Re: scalability question

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On Saturday 18 March 2006 04:31 am, Rory I. Sinclair wrote:
> My question is about the scalability of Bonjour or Avahi or any other
> zeroconf/mDNS/DNS-SD implementation and its suitability for the following:
I agree with Marc - scalability of the protocol (and its assumptions - like=
=20
everything is on the same subnet) is the problem. The implementations do a=
=20
good job of implementing the protocol.

> 1) Presence awareness of the client machines - ie the 'important' server
> hosts will use DNS-SD browse to be notified of any client machines dying.
This type of polling is going to be expensive. I don't know of any clean wa=
y=20
of handling this.

> 2) To allow the client machines to lookup network services by name and
> resolve the host/port information at runtime, rather than maintaining
> lookup tables
I think that a system like Service Location Protocol is going to be better=
=20
than zeroconf at this scale. It can use intermediate caching servers which=
=20
(given a decent network design) can save you a lot of traffic - basically o=
ne=20
or two caches per subnet mean that each query gets asked once per subnet, n=
ot=20
once per machine.

> 3) To allow clients to handle failures in the 'server' machines (eg
> multiple instances of the network services will provide failover)
SLP might help here, but an alternative approaches (load balancing proxies,=
=20
failover with STOMITH or other High Availability techniques) are probably=20
worth a look. To some extent it depends on how much downtime you can tolera=
te=20
in the failover.

Brad

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