it to machine two and ignore the address, and send it to three. Ethernet survived and why…Ethernet was simple that’s the answer it was so basically simple that it thrived, probably for the rest of your lives, you will be working with Ethernet. Test 1 DCN386 questions TWO How does Ethernet work…here is three basic principals on how Ethernet is a base band technology meaning only ONE signal can move down the line at one time (broadband sending 100`s television channels) works CS MA CD, Carrier Sense, first logic in the NIC uses carrier sense, it uses INT52, the NIC looks for digital pulses, if it sees pulses it wont send the data, if theirs no pulses and no one is sending zero data (volts) Carrier sense, no carrier zero volts, no one is sending things, it first makes sure nobody else is using the network, the second pillar of Ethernet wisdom is called multiple access, You can easily simply find the computer on the system , the third is the most important, (CSMA CD), it’s a simplistic design, Ethernet strategy the first work station, the first NIC that detects ugly pulses has a job to do it sends out a high frequency jamming signal, the NIC would try to send it again, Ethernets simplistic approach from this collision will wait on a RANDOM number, > DATA >T L > SA > DA, Zerox ThreeCOM started Ethernet, the original ThreeCOM internet message was like DATA . TYPE . SA. DA, what do you think type stands for…it’s a two bite field that represented which higher protocol, Ethernet has never worked alone it is a delivery boy, a delivery of data. Type (a number) sends the frame to another destination reads the data and looks at the type and understands to send the data to TCP data, it can be all sorts of different TYPE, logic when sending data take note of where its from look at the data and note it should be shot of to TCP program. (HUMAN RESOURCES) IEEE our friends did few things, started making standards which allowed different types of local area networks to communicate with each other. The IEEE came up with the standard 802, this started in 1980 in Feb, they said its going to be called 802.3 and token ring 802.5, 802.11 is wireless, one of the changes was the change of TYPE and made it length, why do you need a length field, well what if you were only sending 25 bytes of data that may or might be not be a important, how does the IEEE know what type of data..they borrowed the first two bites the IEEE solved the confusion of the none 802.3. Ex: Three companies Zerox, Digital Dix, the IEEE solved the problem, today they all worktogether,, not important for dcn 286 theirs a extra thing they put on the frame theirs a preamble, its 64 bits long, 101010101010101010101010 alternating ones and zeros. Think about this you’re a NIC that cost 25$ you can send info to each other, what would happen if you were in a bad mood, and u started sending smaller bits, how does this precision they get insync, very simple very basic that works. Primitive 10baseT 10 million bits persecond using base technology over twisted pair cables, think go Cat5 Cable, Lab wed Cat5 and make the cable straight threw and crossover. Beaware of this Cat5 comes int two types UTP and STP, unshielded twisted pair, and shielded twisted pair. Cat 5 6 7 learn to love next wed. READ up to chapter three.

DCN 286 - Information on TCP....B/C You will be writing Essays On This ALL THE TIME!

What is ip and what does it do, what is ip’s job, Ip’s job is simple is to get our data through the internet as quickly as possible and that all its job is its job is not to make sure your sure data is safe Ip does not care about that and if it looses you’re data oh well, and not their for reliability all it cares about is trying its little best to send your data through the net as quickly as possible, ip runs not only in your computer, but in all the routers in the internet, client and server, all have ip, gets stuff done fast, you’re going to tell in week 14 about the total length (16 bits) it can theoretically take you’re data and put it into pieces 65,535 K the routers hate big packets, so if you accidently sent a big packet it would break it into fragements, if you approach a cisco router CISCOs default is 1500 bytes, you can change the router MTU bigger or smaller (maximum transmission unit) it uses the identification field so all the fragments have unique numbers, the router then takes a fragment offset value and see which position its on, middle first or last fragments so when all the fragments get to destination computer IP will reassemble the fragments in the original , TIME to live is how many hops a packet can go through the network, you can overwrite it depends on you’re OS, if the router can’t go to the destination it will get destroyed , last thing were going to tell him is the IP address, IP addressing 32 bits of total confusion, todays not ip but TCP, Tranfer Control Protocol, essays on TCP for the rest of you’re Seneca carrier, at first glance it looks very simple but very deceptive very complex, TCP provides reliability TCP/IP running on your computer, in the Internet cloud theirs huundred of thousands of routers, and all the routers are interconnected, the routers are also running IP when you pass the IP packet to the router and examines the destionation address. TCP is running in any server you connect to, what are you doing at home maybe you wanna download a picture of Pluto, www.nasa.org, scattered around the would there are DNS they have two database with NAMES AND ADDRESS, when you contact the DNS server send it a name and will return an IP address, TCP is going to provide realiability while you download the picture to do this it is going to use something called a port, a port when talking about TCP is a number a 16 bit number so 65, 535K, IEEE standards organization which came up with a list with internet application, DNS internet application, TELNET, FTP HTTP, anyone who, HTTP port 80, FTP port 21/22, TELNET 23 we are going to use FTP to download the picture of Pluto, the port numbers 0-1000, are reserved port numbers for legitimate internet application called Well known ports, over 1000 free to be used by any computer, Here you go you got the ip from dns and you know nasa, org TCP doesn’t know the address but attached to IP and its going to build a header information, default header size is 20 bytes and its going to start ot build port numbers destination port Destination port is 21, you can send lots of things to nasa.org you can try to telnet to nasa.org but you want to download something so you are using FTP, TCP will generate a random number will be between 1000, 65000, essentially its going to say this to the client machine to the server what your doing is TCP is opening a session between your client and nasa.org, there is now a session being established, to work correctly, when the seassion has been established the two machines can send data with eachother first open a session then send data then end the session, the session to be established though is a little bit complicated, a client machines sends segment to the server and will flip the two numbers around and send them back to you, here is the complicated part, TCP receives confirmation sends a third header switching it again, the two machines, when they are forming a session are negotiating with each other, before they need to send data, two or three things they must know, most important thing is how long does it takes TCP segment to go from here to the network and back again, the client initiates the second sending TCP record number 1 this machines looks at the system clock on the computer and record the time for the request of the session the little fragment goes flying through the network and sends it back and looks at the system clock again and now they know how long the round trip is going to know how long its going to take, lets just say it takes 1 second, but this machine does not know what it is and is the purpose of the third segment, is looks at the system clock, three headers, now both machines understands how long it takes to you’re computer and the server now it know it takes from it to you, other important things are being negotiated when tcp first came out, back when their was 50 computers and the internet tcp used sequence number and acknowledgement number for error checking, if there is no errors its going to send an acknowledgement number for error handling the sequence number in early days, use to start at sequence number 1 then 2,3(Frames) does not happened any , more, early days no hacking, sequence number was a hackers prayer, todays version of tcp, between the negotiation will pick another random number, you got 32 bits, what’s the maximum number 4 bil and change, so ip when its sending the initial request will pick a random number 0 -4bil and will stick it in the sequence number field (init sequence number) it will start counting at five when it gets it and when gets to the server another random number is chosen, to set this session we look at the little 1 bit of information when the client sends the first header its going to turn on the SYN (flag 1) when it sends the reply its going to turn on the ack bit (1) when it sends the third reply its going to turn of the syn(0) and send a reply, you notice tcp full duplex protocol, theirs multiple downloads, so lets see how it transits data, how weird is it? Where going to ftp to send data FTP, is a simple protocol, once the session is established it starts reading in data one byte at a time, when ftp thinks its got enough for one segment it will screen the data 1 byte of a time, and codes the bytes 1, 2, 3(bytes) if you left tcp alone it will leave it in your computer it would literally blow your memory of your computer, TCP says I think its enough data (100) bytes and knows the intial sequence number was 5 now its 105 and its going to do error checking on that 100 bytes, using Checksum an algorithm that makes sure theirs no bit errors and if there is no error bit its going to build the acknowledgement number 106, and turn on the acknowledgement number, then the server goes onto the next 100 bits and acknowledge number is going to go to 205, the data gets send tcp does error checking, the machine will build a twenty byte header and positive acknowledge number 300, if you peer closely of the little 1 bits their was a error, what would the server do? What tcp does is unique, TCP does nothing, TCP was written in such a way, TCP looks at the system clock and record the time, if theirs not a positive ack in 1 sec, tcp will automatically retransmit the packet, TCP will notice that the two packets with the same sequence number and discarded one of them, at the end of the session and all the data is sent it goes through a complex procedure to close down the session and we don’t have to worry about till next semester, Window the third thing the initial size, depending on the OS, link between tcp and the operating software, if your using Windows, windows will direct tcp will have an initial window size of 64K, Linux has much smaller window sizes 2k, the bigger the window size the easier you make the hackers job, when the session is nogiated it’s a initial window size, two tcp start sending data, lets say they start small window size of 2k, tcp will actually monitor the number of errors are their, if tcp ‘thinks’ the network is good today because of no errors either machines can increase the window size, and if even more it will increase, tcp increase and decrease the windows until errors start happening, window size is really how much memory is going to be reserved on each computer, the application determines how much or when to send data, it tells tcp heres enough data, and will turn on the push flag and could receive the blocks of bytes and save it in number, when a tcp receives a packet when its turn on it will saveit and push it into the application, its how much memory in each machine is going to be used, ultimately IP is going to see the packet size, Window size is the amount of memory to save multiple tcp pieces, Urgent Pointer and Urgent bit till next semester, for now all we have to know is TCP header and a big pile of data following the header, lets say for some reason the application wanted you to read a specific data that not right on the front it will turn on the urgent data and will read the password which was 100 bytes in, save till next semester. TCP and IP are mentioned numerous chapters into your computer, write essays in week 14 and put these two topics in test TWO to get some practice.

TCP
Source Port(1001) | Destionation Port (21)
Squence Number (00000101)
Acknowledgement Number
Data Offset| Reserved |URG(1)|ACK(0)|PSH|RST|SYN|FIN | window
Checksum | Urgent Pointer(1)
Options + Padding


VERSION IHL TYPE OF SERVICE TOTAL LENGTH

What is a collusion domain, HUB with ports, you got a HUB the simultaneously the collusion will interfere with all the toerh computer, and the chaos is extened to every machines (CD) and the more machines the more chance of collusions happening, Switches are employeed to reduce the effect of collusions of your network, switches break it up to separate collision domains, SWITCH 5 ports and traditional little network hubs to each port and then attached to networks, no the hubs machines are in a collusion domain but if a collusion hapends here and will have no effect on the other domain, Switches reduce the collisions, everything we put on here is its own little collision domain, today happy networking use a process called micro segmentation, what does that mean, networking guys today have virtually eliminated collision through high quality switches and having one machine on each port on a switch their can be no collisions , micro segmentation imply switches and are all into switches Cut THREW switch does what, when a cut threw switch reads the frame it immediately checks the destination address, will immediately set up a channel source and destination port, if you got a nice safe environment, Seneca college, you use cut threw switches, how ever if the environment is a little shakey, in that environment you use STORE and FORWARD switch that has huge amounts of memory and will read the face and its entirety and store the frame where it does error checking, and if the frame takes it and there is no errors it will send it to its destination,


Does not matter which but it can get to one work station through its port, now we want to talk about subnets, switches are datalink layer devices routers are network layer devices, we are one originations and we sell stuff on the net the switch to the computer and the server, we need to sell stuff on the net so we need to buy a router, we need a domain name, our domain name has a associated ip address 200.1.1.0 (ClassC) we hire a networking switch 200.1.1.254, we got a problem cause were in Toronto and going to Vancouver, to they subnet to create it so they can expand and have their own portion, to create subnets its an easy thing don’t matter what class, you create them the same way you play around with binary numbers,windows create subnets a dumb way, and use a short cut and don’t know when there is a lot of subnets, the correct way is to play with binary numbers, which numbers
Network Address 200.1.1.[0] in control of the 4th octet, to create subnets take the host bits and write them out in binary one rule to be applied to subnets by convention we never use all zeros or ones, so we have two left to indicated subnets 00 01 10 11 so 01 becomes Toronto while 10 becomes Vancouver. [00]000000 to indicate if its Toronto or vancouver
SN
00|000000
01|000001 [65]1*
01|111110 [126]2*7th -2
11|111111

We turn on the host bits and the subnet
255.255.255.192 which is the value of [11]000000
1* the address can be added for example 010000010 and moving the 1 up to the numbers
The last number and the range there for becomes 65 – 126

Vancouver
SN
10|000001[129]
10|111110[190]

NOW WE NEED THREE SUBNET IDS with 001 = T. 010 = V 100=LA
001|00001 [33]
001|11110 [62]

DCN286 - Information on IP...GOOD INFO

Browsers are not internet applications,
HTTP, TELNET, FTP, DNS --- APS
All internet applications were written so they can link with the transport protocol, all these applications work with TranferControlProtocol and UserDatagramProtocol , you can do a lot of things with this write C++, Two guys wrote YouTube.com they used an idea that anyone in the room can do, they wrote an internet application that was very successful, the science behind it is common, DCN386 writing an internet application program…they use a ApplicationProgramInterface…this tool will hook this application right into TCP or UDP, TCP what does it do? Tcp does very little actually it provides reliability into your internet transmission, here is beautiful drawing of the internet CLOUD with a bunch of router drawings along with you on the side at home on the net…and on the left the ISP….The first thing you have to know about the internet and how ti works when you send packets of data in to the internet you sending it into a hostile environment…it is dangerous inside the cloud…ROUTERS which we think is a our best friend…it turns Routers hate packets they detest them they only get rid of them, but the easiest way is to move it to the next router…because its such a hostile environment TCP running in your computer and the SERVER in which your contacting TCP tries its best when Routers destroy you packet TCP will contact the server and ask it to retransmit the packets…TCP will keep trying and keep trying a router does not know anything about retransmitting stuff…so TCP just runs in servers or clients it doesn’t run in the internet its reliability in each end. UDP on the other hand is a stripped down version or TCP…error handling is not in that UDP is unreliable while TCP is reliable…Why would they use the unreliable and a reliable, UDP faster then TCP, depending on what you want to do…the rule says if you sending tiny packets into the network…use UDP because the chances of an error is small so send your tiny packet through the net as fast as you can…ok lets look at a lot of a big picture…going to nasa.com to get a picture of Pluto….nasa.org will create DomainMain(its Name(lol))Service…global system where you type in nasa.org and it will go find NASA’s ip address…so your typing it in and DNS will treat it as data and will look at the data to the closest DNS server….its a tiny amount of data…What do you think DNS uses…obviously UDP…DNS always uses UDP…okay you got the ip addresss… TCP will pass to a program called IP and will send info to nasa.org that has a big file..pluto.jpeg now that’s big files and its going to be downloaded using FTP its going to download a lot of information…big packets are involved…what do you think FTP is going to do? FTP is running on the server nasa.org…it read the file and sends it into the internet FTP always interact with TCP because it doesn’t want any mistakes these two programs only run on the CLIENT or SERVER machine they have to no part into the Internet…it just knows reliability. How does TCP get itself through the network it will read the |data|F(header file)|TCP puts a lot of control information on it 20 byte header to be exact| this then passes down to IP everything uses IP…this get passed down |data|TCP|IP(20bytes of control information|), both have 20 bytes of information its 40 bytes of information must learn all 40 bytes for test two…TCP can deliver anywhere in the world…IP doesn’t know how to get into the cloud its great when its inside the cloud but it has no clue on how to get in their, what does IP do it sends it down to 802.3, NIC you put in it’s a Ethernet NIC…Nic will send it and you ISP is inside the cloud. Ethernet is going to deliver that packet from your computer to your ISP…whats in the Ethernet |data|TCP|IP|Ethernet … when the ISP gets the packet it gets read of the header and strips it off and passes directly to the Router inside the cloud Ethernet delivers the data. Now the IP packets inside the cloud it can be delivered to the destination Address..when it gets close to the router where the information is …its forwards through the routers and before it goes to the ISP and is re-stripped from the Ethernet frame. The internet is a popular their. IP we have to figure out how IP works….first thing we have to know about IP IP like routers does not care about your data…it doesn’t careless if you packet makes it or if it doesn’t. IP makes the best effort through the network as quicklWy as possible…HOSTILE. Where going o look at 20 bytes of infor
0 4 8 16 19 31
| Version | IHL | Type of service | Total Length |
| Identification | Flags | Fragment offset|
| Time to live | Protocol Header | CheckSum |
| Source Address |
| Destination Address |
| Options + padding |

The very first bits look at Version it will look at 0100 the binary level which equals 4 it will all have four bits of information…sooner or later your ISP is going to be version 0110 version 6, a couple of years ago he would say version six will be introduced right away…the IP address is 32 bytes long…the classes made it less effective and proved to be not a great idea and ran out , for a start the IP header has 128 bits, when IP version six comes out, he can go around the world in one square feet increments, in version six each square foot will have million in the square foot…the reason were not panicking anymore came up with something Class List Ip ADDRESSING because of that the full amount of IP address can now be access and now it is being revised…somebody’s brain wave made v4 not needing v6 but Linux. Their will be a compatibility with each other v4 and v6. The next four bits are equally boring Intial Header Length….(20 octets (20 bytes)) if we were creating are own internet application and wanted to test it out we would use something called options…Options is a little bundle of tools that will let us test are application…never do unless you writing your own internet application…..Ever heard of a little application Python…he took look of Python and thought of us…Python already has (application program tool kit to write applications) Python just installed in the Cisco lab…make your own client and make your server…...Type of service.. IP is probably the same age of us it was written quite a while ago..its been around for a couple of decades for 20 years all routers in the internet ignored the 8 bytes…all of a sudden few years ago its become the hottest 8 bits Quality of Service in Networking, we got to worry about the 8 bits…something happened recently another internet ..downloading Movies Voice and Media…Type of Service came important some packets are going to have priority of other packets. Router has serial ports and Ethernet ports…packets come into the router… routers temporarily store IP packets were talking nano seconds it just buffers them in old days they would look at ToS but now routers are starting to examine this Type of Service, this particular packet is in the middle of the buffer but has quality service and will process it first…just understand that some routers can treat some packets as priority packets…Total Length…that means that Total length for Data|TCP|IP the data and the control information ..Ponder how big can an IP packet can be 65536 (64 k) that is a big packet…64 k packet if you were foolish enough to write a program to send out 64 k you would be sorry…. Routers hate big packets they despise… they wont destroy them they will take your big packet and chop it into little fragments of the original packet… all routers do this… hard to comprehend.. when we go to cisco lab on wed and we look at the router and start configuring the router they have a default maximum tramission unit size… if it receives a big packet it will be MTU’s its 1500 bytes… because that’s what Ethernet uses….Lets drop a nice big packet | 4500(chop into three) |(20 byte header)

| (1500)[ID010] | (1500) [ID100]| (1500) [ID001] | - contained in the header info is the destination it chops up and put the header infront of each fragment.

How does the server know that they all belong together because the server gets all the fragments has to put them back together HOW DOES IT KNOW the three fields of identification flags and fragments offsetthis is what indicates the fragments belong together…IP before it sent the packet it picked a random number and put it in the Identification field you’ll notice it will be 16 bits its going going to be 0 – 65535 bytes… when the router breaks the big thing into pieces each fragment will have the same identification number and knows they are fragments and have to be reassembled back into the frame ,….wait theirs a problem went different ways…How does IP manage to reassemble these three fragments…they would look at the fragment offset...
|5000 |3000 |1500 | |byte 0 its going to read them and store them temporarily in memory…it takes the data read the offset and puts it in memory but by the OFFSET of 3000… it takes the 5000 and puts it the 5000 OFFSET…sequence failed, what if the sequence 1 get into the a grumpy router fragments can get fragmented….The Flags are three bits long…only two of the bits are used the first bit is a strange bit.. if the first bit is turned on that means that ip examining this it means DO NOT FRAGMENT its called a do not fragment bit…it was originally designed to send out and see if you get anything back… if a router got that packet with the do not fragment it will destroy it… the second bit means Last Fragment Indicator, this is used so after it knows it has all the fragments because of this bit. It knows it has the last one in the series…8bits Time to LIVE….what does TCP/IP care about to time to live… what if we purposely put a destination address that does not exist, theoretically our packet can go through the world…Time to live when your IP sent the packet out it put a value in TTL it will be some value from windows to LINUX from 1 -255 and the default value is 32bit, it will subtract the value and it will eventually go to zero with the zero packet will destroy it….sending a packet out of Seneca it probably …www.bagpiprepaire.com do a trace route and you’ll see it…. Protocol not a very important field it simply means TCP create the this packet or did UDP create this packet, and will use a different code for each so when the packet delivers the packet it look at it and will be like deliver it to TCP or IP. code maintained by the IEEE, IP can run with a lot of other protocols…Raw sockets, you just use IP on its own… third code….IP does not care about your data….Header Checksum.. Does IP do error checking…yes it does error checking only on the Twenty bits and only looks at the the IP address….WE have to totally understand the IP address because in test 2 we are going do questions called Subnet ting questions and to do Subnet ting we have to understand the IP address really really well. Early start on subnetting. Guys that created the IP standard, origanilly created class addressing… what can you tell to determine the class of the address you simple look at the first byte. IP addresses are four bytes long.. class a determined looking at the first byte they all have a zero of the first bits of the first bytes leaving seven bits , the other three are Host address and class B are 127 (127 is special called LOOPBACK. Used for testing) B 10111111 128-191 C 11011111 192-223, How many class a’s 126, 65535kb, class C 254 hosts. Working in groups of two ooo, we want first stations to the other station through two routers what have to do to achieve this is do something configuration file, basic configurations.. apply IP address to the PORTS we want to apply ip address to those ports.. they will learn how to send stuff through a network… all we do is provide the initial information and press on the routers will figure out what to do, Lets say have an ip network and were going to use a class a address 10.0.0.0 that number means the entire network but to a router they don’t see one big network but THREE subnets, how do we break it into three subnets we are going to use a Subnet Masks, this allows you to create these subnets in the first place… you see if we just had the network number and we plug them in we wouldn’t know which router can get the total packet.. so we use the mask 255.255.0.0 if for some reason we didn’t wanna create subnets we could give an ip address 10.0.0.1 we have to put a 10.0.0.1, 2, 3, 4, 5, 6 in each port, things get broken into subnets…we wouldn’t do it without the subnet and we would still have to have a mask and have a default mask 255.0.0.0 a one byte means this bits parts of the network ID if we wanted to know subnetting we take the second byte and will be used to indicate the bits are subnet bits hence if we wanted to do that we make 255.255.0.0 11111111.11111111.0.0.0, we will change the purpose of the bits and when the router recivies the packets will receive that packets one being the counter and one the subnet….Look up subnetting…

WIN310W6

Last we talked about was root, cash.dns is the root file,


Type of name server, name server is a dns server, FQDN.

Hello.uk are primary, primary zone on the primary server, is the athorratative zone, only 1 primary dns, but can add as many secondary dns, different physical machine, used for backup, load balancing, save bandwidth and connection time. You can promote the secondary to the primary.

Master name serer, responsible to send updates to secondary, can be primary or a secondary, zone transfers from primary to secondary, SOA has a time time limit, and the primary is also responsible to update the second, these are replicas of the main DNS server, Now who is the master of 2 and 3 it’s the primary, there is flexibility here, 2 can be the master of 3, 3 does not have to know 1 but knows 2, 3 will query 2 for updates while 2 is getting updates from 1. OH YEAH SO 1 to 2 to 3 is 15 minutes, if this occurs every 15 minutes the 2 waits 15 then 3 waits 30,

Caching does not have a database, everytime it resolves something it caches it and resolves it for a specific time, u use it so after u don’t need to maintain and the other for quick resolution, SOA start of authority,

AD every single machine is a cheef, makes it so you can go to every location and do administration, and add a record, the record will be replicated on the other directory servers, every single DNS has control over the zone, how would they know which is the latest up date there is a counter, as the other dns respond they look at the version number and the remainder will be sent which is the updates of the server,

Resource Record, what type can we put in the DNS, pg 74, the ownerm it identifies the resources record and who it belong to, name domain the host, this I s basically the owner, there is TTL time to live the life to it, class Internet class, type of record what we doing mapping name to ip address, mail server to a server,m several types of records we can input, cantains resource data, something with the record that is associated with 32 binary, which is the ip address.

SOA – start of authority, original point of domain or zone, the information in the SOA it shows the authoritative server, this is the server hosting the particular zone of domain, you can create as many as you want to, this is is the guy that will be responsible for everything’s, serial number….every time you manage or update the dns is increases by one so because it haws increased u have to give the updates to the other zones. This is the negotiating item.
DNS PORT 53 UDP FOR THE QUERY
53 TCP FOR THE UPDATE

Name server, DNS server responsible for the zone,
A record is a recourse record, the purpose for the A record is the mapping of the assosiacted IP address. 32 integer. \

PTR – point of record, record of a reverse look up. We say what is the ip address of venus what is the name of the ip, its called venus the planet.ca, we need when we have applications have th resovle the name through ip…..from ip address we grab the name

CNAME or an Alias – mapping of a conanical name to an established name \
Like when we go to Seneca cs = cs.senecac.on.ca

Another example- an ftp server, and the name was, ftp, ftp1.banana.ca it can change to ftp2.banana.ca but when every one is conneting they are connecting by ftp, what they are saying is to make an alias, and redirect it

MX = Mail Exchange pg 77 bottom, is in fact is the server that is willing to host your mail, you can have

10 ns1.mail.yahoo.com
20 “”””””””””
50 “””””””””””

This is the priority in which to send the mail.

SV – service locator pg 79, allow to specify server to application, an example is Active Directory, that relies on the server record, and Also
NetLogon Service, this service carries info from the desktop to the server. For example your user name password and domain name.

Two types of queries, Iterative and Recursive

What is a query, it comes form a resolver or the client looking for some assistan what does he want, please tell me the ip address of this particular host,

Iterative, gives you a refferall, the client is looking for sales.contoso.com, he goes to the dns serer, and the dns server gives him an answer to go the .com or root servers, the client himself goes to the other servers gets the answers where contoso is goes to contoso for a name of sales which is sitting within the domain, and obviously gets the ip address for sales.contoso.com, the client has done the work, who cached the information the client.

Recursive, the priouviously the client have done everything, now the the client submits the query to the local dns, asking him what the ip address of sales.contoso.com, and the client waits for the DNS to do all the chasing.

WINS and DNS are in the same business, they both so resolutions, name resolutions, dns sports car, WINS truck, DNS FULL qualified domain name, DNS does FQDN, WINS NetBios, NetBios are computer names, computer23 or 24, wins is faster, but it only works on Microsoft networks. How do they work?
‘
In the dns point it to WINS..

Look what happens a client wants to do DNS. WINS handles 15 chars, the nature of it.

DNS creates a WINS, DNS will truncate the domain name and leave the ACCOUNTING name, dns gets is from wins, then dns puts back the family name into the Microsoft.com

Four types of response you get from the query,

Positive this is the ip address, an example can be something from the cache,

Authritative main server primary server or secondary server

Referral – Iterative nd Recursive
Negative – Answer it don’t exist

PG 87

Zone Transfer – Notify –

AXFR – FULL – launch a secondary DNS
IXFR = Incremental –

Fires a queryin the soa and looks for a response, tcp

Iterative load on client
Recursive load on some other machine

Conditional forwarding you can add more stuff in it, 2 companies for faster resolution to the specific company……microsoft.123.123.321.333

DCN386W6

TCP – get you’re their correctly provide realibility, the network can move your data through the network which is highly error prone, Routers only know IP,

Tcp is only run in client, passes data in ip and pumps it into the internet and goes through the network at high speed, at the other end there is another server.

You can write software that only uses IP, TCP cannot exist on its own, their no purpose for this.

Some are connection-oriented, and some are connectionless, IP is connection less, TCP is connection oriented, that means TCP establishes a session, to establish a session with another computer probably with a server somewhere in the world, to do this, the Cisco course calls it the three way hand shake, This is the tcp header when you log into the internet and try to create a session, your client machine will send 20 bytes of control information,

Source Port, Destination Port, a port is a number a special number,

Few internet applications HTTP, ftp, IEEE got a lot of application so they gave them a number HTTP:80, Telnet:22, FTP:20:21, these numbers are well known ports.

FTP work with TCP to give you a nice picture, TCP will provide the reliability, the

Destination Port will be 20

Source Port – Random number greater then 1000,m less than 65,000, the server knows theirs a session random 6666 SD, because other people want to log in and it will pick another random number for the other client machine.

Something can happen where they pick the same random number, what will happen in this case it will not work cause the session will be already established

This leads us to the three way handshake, when the client request, the server will send 20 bytes of information, SP DP,

Why this three way thing the client and the serer, are establishing certain factors, they are negotiating the parameters that are going to be used in the session.

Clients initiate session, servers never initiate session

the first 1000 numbers are reserved

For test one, only worry about a couple of things that are being negotiated during the three way handshake.

TCP is viewed as a streaming protocol, it streams data from one computer to the next 1 bytes of a time.

Ftp all it does rid stuff of ur data and pumps it into tcp, and tcp starts to carry the bytes 1 2 3 4 5 bytes, its carrying the bytes cause it doesn’t want to loose any, it wants reliability so it counts the bytes.

The Sequence Number ( 4 bytes long )and the Acknowledgement number (4 bytes) keep tracks of the bytes that are transmitted.

Old days the sequence number would be 1000 bytes and so on, so one of the things that is negotiated when you connect to a server, 1st version started at 1, great for the first years, when the internet what new, when you wanted to hack into someones session, you just had to predict someone was establishing a session, you can muscle in the three way handshake and interfere with the process,
What sequence number are we going to start at?
Now it is a random number something between 0 and 4b, one of the three things a three way hand shake does when you send the tcp header it will pick a random number 0 and 4billion.


So SP 6666 | DP 20| SN 2|

Also another bit called the sync bit, the server will flip SP DP, the client machine will pick an initial sequence number, the sequence number is a count of a number of bytes by the tcp program, tcp counts the number of byes, it don’t matter what internet application it is, every byes it precious, the initial sequence number where it will start counting from, lets say its at 100, and tcp receives 100 bytes from ftp, it going to send 100 bytes, because it started at 100 and sent 100 it will then be 200, the server will do error checking, Checksum, it will send back to you in the Acknowledgement, and it will say it got 200 and the next byte it wants is 201, send another 100 then the SN will be 300 and the ack will be 301.

The first thing tcp doing is both machines establish an initial sequence number, they do this by sending one header, the second thing that happens when sending the three way handshake,both macnhines must have a good approximation on how long it takes to send a packet to eachother, tcp relies on time, a great deal, tcp operation relies on understanding how long it takes to send and to get the reply back, don’t forget the internet data can get lost in here, tcp is more accurate than 4 seconds, when the tcp tries to establish a session it will record time on the systems clock, then it will send the packet and send it back,and it will know when it sent and receives stuff, but eh server must also know that’s why we have the third hand shake, the first and second establish the throughput time rate and the third packet is send, then the server machine knows how long it takes from the client to the server and server to the client, vital for tcp, tcp is a weird protocol, TCP all it wants to know how long does it take to send and receive a response.
(IP puts the data in correct order) tcp counts the bytes, makes sure the sequence and ack are consistent,

Two tings negotiated, is identifying the initial sequence number, making sure both machines know the round trip delay time, establish a session number and a time related to sending a receiving data.

Acknowledgement number, - when you send 1000 bytes the client machine will do error checking it will send 20 bytes and it will say ive received 1000 bytes the ack should be 1001, the next time 2001, the next time it will be 3001


ACK 1 bit – a positive acknowledgement, the ack means a positive ack that means your tcp has done error checking on the data you have received. No such thing as a negative ack. Tcp is the only one that does not have an negative ack. If the server does not get a positive ack it will resend the data to the client.

Window – size – is influences by the operating software that tcp it running in, first big surprised TCP works will the OS you are working with, it influences tcp, How big is the windows size, tcp receives data and it counts the bytes, it has a max bytes it automatically sends it. The max amount of bytes is the window size, its 2 bytes long, what the max value, 64k, fact the bigger the window the window size the easier to hack, Microsoft has 64k, Linux it depends like 1k,
2nd things you have to know, its not fixed its a dynamic number, during the actual transmission of data the window size will change, window can start at 1k increments, tcp is changing the window size dynamically, both tcps will send the 20 bytes with or without data increase or decrease the window says, the number or lack of errors,

CHECK SUM – CRC standard error.

Nothing about the urgent pointer, nothing about the last thing,

Fin 1 bit - the server is sending thing to you , the very last byes by the server the final bit will be turned on

First initial sequence number
2 establishment of round trip time
3rd windows size

Ethernet

What does Ethernet do and How does it work?

Its still evlolving, the IEEE and other groups, its still growing protocol, things Power Over Ethernet…..so many….back to beginning.

Created in Xerox corporations, they invents a NIC using a very simple protocol, they called it Ethernet. The reason this survived, far more technical things like Token Ring, why this dispeared it was so simple and basic it literally cant go wrong, its easy to install, a NIC has this,

Tell him next week
Ethernet also known as 802.3 operates on three basic principles, the first principal is called
Carrier Sensing – listen to the wire,

Ethernet is braod band tech, it means it takes the entire bandwidth of the cable which means only one machine can be sending data at a time, here we got four machines on the network, with one server how does it know its not being used by the network, the NIC has a volt metre, send data to nic it compares to data to be tranmitted the volt metre will test the cable to see electrical activity, if theirs zero volts then the network is free, so the nic takes the data sends it, data is not sent until until the network is free, CS,

The second attribute is something calle Multiple Access, fancy way of saying at any point in the network you can install work stations, and it will work admidately, every NIC has a unique MAC address, IEEE will give you a manufactures code number, each NIC has hardwired address the the first three bytes the company, the last three is a sequence number, all nics have different addresses, you can simply attach workstations and they are operational

The third attribute of Ethernet is Collision Detection, it’s a very simple thing, bad form of connection control,

One machine access 1 some 9, both test the line at the same time and both realize the network is idle, they do it at the same time, this results in the two machines building the thernet frame and sending it out, what happens the pulses will destroy eachother, the more machines the more collisions, Ethernet knows it happens Ethernet has a strategy, any machine, the server detects nasty pulses any machine, the NICS are constantly doing this, any machine on the network that discovers a collision sends a very special frequency like a squeal, a jamming signal, to every machine on the network. Both machines retransmit but not at the same time, this is the smart trick, when collisions happen they wait a random amount of time,

The Nic builds the Ethernet frame, the os sends data to the NIC the NIC builds the fram out of your data what does the frame look like, NIC a little bit of memory, what does the frame look like, it will take yuour data and break it up into segments, packets, how big is an Ethernet frame

All protocols segment and reassemble ur data, takes your data and breaks it into frames, the max size of the frame is 1500bytes, breaks data into units called bytes infront of the 1500 bytes its puts header information the
Source Address is the Mac Address 6 bytes long, three bytes man three ,
DA also six bytes, in theirs
2 bytes that can be confusing, is the length of the data.

The IEEE stepped in and all LAN to work together and standardized things and made a change to Ethernet its going to be Type Field.

NOVEL oracle data is a type, apple talk a type, all modern NICs have a type field.

IEEE first couple of bytes indicate length

The front 64 bit preamble 10101010101010101010101010,, used the sync transmission of the frame every frame establishes sync through preamble.

Last piece of into 4 bytes, very effiecent error checking CRC or FCS,

Some equipment such as switches actually do error checking, but there is no provision in Ethernet for handeling erros, NICS and switches do error checking but if there is an error dump the frame, there is nothing in the header for re-transmit the packet.

Ethernet is a delivery boy it relies on high layer protocols to handel any errors, designed for speed.

After reading week CS changes to CA, when u get to gig connection.


Theirs a min for data which is 46 bytes, it will pad the rest of the bytes if its smaller then 46 bytes.