Operation Manual – MPLS Basics
H3C S9500 Series Routing Switches
Chapter 1 MPLS Basics Configuration
1-8
CE 1
PE 1
PE 3
CE 3
PE 2
CE 2
VPN 1
VPN 2
VPN 3
MPLS backbone
Figure 1-6
MPLS-based VPN
Figure 1-6
shows the basic structure of an MPLS-based VPN. Two of the fundamental
components are customer edge device (CE) and service provider edge router (PE). A
CE can be a router, switch, or host. All PEs are on the backbone network.
PE is responsible for managing VPN users, establishing LSP connections between
PEs, and allocating routes among different branches of the same VPN. Route
allocation among PEs is usually implemented by LDP or extended BGP.
MPLS-based VPN supports IP address multiplexing between branches and
interconnection between VPNs. Compared with a traditional route, a VPN route
requires the branch and VPN identification information. Therefore, it is necessary to
extend BGP to carry VPN routing information.
II. MPLS-based TE
MPLS-based TE and the Diff-Serv feature allow not only high network utilization, but
different levels of services based on traffic precedence, providing voice and video
streams with services of low delay, low packet loss, and stable bandwidth guarantee.
Since TE is more difficult to be implemented on an entire network, the Diff-Serv model
is often adopted in practical networking schemes.
The Diff-Serv model maps a service to a certain service class at the network edge
according to the QoS requirement of the service. The DS field (derived from the TOS
field) in the IP packet identifies the service uniquely. Then, each node in the backbone
network performs the preset service policies to diversified services according to the
field to ensure the corresponding QoS.
The QoS classification in Diff-Serv is similar to the MPLS label distribution. In fact, the
MPLS-based Diff-Serv is implemented by integrating the DS distribution into the MPLS
label distribution.
