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Community Member

one basic question

Hi all,

I have a very basic question, is that in TCP/IP, a segment is seperated to more than one packet, and a packet is seperated to more that one frame. But how the seperated frame be back to a whole packet and the seperated packed be back to a whole segment? Because packet and frame do not have sequence number like segment in TCP. Can any one tell me the answer? Thank You!

Best Regards

Teru Lei

2 REPLIES

Re: one basic question

Teru,

Remember, each segment processed at layer 4, produces a header which defines the length of the segment in th header. Now this is send to layer 3 which again puts a header which defines the length of the packet. Now this is given to layer 2, which again puts a header with the length of the frame. So ultimately there are delimiters defined at each layer which defines length of each entity.

When a PC receives the frames, which might constitute, lot of packets, (can be packets for two different applications also). The PC strips off the frame and gets the packet. From each packet, the data segment is stripped off . Now the PC has a collection of segments belonging to different flows, which it still doesnt know, for which protocol it is meant for. Now the layer 4, will categorise these segments into TCP type or UDP type depending on what is on the header. Finally it is given to the corresponding protocol, depending upon the application running on the PC.

So the conclusion is there is no need for a sequencing in the 2nd or 3rd layer level, because, the segments are stripped from the packets and frames. Only the layer 4 sequencing does matter.

Community Member

Re: one basic question

Thank you for your reply. So it means that the size of a frame is larger that the size of the packet (1 frame contains 1 or more packets) and the size of a packet is larger that the size of the segment ( 1 packet contains 1 or more segments)? Because I had thought that the size of a segment is larger than packet and packet is larger that frame.

Best Regards

Teru Lei

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