OCS, QoS, DSCP and RFC's - Something isn't right
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Thursday, September 17, 2009 3:50 AMIf you read the documents on QoE / QoS and OCS - particularly http://www.google.com/url?q=http://www.microsoft.com/downloads/details.aspx%3FFamilyID%3D09115944-625f-460b-b09c-51e3c96e9f7e&ei=-bCxSoT2K9iBkQW89bCVBg&sa=X&oi=spellmeleon_result&resnum=1&ct=result&usg=AFQjCNFnYLgJerf0my2zjQYqrCQdRd7C4A
You will find they talk about DSCP markings for OCS
The documents refer to marking Voice traffic as "EF" or DSCP 40
The thing is - EF is DSCP 46. 40 is the Class boundary, but is not EF
So I'm confused.
In the one document is says DSCP EF is 101110 (46)
Then is says OCS marks it as EF - but states 40. 40 is 101000
40 is a Class Selector Code Point or Class Selector for the same Class as EF, but it is NOT the class EF as deffined by RFC 2598
Can anyone shed some light on this mess?
Thanx
Paul
All Replies
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Thursday, September 17, 2009 12:23 PMModerator
Windows by default uses DSCP markings of 40, but that value can be changed in the local system policy on the computers. Take a look at these article for more details: I've run into the same thing when needing to set 46 (0x2E) for traffic traveling over Cisco switches.
Take a look at these articles for more details:
Enabling DSCP Marking in OCS
http://technet.microsoft.com/en-us/library/dd441192(office.13).asp78
http://communicationsserverteam.com/archive/2009/06/04/458.aspxDSCP & ToS Table
http://www.tucny.com/dscp%26tosCisco - Implementing QoS Policies with DSCP
http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a00800949f2.shtml
The other major point is that OCS will only park packets to-from other OCS endpoints, meaning that only traffic between workstations, Front-End servers, and the Mediation server will be marked. Packets leaving the Mediation server externally for a media gateway or over a Direct SIP trunk will NOT be marked at all. In that case you'll need to use the Policy-based QoS feature of Windows Server, applied to the MediationServerSvc.exe process) to make sure outbound packets are stamped. This is by behavior of OCS and I've verified this with the product group.
Jeff Schertz, PointBridge | MVP | MCITP: Enterprise Messaging | MCTS: OCS- Proposed As Answer by Jeff SchertzMVP, Moderator Tuesday, September 22, 2009 1:22 PM
- Marked As Answer by Gavin-ZhangModerator Friday, September 25, 2009 10:06 AM
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Tuesday, September 22, 2009 1:29 PMModerator Additional details can be found in this blog article: http://blogs.pointbridge.com/Blogs/mcgillen_matt/Pages/Post.aspx?_ID=70
Jeff Schertz, PointBridge | MVP | MCITP: Enterprise Messaging | MCTS: OCS- Marked As Answer by Gavin-ZhangModerator Friday, September 25, 2009 10:06 AM
