Client-server model

A client starts each exchange; a server listens at a well-known port. An application protocol defines message types, syntax, meaning, timing and the transport it rides on (TCP for reliable exchanges, UDP for quick small ones). A TCP server holds one listening socket plus one socket per connection. P2P peers serve each other.

1. NAT · 1 mark

   A server process accepts 25 TCP connections. How many sockets does it have open (including the listening one)?

   Write your answer before opening the key.

2. MCQ · 1 mark

   Which socket call does the server use to wait for a new connection?

   1. connect()
   2. accept()
   3. bind()
   4. send()
3. MSQ · 1 mark

   Which typically use TCP?

   1. Fetching a web page
   2. Sending an e-mail
   3. A single short name lookup
   4. Downloading a file
4. MCQ · 1 mark

   In client-server, the client port is usually:

   1. well-known (0–1023)
   2. ephemeral, chosen by the client's OS
   3. always 80
   4. the same as the server port
5. NAT · 2 marks

   Client-server: 100 copies of a 10⁹-bit file from a 1 Gbps server upload. Minimum time (s)?

   Write your answer before opening the key.

6. MCQ · 1 mark

   Which layer of the 5-layer model contains application protocols?

   1. Transport
   2. Application
   3. Network
   4. Session
7. MCQ · 1 mark

   In P2P file distribution, adding more peers:

   1. always slows everyone down
   2. adds upload capacity as well as demand
   3. removes the need for any server or tracker in all designs
   4. makes TCP unnecessary
8. MSQ · 1 mark

   An application protocol must specify:

   1. the syntax of messages
   2. the meaning of fields
   3. the IP header format
   4. the order of messages