SVSi N-Series Pre-implementation - Manual (Page 8)

8 Networked AV Pre-Implementation Guide www.svsiav.com
3.1 Multicast Routing
SVSi decoders, encoders, networked video recorders, and windowing processors all use IP multicast routing protocols.
This works perfectly for high bandwidth applications such as streaming media because in multicasting there is one source
(sender) sending data to multiple recipients, but there is only a single copy of the data being sent and shared among all of
the recipients. This is accomplished by splitting the single transmission among the multiple users using multicast trees. If
you would like to read more about IP multicast, Cisco® provides many excellent resources such as the document found at
the following wiki link:
http://docwiki.cisco.com/wiki/Internet_Protocol_Multicast#Internet_Group_Management_Protocol
There are two ways to implement multicast routing when using SVSi equipment:
• IGMP (Internet Group Management Protocol): Allows video streams (groups) to be dynamically routed only to
those ports requesting the video stream. The IGMP feature prevents the multicast video traffic from flooding the
network and can significantly reduce traffic in a layer-3 network. This is the recommended setting for SVSi
equipment. For more information, visit the following Cisco website:
http://docwiki.cisco.com/wiki/Internet_Protocol_Multicast#Internet_Group_Management_Protocol
• PIM (Protocol Independent Multicast): Functions independently of IP routing protocol. PIM Dense Mode
(PIM-DM) is less preferred for this application in that it floods the network, using unicast routing protocols to build
routing table. Only PIM Sparse Mode (PIM-SM) is supported. For more information, visit the following Cisco
website:
http://docwiki.cisco.com/wiki/Internet_Protocol_Multicast#Protocol-Independent_Multicast
SVSi’s control signals are TCP/IP unicast and can be routed. Video signals, as described in the previous table (in Section 3
NETWORK PROPERTIES) are multicast and can be routed in certain cases. Many Cisco routers require that the routing
table be pre-loaded so that the processor does not have to touch each packet to determine its destination. Static routing
has been used successfully to route multicast video traffic. Alternatively, existing routing protocols like generic routing
encapsulation (GRE) or equivalent can be used to route video traffic. These protocols generally encapsulate the multicast
packets in unicast wrappers for point-to-point transmission between routers. Once at the intended unicast destination
address, the unicast wrapper is stripped and packers revert to multicast.
Although N1000 and N2000 encoders output only multicast video, N3000 encoders can output unicast video natively at a
bandwidth compatible with lower speed links. N3000 also supports standard streaming protocols like RTP, RTSP, and
HTTP Live commonly used with content delivery services. The N4321 audio transceiver also supports both multicast and
unicast.