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