3Com Switch 8807, Configuration Manual

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Concepts Related to VPLS 637
PW signaling
PW signaling (pseudowire signaling) protocol on which VPLS bases is used to
establish and maintain PW. It can also be used to automatically discover peer PEs
of VSIs. Currently, PW signaling protocol includes label distribution protocol (LDP)
and border gateway protocol (BGP).
Service quality
Service quality maps priority information in the headers of user’s layer 2 packets
and QoS information carried by VSI instances to QoS priority of the public network
before the forwarding of the packets. This feature generally requires the MPLS
network to support traffic-engineering.
As shown in Figure 154, CE3 transmits uplink layer 2 packets to PE1 through AC.
When PE1 receives the packets, the forwarder chooses PW to forward them.
According to PW forwarding entries, the system generates two layers of MPLS
labels (private network labels are used to mark the PWs, and public network labels
are used to pass through tunnels to PE2) and the Ethernet headers of the public
network. After the packets reach PE2 through public network tunnel, the system
pops out private network labels (public network labels have already been popped
out on P device through PHP). PE2 forwarder chooses an AC to forward layer 2
packets from CE3 to CE1.
Concepts Related to
VPLS
MPLS L2VPN An MPLS L2VPN is a VPN that transparently transmits user’s layer 2 packets over
MPLS network. In user’s perspective, an MPLS network is a layer 2 switching
network, over which layer 2 connections can be set up among different sites.
MPLS L2VPN includes VLL and VPLS.
VPLS
This is a kind of point-to-multipoint L2VPN service provided on public networks.
VPLS can connect user sites in different areas together over MAN/WAN as if they
are in a single LAN.
VLL
This is a kind of point-to-point L2VPN service provided on public networks. VLL
can connect two sites with each other as if they are directly connected by cables.
However, it cannot provide switching directly between multiple points at the
service provider level.
CE It is a user device that is directly connected with a service provider’s device.
PE It is an edge router in backbone network connected with CEs. PE is responsible for
VPN service access, it implement packet mapping and forwarding from private
networks to public network tunnels, and vice versa. It has two types: UPE and NPE.
UPE
It is a user-facing PE device, a kind of convergence device for users to access the
VPN.