Avaya 8800 Planning And Engineering, Network Design page 235

The following figure shows an IGAP member connected to an Avaya Ethernet Routing Switch
8800/8600 edge switch (R1) that has two MLT links. The MLT links provide alternative routes to the
RADIUS authentication server and the Content Delivery Network (CDN) server.
Figure 114: Avoiding an interruption of IGAP traffic
The following scenario shows how a potential traffic interruption can occur:
1. An authenticated IGAP member receives multicast traffic. Accounting starts.
2. R1 uses MLT1 to transfer data and accounting messages.
3. MLT1 goes down.
Because the (S,G) entry is deleted, an Accounting Stop message is triggered.
4. MLT2 redistributes the traffic that exists on MLT1.
Because a new (S,G) entry is created with a different session ID, an Accounting Start
message is triggered.
MLT1 is down, so both the Accounting Stop and Accounting Start messages are sent to the
RADIUS server on MLT2. If the Accounting Stop message is sent before OSPF can recalculate the
route change and send an Accounting Start message, the switch drops the User Datagram Protocol
(UDP) packets.
June 2016
Internet Group Membership Authentication Protocol
Planning and Engineering — Network Design
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