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Understanding DSCP Classification for VPLS

You can perform Differentiated Services Code Point (DSCP) classification for IPv4 packets on Ethernet interfaces that are part of a virtual private LAN service (VPLS) routing instance on the ingress provider edge (PE) router. This is supported on the M320 router with Enhanced type III FPC and the M120 router. On the ATM II IQ PIC, the ether-vpls-over-atm-llc encapsulation statement is required. On the Intelligent Queuing 2 (IQ2) or Intelligent Queuing 2 Enhanced (IQ2E) PICs, the vlan-vpls encapsulation statement is required. DSCP for IPv6 and Internet precedence for IPv6 are not supported.

In order to perform DSCP classification for IPv4 packets on Ethernet interfaces that are part of a VPLS routing instance on the ingress PE router, you must make sure of the following:

  • The correct encapsulation statement based on PIC type is configured for the interface.

  • The DSCP classifier is defined (default is allowed) at the [edit class-of-service classifiers] hierarchy level.

  • The defined DSCP classifier is applied to the interface.

  • The interface is included in the VPLS routing instance on the ingress of the PE router.

A VPLS routing instance with the no-tunnel-services option configured has a default MPLS EXP classifier applied to the label-switched interface for all VPLS packets coming from the remote VPLS PE. This default classifier is modifiable only on MX Series routers. On T Series, when no-tunnel-services option is configured, the custom classifier for VPLS instances is not supported.

Note:

With no-tunnel-services configured, a custom classifier for VPLS routing instances on T Series and LMNR based FPC for M320 is not supported. When a wild card configuration or explicit routing instances are configured for VPLS on CoS CLI, the custom classifier binding results in default classifier binding on Packet Forwarding Engine (PFE).

For example, on routing devices with eight queues (Juniper Networks M120 and M320 Multiservice Edge Routers, MX Series 5G Universal Routing Platforms, and T Series Core Routers), the default classification applied to no-tunnel-services VPLS packets are shown in Table 1.

Table 1: Default VPLS Classifiers

MPLS Label EXP Bits

Forwarding Class/Queue

000

0

001

1

010

2

011

3

100

4

101

5

110

6

111

7
Note:

Forwarding class to queue number mapping is not always one-to-one. Forwarding classes and queues are only the same when default forwarding-class-to-queue mapping is in effect. For more information about configuring forwarding class and queues, see Configuring a Custom Forwarding Class for Each Queue.

On MX Series routers, VPLS filters and policers act on a Layer 2 frame that includes the media access control (MAC) header (after any VLAN rewrite or other rules are applied), but does not include the cyclical redundancy check (CRC) field.

Note:

On MX Series routers, if you apply a counter in a firewall for egress MPLS or VPLS packets with the EXP bits set to 0, the counter will not tally these packets.

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