Problem 2
Primitives of the transport service assume asymmetry between the two end points during connection establishment: one end (server) executes LISTEN while the other end (client) executes CONNECT. However, in peer-to-peer applications such file sharing systems, e.g. BitTorrent, all end points are peers. There is no server or client functionality. How can transport service primitives be used to build such peer-to-peer applications?
Problem 3
A chat application using TCP repeatedly calls receive(), and prints the received data as a new message. Can you think of a problem with this approach?
Problem 7
One criteria for deciding whether to have a server active all the time or have it start on demand using a process server is how frequently the service provided is used. Can you think of any other criteria for making this decision?
Problem 8
Suppose that the clock-driven scheme for generating initial sequence numbers is used with a 15-bit wide clock counter. The clock ticks once every 100 msec, and the maximum packet lifetime is \(60 \mathrm{sec}\). How often need resynchronization take place (a) in the worst case? (b) when the data consumes 240 sequence numbers/min?
Problem 11
Consider a connection-oriented transport layer protocol that uses a time-of- day clock to determine packet sequence numbers. The clock uses an 9 -bit counter, and ticks once every \(250 \mathrm{msec}\). The maximum packet lifetime is 32 seconds. If the sender sends 3 packets per second, how long could the connection last without entering the forbidden region?
Problem 12
Imagine that a two-way handshake rather than a three-way handshake were used to set up connections. In other words, the third message was not required. Are deadlocks now possible? Give an example or show that none exist.
Problem 13
Imagine a generalized \(n\)-army problem, in which the agreement of any two of the blue armies is sufficient for victory. Does a protocol exist that allows blue to win?
Problem 18
Some other policies for fairness in congestion control are Additive Increase Additive Decrease (AIAD), Multiplicative Increase Additive Decrease (MIAD), and Multiplicative Increase Multiplicative Decrease (MIMD). Discuss these three policies in terms of convergence and stability.
Problem 21
Why does UDP exist? Would it not have been enough to just let user processes send raw IP packets?
Problem 23
Both UDP and TCP use port numbers to identify the destination entity when delivering a message. Give two reasons why these protocols invented a new abstract ID (port numbers), instead of using process IDs, which already existed when these protocols Were designed.
