CMPE 150 – Winter 09 Lecture 2 January 8, 2009 P.E. Mantey

CMPE Introduction to Computer Networks Instructor: Patrick Mantey Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia Web site: Text: Tannenbaum: Computer Networks (4 th edition – available in bookstore, etc. )

Syllabus

Assignment #1 Available on the web site: 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

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 ) Wireless WANs (e.g )

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 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 Software Protocol 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

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. , 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