Prepare for your exams
Get points
Guidelines and tips
Sell on Docsity
Docsity AI

Prepare for your exams

Study with the several resources on Docsity

Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips

Sell on Docsity

Docsity AI

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents

20 Points

For each uploaded document

Answer questions

5 Points

For each given answer (max 1 per day)

All the ways to get free points

Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

The Data Link Layer-Data Communication Systems-Lecture Slides, Slides of Digital Systems Design

Birla Institute of Technology and Science Digital Systems Design

This lecture is part of lecture series on Data Communication Systems. It was delivered by Prof. Prajin Ahuja at Birla Institute of Technology and Science. Its main points are: Broadcast, Reliable, Error, Correction, Instantiation, Implementation, Various, LInk Layer, Technologies

Typology: Slides

2011/2012

Uploaded on 07/26/2012

shakti 🇮🇳

4.4

(19)

99 documents

1 / 105

This page cannot be seen from the preview

Don't miss anything!

5: DataLink Layer 5-2

Chapter 5: The Data Link Layer

Our goals:

understand principles behind data link layer

services:

error detection, correction

sharing a broadcast channel: multiple access

link layer addressing

reliable data transfer, flow control:

done!

instantiation and implementation of various link

layer technologies

docsity.com

Discover Slides of Digital Systems Design Birla Institute of Technology and Science

Partial preview of the text

Download The Data Link Layer-Data Communication Systems-Lecture Slides and more Slides Digital Systems Design in PDF only on Docsity!

5: DataLink Layer

Chapter 5: The Data Link LayerOur goals: ^

understand principles behind data link layerservices:^ 

error detection, correction  sharing a broadcast channel: multiple access  link layer addressing  reliable data transfer, flow control:

done!

^

instantiation and implementation of various linklayer technologies

5: DataLink Layer

Link Layer ^

5.1 Introduction andservices

^

5.2 Error detectionand correction

^

5.3Multiple accessprotocols

^

5.4 Link-LayerAddressing

^

5.5 Ethernet

^

5.6 Hubs and switches

^

5.7 PPP

^

5.8 Link Virtualization:ATM and MPLS

5: DataLink Layer

Link layer: context ^ Datagram transferred bydifferent link protocolsover different links:

^

e.g., Ethernet on first link,frame relay onintermediate links, 802.11on last link ^

Each

link protocol

provides differentservices^ 

e.g., may or may notprovide rdt over link

transportation analogy ^

trip from Princeton toLausanne^ 

limo: Princeton to JFK  plane: JFK to Geneva  train: Geneva to Lausanne ^

tourist = datagram

^

transport segment =communication link

^

transportation mode =link layer protocol

^

travel agent = routingalgorithm

5: DataLink Layer

Link Layer Services ^

Framing, link access:^ 

encapsulate datagram into frame, adding header, trailer  channel access if shared medium  “MAC” addresses used in frame headers to identifysource, dest

different from IP address!

^

Reliable delivery between adjacent nodes^ 

we learned how to do this already (chapter 3)!  seldom used on low bit error link (fiber, some twistedpair)  wireless links: high error rates

Q: why both link-level and end-end reliability?

5: DataLink Layer

Adaptors Communicating ^ link layer implemented in“adaptor” (aka NIC)

^

Ethernet card, PCMCIcard, 802.11 card ^

sending side:^ 

encapsulates datagram ina frame  adds error checking bits,rdt, flow control, etc.

^

receiving side^ 

looks for errors, rdt, flowcontrol, etc  extracts datagram, passesto rcving node ^

adapter is semi-autonomous

^

link & physical layers

sendingnode

frame

rcvingnode

datagram

frame

adapter

link layer protocol

5: DataLink Layer

Link Layer ^

5.1 Introduction andservices

^

5.2 Error detectionand correction

^

5.3Multiple accessprotocols

^

5.4 Link-LayerAddressing

^

5.5 Ethernet

^

5.6 Hubs and switches

^

5.7 PPP

^

5.8 Link Virtualization:ATM

5: DataLink Layer

Parity Checking^ Single Bit Parity:^ Detect single bit errors

Two Dimensional Bit Parity

Detect

and correct single bit errors 0

5: DataLink Layer

Internet checksumSender:^ 

treat segment contentsas sequence of 16-bitintegers  checksum: addition (1’scomplement sum) ofsegment contents  sender puts checksumvalue into UDP checksumfield

Receiver: ^

compute checksum of receivedsegment ^

check if computed checksumequals checksum field value:^ 

NO - error detected  YES - no error detected.

But

maybe errors nonetheless?More later ….

Goal: detect “errors” (e.g., flipped bits) in transmitted

segment (note: used at transport layer

only)

5: DataLink Layer

CRC ExampleWant:

.D

r 2

XOR R = nG

equivalently:

.D

r 2

= nG XOR R

equivalently:

if we divide D

r. 2

by

G, want remainder R

R^

= remainder[

]

.D

r 2 G

5: DataLink Layer

Link Layer ^

5.1 Introduction andservices

^

5.2 Error detectionand correction

^

5.3Multiple accessprotocols

^

5.4 Link-LayerAddressing

^

5.5 Ethernet

^

5.6 Hubs and switches

^

5.7 PPP

^

5.8 Link Virtualization:ATM

5: DataLink Layer

Multiple Access protocols ^

single shared broadcast channel

^

two or more simultaneous transmissions by nodes:interference^ 

collision if node receives two or more signals at the same time multiple access protocol ^

distributed algorithm that determines how nodesshare channel, i.e., determine when node can transmit

^

communication about channel sharing must use channelitself!^ 

no out-of-band channel for coordination

5: DataLink Layer

The Data Link Layer-Data Communication Systems-Lecture Slides, Slides of Digital Systems Design

Related documents

Partial preview of the text

Download The Data Link Layer-Data Communication Systems-Lecture Slides and more Slides Digital Systems Design in PDF only on Docsity!

Chapter 5: The Data Link LayerOur goals: ^

understand principles behind data link layerservices:^ 

done!

^

instantiation and implementation of various linklayer technologies

Link Layer ^

5.1 Introduction andservices

^

5.2 Error detectionand correction

^

5.3Multiple accessprotocols

^

5.4 Link-LayerAddressing

^

5.5 Ethernet

^

5.6 Hubs and switches

^

5.7 PPP

^

5.8 Link Virtualization:ATM and MPLS

Link layer: context ^ Datagram transferred bydifferent link protocolsover different links:

Each

link protocol

provides differentservices^ 

transportation analogy ^

tourist = datagram

^

transport segment =communication link

^

transportation mode =link layer protocol

^

travel agent = routingalgorithm

Link Layer Services ^

Framing, link access:^ 

Reliable delivery between adjacent nodes^ 

Adaptors Communicating ^ link layer implemented in“adaptor” (aka NIC)

sending side:^ 

^

receiving side^ 

adapter is semi-autonomous

^

link & physical layers

Link Layer ^

5.1 Introduction andservices

^

5.2 Error detectionand correction

^

5.3Multiple accessprotocols

^

5.4 Link-LayerAddressing

^

5.5 Ethernet

^

5.6 Hubs and switches

^

5.7 PPP

^

5.8 Link Virtualization:ATM

Parity Checking^ Single Bit Parity:^ Detect single bit errors

Two Dimensional Bit Parity

Internet checksumSender:^ 

Goal: detect “errors” (e.g., flipped bits) in transmitted

segment (note: used at transport layer

.D

r 2

XOR R = nG

.D

r 2

= nG XOR R

if we divide D

r. 2

by

G, want remainder R

R^

.D