Go Back   Computer Forums > General Computing > Networking | DNS
Click Here to Login
Join Computer forums Today


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 04-19-2005, 11:55 AM   #1
Beta Member
 
Join Date: Apr 2005
Posts: 3
Default help - TCP /IP

can anybody help on this following problem...i really appreciate your help

Assume two hosts, A and B, communicate via a TCP connection. Reliable data transfer is guaranteed by TCP's retransmit mechanism: if host A sends a segment and the segment is lost or corrupted, then it will not be acknowledged by host B. After A's retransmission timer times out, and still no ACK has been received, A will retransmit the segment.

A possible problem with the above scenario is this. Assume that a fast stream of segments is being sent. If a segment is lost, then the receiving host B can notice this quickly from the sequence nunbers. But the segment will be retransmitted only later, when A's retransmission
timer times out, since before it A does not know about the need for retransmission. By that time, however, the segment may become useless in a fast real-time application.

The above problem clearly stems from the fact that A does not know that retransmission is needed, before the timer times out. Even though B knows it earlier from the sequence numbers, it does not have a standard way in the original TCP to notify A about it. If B could somehow notify A to initiate an early retransmission, then the unnecessary delay could
be avoided.

Your task is to propose a simple solution for this problem. Speci»cally, propose a simple modi»cation of the TCP protocol, which makes it possible that the receiver can notify the sender that a segment needs to be retransmitted. The goal is that the sender can learn about the needed retransmission, without having to wait for a timeout. Let us call
this protocol \TCP with Fast Retransmission" and let us abbreviate it as TCP/FT.
Your proposed solution for TCP/FT should satisfy the following requirements:
Simplicity. It should be a simple modification of TCP. Do not attempt to totally redesign TCP.
Failsafe design. To avoid potential interference with existing implementations, you are not allowed to put any new type of information in the TCP header, including the Options field. Thus, for example, it is not acceptable to say: "let's use one of the unused header
bits to include a special flag that instructs the sender for an early retransmit".
Backward compatibility. Your proposed protocol should not cause any problem if the communication takes place between a host that attempts to use TCP/FT, while the other runs standard TCP and does not know anything about TCP/FT.
Present your proposed modification of TCP first by explaining its operation verbally. Then also present it in some more formal way, prefereably by a flowchart or pseudocode. (If you use pseudocode, then add enough comments to make it human readable!)
__________________

nivsah is offline   Reply With Quote
Old 04-21-2005, 08:07 AM   #2
Baseband Member
 
edicWHUN's Avatar
 
Join Date: Jan 2005
Posts: 24
Default

Is this a timeout problem or a transmission problem, where B is not able to communicate with A because A is currently transmitting to B, or is it that you need to bypass the timeout or TTL period?
__________________

edicWHUN is offline   Reply With Quote
Old 04-21-2005, 08:54 AM   #3
Beta Member
 
Join Date: Apr 2005
Posts: 3
Default

transmission problem..

thanks
nivsah
nivsah is offline   Reply With Quote
Old 04-21-2005, 09:29 AM   #4
Baseband Member
 
edicWHUN's Avatar
 
Join Date: Jan 2005
Posts: 24
Default

Correct me if I'm wrong, but if they are communicating in Full Duplex mode wouldnt that eliminate the problem of Host B having to wait until Host A finishes transmitting before it can respond back?
edicWHUN is offline   Reply With Quote
Old 04-21-2005, 09:55 AM   #5
Beta Member
 
Join Date: Apr 2005
Posts: 3
Default

i'm not sure about that..
nivsah is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -5. The time now is 12:55 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Friendly URLs by vBSEO 3.6.0