From: Justin Menga (Justin.Menga@xxxxxxxxxxxxxxxxxx)
Date: Thu Nov 02 2000 - 01:42:46 GMT-3
Yeah you are right for NetBIOS - unsure as to why this is, perhaps the
group/single bit is used in the DSAP?!?
Regards,
Justin Menga MCSE+I CCNP CCSE ASE
WAN Specialist
Computerland New Zealand
PO Box 3631, Auckland
DDI: (+64) 9 360 4864 Mobile: (+64) 25 349 599
mailto: justin.menga@computerland.co.nz
-----Original Message-----
From: Jack Heney [mailto:jheneyccie@hotmail.com]
Sent: Thursday, 2 November 2000 5:00 p.m.
To: Justin.Menga@computerland.co.nz; philip@home.com.hk;
ccielab@groupstudy.com
Subject: RE: Sap type from Cisco technical tips.
Also, doesn't netbios use the MSB in the dsap? I've always understood
netbios traffic could be filtered with a SAP access-list using
0xf0f0 0x0101....The mask seems to indicate that this bit gets used
(although the cannonical/non-cannonical thing might be throwing me off).
Jack
>From: Justin Menga <Justin.Menga@computerland.co.nz>
>Reply-To: Justin Menga <Justin.Menga@computerland.co.nz>
>To: "'Philip Lai'" <philip@home.com.hk>, ccielab@groupstudy.com
>Subject: RE: Sap type from Cisco technical tips.
>Date: Thu, 2 Nov 2000 16:23:51 +1300
>
>Hi,
>
>The MSB in the SSAP is actually used for the Command/Response bit. The
>remaining 7 bits are used for the actual SAP. The order is reversed due to
>the non-canonical nature. Thus if you have a SAP of 4 (00001000), this
>represents a SAP of 4 command. If you have a SAP of 5 (00001001), this
>represents a SAP of 4 response.
>
>In the DSAP, the MSB represents if the DSAP is an individual (0) or group
>(1) DSAP. As far as I am aware, only 0 is used, hence the DSAP is never
>unchanged.
>
>Check out http://www.protocols.com/pbook/lan.htm#LLC to see the DSAP and
>SSAP field representations.
>
>Regards,
>
>Justin Menga MCSE+I CCNP CCSE ASE
>WAN Specialist
>Computerland New Zealand
>PO Box 3631, Auckland
>DDI: (+64) 9 360 4864 Mobile: (+64) 25 349 599
>mailto: justin.menga@computerland.co.nz
>
>
>-----Original Message-----
>From: Philip Lai [mailto:philip@home.com.hk]
>Sent: Sunday, 29 October 2000 6:09 p.m.
>To: ccielab@groupstudy.com
>Subject: Sap type from Cisco technical tips.
>
>
>Hi,
>When I reading SAP type in
>http://www.cisco.com/warp/customer/698/acl200.html , it list all the sap
>type there.
>I am wondering what the the meaning for the sap type for 00 and 01. Are
>they
>the explorer frame or the command and respond ? Will the explorer frame
>have
>a fixed value of sap type ?
>
>________
>Another point to consider when designing the ACL is that SAP values change
>depending on if they are commands or responses. The SSAP includes the
>command/response (C/R) bit to differentiate between them. The C/R is set to
>0 for commands and to 1 for responses. Therefore, the ACL must allow or
>block commands as well as responses. For example, sap 0x05 (used for
>responses) is just SAP 0x04 with the C/R set to 1. The same applies to sap
>0x09 (sap 0x08 with C/R set to 1), 0x0D, and 0x01.
>
>Thanks
>Philip Lai
>NCR HK Email: philip.lai@ncr.com
>Phone: (852) 2859-6076 Fax: (852) 2294-3055
>
>
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 08:25:40 GMT-3