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Setting Up IP Multicast Forwarding

Configuring multicast forwarding

Forwarding from an MBONE router on a WAN link

Configuring multicast forwarding

When using the MBONE, the MAX looks like a multicast client. It responds as a client to Internet Group Membership Protocol (IGMP) packets it receives from MBONE routers. The packets can be IGMP version-1 or version-2, including IGMP multicast trace (MTRACE) packets.

To multicast clients on a WAN or Ethernet interface, the MAX looks like a multicast router. Like a router, it sends those clients IGMP queries, receives responses, and forwards multicast traffic. In this implementation, multicast clients are not allowed to source multicast packets. If they do, the MAX discards the packets.

Following are the parameters (shown with sample settings) for configuring multicast forwarding:

Ethernet
      Mod Config
            Multicast...
                  Forwarding=Yes
                  Membership Timeout=60
                  Mbone Profile=
                  Client=No
                  Rate Limit=5 
                  Grp Leave Delay=
                  HeartBeat Addr=224.0.1.1
                  HeartBeat Udp Port=123
                  HeartBeat Slot Time=10
                  HeartBeat Slot Count=10
                  Alarm threshold=3
                  Source Addr=128.232.0.0
                  Source Mask=0.0.0.0

Ethernet
      Connections
            any Connection profile
                  Ip options...
                        Multicast Client=No
                        Multicast Rate Limit=5

Forwarding

When you change the Forwarding parameter from No to Yes, the multicast subsystem reads the values in the Ethernet profile and initiates the forwarding function.

Membership Timeout

Mbone Profile

Client and Rate Limit

Rate Limit specifies the rate at which the MAX accepts multicast packets from its clients. It does not affect the MBONE interface. The default setting is 100, which disables multicast forwarding on the interface. The forwarder handles IGMP packets, but does not accept packets from clients or forward multicast packets from the MBONE router.

To begin forwarding multicast traffic on the interface, you must set the Rate Limit parameter to a number less than 100. For example, if you set it to 5, the MAX accepts a packet from multicast clients on the interface once every five seconds. The MAX discards any subsequent packets received in that five-second window.

Grp Leave Delay

When the MAX receives a leave group message for a WAN interface for which you configure a value for Grp Leave Delay, it sends a query to the WAN interface, requesting that any active members of the group respond. If the MAX receives a response within the time period of time you specify in the Grp Leave Delay parameter, it does not forward the leave group message to the MBONE. Otherwise, it sends a leave group message to the MBONE, and it clears the IGMP group session from its tables.

HeartBeat

Trap type: TRAP_ENTERPRISE
Code: TRAP_MULTICAST_TREE_BROKEN (19)
Arguments:
1) Multicast group address being monitored (4 bytes),
2) Source address of last heartbeat packet received (4 bytes),
3) Slot time interval configured in seconds (4 bytes),
4) Number of slots configured (4 bytes).
5) Total number of heartbeat packets received before the MAX started sending SNMP Alarms (4bytes).

To set up heartbeat monitoring, you configure several parameters that define the packets to be monitored, how often and for how long to poll for multicast packets, and the threshold for generating an alarm. Following are the parameters you use to specify these settings:

Setting	Parameters
Packets to be monitored	HeartBeat Address specifies a multicast address. If set, causes the MAX to listen for packets to and from the specified address. HeartBeat UDP Port specifies a UDP port number. If set, causes the MAX to listen only to packets received through the specified port. Source Addr and Source Mask specify an IP address and subnet mask. If you specify an address, the MAX ignores packets from that source for monitoring purposes.
How often and for how long to poll for multicast packets	HeartBeat Slot Time specifies an interval (in seconds). The MAX polls for multicast traffic, waits for the duration of the interval, then polls again. HeartBeat Slot Count specifies how many times to poll before comparing the number of heartbeat packets received to the Alarm Threshold.
Threshold for generating an alarm	Heartbeat Alarm Threshold specifies a number. If the number of monitored packets falls below this number, the MAX sends the SNMP alarm trap.

Multicast Client

When you set Multicast Client to Yes, the MAX begins handling IGMP requests and responses on the interface. It does not begin forwarding multicast traffic until the rate limit is set. When you set Multicast Client to No, the MAX specifies that the MAX not respond to multicast clients on the interface. The default is No.

Multicast Rate Limit

To begin forwarding multicast traffic on the interface, you must set the rate limit to a number less than 100. For example if you set it to 5, the MAX accepts a packet from multicast clients on the interface every 5 seconds. Any subsequent packets received in that 5-second window are discarded. You can specify a number lower than the default 100 to begin forwarding multicast traffic on the interface.

Implicit priority setting for dropping multicast packets

• Traffic on ports 0-16384 (unclassified traffic) has the lowest priority (50).

• Traffic on ports 16385-32768 (Audio traffic) has the highest priority (70).

• Traffic on ports 32769-49152 (Whiteboard traffic) has medium priority (60).

• Traffic on ports 49153-65536 (Video traffic) has low priority (55).

Forwarding from an MBONE router on Ethernet

Figure 12-1. MAX forwarding multicast traffic to dial-in multicast clients

As an example of this type of multicast configuration, the following procedure specifies the MBONE interface as the Ethernet port, and uses the heartbeat group address of 224.1.1.1:

1. Open Ethernet > Mod Config > Multicast.

2. Enable multicast forwarding, and leave the default values for the Mbone Profile, Client, and Rate Limit parameters:

   Ethernet
         Mod Config
               Multicast...
                     Forwarding=Yes
                     Membership Timeout=60
                     Mbone Profile=
                     Client=No
                     Rate Limit=5 
   

3. Specify a heartbeat group address and UDP port for monitoring heartbeat packets. For example:

                       HeartBeat Addr=224.1.1.1
                     HeartBeat Udp Port=16387
   

4. Specify the time, count, and alarm threshold parameters. For example:

                     HeartBeat Slot Time=10
                     HeartBeat Slot Count=10
                     Alarm threshold=3
                     Source Addr=0.0.0.0
                     Source Mask=0.0.0.0
   

5. Close the Ethernet profile.

1. Open the Connection profile for a multicast client site.

2. Open the IP Options subprofile and set Multicast Client to Yes. If appropriate, specify a rate limit other than the default of 5.

   Ethernet
         Connections
             any Connection profile
                   Ip options...
                         Multicast Client=Yes
                         Multicast Rate Limit=5
   

3. Close the Connection profile.

Forwarding from an MBONE router on a WAN link

Figure 12-2. MAX acting as a multicast forwarder on Ethernet and WAN interfaces

This section presents a sample configuration for the local MAX unit in Figure 12-2. The configuration specifies the MBONE interface as a WAN link accessed through a Connection profile #20.

Configuring the MAX to respond to multicast clients

1. Open Ethernet > Mod Config > Multicast.

2. Enable multicast forwarding, specify the number of the Connection profile for the MBONE interface, and set Client to Yes:

   Ethernet
   Mod Config
   Multicast...
   Forwarding=Yes
   Membership Timeout=60
   Mbone Profile=20
   Client=Yes
   

3. In the same profile, set Multicast Rate Limit to a number lower than the default of 100:

             Rate Limit=5
   

4. Close the Ethernet profile.

1. Open the Connection profile for an MBONE interface (in this example, profile #20).

2. Open the IP options subprofile and set Multicast Rate Limit to a number lower than the default of 100:

   Ethernet
         Connections
               profile #20...
                     Ip options...
                           Multicast Client=No
                           Multicast Rate Limit=5
   

3. Close the Connection profile.

1. Open the Connection profile for a multicast client site.

2. Open the IP options subprofile.

3. Set Multicast Client to Yes, and set Multicast Rate Limit to a number lower than the default of 100:

   Ethernet
         Connections
             any Connection profile
                   Ip options...
                         Multicast Client=Yes
                         Multicast Rate Limit=5
   

4. Close the Connection profile.

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Copyright © 1998, Ascend Communications, Inc. All rights reserved.