Dell PowerConnect J-8216 Software Guide for JUNOS version 10.3 - Page 3136

Dell PowerConnect J-Series Ethernet Switch Complete Software Guide for Junos OS Understanding Using CoS with MPLS Networks on J-EX Series Switches You can use class of service (CoS) within MPLS networks to prioritize certain types of traffic during periods of congestion. J-EX Series Switches support Differentiated Service Code Point (DSCP) or IP precedence and IEEE 802.1p CoS classifiers on the customer-edge interfaces of the ingress provider edge (PE) switch. DSCP or IP precedence classifiers are used for Layer 3 packets. IEEE 802.1p is used for Layer 2 packets. When a packet enters a customer-edge interface of the ingress PE switch, the switch associates the packet with a particular CoS servicing level prior to putting the packet onto the label-switched path (LSP). The switches within the LSP utilize the CoS value set at the ingress PE switch. The CoS value that was embedded in the DSCP, IP precedence, or IEEE 802.1 p classifier is translated and encoded in the MPLS header by means of the EXP or experimental bits. J-EX Series switches enable a default EXP classifier and a default EXP rewrite rule. You can configure a custom EXP classifier and a custom EXP rewrite rule if you prefer. However, the switch supports only one type of EXP classifier (default or custom) and only one EXP rewrite rule (default or custom). You do not bind the EXP classifier or the EXP rewrite rule to individual interfaces. The switch automatically and implicitly applies the default or the custom EXP classifier and the default or the custom EXP rewrite rule to the appropriate MPLS-enabled interfaces. Because rewrite rules affect only egress interfaces, the switch applies the EXP rewrite rule only to those MPLS interfaces that are transmitting MPLS packets (not to the MPLS interfaces that are receiving the packets). This topic includes: • Guidelines for Using CoS Classifiers on CCCs on page 3064 • Using CoS Classifiers with IP over MPLS on page 3065 • Default Classifiers and Default Rewrite Rules on page 3065 • EXP Rewrite Rules on page 3065 • Policer on page 3066 • Schedulers on page 3066 Guidelines for Using CoS Classifiers on CCCs When you are configuring CoS for MPLS over circuit cross-connect (CCC), there are some additional guidelines, as follows: • You must explicitly bind a CoS classifier to the CCC interface on the ingress PE switch. • You cannot use more than one type of DSCP/IP precedence and not more than one type of IEEE 802.1p classifier on the CCC interfaces. Thus, if you configure one CCC interface to use DSCP1, you cannot configure another CCC interface to use DSCP2. Likewise, if you configure one CCC interface to use IEEE1, you cannot configure another 3064