R2511-HP MSR Router Series MPLS Configuration Guide(V5)

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Mode
VC label encapsulation
and distribution
Advantages and disadvantages
Application
scenario
Martini
VC label encapsulation:
two levels of labels
VC label distribution: LDP
Advantages:
• On a carrier network, only PEs need to save a
few VC label to LSP mappings. The P devices do
not need to save any Layer 2 VPN information.
• To add a new VC, you only need to configure
the PEs of the VC, without interrupting network
operation.
Disadvantage: Supports only remote connections.
Sparse Layer 2
connections,
such as a star
topology.
Kompella
VC label encapsulation:
two levels of labels
VC label distribution:
BGP
Advantages:
• Introduces the concept of VPN to prevent CEs in
different VPNs from communicating with each
other.
• Uses label blocks to assign additional labels to
user VPNs for future use, greatly reducing the
VPN deployment and configuration workload
in the case of expansion.
• To add a CE to the network, you only need to
configure the PE to which the CE is connected.
The configuration workload is small and does
not interrupt network operation.
• Supports local and remote connections.
Disadvantage: The implementation is relatively
complicated.
Full-mesh
network.
VC encapsulations types
Before adding a VC label to a Layer 2 packet, a PE encapsulates the Layer 2 packet according to the AC
link type. VC encapsulation types and AC link types are closely related, as shown in Table 2.
Table 2 Relationship b
etween AC link types and VC encapsulation types
AC link type VC encapsulation type
PPP PPP
HDLC HDLC
FR
FR DLCI mode
FR port mode
Ethernet
Ethernet
VLAN
ATM ATM AAL5 transparent transport
VC encapsulation type for PPP/HDLC links
If the AC link type is PPP, the VC encapsulation type is PPP. If the AC link type is HDLC, the VC
encapsulation type is HDLC.
In PPP encapsulation or HDLC encapsulation mode, a PE processes a PPP or HDLC packet as follows: