Digital Communications II

Digital Communication II

Lecturer: Professor I.M. Leslie and others (iml@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

• Review of basic principles. Abstraction, layering. Concept of channel. OSI reference model. Standards bodies. [IML/1 lecture]

• TCP/IP Details and Gore. IP stack. Concurrency and buffering in BSD. Socket implementation. IP addresses and routing. IP Checksum. Datagrams: IP fragments, UDP/IP, NFS. TCP: states, coding, MSS, ACKs, retransmission. Congestion control. More TCP. Routing: CIDR, ASes, EGP/IGP. Distance vector schemes (e.g. RIP). Link state schemes (e.g OSPF). IP Multicast. [SMH/3 lectures]

• Quality of service and ATM. Guarantees versus best effort. Architecture, motivation. Relation to packet switching, circuit switching. Quality of service considerations. Resource management. Performance quantities. VR performance, effective bandwidth. ABR strategies. [IML/2 lectures]

• Transmission and Technology. Access networks: xDSL, Cable modems, LMDS, satellites, etc. Wide area networks: fibre, DWDM, IP over ATM/Sonet/"fibre". System area networks. [IAP/3 lectures]

• QoS in the Internet. Guarantees versus best effort. Flow specs. IntServ and DiffServ. RSVP. Economic models. [IML/1 lecture]

• Additional Topics. [DCL/2 lectures]

Objectives

At the end of the course students should be able to

• enumerate and explain the layers of the OSI reference model

• define effective bandwidth

• describe how TCP attempts to handle congestion in the network

• compare and contrast connectionless and connection-oriented networks

• explain how IP routing works

• argue for or against the provision of Quality of Service (QoS) in the Internet

• understand the motivation behind and operation of admission control algorithms

• give a basic explanation of how the TCP protocol works

• differentiate between the IntServ and DiffServ approaches to QoS

• realise the O/S issues in supporting TCP urgent data

• compare and contrast switching and routing

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 past exam questions are also on line.