Table Of Contents
RSVP Refresh Reduction and Reliable Messaging
The RSVP Refresh Reduction and Reliable Messaging feature includes refresh reduction, which improves the scalability, latency, and reliability of Resource Reservation Protocol (RSVP) signalling to enhance network performance and message delivery.
Feature Specifications for RSVP Refresh Reduction and Reliable Messaging
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Prerequisites for RSVP Refresh Reduction and Reliable Messaging
RSVP must be configured on two or more routers 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 messaging and summary refresh features.
Information About RSVP Refresh Reduction and Reliable Messaging
To configure RSVP Refresh Reduction and Reliable Messaging, you need to understand the following concepts:
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 using 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.
Note RSVP packets consist of headers that identify the types of messages, and object fields that contain attributes and properties describing how to interpret and act on the content.
Types of Messages in RSVP Refresh Reduction and Reliable Messaging
The RSVP Refresh Reduction and Reliable Messaging feature includes refresh reduction, which improves the scalability, latency, and reliability of RSVP signalling by introducing the following extensions:
•Reliable messages (MESSAGE_ID, MESSAGE_ID_ACK objects (Figure 1), and ACK messages)
•Bundle messages (reception and processing only)
•Summary refresh messages (MESSAGE_ID_LIST and MESSAGE_ID_NACK objects)
Figure 1 RSVP Refresh Reduction and Reliable Messaging
The reliable messages extension supports dependable message delivery among neighboring routers 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, then the receiver transmits a MESSAGE_ID_ACK object to the sender to confirm delivery.
A bundle message consists of several standard RSVP messages 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 router receives a bundle message that is not addressed to one of its local IP addresses, it forwards the message.
Note In this release, bundle messages can be received, but not sent.
Summary Refresh Messages
A summary refresh message supports refreshing the 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 are 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.
Improved Message Delivery
The MESSAGE_ID and the MESSAGE_ID_ACK objects ensure the reliable delivery of messages and support rapid state refresh when a network problem occurs. For example, MESSAGE_ID_ACK objects are used to detect link transmission losses.
How to Configure RSVP Refresh Reduction and Reliable Messaging
This section contains the following procedures:
•Enabling RSVP on an Interface (required)
•Enabling RSVP Refresh Reduction (required)
Enabling RSVP on an Interface
Perform this task to enable RSVP on an interface.
2. configure terminal
3. interface [type number]
4. ip rsvp bandwidth [interface-kbps [sub-pool]]
Enabling RSVP Refresh Reduction
Perform this task to enable RSVP refresh reduction.
2. configure terminal
3. ip rsvp signalling refresh reduction
Verifying RSVP Refresh Reduction and Reliable Messaging
Perform this task to verify that the RSVP Refresh Reduction and Reliable Messaging feature is functioning.
2. clear ip rsvp counters [confirm]
3. show ip rsvp
4. show ip rsvp counters [interface interface_unit | summary | neighbor]
5. show ip rsvp interface [interface-type interface-number] [detail]
6. show ip rsvp neighbor [detail]
Configuration Examples for RSVP Refresh Reduction and Reliable Messaging
This section provides the following configuration example:
RSVP Refresh Reduction and Reliable Messaging Example
In the following example, RSVP refresh reduction is enabled:Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# interface Ethernet1Router(config-if)# ip rsvp bandwidth 7500 7500Router(config-if)# exitRouter(config)# ip rsvp signalling refresh reductionRouter(config)# end
The following example verifies that RSVP refresh reduction is enabled:Router# show running-configBuilding configuration...Current configuration : 1503 bytes!version 12.2no service single-slot-reload-enableservice timestamps debug uptimeservice timestamps log uptimeno service password-encryptionservice internal!hostname router!no logging bufferedlogging rate-limit console 10 except errors!ip subnet-zeroip cef!ip multicast-routingno ip dhcp-client network-discoverylcp max-session-starts 0mpls traffic-eng tunnels!!interface Loopback0ip address 192.168.1.1 255.255.255.0ip rsvp bandwidth 1705033 1705033!interface Tunnel777no ip addressshutdown!interface Ethernet0ip address 192.168.0.195 255.0.0.0no ip mroute-cachemedia-type 10BaseT!interface Ethernet1ip address 192.168.5.2 255.255.255.0no ip redirectsno ip proxy-arpip pim dense-modeno ip mroute-cachemedia-type 10BaseTip rsvp bandwidth 7500 7500!interface Ethernet2ip address 192.168.1.2 255.255.255.0no ip redirectsno ip proxy-arpip pim dense-modeno ip mroute-cachemedia-type 10BaseTmpls traffic-eng tunnelsip rsvp bandwidth 7500 7500!interface Ethernet3ip address 192.168.2.2 255.255.255.0ip pim dense-modemedia-type 10BaseTmpls traffic-eng tunnels!!router eigrp 17network 192.168.0.0network 192.168.5.0network 192.168.12.0network 192.168.30.0auto-summaryno eigrp log-neighbor-changes!ip classlessno ip http serverip rsvp signalling refresh reduction!!!!line con 0exec-timeout 0 0line aux 0line vty 0 4logintransport input pad v120 telnet rlogin udptn!end
The following sections provide additional references related to the RSVP Refresh Reduction and Reliable Messaging feature:
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
MIBs1 MIBs Link
•RFC 2206, RSVP Management Information Base using SMIv2
•RFC 2702, Requirements for Traffic Engineering over MPLS
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
1 Not all supported MIBs are listed.
Resource Reservation Protocol
RSVP—Version 1 Message Processing Rules
The Use of RSVP with IETF Integrated Services
Specification of the Controlled-Load Network Element Service
Common Open Policy Service (COPS) Usage for RSVP
RSVP Extensions for Policy Control
SBM Subnet Bandwidth Manager: A Protocol for RSVP-based Admission Control over IEEE 802-style networks
RSVP Refresh Overhead Reduction Extensions
Format of the RSVP DCLASS Object
1 Not all supported RFCs are listed.
This section documents new and modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command reference publications.
ip rsvp signalling refresh interval
To specify the interval between sending refresh messages for each Resource Reservation Protocol (RSVP) state, use the ip rsvp signalling refresh interval command in global configuration mode. To set the interval to its default value, use the no form of the command.
ip rsvp signalling refresh interval interval-value
no ip rsvp signalling refresh-interval
Time between sending refreshes for each RSVP state. Specified in milliseconds and ranges from 5000 to 4294967295 milliseconds; default value is 30000 milliseconds (30 seconds).
Use the ip rsvp signalling refresh interval command to specify the interval between sending refresh messages for each RSVP state.
The RSVP protocol relies on a soft-state mechanism to maintain state consistency in the face of network losses. This mechanism is based on continuous refresh messages to keep a state current. Each RSVP router is responsible for sending periodic refresh messages to its neighbors.
The following example specifies a refresh interval of 60000 milliseconds (60 seconds):Router(config)# ip rsvp signalling refresh interval 60000
The following example returns the refresh interval to the default value of 30 seconds:Router(config)# no ip rsvp signalling refresh interval
Specifies the number of successive refresh messages that can be missed before RSVP removes a state from the database.
ip rsvp signalling refresh misses
To specify the number of successive refresh messages that can be missed before Resource Reservation Protocol (RSVP) removes a state from the database, use the ip rsvp signalling refresh misses command in global configuration mode. To return the missed refresh limit to its default value, use the no form of this command.
ip rsvp signalling refresh misses msg-count
no ip rsvp signalling refresh misses
Number of successive refresh messages that can be missed before RSVP considers the state expired and tears it down. Range is 2 to 10.
Use the ip rsvp signalling refresh misses command to specify the number of successive refresh messages that can be missed before RSVP regards the router state as expired and removes that state from the database.
The following example specifies a missed refresh limit of 6 messages:Router(config)# ip rsvp signalling refresh misses 6
The following example returns the refresh misses limit to the default value of 4:Router(config)# no ip rsvp signalling refresh misses
Specifies the interval between sending refresh messages for each RSVP state.
show ip rsvp
To display specific information for Resource Reservation Protocol (RSVP) categories, use the show ip rsvp command in EXEC mode.
show ip rsvp [counters | fast-reroute | hello | host | installed | interface | listeners | neighbor | request | reservation | sender | signalling]
No default behavior or values
The following example shows RSVP rate-limiting, refresh-reduction, and neighbor information:Router# show ip rsvpRSVP:enabled (on 2 interface(s))Signalling:Refresh interval (msec):100000Refresh misses:6Rate Limiting:enabledMax msgs per interval:4Interval length (msec):20Max queue size:500Max msgs per second:200Refresh Reduction:enabledACK delay (msec):250Initial retransmit delay (msec):1000Local epoch:0x16528CMessage IDs:in use 580, total allocated 3018, total freed 2438Neighbors:1RSVP encap:1 UDP encap:0 RSVP and UDP encap:0Local policy:COPS:Generic policy settings:Default policy:Accept allPreemption: Disabled
Table 1 describes the significant fields shown in the display.
flow—A stream of data traveling between two endpoints across a network (for example, from one LAN station to another). Multiple flows can be transmitted on a single circuit.
latency—The delay between the time a device receives a packet and the time that packet is forwarded out the destination port.
MPLS—Multiprotocol Label Switching. A method for directing packets primarily through Layer 2 switching rather than Layer 3 routing. In MPLS, packets are assigned short, fixed-length labels at the ingress to an MPLS cloud by using the concept of forwarding equivalence classes. Within the MPLS domain, the labels are used to make forwarding decisions mostly without recourse to the original packet headers. MPLS is formerly known as tag switching.
packet—A logical grouping of information that includes a header containing control information and (usually) user data. Packets most often refer to network layer units of data.
refresh message—A message that represents a previously advertised state, contains the same objects and information as a previously transmitted message, and is sent over the same path.
router—A network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.
RSVP—Resource Reservation Protocol. A protocol that supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (bandwidth, jitter, maximum burst, and so on) of the packet streams they want to receive.
soft state—The status that RSVP maintains in routers and end nodes so that they can be updated by certain RSVP messages. The soft state characteristic permits an RSVP network to support dynamic group membership changes and adapt to changes in routing.
subpool—A division of bandwidth such that no one tunnel dominates.
tunnel—A secure communication path between two peers, such as routers.
Note Refer to the Internetworking Terms and Acronyms for terms not included in this glossary.
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