If a downstream LSR determines that it received an erroneous path message, it sends
a patherr message to the sender. If a reservation (label) request fails, the request
initiator sends a resverr message to the downstream LSRs. Both of these messages
are advisory and do not alter path or resv state.
RSVP-TE State Refresh and Reliability
RSVP-TE employs refresh messages to synchronize state between neighbors and to
recover from lost RSVP-TE messages of other types. RSVP-TE by default does not
provide for reliable transmission. Each node is responsible for the transmission of
RSVP-TE messages to its neighbors and relies on periodic state refreshes to recover
from lost messages.
RSVP-TE refresh reduction provides a means to increase reliability while reducing
message handling and synchronization overhead. Issuing the
mpls rsvp
refresh-reduction
command enables the following features:
■
The message ID object is included in RSVP-TE messages to provide a unique
message ID on a per-hop basis. In refresh messages, it indicates to the receiving
node that the message is a refresh message, eliminating the need for the node
to completely analyze the message and thus reducing the processing overhead
at the receiver.
■
RSVP-TE uses a message acknowledgment mechanism to support reliable
message delivery on a per-hop basis. Messages that include the message ID
object also include a request for acknowledgment. Upon receipt, the receiving
node returns a message ack object, enabling the sending node to determine
whether a message was lost and triggering a retransmission as necessary.
■
Summary refresh (srefresh) messages refresh the state previously advertised in
path or resv messages that included message ID objects. The srefresh message
carries the unique message ID as state identifier, eliminating the need to send
whole refresh messages and reducing the overhead needed to maintain RSVP-TE
state synchronization. This method maintains RSVP-TE's ability to indicate when
the state is lost and to adjust to changes in routing. The srefresh message can
carry message IDs for multiple RSVP-TE sessions.
Issuing the
mpls rsvp message-bundling
command enables RSVP-TE to use bundle
messages, each of which includes multiple standard RSVP-TE messages, to reduce
the overall message processing overhead.
BGP Signaling
You can use BGP as a label distribution protocol both for IP routes and for VPN routes.
When BGP distributes a particular IP route, it can also distribute an MPLS label that
has been mapped to that route, as described in RFC 3107. The MP-BGP extensions
(RFC 2858) enable the BGP update message to carry both the route and the label
mapping information for the route. The label is encoded into the NLRI field of the
attribute, and the SAFI field is set to 4 to indicate that the NLRI contains a label. A
BGP speaker can use BGP to send labels to a particular BGP peer only if that peer
advertised the capability to process update messages with SAFI 4. BGP speakers
232
■
MPLS Label Distribution Protocols
JUNOSe 11.0.x BGP and MPLS Configuration Guide
Содержание JUNOSE
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Страница 37: ...Part 1 Border Gateway Protocol Configuring BGP Routing on page 3 Border Gateway Protocol 1...
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Страница 234: ...198 Monitoring BGP JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 236: ...200 Multiprotocol Layer Switching JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 298: ...262 Point to Multipoint LSPs Configuration JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 346: ...310 Example Traffic Class Configuration for Differentiated Services JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 535: ...There is no no version See undebug ip mbgp Monitoring BGP MPLS VPNs 499 Chapter 5 Configuring BGP MPLS Applications...
Страница 536: ...500 Monitoring BGP MPLS VPNs JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 538: ...502 Layer 2 Services Over MPLS JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 592: ...556 Multiple ATM Virtual Circuits over a Single Pseudowire Example JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 604: ...568 Virtual Private LAN Service JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 618: ...582 VPLS References JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 642: ...606 VPLS Configuration Example with LDP Signaling JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 674: ...638 Virtual Private Wire Service JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 718: ...682 Monitoring MPLS Forwarding Table for VPWS JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 719: ...Part 6 Index Index on page 685 Index 683...
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