Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring MPLS and H-VPLS (Rev. 03)
Resource Reservation Protocol Traffic Engineering (RSVP-TE)© 2008 Foundry Networks, Inc
Page 76 of 113
PLR considers an LSP to have asked for local protection if the “local protection desired” flag is set
in the SESSION_ATTRIBUTE object and/or the FAST_REROUTE object is included. If the
FAST_REROUTE object is included, it considers providing Facility Backup if the “facility backup
desired”flag is set.
Signaling a Backup Path
A number of objectives must be met to obtain a satisfactory signaling solution. These are as
follows:
1. Unambiguously and uniquely identifying backup paths.
2. Unambiguously associating protected LSPs with their backup paths.
3. Working with both global and non-global label spaces.
4. Allowing merging of backup paths.
5. Maintaining RSVP state during and after fail-over.
LSP tunnels are identified by a combination of the SESSION and SENDER_TEMPLATE objects.
The relevant fields are as follows.
IPv4 tunnel end point address
IPv4 address of the egress node for the tunnel.
Tunnel ID
A 16-bit identifier used in the SESSION that remains constant over the life of the tunnel.
Extended Tunnel ID
A 32-bit (IPv4) identifier used in the SESSION that remains constant over the life of the tunnel.
Normally it is set to all zero. Ingress nodes that wish to narrow the scope of a SESSION to the
ingress-egress pair may place their IP address here as a globally unique identifier.
IPv4 tunnel sender address
IPv4 address for a sender node.
LSP ID
A 16-bit identifier used in the SENDER_TEMPLATE and the FILTER_SPEC, which can be
changed to allow a sender to share resources with itself.
The first three of these are in the SESSION object and are the basic identification for the tunnel.
Setting the "Extended Tunnel ID" to an IP address of the head-end LSR allows the scope of the
SESSION to be narrowed to only LSPs sent by that LSR. A backup LSP is considered part of the
same session as its protected LSP; therefore these three cannot be varied.
The last two are in the SENDER_TEMPLATE. Multiple LSPs in the same SESSION may be
protected and may take different routes; this is common when a tunnel is rerouted using make-
before-break. A backup path must be clearly identified with its protected LSP to allow correct
merging and state treatment. Therefore, a backup path must inherit its LSP ID from the associated
protected LSP. Thus, the only field in the SESSION and SENDER_TEMPLATE objects that
could be varied between a backup path and a protected LSP is the "IPv4 tunnel sender address" in
the SENDER_TEMPLATE.
Signaling for Facility Protection
A PLR may use one or more bypass tunnels to protect against the failure of a link and/or a node.
These bypass tunnels may be set up in advance or may be dynamically created as new protected
LSPs are signaled.