Introduction to layer 2 Multicast CAC

CAC is short for Call Admission Control. Layer 2 multicast CAC is involved in the IPTV multicast scheme and is mainly used to control the number of IPTV channels in the Layer 2 multicast scenario, thereby preventing users from requesting additional channels and ensuring high service qualities for existing users.

With the development of the IPTV, the number of channels increases rapidly. If the number of channels demanded by users keeps increasing, which results in overloads on the devices at the convergence layer and degrades the user satisfaction degree. Moreover, if multicast-based network attacks exist, devices on the network may be busy with processing a high volume of attack packets and thus cannot respond to normal processing requests on the network.

Therefore, when providing the IPTV service, operators should consider whether their networks can bear the excessive channels. If the network bandwidth is insufficient, requests for joining new channels need to be denied to sacrifice parts of users' satisfaction degree for service qualities of most users.

Layer 2 multicast CAC is a technology to control user access from different dimensions. It accurately controls multicast services, and ensures service qualities of most users. In addition, it reduces multicast attacks to some extent.

You can check for more information these RFC

• RFC 1112     Host Extensions for IP Multicasting

• RFC 2236   Internet Group Management Protocol, Version 2

• RFC 4541   Considerations for IGMP and MLD Snooping Switches