6 votes 6 votes In Transport layer either in TCP header or UDP header in checksum field we calculate checksum for Pseudo header of IP + header of TCP/UDP + data of TCP/UDP. Transport layer should fill checksum field in header before the Segment pass to Network layer. Here my doubt is how TL knows the IP header which is going to create in next step NL ? Computer Networks transport-layer computer-networks tcp udp header checksum + – SaiPrasadKousika asked Aug 27, 2016 • edited Aug 27, 2016 by SaiPrasadKousika SaiPrasadKousika 1.7k views answer comment Share Follow See 1 comment See all 1 1 comment reply smsubham commented Mar 5, 2020 reply Follow Share https://stackoverflow.com/questions/359045/what-is-the-significance-of-pseudo-header-used-in-udp-tcp 0 votes 0 votes Please log in or register to add a comment.
3 votes 3 votes Upper layer can communicate to lower layer so transport layer can communicate to network layer. in Pseudo IP Header included important field which did not change during transmission like source ip,destination ip,protocol,TCP/UDP segment bit diamond.17 answered Aug 5, 2017 diamond.17 comment Share Follow See all 2 Comments See all 2 2 Comments reply Paras Nath commented Sep 7, 2017 reply Follow Share But how ? Can u explain it more clearly? 0 votes 0 votes Paras Nath commented Sep 7, 2017 reply Follow Share Instead of computing the checksum over only the actual data fields of the TCP segment, a 12-byte TCP pseudo header is created prior to checksum calculation. This header contains important information taken from fields in both the TCP header and the IP datagram into which the TCP segment will be encapsulated. But My Quetion is how TCP know IP pseudo header ??????? 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Yes, the layer concept is violated in this case but to provide reliable transmission it uses the IP header which is available in next layer Pavan Kumar Munnam answered Aug 29, 2016 Pavan Kumar Munnam comment Share Follow See all 0 reply Please log in or register to add a comment.