Dr Sandra I. Woolley

EE3A2 Computer Networking

The lecture slides and content will be subject to minor updates prior to presentations.

Course Text

The book website http://highered.mcgraw-hill.com/sites/007246352x/ contains selected "hints and answers" and copies of the figures.

See the CANVAS course page for erratas for editions 1 and 2.

Course Resources

Laboratory Activity Notes

• Laboratory Notes (This is a recommended unassessed laboratory activity).

Lecture Slides and Tutorial Questions

• Introduction to the course
• Computer networks and layered architectures
• Local area networks, medium access control and Ethernet
• Packet switching networks
  Packet capture example and 2008 exam Bellman-Ford routing example.
• Error control coding
• Cryptography (3a2handouts.doc in CANVAS contains additional example notes on Diffie-Helman-Merkle key exchange example and RSA).
  
  • Notes on privacy and disinhibition and Suler's six disinibition effect factors.
• An overview of network management and security
• TCP/IP
• Quality-of-Service (QoS)
• Delay and Loss Performance (private study)


• Tutorial 1 Questions
• Tutorial 2 Questions
• Tutorial 3 Questions


• A few notes on reading
• Revision slides

Miscellaneous

• Internet Society Membership
• ISOC England Chapter
• Could your fridge send you spam?
• Bletchley Park Museum
• Porthcurno Telegraph Museum
• Meet the seven people who hold the keys to worldwide internet security
• RFC 2324 - Hyper Text Coffee Pot Control Protocol
• and April Fool's Day RFC's
• National Cipher Challenge
• Window Surfing: the weak link in banking security?
• Cell phone tapping
• Peering
• NYTimes on Passwords (Top 32 RockYou passwords)
• Samy Kamar talks about his hacking experiences (including MySpace, evercookies and, more recently, drones)
• Monitis Traceroute
• Lectures slides on 802.11 Wireless LAN (NOT assessed)



Minor Notes and Corrections for the 2nd Edition of the Course Text

• pg368. A note. "In broadcast networks a single transmission medium is shared by a community of users. For this reason, we also refer to theses networks as multiple access networks." CSMA is indeed an abbreviation of Carrier Sense Medium Access. But "multiple access" is an ambiguous descriptor that does not discriminate between broadcast and non-broadcast networks. Non-broadcast networks can also be "multiple access" networks (Wikipedia Non-broadcast Multiple Access Network).
• pg 428. A correction. End of first paragraph: "A minislot time defines a time duration that is at least as big as two propagation delays." Then in 2nd paragraph: "When allowances are made for four repeaters, the delay translates into a maximum end-to-end propagation delay of 51.2 microseconds." The end-to-end propagation delay is tprop, If the "minislot time" is at least 2tprop then it is at least 102.4 microseconds. However, the commonly quoted Ethernet slot time is 51.2 microseconds. I believe the confusion of the factor of 2 is due either to a muddling of end-to-end delay (tprop) and round-trip delay (2tprop) or because there is a factor of 2 engineering tolerance between the round-trip delay caused by the physical maximum distance of the network and the slot time. If one estimates the length of the maxium network based on frames of 512bits and a signal propagation of about 2x10^5 km/s then one finds that the Ethernet standard allows a network of about half this size. If there were no engineering tolerance, there would be no allowance for delays introduced by repeaters and no allowance for a segment being a centrimetre longer than it should.
• pg523. A correction. "The Bellman-Ford algorithm (also called the Ford-Fulkerson algorithm) .." This is not correct. Lester R. Ford worked on both algorithms. The Ford Fulkerson algorithm computes maximum flow in a network. The Bellman-Ford algorithm computes shortest paths. The algorithms are distinct.

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