Mpls And Routing Protocols; Applications Of Mpls - H3C S9500 Series Operation Manual

Operation Manual – MPLS Basics
H3C S9500 Series Routing Switches
An LER forwards both labeled packets and IP packets on the forwarding plane and
therefore uses both the LFIB and the FIB. An ordinary LSR only needs to forward
labeled packets and therefore uses only the LFIB.

1.1.3 MPLS and Routing Protocols

When establishing an LSP hop by hop, LDP uses the information in the routing tables of
the LSRs along the path to determine the next hop. The information in the routing tables
is provided by routing protocols such as IGPs and BGP. LDP only uses the routing
information indirectly; it has no direct association with routing protocols.
On the other hand, existing protocols such as BGP and RSVP can be extended to
support label distribution.
In MPLS applications, it may be necessary to extend some routing protocols. For
example, MPLS-based VPN applications requires that BGP be extended to propagate
VPN routing information, and MPLS-based traffic engineering (TE) requires that OSPF
or IS-IS be extended to carry link state information.

1.1.4 Applications of MPLS

By integrating both Layer 2 fast switching and Layer 3 routing and forwarding, MPLS
features improved route lookup speed. However, with the development of the
application specific integrated circuit (ASIC) technology, route lookup speed is no
longer the bottleneck hindering network development. This makes MPLS not so
outstanding in improving forwarding speed.
Nonetheless, MPLS can easily implement the seamless integration between IP
networks and Layer 2 networks of ATM, frame relay, and the like, and offer better
solutions to quality of service (QoS), traffic engineering (TE), and virtual private network
(VPN) applications thanks to the following advantages.
I. MPLS-based VPN
Traditional VPN depends on tunneling protocols such as GRE, L2TP, and PPTP to
transport data between private networks across public networks, while an LSP itself is a
tunnel over public networks. Therefore, implementation of VPN using MPLS is of
natural advantages.
MPLS-based VPN connects geographically different branches of a private network to
form a united network by using LSPs. MPLS-based VPN also supports the
interconnection between VPNs.
Chapter 1 MPLS Basics Configuration
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