You are right. Thanks everybody! I trust RFC! ""Chuck Larrieu"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > actually, an IP header can contain options which can in turn lengthen the > field. The presence of these options is indicated in the IHL field ( bits 4 > thru 7 in the header ) > > check out RFC 791 for more detail. > > ftp://ftp.isi.edu/in-notes/rfc791.txt > > one use of the IP header options is to record hop addresses as packets > travel through a network. there are a number of other options defined. > > Same for the TCP header. there is an optional options field of 4 bytes. my > quick glance through RFC 761 tells me this field never exceeds that 4 byte > length, but I am not very familiar with it. > > ftp://ftp.isi.edu/in-notes/rfc761.txt > > I bring this up because most of the study materials state ex cathedra that > the IP and the TCP headers are 20 bytes. Having browsed the RFC's at one > time or another, I vaguely recalled the options, looked it up, and sure > enough, there they are. I don't recall much study material covering the > options and their uses. > > Chuck > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > xie rootstock > Sent: Tuesday, July 24, 2001 8:46 PM > To: [EMAIL PROTECTED] > Subject: RE: IP header question, Fixed 20 bytes or can be more? > [7:13700] > > > IP and TCP header has 20bytes Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=13712&t=13712 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
