QOS in an MPLS network

[carl_townshend]

Hi All

Can anyone tell me how QOS is managed throughout an MPLS network

For example on the PE router our provider will apply priority to our EF traffic and police it to a certain amount, my question is if we have a large MPLS network with each site having there own policy etc, how is this policy mapped through the provider part of the network? Or do they only generally do it on the ingress to the network?

cheers

[Joseph W. Doherty]

Cannot say for all providers, but for a provider's interior network, QoS could be used as it would on most interior networks, i.e. to provide better service to some traffic during times of congestion.

[Dean Romanelli]

Hi Carl,

As Joseph said, it depends on the provider, but if you are asking how that would work exactly:  Assuming the QoS configurations are being done on your ISP's router at the edge of each of your sites, subsequent hops throughout the MPLS network are configured to trust the markings they receive from each branch PE router end to end. So basically the actual QoS policy and configuration is usually only done on each PE router at the branch edges, and the upsteam nodes within the ISP's transport beyond those PE routers are configured to trust and honor whatever QoS markings they receive from the previous hop. This behavior will last end-to-end for every hop the traffic passes through that honors the markings, but if it ever passes through a hop that is not honoring markings, those markings will get dropped and the traffic will default back to best effort at the node that isn't honoring the markings and will stay best effort all the way to the destination.  One of the benefits of MPLS though is end-to-end QoS because your MPLS ISP controls all hops usually, so if you want QoS and you convey that to them, they can usually ensure mark honoring end to end.