Internet Group Membership Authentication Protocol; Igap And Mlt - Avaya 8800 Planning And Engineering, Network Design

Multicast network design
Another performance-affecting factor that you need to be aware of is the error rate of the physical
medium. It also affects the proper choice of LMQI values. For links that have high packet loss, you
may find it necessary to adjust the robustness variable to a higher value to compensate for the
possible loss of IGMP queries and reports.
In such cases, leave latency is adversely impacted as numerous group-specific queries are
unanswered before the stream is pruned. The number of unanswered queries is equal to the
robustness variable (default two). The assignment of a lower LMQI may counterbalance this effect.
However, if you set it too low it may actually exacerbate the problem by inducing storms of reports
on the network. Keep in mind that LMQI values of three and ten, with a robustness value of two,
translate to leave latencies of six tenths of a second and two seconds, respectively.
When you choose a LMQI, consider all of these factors to determine the best setting for the given
application and network. Test that value to ensure that it provides the best performance.
Important:
In networks that have only one user connected to each port, Avaya recommends that you use
the Fast Leave feature instead of LMQI, since no wait is required before the stream stops.
Similarly, the robustness variable does not impact the Fast Leave feature, which is an additional
benefit for links with high loss.

Internet Group Membership Authentication Protocol

Internet Group Membership Authentication Protocol (IGAP) is a multicast authentication and
accounting protocol. With IGAP authentication and accounting features, service providers and
enterprises can manage and control multicast groups on their networks.
IGAP is an IETF Internet draft that extends the functionality of the Internet Group Management
Protocol (IGMPv2) and uses a standard authentication server with IGAP extensions.
The Avaya Ethernet Routing Switch 8800/8600 processes messages according to the following
rules:
• On IGAP-enabled interfaces, the switch processes IGAP messages and ignores all other IGMP
messages.
• On IGMP-enabled interfaces, the switch processes IGMP messages and ignores IGAP
messages.
• IGAP operates with Fast Leave only and does not generate Group-Specific-Queries as
IGMPv2 does. The Ethernet Routing Switch 8800/8600 supports the Single User and Multiple
User Fast Leave modes for IGAP.
For more information about IGAP, see Avaya Ethernet Routing Switch Configuration — IGAP,
NN46205-512.

IGAP and MLT

In an IGAP/MLT environment, if an MLT link goes down, it can potentially interrupt IGAP traffic.
June 2016 Planning and Engineering — Network Design
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