The copperbelt university

1. 
   List three reasons why most network specialists prefer Link State Routing instead of Distance Vector Routing. [3 marks]
   
2. 
   Explain in detail how the traceroute program works. [3 marks]
   
3. 
   Explain briefly the Dynamic Server Creation concept [4 marks]
   
4. 
   Give the sequence of procedure calls for both server and client for connection-oriented application. [4 marks]
   
5. 
   Draw the format of ICMP header [2 marks]
   
6. 
   Suppose you need to send one message to three different users: user1@example.com, user2@example.com, and user3@example.com. Is there any difference between sending one separate message per user vs. sending only one message with multiple (i.e., three) recipients? Please explain. [2 marks]
   
7. 
   Suppose a TCP SYN message is sent from a client with IP address 128.119.40.186 and client port number 5345 to a server with IP address 41.123.7.94 and server port number 80 HTTP). Once the TCP connection has been established, what will be the client-side IP address, client--‐side port number, server‐side IP address and server-side port number of the TCP segment carrying the HTTP GET message. [2 marks]
   

ANSWER

1. 
   Fast, loopless convergence.
   

2. 
   Traceroute sends a series of packets for which it sets the IP “Time To Live” (TTL) hop-count field to different values. Setting the TTL to N will result in the Nth router generating a “Time Exceeded” ICMP message which it sends back to the originating host. Because ICMP messages are sent using IP packets, traceroute can extract from their source address the IP address associated with the router at the Nth hop. (Strictly speaking it’s not the IP address associated with the router, since routers have one IP address for each of their interfaces.)
   
3. 
   Most concurrent servers operate dynamically. The server creates a new thread for each request that arrives. The server program, actually, is constructed in two parts: one that accepts requests and creates a new thread for the request, and another that consists of the code to handle an individual request. When a concurrent server starts executing only the first part runs. That is, the main server thread waits for a request to arrive. When a request arrives, the main thread creates a new service thread to handle the request. The service thread handles one request and then terminates. Meanwhile, the main thread keeps the server alive - after creating a thread to handle a request, the main thread waits for another request to arrive. If N clients are using a given service on a single computer, there are N + 1 threads providing the service: the main thread is waiting for additional requests, and N service threads are each interacting with a single client.
   
4. 
   

getprotobyname gethostbyname

socket getprotobyname

listen

5. 
   ICMP is an error reporting protocol. ICMP uses IP to transport each error message. ICMP header contains an 8-bit integer message TYPE field that identifies the message, an 8-bit CODE field that provides further information about the message type, and a 16-bit Checksum field.
   

6. 
   If a separate message is sent for each of the users, one MAIL, one RCPT, and one DATA command will be issued for each of the messages, resulting in the transmission of three copies of the message data. If only one message with multiple recipients (three) is sent, one MAIL, multiple RCPT, and one DATA command will be issued, resulting in the transmission of only one copy of the message data.
   

7. 
   Exactly as specified in the problem statement.