Brocade Network Advisor SAN + IP User Manual v12.1.0 - Manual (Page 1395)

1346 Brocade Network Advisor SAN + IP User Manual
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VLL manager
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The PE router pushes two labels onto the packet:
• The inner VC label is used for determining what happens to the packet once it reaches the
VLL peer. This label is significant only to the VLL peer.
• The outer tunnel label is used for forwarding the packet through the MPLS domain. This
label corresponds to an RSVP-signalled tunnel LSP.
After applying the two labels to the packet, the PE router forwards it to the next LSR in the
tunnel LSP.
3. The penultimate LSR in the tunnel LSP removes the tunnel label and forwards the packet (now
with the VC label as the top label) to the PE router at the other edge of the MPLS domain.
4. The VLL peer at the egress of the tunnel LSP examines the VC label. This VC label is mapped to
an endpoint for the VLL. The endpoint of a VLL specifies what happens to packets exiting the
VLL.
The endpoint can specify either an untagged port or a tagged port. For untagged ports, the
endpoint consists of an interface. For tagged ports, the endpoint consists of an interface and
the Outer VLAN ID and Inner VLAN ID. The egress LER removes the VC label and forwards the
packet out the interface specified as the endpoint. If the endpoint is a tagged port, the product
transmits the packet with the specified VLAN ID, forwarding it out the specified interface to the
CE product.
The two VLL peers advertise VC labels to each other using the Label Distribution Protocol (LDP).
Each PE router attempts to initiate an LDP session with its VLL peer. After the LDP session is
established, the locally assigned VC label, along with a VLL VC ID, is advertised to the VLL peer. In a
similar way, the PE also learns the remotely assigned VC label from the VLL peer. Alternatively, you
can configure static local and remote VC labels manually on both VLL peers; in this case, LDP is not
used.
NOTE
If MTUs are mismatched on both sides of a VLL session, the session does not come up.
VLL manager
The VLL Manager allows you to manage VLL instances. You can perform the following tasks from
the VLL manager:
• View current VLL instances.
• View VLL configurations.
• Add, edit, duplicate, or delete VLL instances.
NOTE
When configuring a VLL, a check is made to determine if there are LSPs configured for the target
products. You may proceed with configuration, but an LSP is needed for a working connection.