1.2 Requirements (1.1)
1.3 Network architecture (eg layers) (1.2)
1.5 Performance (1.1.4)
2.1 Nodes and Links
2.2 Encoding: Manchester, 4B/5B, etc
not on the exam!
2.3 Framing: byte-oriented, bit-oriented, Sonet
not on the exam!
2.5 Sliding windows
2.6 Ethernet (see also my ethernet notes)
(link fixed!)
3.1 Switching and Forwarding (but not virtual circuits)
3.2 Bridges and LAN switching
4.1 Basic IP, ARP
4.2.1 Routing-table basics
4.2.2 Distance Vector/RIP
4.3.1 Subnets
5.1 UDP
5.2 TCP (most of the entire section; at least through 5.2.4)
Basics of WUMP: how the protocol works, duplicate REQ, lost packets, anomalous cases
The following exercises from the book should give you a fair idea of
what
to expect on the exam; you shouldn't necessarily complete every detail of these,
but you should
study the text until you're reasonably confident you know how to
approach them. Exercise numbers are from the third edition, but where available
I've also given the number of the corresponding exercise from the
second edition.
Here are two further study problems:
1. The following problem deals with IP routing tables as maintained by routers; machines A, B, C, D, etc. are routers. No host machines are shown. The special machine DEFAULT is also a router, but you need not give its routing table (it represents a default destination). Nets involved are all class C, with addresses 200.0.5, 200.0.6, 200.0.7,.... The following convention is used: machine A always has host portion of its address equal to 1; e.g. 200.0.5.1, 200.0.6.1, etc. Similarly, B has host portion 2, C has 3, D has 4. The special machine DEFAULT has host portion 100.
(a). Give the routing tables for the following connections. You may use symbolic names (A, B, C...) for routers instead of IP addresses. Use default routes whenever possible, but be sure that a packet destined for some net other than 200.0.x gets routed to machine DEFAULT.
net
net
net
net
200.0.5____A_____200.0.6_____B______200.0.7_______D____200.0.8______DEFAULT
|
200.0.8.100
net 200.0.9
|
C
|
net 200.0.10
b. Do the same for the following configuration.
B
/ \
net
200.0.5
net 200.0.6
/
\
A
D------------200.0.9
\
/
\
net
200.0.7
net
200.0.8
DEFAULT
\
/
C
c. Suppose two routers, A and B, have tables as below. What will happen to an IP packet sent from A to address 147.126.4.9?
200.0.5----A----------------------B----200.0.6
A:
___________________
B: ___________________
200.0.5 |
direct
200.0.6 | direct
default |
B
default | A
2. In real implementations of ARP, hosts are allowed to extract address mapping info from any broadcast ARP query packet: every machine sending such a packet includes its own IP-to-physical address binding info, and every machine receiving such a broadcast (whether or not intended for that machine) adds the source IP-to-physical address info to its ARP cache. Thus, in the example above, not only would A get B's address info but also every machine on the net would get A's address info.
(a). Explain why this means that if
1. A broadcasts an ARP query "where is B?"
2. A sends B a regular IP packet
3. B wants to send an IP packet in reply to
A
then A's physical address will already be in B's
ARPcache.
(b). Suppose A broadcasts a request "where is B", but inadvertently lists the physical address of another machine C instead of its own (i.e. the ARP packet has IP src=A, phys src = ethernet addressof C).
What will happen? Specifically, will A get a reply? What entries will be made in the ARP caches on A, B, C, and a 4th machine D?
Suppose D uses its newly updated cache to send to A. Will the packet arrive at A? What if C tries to send to A?
3. Suppose two WUMP file transfers are made one right after the
other, and suppose both the client side and the server side reuses the
same port as before for the second transfer. Outline how a packet from
the first transfer might be accepted, erroneously but without
detection, in the second transfer. What else, besides the port-number
reuse, has to happen for this event to occur?