SD-WAN

In my network, I have multiple different upstream providers that I peer with (for the sake of example, lets say "ISP-1" and "ISP-2"). Also, within my network I have an established DiffServe domain with an enforced set of DSCP markings throughout.

 For traffic within my network, I am able to use service-policies and service-classes to ensure traffic is prioritized and marked per my internal network policy. ISP-1 and ISP-2 also support prioritization in their queues based on DSCP values, however they each use different markings for their high, medium, low, and best-effort queues. For example, high is DSCP value 46 in my network, but it is 32 in ISP-1's network, and 18 in ISP-2's network.

 When packets are arriving at my interfaces peering with ISP-1 and ISP-2, I understand that I can use a dscp-map to ensure packets marked with their network DSCP values get mapped into my appropriate priorities...but what about packets egressing to ISP-1 and ISP-2? Is there some way that I can override the markings specified in a given service-class, and map it to a different DSCP value based on the egress interface?

#DSCP

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Scott A McCulley may be able to answer this.

Hi Greg,

 

Currently the dscp-map associated with a network-interface only applies to ingress and is not used in concert with the rewrite-dscp configuration option to determine an egress DSCP marking value. To date, the DSCP value configured in service-class is the only way to change the marking in a packet and unfortunately that has no notion of which egress interface the packet is destined for.

 

Thanks,

Scott McCulley

 

I have a follow-on question: service-class object has the following setting - DSCP Value To Assign (required).  You cannot leave it blank.  This seems problematic, as for some services I want be able to assign priority for queueing purposes, but do not want to mess with the DSCP markings.  How do I do that if service-class requires me to have some value in that field?  I certainly can't set Rewrite DSCP = FALSE on the egress interface, because there are other service-classes leaving this interface, which do require their DSCP re-written.  Need some help to resolve these conflicting settings and requirements.

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Gene Shtirmer
Sales Engineer
Randolph NJ
(973) 610-5676
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Original Message:
Sent: 10-16-2018 00:00
From: Scott A McCulley
Subject: How can I map service-classes to a new DSCP value based on egress interface?

Hi Greg,

 

Currently the dscp-map associated with a network-interface only applies to ingress and is not used in concert with the rewrite-dscp configuration option to determine an egress DSCP marking value. To date, the DSCP value configured in service-class is the only way to change the marking in a packet and unfortunately that has no notion of which egress interface the packet is destined for.

 

Thanks,

Scott McCulley