Specifications
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Internet routes but the core is only involved in the IGP and MPLS signaling) and
where traffic engineering is not required.
3.3.2 Tunneling LDP LSPs in RSVP LSPs
LDP is intended to be used as the label distribution protocol of choice for non-
traffic engineered applications. The de-facto standard for label distribution for
traffic engineering applications is RSVP (MPLS-RSVP).
If a provider wants to provide services like L2 VPNS or L3 VPNS (RFC2547) they
must use LDP and thus lose the ability to traffic engineer their networks.
This feature extends the Junos existing LDP implementation to remove the
restriction of choosing between having traffic engineering and having a large
network provide advanced services that use MPLS. This change allows a traffic
engineered cored with a larger cloud around the core that runs LDP. This
approach combines the advantages of RSVP-signaled traffic engineering with the
ease of configuration and scalability.
The LDP specification has hooks for supporting LDP session between LSRs that
are not directly connected at the link layer. Thus Junos effectively tunnels the
LDP LSP through an RSVP signaled LSP when the former is traversing the traffic
engineered core and this is done without any changes to the underlying LDP
protocol.
Only the data traffic traversing the LDP LSP gets tunneled. The control traffic for
setting up the LDP session between non-directly connected LSRS goes hop by
hop.
MPLS
MPLS
TE Core
TE Core
LDP LDP
LDP
LDP
LDP
LDP
LDP
LDP
LDP LDP