>!Hola! > >> Same for the TCP header. there is an optional options field of 4 bytes. my > >s/4 bytes/4 bits/ ? And the size for options fields is 40 (2^15 * 4 - 20) >bytes (the "data offset field" is sized to 4 bits) > >> 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 > >Why did you refer 761 instead of 793 ? 760 is actually the original IP RFC (761 is TCP). It had no concept of classes, just a fixed 8-byte network field. 791 is the "main" IP specification. Classes but no subnetting. 950 introduced subnetting CIDR is in multiple RFCs, primarily 1517-1520. > >> 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. > >It has been a long time, but i believe that Comer talks about options. There are options, but they are rarely used. Off the top of my head, security, source recording, and I think some timestamping. > >> Chuck > >Saludos, > HoraPe >--- >Horacio J. Peqa >[EMAIL PROTECTED] >[EMAIL PROTECTED] >[EMAIL PROTECTED] >[EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=13754&t=13754 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
