20 August 2010

Belas Blog: Daisychaining in the clouds

Belas Blog: Daisychaining in the clouds. Interesting idea, although I would generally go for a more traditional fan-out model that looks like a tree rather than a daisy chain.
The idea is that, instead of sending a message to N-1 members, we only send it to our neighbor, which forwards it to its neighbor, and so on. For example, in {A,B,C,D,E}, D would broadcast a message by forwarding it to E, E forwards it to A, A to B, B to C and C to D. We use a time-to-live field, which gets decremented on every forward, and a message gets discarded when the time-to-live is 0.

The advantage is that, instead of taxing the link between a member and the switch to send N-1 messages, we distribute the traffic more evenly across the links between the nodes and the switch. Let's take a look at an example, where A broadcasts messages m1 and m2 in cluster {A,B,C,D}, '-->' means sending:

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