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
2.3 Framing: byte-oriented, bit-oriented, Sonet
2.4 Basic error detection (not
CRC!)
2.5 Sliding windows
2.6 Ethernet (see also my ethernet notes)
(link fixed!)
3.1 Switching and Forwarding
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; port-number abstraction
5.2.1-5.2.3 Basic TCP
The following exercises from the book should give you a fair idea of
what
to expect on the exam;you shouldn't necessarily complete 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.
Solutions will be here the Monday before.
Here are two further study problems:
1. The following problem deals with IP routing tablesas maintained by routers; machines A, B, C, D, etc. are routers. No hostmachines are shown. The special machine DEFAULT is also a router, but youneed 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 portionof its address equal to 1; e.g. 200.0.5.1, 200.0.6.1, etc. Similarly, Bhas host portion 2, C has 3, D has 4. The special machine DEFAULT has hostportion 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 destinedfor 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 allowedto
extract
address mapping info from any broadcast ARP query packet: everymachine
sending
such a packet includes its own IP-to-physical address bindinginfo, and
every
machine receiving such a broadcast (whether or not intendedfor that
machine)
adds the source IP-to-physical address info to its ARPcache. Thus, in
the
example above, not only would A get B's address infobut 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 replyto
A
then A's physical address will already be in B's
ARPcache.
(b). Suppose A broadcasts a request "where is B", butinadvertently lists the physical address of another machine C instead ofits 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?