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ECE544: Communication Networks-II, Spring 2008. D. Raychaudhuri Lecture I. Includes teaching materials from L. Peterson & L. Govidan. Today’s Lecture. Administrative matters Course Overview topics covered design & prototyping projects Introduction to networking. Class Structure.

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Ece544 communication networks ii spring 2008

ECE544: Communication Networks-II, Spring 2008

D. Raychaudhuri

Lecture I

Includes teaching materials from L. Peterson & L. Govidan


Today s lecture
Today’s Lecture

  • Administrative matters

  • Course Overview

    • topics covered

    • design & prototyping projects

  • Introduction to networking


Class structure
Class Structure

  • Friday 4:45-7:30pm

  • Lecture format

    • Slides, Board, …

    • Interactive

  • Two 80 min sessions

    • with a 10 min break in between


Contact information
Contact Information

  • Instructor: Prof. D. Raychaudhuri

    • Email: ray@winlab.rutgers.edu

    • Office Hours: by appt, WINLAB Tech Center or Core 501

  • TA (for project): KC Huang

    • Email:therom@eden.rutgers.edu

    • Office hours: tbd

  • Class Resources

    • Web page: http://www.winlab.rutgers.edu/comnet2 (~1/30)

    • Mailing list: comnet2@winlab.rutgers.edu

    • Sign up for mailing list at: http://lists.winlab.rutgers.edu/listinfo/comnet2


Course readings
Course Readings

  • Textbook (required, to be used for ~60% material)

    • Peterson & Davie, “Computer Networks: A Systems Approach”, Morgan Kaufman, 3rd ed

  • Research papers in networking

    • to be distributed either online or in class

    • collection of classical and topical research

      • ~10 papers and standards documents

      • required reading to supplement text book overview


Course grading
Course Grading

  • Class participation & homework: 5%

    • Brief in-class presentations

    • Assigned homework from textbook

  • Midterm (25%) and Final (40%)

    • Open book, 1 page of notes permitted; includes both descriptive and numerical problems

  • Design & Prototyping Assignments: 30%

    • network architecture paper 10%

    • protocol project & report 20%

  • No makeup exams, no extra credit work


Student commitments
Student Commitments

  • Keep up with your reading

    • read applicable text book chapter and distributed papers/RFC’s before and after each class

  • Sharpen your programming skills

    • study C/C++ & Unix programming as needed and work on simple programming exercises early in the semester

  • Work independently

    • no “collaboration” of any sort

  • Turn in assignments on time

  • Make sure assignments are gradable

    • follow project and program submission rules


Prerequisites
Prerequisites

  • Curricular prerequisites

    • Computer Networks I or equivalent

    • General communications and computer architecture/OS background

  • Skills

    • C/C++ programming

      • significant programming project

    • use of design and analysis tools


Course topics

Introduction

Network Principles

Shared Media/MAC

Pkt switching (ATM)

IP Basics

IP Advanced

Mobility Protocols

-- mid-term

Network security

Transport layer

Higher-layer protocols

Hardware issues

Case studies and research topics

optical IP network

ad-hoc mobile net

future Internet

Course Topics


Projects

Network architecture paper

- top-down design

- requirements

- specifications

- system analysis

Projects

  • Warm-up Projects

    - C/C++programming exercises

    - Unix sockets, etc.

    - simple link protocols

  • Network software project

    - new routing protocol

    - software platform provided

    - student teams will write competing protocol specs

    - meeting to select “standard”

    - system integration & demo


What is the problem
What is the problem?

Applications

The Global Network

Scale

Technology

Robustness


Application considerations
Application Considerations

  • Application input to network

    • traffic data rate

    • traffic pattern (bursty or constant bit rate)

    • traffic target (multipoint or single destination, mobile or fixed)

  • Network service delivered to application

    • delay sensitivity

    • loss sensitivity


Ece544 communication networks ii spring 2008

A Multimedia Application

Chapter 1, Figure 7


Reliable file transfer
Reliable File Transfer

  • Loss sensitive

  • Not delay sensitive relative to round trip times

  • Point-to-point or multipoint

  • Bursty


Remote login
Remote Login

  • Loss sensitive

  • Delay sensitive

    • subject to interactive constraints

    • can tolerate up to several hundreds of milliseconds

  • Bursty

  • Point to point


Network audio
Network Audio

  • Relatively low bandwidth

    • Digitized samples, packetized

  • Delay variance sensitive

  • Loss tolerant

  • Possibly multipoint, long duration sessions

    • natural limit to number of simultaneous senders


Network video
Network Video

  • High bandwidth

  • Compressed video, bursty

  • Loss tolerance function of compression

  • Delay tolerance a function of interactivity

  • Possibly multipoint

  • Larger number of simultaneous sources


Ece544 communication networks ii spring 2008
Web

  • Transactional traffic

    • short requests, possibly large responses

  • Loss (bug?) tolerant

  • Delay sensitive

    • human interactivity

  • Point-to-point (multipoint is asynchronous)


What is
What is….

The Global Network

  • Structure

  • Metrics

  • Failure modes

  • Functions


Network structure
Network Structure

Backbones

Regionals

Campus LANs


Network metrics
Network Metrics

  • Bandwidth

    • transmission capacity

  • Delay

    • queueing delay

    • propagation delay (limited by c)

  • Delay-Bandwidth product

    • important for control algorithms


Bandwidth versus latency
Bandwidth versus Latency

  • Relative importance

    • 1-byte: 1ms vs 100ms dominates 1Mbps vs 100Mbps

    • 25MB: 1Mbps vs 100Mbps dominates 1ms vs 100ms

  • Infinite bandwidth

    • RTT dominates

      • Throughput = TransferSize / TransferTime

      • TransferTime = RTT + 1/Bandwidth x TransferSize

    • 1-MB file to 1-Gbps link as 1-KB packet to 1-Mbps link


Delay x bandwidth product
Delay x Bandwidth Product

  • Amount of data “in flight” or “in the pipe”

  • Example: 100ms x 45Mbps = 560KB


Ece544 communication networks ii spring 2008

10,000

5000

2000

1000

500

1-MB object, 1.5-Mbps link

200

1-MB object, 10-Mbps link

Perceived latency (ms)

2-KB object, 1.5-Mbps link

100

2-KB object, 10-Mbps link

50

1-byte object, 1.5-Mbps link

1-byte object, 10-Mbps link

20

10

5

2

1

10

100

R

TT (ms)

Chapter 1, Figure 9


Network failures
Network Failures

  • Packet loss

    • queue overflows

    • line noise

  • Node or link failures

  • Routing transients or failures


Statistical multiplexing gain
Statistical Multiplexing Gain

1 Mbps link; users require 0.1 Mbps when transmitting; users active only 10% of the time.

  • Circuit switching: can support 10 users

  • Packet switching: with 35 users, probability that >=10 are transmitting at the same time = 0.0004.



Then came tdm
Then came TDM..

mux

demux




Packet switching
Packet Switching

Interleave packets from different sources

  • Efficient: resources used on demand

    • statistical multiplexing

  • General

    • multiple types of applications

  • Accommodates bursty traffic


Characteristics of packet switching
Characteristics of Packet Switching

  • Store and forward

    • packets are self contained units

    • can use alternate paths - reordering

  • Contention

    • congestion

    • delay


Protocols
Protocols

  • On top of a packet switched network, need

  • Set of rules governing communication between network elements (applications, hosts, routers)

  • Protocols define:

    • format and order of messages

    • actions taken on receipt of a message


Protocols contd
Protocols (contd.)

  • Building blocks of a network architecture

  • Each protocol object has two different interfaces

    • service interface: operations on this protocol

    • peer-to-peer interface: messages exchanged with peer

  • Term “protocol” is overloaded

    • specification of peer-to-peer interface

    • module that implements this interface


Layering
Layering

Teleconferencing

User A

User B

Peers

Application

Transport

Network

Link

Host

Host

Layering: technique to simplify complex systems


Layering characteristics
Layering Characteristics

  • Each layer relies on services from layer below and exports services to layer above

  • Interface defines interaction

  • Hides implementation - layers can change without disturbing other layers (black box)


Iso architecture
ISO Architecture

End host

End host

Application

Application

Presentation

Presentation

Session

Session

Transport

Transport

Network

Network

Network

Network

Data link

Data link

Data link

Data link

Physical

Physical

Physical

Physical

One or more nodes

within the network


Internet architecture

FTP

HTTP

NV

TFTP

UDP

TCP

IP

NET

NET

NET

2

1

n

Internet Architecture

  • Defined by Internet Engineering Task Force (IETF)

  • Hourglass Design

  • Application vs Application Protocol (FTP, HTTP)


Layering general issues
Layering General Issues

  • Reliability

  • Flow control

  • Fragmentation

  • Multiplexing

  • Connection setup (handshaking)

  • Addressing/naming (locating peers)


Example transport layer
Example: Transport layer

  • First end-to-end layer

  • End-to-end state

  • May provide reliability, flow and congestion control


Example network layer
Example: Network Layer

  • Point-to-point communication

  • Network and host addressing

  • Routing


Inter process communication

Host

Host

Application

Host

Channel

Application

Host

Host

Inter-Process Communication

  • Turn host-to-host connectivity into process-to-process communication.

  • Fill gap between what applications expect and what the underlying technology provides.


Ipc abstractions
IPC Abstractions

  • Stream-Based

    • video: sequence of frames

      • 1/4 NTSC = 352x240 pixels

      • (352 x 240 x 24)/8=247.5KB

      • 30 fps = 7500KBps = 60Mbps

    • video applications

      • on-demand video

      • video conferencing

  • Request/Reply

    • distributed file systems

    • digital libraries (web)


Interfaces
Interfaces

Host1

Host2

Service

High-level

High-level

interface

object

object

Protocol

Protocol

Peer-to-peer

interface


Ece544 communication networks ii spring 2008

Interfaces (contd.)

Chapter 1, Figure 21


Ece544 communication networks ii spring 2008

Interfaces (contd.)

Chapter 1, Figure 22


Protocol machinery
Protocol Machinery

  • Protocol Graph

    • most peer-to-peer communication is indirect

    • peer-to-peer is direct only at hardware level

Host 2

Host 1

Digital

Digital

Video

Video

File

File

library

library

application

application

application

application

application

application

RRP

MSP

RRP

MSP

HHP

HHP


Machinery cont
Machinery (cont)

  • Multiplexing and Demultiplexing (demux key)

  • Encapsulation (header/body)

Host 1

Host 2

Application

Application

program

program

Data

Data

RRP

RRP

RRP

Data

RRP

Data

HHP

HHP

HHP

RRP

Data


Network architecture
Network Architecture

  • Identify basic service requirements

    • transport service(s)

    • bit-rates to be supported

    • network API

    • # of users

    • terminal type (fixed, portable, etc.)

  • Outline network topology

    • access network type (wired/wireless, span, etc.)

    • core network if any (node locations, span, etc.)


Example 1 broadband wireless access
Example 1: Broadband Wireless Access

  • Draw a general conceptual network diagram to start...

Metro-area

wireless access network

(~Km)

telco-BWA

gateway

Switched Telecom

Network

Mobile Comm

Devices

~0.1-10 Mbos

Broadband Wireless

Access Network

Mobile PDA/PIA

Semi-mobile

Laptop, etc.

Internet

IP-BWA

gateway

Multiservice

interface with

voice/data ,

QoS support,

and mobility

support

Fixed PC/WS


Ece544 communication networks ii spring 2008

Example 2: Infostations

  • Mobile user passes through Infostations in sec during which ~MB files are downloaded from (or uploaded to) network

    • Requires fast synchronization and service setup

    • Motivates 2-tier architecture with ~10m service zone (for high-speed data transfer) and ~50m access control zone (for sync, authentication, ..)

Infostations

access point

Data cache

Low-speed control channel

(for synch & service setup)

~100 MB/s

Fast transfer

Service

Zone

Access Control

Zone

Transit time ~sec

Total transit time ~10sec


Requirements contd
Requirements (contd.)

  • List additional service and network features

    • QoS, video/audio, etc.

    • special routing (mcast, broadcast,..)

    • mobility

    • availability

    • reliability

    • security/authentication

  • Rough system capacity (Mbps) and cost estimates ($/MB or $/user/mo)


Requirements analysis
Requirements Analysis

Transport services

CBR, VBR-rt,..

  • Summary table listing key requirements

Bit rate

0.1-10 Mbps

# of users

~1000’s per access network

Terminal type

portable/mobile, fixed wireless

Topology

hierarchical, access/core

QoS features

selectable BW, stream support

99.9%

Availability

99.99%

Reliability

Security features

mobile authentication, on-air encryption

Cost

$0.1/MB or $50/mo/user


Network components
Network Components

  • Key hardware components of a network

    • NIC ~10, 100, 155, 622, 1000 Mbps

    • shared media channels (Ethernet, HFC, wireless, satellite, ..) ~Mbps

    • point-to-point links (DSL, CAT-5, microwave, fiber,..)

    • switches (Ethernet, ATM, MPLS/IP) ~ Gbps -Tbps

    • routers (IP) ~Mbps - Gbps


High level design
High-Level Design

  • Select network topology based on geographic, capacity, reliability, etc.

  • Partition into access network, core network, etc. as required

  • Assign network hardware components to each subnetwork based on service and QoS requirements

  • Define service API and protocol stacks

  • Analyze network performance & cost and iterate until requirements are met


Today s homework
Today’s Homework

  • Peterson & Davie, Chap 1 (3rd ed)

    -1.1

    -1.3

    -1.15

    -1.17

    -1.23

    -1.28