CMPE 150 – Winter 09

Lecture 2

January 8, 2009

P.E. Mantey

CMPE 150 -- Introduction to Computer Networks

Instructor: Patrick Mantey mantey@soe.ucsc.edu http://www.soe.ucsc.edu/~mantey/

Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia akia@soe.ucsc.edu Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/

Text: Tannenbaum: Computer Networks (4th edition – available in bookstore, etc. )

Syllabus

Assignment #1

Available on the web site:http://www.soe.ucsc.edu/classes/cmpe150/Winter09/

Due Thursday January 15, 2009

Today’s Agenda

“Big Picture”, terminology Networking Overview (continued) Protocol Concepts Network Software Architecture(s) History (ARPA Net, NSF Net) Networks Today: ATM, Ethernet, etc.

Network Hardware Local Area Networks Metropolitan Area

Networks Wide Area Networks Wireless Networks Home Networks Internetworks

Classification of Networks by Transmission Technologies

Broadcast Selection by addressing Multicast

Point-to-Point unicast

Classification of interconnected processors by scale

Home Network Categories

Computers (desktop PC, PDA, shared peripherals Entertainment (TV, DVD, VCR, camera, stereo,

MP3) Telecomm (telephone, cell phone, intercom, fax) Appliances (furnace, air conditioner, oven,

clothes dryer, pool pump, lights, microwave, refigerator..)

Telemetry (utility meter, burglar alarm, babycam).

Local Area Networks

Two broadcast networks (a) Bus (b) Ring (e.g. IEEE 802.5)

Metropolitan Area Networks

A metropolitan area network based on cable TV -- New alternative is “WiMax” – IEEE 802.16

Wide Area Networks

Relation between hosts on LANs and the subnet.

Wide Area Networks (2)

A stream of packets from sender to receiver-routers “store and forward” – “packet switching”

Wireless Networks Categories of wireless networks: System interconnection

Master/slave Wireless LANs (e.g. 802.11) Wireless WANs (e.g. 802.16)

Wireless Networks (a) Bluetooth

configuration (b) Wireless LAN

Protocols Used for communications between entities in a

system Must speak the same language Entities

User applications e-mail facilities terminals

Systems Computer Terminal Remote sensor

Layered Architecture Each layer offers a service Details of how service is offered in

hidden Each layer talks to the layer

immediatley “above” and the layer “below”

“protocol”: communication rules

Key Elements of a Protocol Syntax

Data formats Signal levels

Semantics Control information Error handling

Timing Speed matching Sequencing

Network SoftwareProtocol Hierarchies

Layers, protocols, and interfaces.

Protocol Architecture

Task of communication broken up into modules

For example file transfer could use three modules File transfer application Communication service module Network access module

Connection-Oriented and Connectionless Services

Six different types of service.

Service Primitives

Five service primitives for implementing a simple connection-oriented service

(Tannenbaum, pg. 35-6)

Service Primitives (2)

Packets sent in a simple client-server interaction on a connection-oriented network.

Services to Protocols Relationship

The relationship between a service and a protocol.

Simplified File Transfer Architecture

Stallings Chapter 1

A Three Layer Model

Application Layer Transport Layer Network Access Layer

Network Access Layer

Exchange of data between the computer and the network

Sending computer provides address of destination

May invoke levels of service Dependent on type of network

used (LAN, packet switched etc.)

Transport Layer

Reliable data exchange Independent of network being

used Independent of application

Application Layer

Support for different user applications

e.g. e-mail, file transfer

Addressing Requirements

Two levels of addressing required Each computer needs unique

network address Each application on a (multi-

tasking) computer needs a unique address within the computer The service access point or SAP

Protocol Architectures and Networks

Stallings Chapter 1

Protocols in Simplified Architecture

Stallings Chapter 1

Protocol Data Units (PDU)

At each layer, protocols are used to communicate Control information is added to user data at each

layer Transport layer may fragment user data Each fragment has a transport header added

Destination SAP Sequence number Error detection code

This gives a transport protocol data unit

Network PDU

Adds network header network address for destination

computer Facilities requests

Operation of a Protocol Architecture

TCP/IP Protocol Architecture

Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET)

Used by the global Internet No official model but a working

one.

TCP/IP Reference Model Application layer Transport layer (Host-to-host layer) Internet layer Host-to-Network layer

Network access layer Physical layer

Physical Layer Physical interface between data

transmission device (e.g. computer) and transmission medium or network

Characteristics of transmission medium

Signal levels Multiplexing / demultiplexing Data rates etc.

Network Access Layer(Host-to-Network Layer)

Exchange of data between end system and network

Destination address provision Invoking services like priority

Internet (Network) Layer (IP)

Systems may be attached to different networks

Routing functions across multiple networks

Implemented in end systems and routers

Transport Layer (TCP)

Reliable delivery of data Ordering of delivery

Application Layer

Support for user applications e.g. http, SMPT

TCP/IP Protocol Architecture Model

Stallings Chapter 1

OSI Model

Open Systems Interconnection Developed by the International

Organization for Standardization (ISO)

Seven layers A theoretical system delivered too

late! TCP/IP is the de facto standard

OSI Layers

Application Presentation Session Transport Network Data Link Physical

OSI vs TCP/IP (From Stallings, Ch. 1)

Internet Layering

Level 5 -- Application Layer (rlogin, ftp, SMTP, POP3, IMAP, HTTP..)

Level 4 -- Transport Layer(a.k.a Host-to-Host)(TCP, UDP, ARP, ICMP, etc.)

Level 3 -- Network Layer (a.k.a. Internet) (IP)Level 2 -- (Data) Link Layer / MAC sub-layer

(a.k.a. Network Interface or Network Access Layer)

Level 1 -- Physical Layer