QoS: RSVP Configuration Guide, Cisco IOS XE Release 3S
RSVP Refresh Reduction and Reliable Messaging
RSVP Refresh Reduction and Reliable Messaging
Last Updated: April 1, 2013
The RSVP Refresh Reduction and Reliable Messaging feature includes refresh reduction, which improves the scalability, latency, and reliability of Resource Reservation Protocol (RSVP) signaling to enhance network performance and message delivery.
History for the RSVP Refresh Reduction and Reliable Messaging Feature
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Prerequisites for RSVP Refresh Reduction and Reliable Messaging
RSVP must be configured on two or more devices within the network before you can use the RSVP Refresh Reduction and Reliable Messaging feature.
Restrictions for RSVP Refresh Reduction and Reliable Messaging
Multicast flows are not supported for the reliable messages and summary refresh features.
Information About RSVP Refresh Reduction and Reliable Messaging
Feature Design of RSVP Refresh Reduction and Reliable Messaging
RSVP is a network-control, soft-state protocol that enables Internet applications to obtain special qualities of service (QoS) for their data flows. As a soft-state protocol, RSVP requires that state be periodically refreshed. If refresh messages are not transmitted during a specified interval, RSVP state automatically times out and is deleted.
In a network that uses RSVP signaling, reliability and latency problems occur when an RSVP message is lost in transmission. A lost RSVP setup message can cause a delayed or failed reservation; a lost RSVP refresh message can cause a delay in the modification of a reservation or in a reservation timeout. Intolerant applications can fail as a result.
Reliability problems can also occur when there is excessive RSVP refresh message traffic caused by a large number of reservations in the network. Using summary refresh messages can improve reliability by significantly reducing the amount of RSVP refresh traffic.
Types of Messages in RSVP Refresh Reduction and Reliable Messaging
The RSVP Refresh Reduction and Reliable Messaging feature (see the figure below) includes refresh reduction, which improves the scalability, latency, and reliability of RSVP signaling by introducing the following extensions:
The reliable messages extension supports dependable message delivery among neighboring devices by implementing an acknowledgment mechanism that consists of a MESSAGE_ID object and a MESSAGE_ID_ACK object. The acknowledgments can be transmitted in an ACK message or piggybacked in other RSVP messages.
Each RSVP message contains one MESSAGE_ID object. If the ACK_Desired flag field is set within the MESSAGE_ID object, the receiver transmits a MESSAGE_ID_ACK object to the sender to confirm delivery.
A bundle message consists of several standard RSVP messages that are grouped into a single RSVP message.
A bundle message must contain at least one submessage. A submessage can be any RSVP message type other than another bundle message. Submessage types include Path, PathErr, Resv, ResvTear, ResvErr, ResvConf, and ACK.
Bundle messages are addressed directly to the RSVP neighbor. The bundle header immediately follows the IP header, and there is no intermediate transport header.
When a device receives a bundle message that is not addressed to one of its local IP addresses, it forwards the message.
Summary Refresh Messages
A summary refresh message supports the refreshing of RSVP state without the transmission of conventional Path and Resv messages. Therefore, the amount of information that must be transmitted and processed to maintain RSVP state synchronization is greatly reduced.
A summary refresh message carries a set of MESSAGE_ID objects that identify the Path and Resv states that should be refreshed. When an RSVP node receives a summary refresh message, the node matches each received MESSAGE_ID object with the locally installed Path or Resv state. If the MESSAGE_ID objects match the local state, the state is updated as if a standard RSVP refresh message were received. However, if a MESSAGE_ID object does not match the receiver's local state, the receiver notifies the sender of the summary refresh message by transmitting a MESSAGE_ID_NACK object.
When a summary refresh message is used to refresh the state of an RSVP session, the transmission of conventional refresh messages is suppressed. The summary refresh extension cannot be used for a Path or Resv message that contains changes to a previously advertised state. Also, only a state that was previously advertised in Path or Resv messages containing MESSAGE_ID objects can be refreshed by using a summary refresh message.
Benefits of RSVP Refresh Reduction and Reliable Messaging
Enhanced Network Performance
Refresh reduction reduces the volume of steady-state network traffic generated, the amount of CPU resources used, and the response time, thereby enhancing network performance.
How to Configure RSVP Refresh Reduction and Reliable Messaging
Enabling RSVP on an Interface
Enabling RSVP Refresh Reduction
Verifying RSVP Refresh Reduction and Reliable Messaging
Perform the following task to verify that the RSVP Refresh Reduction and Reliable Messaging feature is functioning.
Configuration Examples for RSVP Refresh Reduction and Reliable Messaging
Example RSVP Refresh Reduction and Reliable Messaging
In the following example, RSVP refresh reduction is enabled:
Device# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Device(config)# interface Ethernet1 Device(config-if)# ip rsvp bandwidth 7500 7500 Device(config-if)# exit Device(config)# ip rsvp signalling refresh reduction Device(config)# end
The following example verifies that RSVP refresh reduction is enabled:
Device# show running-config Building configuration... Current configuration : 1503 bytes ! version 12.2 no service single-slot-reload-enable service timestamps debug uptime service timestamps log uptime no service password-encryption service internal ! hostname Device ! no logging buffered logging rate-limit console 10 except errors ! ip subnet-zero ip cef ! ip multicast-routing no ip dhcp-client network-discovery lcp max-session-starts 0 mpls traffic-eng tunnels ! ! interface Loopback0 ip address 192.168.1.1 255.255.255.0 ip rsvp bandwidth 1705033 1705033 ! interface Tunnel777 no ip address shutdown ! interface Ethernet0 ip address 192.168.0.195 255.0.0.0 no ip mroute-cache media-type 10BaseT ! interface Ethernet1 ip address 192.168.5.2 255.255.255.0 no ip redirects no ip proxy-arp ip pim dense-mode no ip mroute-cache media-type 10BaseT ip rsvp bandwidth 7500 7500 ! interface Ethernet2 ip address 192.168.1.2 255.255.255.0 no ip redirects no ip proxy-arp ip pim dense-mode no ip mroute-cache media-type 10BaseT mpls traffic-eng tunnels ip rsvp bandwidth 7500 7500 ! interface Ethernet3 ip address 192.168.2.2 255.255.255.0 ip pim dense-mode media-type 10BaseT mpls traffic-eng tunnels ! ! router eigrp 17 network 192.168.0.0 network 192.168.5.0 network 192.168.12.0 network 192.168.30.0 auto-summary no eigrp log-neighbor-changes ! ip classless no ip http server ip rsvp signalling refresh reduction ! ! ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login transport input pad v120 telnet rlogin udptn ! end
The following sections provide references related to the RSVP Refresh Reduction and Reliable Messaging feature.
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