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



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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
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How does it work?

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

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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
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If you have a router of ur own u can take out the HDLC module and put in a FR modeuls
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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

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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.
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Subnetting:

11.0.0.0

Require 5000 Subnets




00000000.00000|000.00000000

10.0.0.0 internal address

Classless /26