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Community Member

CE/PE setup for IP diffserv connections

I'm doing some coding for a piece of monitoring software and would like to know what diffserv mechanism is actually used in the real world, ie CAR, QOS or what?

If CAR or QOS, where is coloring/policing done - CE, PE or combination of both, and ingress or egress ?

There are plenty of ways IP differential services could be achieved, but I've not managed to talk to anyone who has actually done a real-world implementation.

Many thanks in advance.

Paul Sweeney

Kolossi Consultants

"Innovation with Integrity"


Re: CE/PE setup for IP diffserv connections

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Community Member

Re: CE/PE setup for IP diffserv connections


diffserv is used at the PE router at both ingress and egress egde of the VPN. Its basically done for implementing QoS, offering various class or service on the VPNs to prioritise real time traffic from normal bes-effort based traffic.

Community Member

Re: CE/PE setup for IP diffserv connections

What method do you use to implement this - CAR, QOS or something else?

Community Member

Re: CE/PE setup for IP diffserv connections

Last time I did it was with CAR, on the ingress side of the PE. Of course, that depends on your definition (and application) of diffserv :)

Community Member

Re: CE/PE setup for IP diffserv connections

Subject: real world diffserv

I myself have noticed that there is a abscence of any real world implementations. The only thing that comes close is the work that is being done by the I2 ( qos working group.

Most of the Cisco employees I have talked to have little of no knowledge on the subject.

Community Member

Re: CE/PE setup for IP diffserv connections

I have to agree, it's a nice buzzword with not much happening. I have actually implemented it, but the client is now out of business... sign of the times, or victim of poorly marketed & accepted technology??

Community Member

Re: CE/PE setup for IP diffserv connections

I think Cisco and other companies have been waiting for IPV6 protocol implementation and stanardization to gel. As I understand it diffserv was standards were formally adopted at end of last year.

The 3com people told me that they were releasing a new ios that has support for diffserv.

What is strange however is that IBM has had support for diffserv for almost 2 years. Cisco has purchased a lot of the IBM Network processor chips (Ranier) which has native support for traffic classification. Personally I think Cisco has been sitting on the technology.

Community Member

Re: CE/PE setup for IP diffserv connections


I´m also starting some DiffServ-Testing to implement

QoS in a Multivendor Environment. I saw the Java-Applet QDM.tar available on CCO as very helpful to monitor the results. I would like to start with only 3 AF-classes and only one DSCP per Class for data purposes only.

To mark the pakets I had some pbs understanding the burst params of CAR, therefore I´m now using policy-maps (without policer and shaper).

At this time I´ve no idea on the impact on Router

performance and throughput using policy-maps on E1 and E3 links and on LAN-Interfaces for input-marking.

Whats also unclear for me is the relation

between the dscp-based WRED IOS values for the AF classes (in some examples on CCO AFx3 has higher drop denotiators and higher Min-Thresholds as AFx1) and the intentions in the RFC for the AF classes (AFx1 is better/more reliable service than AFx3)

Any contact welcome,

best regards,


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