RSVP Multicast CAC
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RSVP Multicast CAC

Last Updated: March 13, 2012

This module describes how to configure the Resource Reservation Protocol (RSVP) Mulicast Call Admission Control (CAC) to permit or denie multicast flows on interfaces based on RSVP messages.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for RSVP Multicast CAC

  • IP multicast must be enabled and all Protocol Independent Multicast (PIM) interfaces must be configured. See the "Configuring Basic IP Multicast" module of the IP Multicast PIM Configuration Guide for configuration information.
  • In order for a device to participate in RSVP, RSVP must be enabled on the appropriate interfaces by using the ip rsvp bandwidth command in interface configuration mode. See the QoS: RSVP Configuration Guide for configuration information.
  • ACLs to be subject to RSVP must be configured by using the ip access-list command.

Restrictions for RSVP Multicast CAC

If an application is not RSVP compliant, it will neither be blocked nor reserved by RSVP multicast CAC, but will be forwarded best-effort.

Information About RSVP Multicast CAC

RSVP Multicast CAC

Multicast architecture separates control and forwarding by using a Multicast Routing Information Base (MRIB) database, which regulates communication, including the writing (by owners) and notifying (to interested parties) of various (S,G) entries and interface flags, between its clients. MRIB provides modularity and separation between the multicast control plane, Protocol Independent Multicast (PIM) and Internet Group Management Protocol (IGMP), and the Multicast Forwarding Information Base (MFIB) forwarding plane. Multicast data packet forwarding is controlled by MFIB using F flags.

Multicast protocols, such as PIM, decide on which interfaces to forward a flow. At any node in the network, the multicast state can have multiple outgoing interfaces. Some interfaces may or may not have RSVP bandwidth available for an RSVP compliant application. If an RSVP application decides to stop sending because of insufficient RSVP bandwidth, the chance to forward over outgoing interfaces that have sufficient RSVP bandwidth is missed. The RSVP Multicast CAC feature enables the network, rather than the application, to decide where to block or forward a flow based upon RSVP reservations. RSVP multicast CAC acts only upon interfaces that are in an outgoing interface list that is maintained by PIM. RSVP multicast CAC cannot alter, add, or remove an outgoing interface list.

When RSVP notifies about adding (permits) the reservation for a flow, multicast sets the F flag in the MFIB database to forward the flow on the given interface, on the entry in the outgoing interface list that corresponds to the given source and destination. Conversely, when RSVP deletes (denies) the reservation, multicast clears the F flag to block the flow. If a sender explicitly tears down a reservation, multicast sets the F flag to forward again on all outgoing interfaces. This mechanism results in forwarding if, and only if, the flow is RSVP reserved or if no reservation is requested. Just like for unicast, the RSVP subsystem arranges with the forwarding classification subsystems to forward best-effort when no reservation is required.

If a flow does not match the configured ACL, it is not subject to outgoing interface blocking by RSVP multicast CAC. A flow that is not subject to RSVP multicast CAC will forward best-effort if it does not have a reservation. Conversely, a previously blocked interface will be unblocked after an ACL is reconfigured and the matching state changes.

Reconfiguring an ACL can result in oversubscription when, for example, initially two flows (F1 and F2) match and one flow (F2) is blocked. Then, after reconfiguration, F2 no longer matches and is unblocked. RSVP does not know about the ACL and does not know it would be better to block F1 now. Note that not matching an ACL is equivalent to not requesting a reservation.

How to Configure RSVP Multicast CAC

Configuring RSVP for Controlling Multicast Flows

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip rsvp policy preempt

4.    ip mulicast [vrf vrf -name] rsvp access-list

5.   exit


DETAILED STEPS
 Command or ActionPurpose
Step 1
enable


Example:

Device> enable

 
Enables privileged EXEC mode.
  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Device# configure terminal

 

Enters global configuration mode.

 
Step 3
ip rsvp policy preempt


Example:

Device(config)# ip rsvp policy preempt

 

Enables the preemption parameter for all configured local and remote policies.

 
Step 4
ip mulicast [vrf vrf -name] rsvp access-list


Example:

Device(config)# ip multicast rsvp mcast-rsvp

 

Specifies which multicast flows are to be blocked on all interfaces when no RSVP reservation is available and which are to be forwarded when an RSVP reservation is available, depending on the configuration of the ACL. Repeat this step to specify each ACL that is to be subject to RSVP.

 
Step 5
exit


Example:

Device(config)# exit

 

Exits from global configuration mode to privileged EXEC mode.

 

Viewing Blocked Outbound Interfaces

SUMMARY STEPS

1.    enable

2.    show ip mroute [vrf vrf-name] [interface type number]


DETAILED STEPS
 Command or ActionPurpose
Step 1
enable


Example:

Device> enable

 
Enables privileged EXEC mode.
  • Enter your password if prompted.
 
Step 2
show ip mroute [vrf vrf-name] [interface type number]


Example:

Device# show ip mroute 192.0.2.2



Example:

Device# show ip mroute 192.0.2.2 IP Multicast Routing Table Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected, L - Local, P - Pruned, R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet, X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group, V - RD & Vector, v - Vector Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 192.0.2.2), 00:05:38/00:02:57, RP 200.0.0.2, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Ethernet0/1, Forward/Sparse-Dense, 00:05:38/00:02:57 (205.165.201.2, 192.0.2.2), 00:04:34/00:03:15, flags: T Incoming interface: Ethernet0/0, RPF nbr 40.0.1.1 Outgoing interface list: Ethernet0/1, Forward/Sparse-Dense, 00:04:34/00:02:57 Ethernet0/2, Forward/Sparse-Dense, 00:04:16/00:02:33 Blocked

 

Displays contents of mroute table.

 

Configuration Examples for RSVP Multicast CAC

Example RSVP Multicast CAC


Note
IP multicast must be enabled and all Protocol Independent Multicast (PIM) interfaces must be configured. RSVP must be enabled on the appropriate interfaces for a device to participate in RSVP.

The following example shows how to configure a standard ACL named mcast-rsvp: 

Device> enable
Device# configure terminal
Device(config)# ip access-list standard mcast-rsvp
Device(config-std-nacl)# permit 192.0.2.0 0.0.0.255
Device(config-std-nacl)# permit 10.88.0.0 0.0.255.255
Device(config-std-nacl)# permit 10.0.0.0 0.255.255.255

The following example shows how to enable RSVP multicast CAC. The specified ACL will be subject to RSVP. 

Device(config-std-nacl)# exit
Device(config)# ip rsvp policy preempt 
Device(config)# ip multicast rsvp mcast-rsvp

The following partial sample output from the show running- config command shows how to permit all flows from all devices on network 192.0.2.0 (ACL mcast-rsvp) when an RSVP reservation is available: 

Device# show running-config
.
.
.
ip rsvp policy preempt
!
ip access-list standard mcast-rsvp
 permit   192.0.2.0 0.0.0.255
 permit 10.88.0.0 0.0.255.255
 permit 10.0.0.0 0.255.255.255

Additional References

Related Documents

Related Topic Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco IP multicast commands

Cisco IOS IP Multicast Command Reference

RSVP Quality of Service (QoS)

QoS: RSVP Configuration Guide

IP multicast configuration information

"Configuring Basic IP Multicast" module of the IP Multicast PIM Configuration Guide

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Feature Information for RSVP Multicast CAC

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 1Feature Information for RSVP Multicast CAC
Feature Name Releases Feature Information

RSVP Multicast CAC

15.2(3)T

Provides multicast Call Admission Control (CAC) functionality based on Resource Reservation Protocol (RSVP) messages.

The following commands were introduced or modified: clear ip multicast rsvp, ip multicast, show ip mroute, show ip multicast.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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