Question

1.DNS can not work if the hostnames are not hierarchal? Explain?

2. Give two scenarios where DNS protocols (from two hosts) gets two different IP address for the same hostname.

3. If you have a 100% reliable network layer, should you use TCP or UDP at the Transport layer? Explain your answer?

4.Is it is possible for an application on top of UDP to have a reliable data transfer? Explain?

5.Suppose that a Web server runs in Host C on port 80. Suppose this Web server uses persistent connections and is currently receiving requests from two different Hosts, A and B. Are all of the requests being sent through the same socket at Host C? If they are being passed through different sockets, do both of the sockets have port 80? Discuss and explain.

6. What are the layers that run in the network core?

7.What are the two layers the run exclusively at the network edges?

8. Would the DNS protocol work if IP addresses are not hierarchical? Explain why?

9.You live in a remote town with a relatively slow Internet connection of 1 G bit/s. You decided to provide faster Internet connectivity for your community. Being a network expert and know that following quotation:

Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.–Andrew Tanenbaum, 1981

Assume you can fit 100 tapes in your station wagon and each tape can store up to 10 TB, the closest fast Internet provider is about 100 miles from your town.

For your proposed idea-Compute the effective bandwidth?-What is the main drawback? -How to improve the solution?

Answer 1

1. The DNS full form is Domain Name System. It is a central part of internet. Users can access information through internet using domain names example:www.information.com, www.education.com etc. It will provide a way to match the domain name to IP address of a system. DNS translates domain name to IP addresses to load internet information.The users don't need to remember the IP address of the system.

The DNS convert a host name to computer friendly IP-address.A Transaction happen between the IP address and the DNS the user typed in web browser and to locate on the webpage the user needs.

The DNS hierarchy is used to manage the distributed database system. It is an inverted tree which has single domain at top of structure that is root of hierarchy.It contains following elements

1) Root Level

2)Top Level

3) Second Level

4) Sub-Domain

5)Host

A host name consist of variable,alphabets, numerical characters it is identified by IP address. An IP address consist of four bytes and it is hierarchical structure.So for a DNS to match the hostname should be in hierarchrcy so that it can translate to IP address .

2.The DNS can have multiple IP address with same host name.It can return list of IP address with same domain name. A website can have multiple IP address if you are hosted in multiple locations or servers.

3. TCP is more reliable than UDP layer .The data send through the TCP will reach the reciver without any problem.TCP check the data packet before it is transferred to avoid corruption of data.UDP is unreliable it does not guarantee for package to reach its destination without any corruption.

4. Yes it is possible for an application to have reliable transportation over UDP protocol layer.The TCP convention control can throttle applications sending rate during congention.We can make a UDP layer more reliable by

• Acknowledging whether the packets are receiving.
• Controlling flow of the data .
• Retransmitting of lost data