transport layer Question 1 The UDP header does not contain any information that

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transport layer

Question 1

The UDP header does not contain any information that is not present in the TCP header (verify this for yourself). That being the case, why do you, as a programmer, have to specify the header information (ports and IP addresses) whenever you send a UDP packet; but you don't when you send a TCP packet?

Question 2

Protocol design decisions often have unexpected perfomance consequences. HTTP 1.0 is an example of a protocol design where lower layer protocol behaviour impacted directly on the performance of the higher layer protocol.

What is the difference between HTTP 1.1 and HTTP 1.0 in terms of transport layer connections? What two transport layer issues do the changes to HTTP address? How does the change improve HTTP performance?

Question 3

Consider congestion control in TCP Reno (most common algorithm). How might application designers exploit the Internet's use of TCP to get higher data rates at the expense of other data flows that are using TCP?

Question 4

Selective Repeat does not resend all packets on timeout, so it must timeout packets individually. However, in our implementation we only have one timer. How might we solve this problem? What would happen if we re-start the timer every time a packet is sent? What would happen if we re-start the timer when the oldest packet is ACKed?

Explanation / Answer

Question 1:

Suppose sender is sending a packet to destination , if IP address is not there, it's not able to reach destination. Now there may be many ports in that IP address, which port we want to connect that neeeds to be mentioned. That is the reason we need IP address and port number.

Question 2:

The main deifference between HTTP1.0 and HTTP 1.1 is: In case of HTTP 1.1 - it requires Host header, but in case of HTTP 1.0 we may or may not use. The header is usefule in the sense that it can identify and route the message through proxy servers.

HTTP 1.1 is persistent where as HTTP1.0 is not. So each time we need a new connection to open.

Question 3:

Basically a TCP sender is supposed to monitor is transmission rate and take the decision. It will try to cooperate with routers to get the data. For that they will share a common resource also.

Question 4:

Considering there is one timer. after sending the packet start the timer, if timeout occurs then send the not acknowledged packets, again start the transmission of the packet and start the timer.

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