Broadcast And Multicast Rate Limiting; Directed Broadcast Suppression; Prioritization Of Control Traffic; Cp-Limit Recommendations - Avaya 8800 Planning And Engineering, Network Design

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CP-Limit recommendations

• ARP request threshold recommendations
• Multicast Learning Limitation

Broadcast and multicast rate limiting

To protect the switch and other devices from excessive broadcast traffic, you can use broadcast and
multicast rate limiting on a per-port basis.
For more information about setting the rate limits for broadcast or multicast packets on a port, see
Avaya Ethernet Routing Switch 8800/8600 Configuration — Ethernet Modules, NN46205-503.

Directed broadcast suppression

You can enable or disable forwarding for directed broadcast traffic on an IP-interface basis. A
directed broadcast is a frame sent to the subnet broadcast address on a remote IP subnet. By
disabling or suppressing directed broadcasts on an interface, you cause all frames sent to the
subnet broadcast address for a local router interface to be dropped. Directed broadcast suppression
protects hosts from possible DoS attacks.
To prevent the flooding of other networks with DoS attacks, such as the Smurf attack, the Avaya
Ethernet Routing Switch 8800/8600 is protected by directed broadcast suppression. This feature is
enabled by default. Avaya recommends that you not disable it.
For more information about directed broadcast suppression, see Avaya Ethernet Routing Switch
8800/8600 Security, NN46205-601.

Prioritization of control traffic

The Avaya Ethernet Routing Switch 8800/8600 uses a sophisticated prioritization scheme to
schedule control packets on physical ports. This scheme involves two levels with both hardware and
software queues to guarantee proper handling of control packets regardless of the switch load. In
turn, this guarantees the stability of the network. Prioritization also guarantees that applications that
use many broadcasts are handled with lower priority.
You cannot view, configure, or modify control traffic queues.
CP-Limit recommendations
CP-Limit prevents the CPU from overload by excessive multicast or broadcast control or exception
traffic. This ensures that broadcast storms do not impact the stability of the system. By default, CP-
Limit protects the CPU from receiving more than 14 000 broadcast/multicast control or exception
packets per second within a duration that exceeds 2 seconds.
June 2016
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Planning and Engineering — Network Design
Comments on this document? infodev@avaya.com
DoS protection mechanisms
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