Internet2 to Sunset Interdomain Any Source Multicast
By Chris Wilkinson and Mark Brochu
Internet2, in response to community and Internet Engineering Task Force (IETF) recommendations, as well as interoperability concerns with future growth, will begin the sunset of Interdomain Any Source Multicast (ASM).
As part of this transition, Internet2 will coordinate with members to begin the decommission of Multicast Source Discovery Protocol (MSDP) peerings. This is already occurring with various members and we are seeing an accelerated trend since the release of the Deprecating ASM for Interdomain Multicast Abstract. Internet2 is recommending that the few members that still have active ASM sources transition these to SSM.
If this is technically impractical, our technical staff can work with your organization and your multicast subscribers to transition to private multicast peerings, such as layer 2 circuits between receivers, and/or the provisioning of private multicast VPNs (mvpns) between participants. Internet2 will be available for feedback and questions during the 2018 Technology Exchange on Oct 15-18. Starting on October 28, Internet2 will begin formally sending notification to any existing MSDP peers that a disconnect will be scheduled. We hope to have all MSDP sessions removed by Dec 15, 2018.
There are two well-known flavors of IP multicast: Any Source Multicast (ASM), and Source Specific Multicast (SSM). Initially, many applications were written to leverage ASM addressing. This was mostly due to the fact that several operating systems lacked support for IGMPv3, a necessary component of SSM. As such, autonomous networks would exchange information using the Multicast Source Discovery Protocol, or MSDP.
MSDP was implemented in 2003 and has remained in “experimental” status. The low demand across operators for this feature has led to deficiencies which have not been addressed, leading to liabilities on the Internet2 network. These deficiencies include flooding of network state information, lack of state attack protection, and undesired source filtering.
As time progressed, it became clear that the use case for ASM was not as relevant in the interdomain setting. That is, between domains, usually only one source would send data to multiple receivers, something better suited to SSM. Major operating systems have also been supporting SSM for some time (Windows, MacOS, Linux/Android).
As Internet2 continues to evolve its network, it has become clear that our continued support of MSDP would hinder future growth, in part by the lack of attention the protocol has received from vendors, resulting in the deficiencies listed above. In response, the IETF felt it necessary to issue a draft BCP recommending the deprecation of Inter-domain ASM. Internet2 supports the IETF draft and believes this is the best path forward for the community.
Please note that this does NOT mean that Internet2 will stop supporting Interdomain Multicast. PIM SSM and IPv6 will both be supported mechanisms for interdomain multicast applications across the Internet2 footprint.