How to help OCS to not drop words, applying Voice QOS for OCS on WANtraffic

How to applying the correct QOS for OCS 2007 traffic over the WAN, this has been a hot topic (at least for me) as I believe that all of voice traffic requires over WAN links.

I will introduce some QOS terminology in this post, and later will tell you how to apply QOS for OCS traffic.

Quality of Service Models

There are 3 service models:

• Best Effort No QOS policies are implemented.
• Integrated Services (IntServ) Resource Reservation Protocol (RSVP) is used to reserve bandwidth per flow across all nodes in a path, uses the Resource Reservation Protocol (RSVP) to reserve network resources in advance of the data actually traveling across the network. Once the end-to-end bandwidth reservation is in place, the data is transmitted.
• Differentiated Services (DiffServ) Packets are individually classified and marked; policy decisions are made independently at each node in a path, DiffServ doesn't use RSVP, but instead uses hop by hop Behavior or per hop behavior (PHB) to allow each router/hop across the network to examine the packet and decide what service level it should receive.

IP QOS Markings

We currently use 2 QOS marking methods:

• Precedence The first three bits of the IP TOS field are evaluated; compatible with Ethernet COS and MPLS EXP values.
• DSCP The first six bits of the IP TOS are evaluated to provide more granular classification; backward-compatible with IP Precedence.

The following table contains the Precedence Values:



The following table lists the DSCP marking Values:



How to reserve the Bandwidth:

You can use any of the following methods:

• Policing · Creates an artificial ceiling on the amount of bandwidth that may be consumed; traffic exceeding the cap and be remarked or dropped.
• Shaping · Similar to policing but buffers excess traffic for delayed transmission; makes more efficient use of bandwidth but introduces a delay.