The Long and Winding Road wrote: > > ""Priscilla Oppenheimer"" wrote in > message > news:[EMAIL PROTECTED] > > KW S wrote: > > > > > > Can someone tell me what is the function of the protocol > field > > > in the IP header. > > > > > > I get a little confused after reading from some many > sources. > > > > > > Regards > > > kws > > > > The Protocol field identifies the next layer, in other words > the type of > > payload that IP is carrying. Almost every protocol has a way > of > identifying > > what the next layer is. The recipient layer uses this > information to > figure > > out which process to pass the payload to. > > > Given previous discussions here regarding "next layer"
What discussions of next layer? > may I > offer that this > does not refer to the "next OSI layer" but rather something > else? > I'm referring to layers in a packet obviously. The word "layer" is widely used in the English language without OSI attached to it. Packets come in layers. For example, recently I got the Server Message Block (file sharing protocol used on Windows) running across a GRE tunnel that was being carried on a VPN that was crossing a DLSw+ serial link using DLSW+ TCP encapsulation. Here were the layers in the packets: HDLC TCP 802.5 802.2 SNAP IP IPSec IP GRE TCP NetBIOS SMB Does that look like the OSI 7-layer model to you? > Otherwise we will have to go through anopther cycle of people > thinking they > are being told that OSPF operates at layer 4. :-> Read Howard's discussions of the control, management, and user planes. > > > > > > Ethernet II has EtherType. > > IEEE 802.3 has the 802.2 Logical Link Control (LLC) Service > Access Points > > (SAPs). > > IP has the Protocol field. > > UDP and TCP have port numbers. > > > > The IP Protocol field identifies the next layer as being one > of these: > > > > Protocol Type in Decimal > > ICMP 1 > > IGMP 2 > > IP 4 (tunneling) > > TCP 6 > > IGRP 9 > > UDP 17 > > GRE 47 > > ESP 50 > > AH 51 > > EIGRP 88 > > OSPF 89 > > > > There are others but those are the most common. > > _______________________________ > > > > Priscilla Oppenheimer > > www.troubleshootingnetworks.com > > www.priscilla.com > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65795&t=65718 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
