Panasonic NN46240-710 - Manual (Page 161)

5 VPLS troubleshooting
Nortel Secure Router 8000 Series
_________ Troubleshooting - VPN
5.1 VPLS overview
This section covers the following topics:
• Related concepts of VPLS
• Encapsulation type
• MTU
The development of Ethernet has made it a dominant LAN technology and it is increasingly
applied as an access solution in the Metropolitan Area Network (MAN) and in the Wide Area
Network (WAN).
Virtual Private LAN Service (VPLS) connects more than one Ethernet LAN segment through
the Packet Switched Network (PSN), to enable them to operate as if in a LAN.
VPLS is also called Transparent LAN Service (TLS) or Virtual Private Switched Network
service (VPSN). Unlike the common Layer 2 VPN point-to-point service, service providers use
VPLS to offer Ethernet-based multi-point service over the MPLS backbone network.
5.1.1 Related concepts of VPLS
PW
Tunnel
AC
A Pseudo Wire (PW) is a virtual connection that transmits frames between two provider edges
(PE). In the VPLS packet, PW corresponds to the inner label.
The PE sets up and maintains a PW, at both ends.
The setup of a PW is a process of generating local and remote labels by using signaling.
Currently, the Secure Router 8000 Series supports Label Distribution Protocol (LDP) signaling
and Border Gateway Protocol (BGP) signaling.
The following conditions must be met before the PW status is Up:
• At least one AC is Up at the local end.
• At least one Virtual Switch Instance (VSI) is Up at the remote end, and the negotiation
parameters are consistent at both ends of the PW.
A tunnel is a direct virtual path, that transparently transmits data.
The VPLS tunnel carries PWs. Multiple PWs can be delivered on a single tunnel. To set up a
PW to the remote end, a tunnel to the remote end must be available first.
The tunnel is set up by the tunnel management module. VPLS queries the tunnel against the
tunnel management module according to the remote destination address of a PW If no tunnel to
the remote destination address exists, the PW cannot be set up.
VPLS supports using the tunnel policy to choose a tunnel.
The customer edge (CE) connects the PE through the Attachment Circuit (AC) in a Layer 2
VPN.
5-2 Nortel Networks Inc. Issue 5.3 (30 March2009)