EE228a - Fall 2001 Communication Networks Prof. Jean Walrand Department of EECS University of California Berkeley.

EE228a - Fall 2001 Communication Networks

Prof. Jean WalrandDepartment of EECS

University of CaliforniaBerkeley

Course Objectives & Contents

Explain Internet and related networksModels and Evaluation Technology

Links: ADSL, Cable Modem, Optical LANs: Ethernet Routers, Switches

Protocols Routing, Transport, Applications

Organization

One lecture every week: W 2:30 – 4:30

Grading: Quizzes: 30%, 2 Midterms: 30%, Project Report: 20%, Project Presentation: 20%

Instructor: Prof. Jean Walrand; OH: M 11:00 – 12:00

Web site: See Prof. Walrand’s home page

Contents

8/29: How Internet Works9/05: Ethernet, ATM, ADSL, Cable Modems9/12: Models, Analysis, Simulation9/19: Routing: OSPF, BGP, Ad Hoc, …9/26: Transmission Control10/03: Switching – Midterm 110/10: Optical Networks10/17: Wireless Networks10/24: Networks and Services Management –

Midterm 210/31: TM, NP, SAN, etc.11/07,11/14, 11/28: Student Presentations

Introduction

WebVoice over IP

Web

ExampleLocating Resource: DNSConnectionEnd-to-endPacketsBitsPoints to remember

Click -> get page page from local

or remote computer link:

http://cnn.com

specifies - protocol (http) - location (cnn.com)

Web: Example

Web: Example

Click -> get page page from local

or remote computer link:

http://cnn.com

specifies - protocol (http) - location (cnn.com)

Web: Example

Click -> get page page from local

or remote computer link:

http://cnn.com

specifies - protocol (http) - location (cnn.com)

Web: Locating Resource

cnn.com is the name of a computer (and, implicitly, of a file in that computer)

To find the address, the application uses a hierarchical directory service called theDomain Name System

loca l

com

host

cnn.com ?

cnn.com ?IP = a .b .c.d

IP = a .b .c.d

Web: Connection

The protocol (http) sets up a connection between the host and cnn.com to transfer the page

The connection transfers the page as a byte stream, without errors: pacing + error control

H ost cnn.com

Web: End-to-end

The byte stream flows from end to end across many links and switches: routing (+ addressing)

That stream is regulated and controlled by both ends: retransmission of erroneous or missing bytes; pacing

H O ST

C N N .C O M

end-to -end pacing anderro r con tro l

rou ting

Web: Packets

The network transports bytes grouped into packets

The packets are “self-contained” and routers handle them one by one

The end hosts worry about errors and pacing:Destination sends ACKsSource checks losses

C

H O S T: B

C N N .C O M : AA | B | # , C R C | bytes

B : toC

Web: Bits

Equipment in each node sends the packets as a string of bits

That equipment is not aware of the meaning of the bits

01011...011...110

Transm itte r P hysica l M edium R ece iver

01011...011...110

O ptica lC opperW ire less

Web: Points to remember

Separation of tasks send bits on a link: transmitter/receiver [clock, modulation,

…]

send packet on each hop [framing, error detection,…]

send packet end to end [addressing, routing]

pace transmissions [detect congestion]

retransmit erroneous or missing packets [acks, timeout]

find destination address from name [DNS]

Scalability routers don’t know about connections names and addresses are hierarchical

Voice Over IP: VoIP

General Operations

VoIP: General Operations

Gateways must reproduce the signaling and voice

Signaling: dialed digits, dial tone, ringingVoice: Packetize and absorb delay jitterNote: Routing problem

In ternetPSTN

PSTN

signa ling

vo ice s igna l