Tunneling Model For Differentiated Services Overview; Pipe And Short Pipe Models - Juniper JUNOSE SOFTWARE FOR E SERIES 11.0.X - BGP AND MPLS CONFIGURATION GUIDE 2009-12-30 Configuration Manual

Consequently, when the last LSP is torn down between the interfaces, the BFD session
is no longer required and is brought down as well.
Each adjacent pair of peers negotiates an acceptable transmit interval for BFD packets.
The negotiated value can be different on each peer. Each peer then calculates a BFD
liveness detection interval. When a peer does not receive a BFD packet within the
detection interval, it declares the BFD session to be down and purges all routes
learned from the remote peer.
Related Topics

Tunneling Model for Differentiated Services Overview

The JUNOSe software supports both the pipe model and the uniform model for
tunneling with the mpls tunnel-model command. The router also provides a way
to implement the functionality of the short pipe model for IP packets.

Pipe and Short Pipe Models

In the pipe and short pipe models, any traffic conditioning (that is, in a pure JUNOSe
environment, a change in traffic class/color combination) that is applied when traffic
goes through the tunnel has no effect on the EXP bits coding in the inner header. In
other words, when traffic exits an LSP (when a label is popped) or when traffic enters
an LSP, the inner header's EXP bits coding is not changed.
The pipe and short pipe models differ in the header that the tunnel egress uses when
it determines the PHB of an incoming packet. With the short pipe model, the tunnel
egress uses an inner header that is used for forwarding. With the pipe model, the
outermost label is always used. Because of this, you cannot use PHP with the pipe
model.
The pipe model is the default JUNOSe behavior, which you can configure with the
mpls tunnel-model command. You cannot configure the short pipe model with this
command. In fact, on ingress line modules the traffic class/color combination is
always determined from the outermost label, so fabric queuing is also based on the
outermost label. However, on the egress line module you can achieve the queuing
behavior expected with the short pipe model by attaching IP policies to egress
interfaces to reset the traffic class/color combinations based on the IP header.
However, this method requires that the outgoing packets to be IP. If the outgoing
packets are MPLS, then this short pipe model of queuing is not supported.
At least one RSVP-TE LSP exists between (passes through) a pair of directly
connected RSVP-TE major interfaces.
Both interfaces are BFD-enabled.
For general information about configuring and monitoring the BFD protocol, see
JUNOSe IP Services Configuration Guide.
Tunneling Model for Differentiated Services Overview
Chapter 2: MPLS Overview
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