Zte ZXR10 8900 Product Description page 75

main LSP. The ultimate aim of MPLS TE fast reroute is to protect main path by using
fast reroute tunnel to bypass the link or node with failure.
Fast reroute LSP and main LSP establishment involves every component of MPLS TE
system.
MPLS TE fast reroute is based on RSVP TE implementation and conforms to RFC4090
protocol.
There are two ways to implement fast reroute:
•
One-to-one Backup: establish one backup protective LSP for a main LSP. The
backup LSP is called Detour LSP.
•
Facility Backup: one-to-multiple backup protection, establish one backup protective
LSP for multiple main LSP. The backup LSP becomes Bypass Tunnel.
Facility way is often adopted in MPLS TE FRR deployment. Establishment of main LSP
is the same with that of common LSP. RSVP sends PATH message to downstream from
the head node hop-by-hop. RSVP distributes labels when processing RESV message,
reserve resources and establish LSP. Bypass Tunnel could be established in two ways:
manual and automatic.
Bypass Tunnel could be manually configured to protect physical interface of the tunnel
when main LSP FRR is not configured with FRR. Manual Bypass Tunnel establishment
is triggered by PLR manual configuration. It is basically the same with that of common
LSP with the difference that it cannot configure fast reroute attribute. That is to say,
Bypass Tunnel couldn't act as main LSP at the same time. And LSP couldn't be
protected in nested way.
Automatic Bypass Tunnel simplifies manual configuration. When main LSP needs
protection from FRR, PLR can select or automatically create a Bypass Tunnel to protect
the main LSP.
Fast Reroute can implement link protection or node protection. When Bypass Tunnel is
needed, the links or nodes need protecting should be planned and which to choose
between link protection and node protection should be decided. Node protection can
also protect the link between the nodes being protected and PLR nodes being protected.
•
Bypass Tunnel is usually idle without forwarding data packets. If Bypass Tunnel is
also required to take common data packets forwarding task besides protecting main
LSP, enough bandwidth should be configured.
When link or node failure occurs, data packets can be automatically switched to
protective link if FRR is configured at interface. When link or data recovers from the
failure, normal forwarding path will automatically reconstruct.
MPLS TE FRR usually needs to be deployed in MPLS TE network, which is determined
by the feature of MPLS TE itself. In pure IP network, when local failure occurs, packets
will be forwarded via other available routes to the same destination. This mechanism
alone can implement local failure protection quickly before route changes caused by
failure spreading to the whole network. In MPLS network without configuring TE, LDP
establishing LSP based on DU is often adopted. When local failure occurs, LDP initiates
LSP establishment to upstream nodes if there are other available routes. Since needs
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ZXR10 8900 Product Description
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