Enabling Multicast Services over L2TP

Feature Summary and Revision History

Summary Data

Applicable Product(s) or Functional Area

P-GW

Applicable Platform(s)

  • ASR 5500

  • VPC-DI

  • VPC-SI

Feature Default

Disabled - Configuration Required

Related Changes in This Release

Not Applicable

Related Documentation

Not Applicable

Revision History

Revision Details

Release

In this release, P-GW supports Multicast Services over L2TP.

21.21.1

Feature Description

When a multicast service is set up for the mobile Customer Premises Equipment (CPE), the APN is configured with L2TP tunnel and P-GW works as L2TP Access Concentrator (LAC). To set up the multicast session, the video client/mobile CPE need to send or receive the PIM (Protocol Independent Multicast) message (with TTL=1) to or from Video headend server over SGi L2TP tunnel.

The P-GW follows the default L2TP LAC to inspect and process the encapsulated IP traffic inside the L2TP tunnel. This process prevents certain applications between CPE and LNS that sends TTL=1 traffic to function. Prior to 21.21.1 release, when an IP packet is sent, the Time to Live (TTL) value (for example, 255) was decremented by 1 at each hop. The P-GW dropped the packet with TTL value 0 or 1, decremented (when TTL > 1) the TTL value and the new checksum for the data packet was calculated. In this release, by enabling multicast session over L2TP feature through CLI:

  • P-GW ignores the TTL value and forwards the packet.

  • The L2TP and regular packets gets differentiated by L2TP tunnel type at sessmgr_ipv4.c and it verifies the CLI configuration mode enabled.

Configuring Multicast Services over L2TP

Use the following CLI commands to enable or disable the multicast session over L2TP feature. By default, this feature is disabled.

configure 
   context context_name 
      lac-service service_name 
         ttl-ignore 
         end

Notes:

  • ttl-ignore : Ignores the TTL value and forwards the packets.