Mpls And Routing Protocols; Mpls And Other Protocols; Mpls Extension By Rsvp; Mpls Application - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
information is the exact designation of all the LSRs along the path; and loose explicit
routing where only some of the LSRs along the path are specified.

1.5 MPLS and Other Protocols

1.5.1 MPLS and Routing Protocols

When LDP establishes LSP in hop-by-hop mode, the next hop will be determined by
using the information that is usually collected via such routing protocols as IGP, BGP in
each LSR route forwarding table on the way. However, LDP just uses the routing
information indirectly, rather than being associated with various routing protocols
directly.
On the other hand, although LDP is the special protocol for implementing label
distribution, but it is not the sole protocol for label distribution. The existing protocols
such as BGP, RSVP, after being extended, can also support MPLS label distribution.
For some MPLS applications, it is also necessary to extend some routing protocols. For
example, MPLS-based VPN application needs the extension of BGP so that the BGP is
capable of supporting the sending of VPN routing information. In addition, MPLS-based
Traffic Engineering (TE) needs the extension of OSPF or IS-IS protocol to carry link
status information.

1.5.2 MPLS Extension by RSVP

Resource Reservation Protocol (RSVP), after being extended, can support MPLS label
distribution. At the same time, while transmitting label-binding message, it is also
capable of carrying resource reservation information. The LSP established in this way
is of resource reservation function, namely, the LSRs on the way can distribute some
resources for this LSP to ensure the service transmitted on it.
The extension of RSVP mainly refers to adding new objects in its Path message and
Resv message. Besides carrying label binding information, these new objects are also
capable of carrying the constrain information for searching path for the LSRs on the
way, thus supporting LSP constraining function on routing. The extended RSVP also
supports fast rerouting, namely, when it is necessary to change LSP under some
condition, the original service flow can be rerouted to the newly established LSP
without interrupting the customer service.

1.6 MPLS Application

1.6.1 MPLS-Based VPN

For traditional VPN, the transmission of the data flow between private networks on the
public network is usually realized via such tunneling protocols as GRE, L2TP and PPTP,
and LSP itself is the tunnel on the public network. The implementation of VPN using
MPLS is of natural advantages. MPLS-based VPN connects the geographically
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Chapter 1 MPLS Architecture