Digital Communications II

Digital Communication II

Lecturers: Dr S.M. Hand and Dr I.A. Pratt
(smh22@cl.cam.ac.uk and iap10@cl.cam.ac.uk)

No. of lectures: 12

Prerequisite course: Digital Communication I

This course is a prerequisite for Security (Part II).

Aims

This course aims to provide a detailed understanding of how (wide area) computer networks operate, and to present the issues which are involved in building such systems. It also hopes to cover a selection of topics which relate to recent trends in digital communications systems.

Lectures

• Introduction. [IAP] Course overview. Abstraction, layering. OSI reference model.

• The Internet: IP, UDP, RPC. [SMH] IP overview/review. Networking in Unix: structures, buffering, sockets, network interfaces. IP addresses and (simple) routing. Subnetting. IP checksum. Fragmentation. UDP, RPC, NFS. [2 lectures]

• The Internet: TCP, QoS and multicast. [SMH] TCP operation, state transitions. Handling loss: acks and retransmissions. Estimating RTT. Basic congestion control. Improving things: TCP vegas. QoS in the Internet. IntServ and Diffserv. Internet multicast model. Applications. Basic implementation. Refinements. [2 lectures]

• The Internet: routing. [SMH] ROADS and CIDR. Terminology: AS, IGP, EGP. Routing protocols: distance vector versus link state. Examples: RIP, OSPF. AS routing: I-BGP/E-BGP, metrics. The future.

• The Internet: IPv6. [RJB] Model and motivation. Practical considerations. The future.

• The Internet: Congestion Pricing. [DM] Model and motivation. Practical considerations. The future.

• ATM case study [IAP] Multiplexing and virtual circuits. Signalling. ATM Adaption Layers. Quality of Service CBR, VBR, ABR. [2 lectures]

• Wide Area Networks. [IAP] Fibre Technology. Long-haul link design. Dense Wave Division Multiplexing. Sonet/SDH. MPLS. Packet over SONET. Optical switching.

• Access Networks. [IAP] Cable Modems. xDSL. Fixed wireless. Satellite. Firewalls and Network Address Translation.

Objectives

At the end of the course students should be able to

• enumerate and explain the layers of the OSI reference model

• describe how TCP attempts to handle congestion in the network

• compare and contrast connectionless and connection-oriented networks

• explain how IP routing works

• understand the motivation behind and operation of admission control algorithms

Recommended books

Comer, D. & Stevens, D. (1995). Internetworking with TCP-IP, vol. 1 and 2. Prentice-Hall (3rd ed.).
Halsall, F. (1992). Data Communications, Computer Networks and Open Systems. Addison-Wesley (3rd ed.).
Schwartz, M. (1987). Telecommunication Networks: Protocols, Modeling and Analysis. Addison-Wesley.

Useful Links

• IETF Home Page
• RFCs etc
• IP Hacks & Attacks
• TCP/IP FAQ

The notes for the section on the OSI Model and layering (lecture 1) are available here in gzip'd postscript format.

The notes for the main Internet section of the course (lectures 2 thru 6) are available here in gzip'd postscript format.

The notes for the IPv6 section of the course (lecture 7) are available here in PDF format (Copyright Richard Black).

The notes for the section on ATM (lectures 9 and 10) are available here in gzip'd postscript format.

The notes for the section on Wide Area Networks (lecture 11) are available here in PDF format.

The notes for the section on Access Networks (lecture 12) are available here in PDF format.

The past exam questions are also on-line.