From: Michael Snyder (msnyder@xxxxxxx)
Date: Thu Aug 23 2001 - 19:06:35 GMT-3
For a Change I thought I would anwser my own question.
There's a Quote from http://www.wildpackets.com/compendium/REF/REF-SAP.html
posted below.
I searched the web and didn't find much other than the link above and 1080 CCO
web hits, most related to how to use lsaps. Started checking my library,
Guess what, Doyle Vol 1 only had one page (7) referenced in the index. I feel
a bit better not knowing some of this, before now. I moved on, Caslow had
two good chapters, #21 and #26. They are on my reading list for tonight.
Roosevelt Giles had some stuff, etc.
To keep this email short, What I got from my search is that, is that LSAP's
live at layer two, as part of the LLC1 and LLC2 LLC sublayer. They are part
of the layer two frames that tell the client tcp stack which process (of the
stack) to pass the frame too. In this regard, they act much like layer three
port numbers. Identifying what to do once all all those bits arrive at the
interface.
One question to verify that I'm on the right track. If I block LSAP 0x98 on a
interface, that would break ARP, correct?
Thanks for Your Time,
Michael
The Service Access Point ("SAP", pronounced like the sap that comes from a
tree to make maple syrup) is used to identify which protocol handler should
process an incoming frame. A Service Access Point is a data structure and
identifier for a buffer area in system memory that is actually a broad
concept. The Open Systems Interconnect (OSI) model uses a SAP to define the
communication between layers (like Network, Transport, Session, and the other
layers of the Seven-Layered Model). Unless you are studying the OSI model or
the OSI protocols, you aren't going to encounter that definition of SAP. The
most common reference to a Source Service Access Point (SSAP) or a Destination
Service Access Point (DSAP) refers to the boundary between the Data Link Layer
and the Network Layer.
00 Null LSAP
02 Individual LLC Sublayer Management Function
03 Group LLC Sublayer Management Function
04 IBM SNA Path Control (individual)
05 IBM SNA Path Control (group)
06 ARPANET Internet Protocol (IP)
08 SNA
0C SNA
0E PROWAY (IEC955) Network Management & Initialization
18 Texas Instruments
42 IEEE 802.1 Bridge Spanning Tree Protocol
4E EIA RS-511 Manufacturing Message Service
7E ISO 8208 (X.25 over IEEE 802.2 Type 2 LLC)
80 Xerox Network Systems (XNS)
86 Nestar
8E PROWAY (IEC 955) Active Station List Maintenance
98 ARPANET Address Resolution Protocol (ARP)
BC Banyan VINES
AA SubNetwork Access Protocol (SNAP)
E0 Novell NetWare
F0 IBM NetBIOS
F4 IBM LAN Management (individual)
F5 IBM LAN Management (group)
F8 IBM Remote Program Load (RPL)
FA Ungermann-Bass
FE ISO Network Layer Protocol
FF Global LSAP
http://www.wildpackets.com/compendium/REF/REF-SAP.html
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