Note	Support for the PGM Host feature has been removed. Use of this feature is not recommended.

Pragmatic General Multicast (PGM) is a reliable multicast transport protocol for multicast applications that require reliable, ordered, duplicate-free multicast data delivery from multiple sources to multiple receivers. PGM guarantees that a receiver in a multicast group either receives all data packets from transmissions and retransmissions, or can detect unrecoverable data packet loss. PGM is intended as a solution for multicast applications with basic reliability requirements. PGM has two main parts: a host element (also referred to as the transport layer of the PGM protocol) and a network element (also referred to as the network layer of the PGM protocol).

The transport layer of the PGM protocol has two main parts: a source part and a receiver part. The transport layer defines how multicast applications send and receive reliable, ordered, duplicate-free multicast data from multiple sources to multiple receivers. PGM Host is the Cisco implementation of the transport layer of the PGM protocol.

The network layer of the PGM protocol defines how intermediate network devices (such as routers and switches) handle PGM transport data as the data flows through a network. PGM Router Assist is the Cisco implementation of the network layer of the PGM protocol.

Note	PGM contains an element that assists routers and switches in handling PGM transport data as it flows through a network. Unlike the Router Assist element, the Host element does not have a current practical application.

PGM is network-layer independent; PGM Host and Router Assist in the Cisco IOS software support PGM over IP. Both PGM Host and Router Assist use a unique transport session identifier (TSI) that identifies each individual PGM session.

The figure shows a simple network topology using the PGM Host and Router Assist feature.

Figure 1

Network Topology Using PGM Host and Router Assist

When the router is functioning as a network element (PGM Router Assist is configured) and PGM Host is configured (Router A in the figure), the router can process received PGM packets as a virtual PGM Host, originate PGM packets and serve as its own first hop PGM network element, and forward received PGM packets.

When the router is functioning as a network element and PGM Host is not configured (Router B in the figure), the router forwards received PGM packets as specified by PGM Router Assist parameters.

When the router is not functioning as a network element and PGM Host is configured (Router C in the figure), the router can receive and forward PGM packets on any router interface simultaneously as specified by PGM Host feature parameters. Although this configuration is supported, it is not recommended in a PGM network because PGM Host works optimally on routers that have PGM Router Assist configured.

Note	Support for the PGM Host feature has been removed. Use of this feature is not recommended.

When enabling PGM Host on your router, you must source PGM packets through a vif or out a physical interface installed in the router.

Sourcing PGM packets through a vif enables the router to send and receive PGM packets through any router interface. The vif also serves as the interface to the multicast applications that reside at the PGM network layer.

Sourcing IP multicast traffic out a specific physical or logical interface type (for example, an Ethernet, serial, or loopback interface) configures the router to send PGM packets out that interface only and to receive packets on any router interface.

• Prerequisites
• Enabling PGM Host with a Virtual Host Interface
• Enabling PGM Host with a Physical Interface

Note	Support for the PGM Host feature has been removed. Use of this feature is not recommended.

To verify that PGM Host is configured correctly on your router, use the following show commands in EXEC mode:

• Use the show ip pgm host sessions command to display information about current open PGM transport sessions:

Router> show ip pgm host sessions
Idx  GSI           Source Port  Type     State   Dest Port  Mcast Address
1    000000000000  0            receiver listen  48059      224.3.3.3
2    9CD72EF099FA  1025         source   conn    48059      224.1.1.1

Specifying a traffic session number or a multicast IP address with the show ip pgm host sessionscommand displays information specific to that PGM transport session:

Router> show ip pgm host sessions 2
Idx  GSI           Source Port  Type     State   Dest Port  Mcast Address
2    9CD72EF099FA  1025         source   conn    48059      224.1.1.1
 
    stream-type (apdu), ttl (255)
 
    spm-ambient-ivl (6000), txw-adv-secs (6000)
    txw-adv-timeout-max (3600000), txw-rte (16384), txw-secs (30000)
    ncf-max (infinite), spm-rpt-ivl (3000), ihb-min (1000)
    ihb-max (10000), join (0), tpdu-size (16384)
    txw-adv-method (time), tx-buffer-mgmt (return)
 
    ODATA packets sent                       0
          bytes sent                         0
    RDATA packets sent                       0
          bytes sent                         0
    Total bytes sent                         0
    ADPUs sent                               0
    APDU  transmit memory errors             0
    SPM   packets sent                       6
    NCF   packets sent                       0
    NAK   packets received                   0
          packets received in error          0
    General bad packets                      0
    TX window lead                           0
    TX window trail                          0

• Use the show ip pgm host trafficcommand to display traffic statistics at the PGM transport layer:

Router> show ip pgm host traffic
General Statistics :
 
    Sessions in                              0
             out                             0
    Bytes    in                              0
             out                             0
 
Source Statistics :
 
    ODATA packets sent                       0
          bytes sent                         0
    RDATA packets sent                       0
          bytes sent                         0
    Total bytes sent                         0
    ADPUs sent                               0
    APDU  transmit memory errors             0
    SPM   packets sent                       0
    NCF   packets sent                       0
    NAK   packets received                   0
          packets received in error          0
 
Receiver Statistics :
          
    ODATA packets received                   0
          packets received in error          0
          valid bytes received               0
    RDATA packets received                   0
          packets received in error          0
          valid bytes received               0
    Total valid bytes received               0
    Total bytes received in error            0
    ADPUs received                           0
    SPM   packets received                   0
          packets received in error          0
    NCF   packets received                   0
          packets received in error          0
    NAK   packets received                   0
          packets received in error          0
          packets sent                       0
    Undeliverable packets                    0
    General bad packets                      0
    Bad checksum packets                     0

When enabling PGM Router Assist on your router, you must set up your router to forward PGM packets through a vif or out a physical interface installed in the router.

Setting up your router to forward PGM packets through a vif enables the router to forward PGM packets through any router interface. The vif also serves as the interface to the multicast applications that reside at the PGM network layer.

Setting up your router to forward PGM packets out a specific physical or logical interface type (for example, an Ethernet, serial, or loopback interface) configures the router to forward PGM packets out that interface only.

• Prerequisites
• Enabling PGM Router Assist with a Virtual Host Interface
• Enabling PGM Router Assist with a Physical Interface

This section provides information on monitoring and maintaining the PGM Host and Router Assist feature.

• Monitoring and Maintaining PGM Host
• Monitoring and Maintaining PGM Router Assist