How It Works; Figure 7 - Multicast Over Shortest Path Bridging Overview - Avaya ERS 8800 Technical Configuration Manual

8.1 How it works

The SPB Virtual Services Fabric consists of Backbone Core Bridges (BCBs) and Backbone Edge Bridges
(BEBs). Backbone Edge Bridges (BEB) act as the boundary between the Multicast domain and the
Shortest Path Bridging (SPB) domain – currently only with dynamic or static IGMP. Multicast Senders
(Sources) and Receivers are either connected directly or indirectly (via Layer 2 switches) to the BEBs.
SPB Multicast services can be enabled for Layer 2 VSNs, Layer3 VSNs and the Global Routing Instance
(GRT).
All the Multicast streams are constrained within the level in which they originate i.e. the "scope" level. In
other words, if a sender sends a Multicast stream to a BEB on a C-VLAN (C-VLAN is a VLAN that is
mapped to an I-SID i.e. a L2 VSN) with SPB Multicast enabled, only receivers that are part of the same C-
VLAN or L2 VSN can receive that stream. Similarly, if a sender sends a Multicast stream to a BEB on a
VLAN that is part of the GRT or a L3 VSN with SPB Multicast enabled, only receivers that are part of the
same Layer 3 instance i.e. GRT or L3 VSN can receive that stream.
A Multicast stream received at
the edge of the SPB fabric is
mapped to a dedicated Multicast
Service Identifier (I-SID)
Multicast
Sender
(Group 239.0.0.10)
Multicast
Sender
(Group 239.0.0.11)
Figure 7 – Multicast over Shortest Path Bridging Overview
On receiving IP Multicast data from a Sender, a BEB allocates a data Service Identifier (I-SID) in the
range of 16,000,000 and higher for the stream (the stream is identified by the Source IP address, Group
IP Address and the local VLAN the stream is received on, i.e., by the S,G,V tuple) and sends an IS-IS
LSP update with applicable TLVs to its neighbors informing them of the presence of an IP Multicast
stream. The "scope" of the stream is either the Global Routing Table or the I-SID value of the Layer 2 or
Layer 3 VSN associated with the local VLAN or VRF that the IP Multicast data was received on. This
information is propagated through the SPB cloud and all BEBs will now know which Data I-SID to use to
request that particular multicast stream and its "scope". Note that the Data I-SID is a child of the scope or
VSN I-SID. Also note that IP Multicast data from Senders is dropped on ingress at the receiving BEB and
no multicast tree is created in the SPB fabric until the stream is requested by a receiver.
March 2013
BEB
IS-IS
SPB Fabric
IS-IS
BEB
IS-IS
IS-IS
IS-IS advertises the stream
to the rest of the fabric.
The stream is not
forwarded until a receiver
requests it.
Avaya Inc. – External Distribution
IS-IS advertises the stream to the
rest of the fabric.
The stream is forwarded ONLY to
those receivers who requested it
IS-IS
BEB
IS-IS
BCBs
BEB
IS-IS
IS-IS
avaya.com
Receiver
IGMP Join sent to Group
239.0.0.10
Receiver
IGMP Join sent to Group
239.0.0.10
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