Classifying Traffic For Differentiated Services; Table 29: Incoming L-Lsp Phb Determination - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

5.
Related Topics

Classifying Traffic for Differentiated Services

In a differentiated services domain, traffic is classified into a behavior aggregate (BA),
based on the type of diff-serv behavior for the traffic. At each node, traffic belonging
to a particular BA is mapped to the corresponding per-hop behavior (PHB), which
provides the scheduling behavior and drop probability required by the traffic.
MPLS uses the EXP bits in the shim header to support differentiated services. The
JUNOSe software supports both statically configured and signaled mapping between
the EXP bits and the PHB of traffic.
In a signaled environment, you can configure on the ingress node the set of PHBs
that a tunnel supports, and then the set of PHBs is signaled end to end.
To support differentiated services, MPLS employs two types of LSPs: E-LSPs and
L-LSPs. The two types differ in how their PHB is determined. In the JUNOSe software,
the PHB is a combination of traffic class (also called per-hop scheduling class, or PSC)
and drop precedence (color).

Table 29: Incoming L-LSP PHB Determination

host1(config-policy-list-classifier-group)#color green
host1(config)#interface pos 0/0
host1(config-subif)ip policy output core-ip-policy
For traffic from the core, configure per-VR rules or per-LSP policies to set the
traffic-class/color combination and therefore shape the egress traffic
queue according to the value of the EXP bits in the base label. This action causes
host1(config)#mpls match exp-bits <value> set traffic-class <className> color
Configuring MPLS and Differentiated Services on page 299
Configuring EXP Bits for Differentiated Services on page 300
Classifying Traffic for Differentiated Services on page 303
E-LSPs (EXP-inferred-PSC LSP) can transport as many as eight BAs. For E-LSPs,
the traffic's PHB is learned from the MPLS shim header.
L-LSPs (Label-only-inferred-PSC LSP) transport a single PSC. The PHB is
determined from a combination of the packet's label, which indicates the traffic
class, and the EXP field of the shim header, which indicates the drop precedence.
Table 29 on page 303 indicates how the PSC (column 1) is combined with
the EXP field (column 2) to determine the PHB for incoming traffic on L-LSPs.
PSC + EXP Field
BE 000
CSn 000
= PHB
BE
CSn
Classifying Traffic for Differentiated Services
Chapter 3: Configuring MPLS
303