1) Specify the first usable host address and
the total number of usable host addresses available
for the following network:
2) If a network has a maximum packet data
size of 128 bytes, a maximum packet time-to-live of
30 seconds and an 8 bit sequence number, what is the
maximum data rate per connection for this network?
3) TCP uses a host-oriented, window-based, feedback
mechanism for resource allocation. How might TCP
have been designed to use
a) Host-oriented, rate-based feedback
b) Router-oriented and feedback based
Explain how your system would work and an
advantage and disadvantage of each.
4) Packet fragmentation and reassembly is handled
by the IP layer and that process is invisible to the
TCP layer. Given the IP layer doing this work,
does TCP need to worry about packets arriving out of
5) Assume that you have a new TCP with an extension
to allow a window size larger than 64 KB. You have a
50 Mbps link with a latency of 100 ms to transfer a
50 MB file and the TCP receive window is 1 MB. If
TCP sends 1-KB packets, assuming no congestion or
a) How many RTT does it take until slow start
opens the send window to 1 MB?
b) How many RTT does it take to send the file?
c) What percentage of the link bandwidth is
6) Calculate the time required to transmit a one
GigaByte file in the following cases assuming
a round trip time (RTT) of 30 ms, a packet size of
1.5 KB and an initial three 1/2 RTT of handshake to
establish the connection. (B= Bytes, b=bits)
a) Bandwidth is 100 Mbps (Ethernet MAN) and data
can be sent continuously.
b) Bandwidth is 100 Mbps and the protocol is stop
& go, i.e an acknowledgment is required after
each packet taking up one RTT.
c) Bandwidth is 1 Mbps and an acknowledgment is
required after every 10 packets, requiring one RTT
d) Bandwidth is infinite and 10 packets can be
sent before a one RTT acknowledgment.
7) If reliable delivery is left to the TCP layer,
why does IP have a checksum in the header?
8) IP v 6 uses 16 byte addresses. If a block of 1
billion hosts is assigned every picosecond, how long
will the pool of addresses last?
9) Use the Unix traceroute or Windows tracert
program to trace the route from you computer to the
following: www.google.com, classes.cs.uchicago.edu,
www.usyd.edu.au, www.berkeley.edu, www.apple.com,
www.ucl.ac.uk (No need to turn in anything for
10) A router can process 300 million packets/sec.
The load is 100 million packets per second. If a
route from source to destination contains 25 such
routers, how much time does a packet spend being
queued and serviced by the routers.
11) In class we talked about the problem of
sequence numbers wrapping around. An optical
fiber link could run as fast as 75 Tbps, so given a
link that fast, whas is the maximum packet lifetime
required to make sure that that 64 bit sequence
numbers do not wrap around. Assume that each
byte of data will need its own sequence number, like
12) List two application for which a connection
oriented protocol would make sense and two
applications for which a connection-less protocol
would make the most sense and explain why.
13) Imagine there is a two way initial
handshake rather than a 3 way handshake to setup
connections. Can deadlocks occure on this
style of connection setup? (Hint, imagine that
multiple acks are lost.)
14) Why does UDP exits? Why not just
send raw IP packets if you don't want the enhanced
reliability and other services of TCP?