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3.2.2. Clos Topology Properties

3.2.2. Clos Topology Properties​

The following are some key properties of the Clos topology:

  • The topology is fully non-blocking, or more accurately non-interfering, if M >= N and oversubscribed by a factor of N/M otherwise. Here M and N is the uplink and downlink port count respectively, for a Tier 2 switch as shown in Figure 2.

  • Utilizing this topology requires control and data-plane support for ECMP with a fan-out of M or more.

  • Tier 1 switches have exactly one path to every server in this topology. This is an important property that makes route summarization dangerous in this topology (see Section 8.2 below).

  • Traffic flowing from server to server is load balanced over all available paths using ECMP.

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