Some notes about avahi/zeroconf and scalability.
--Chris
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Hi Nick,
On Jun 16, 2006, at 12:28 PM, Nicholas Andrews wrote:
In a talk Stuart Cheshire gave at Google
(http://video.google.com/videoplay?docid=-7398680103951126462&q=bonjour
)
he goes as low as 100 hosts as already being too many. He isn't clear,
however, on if that means that it would generate too much chatter to
be practical or just more than what the protocol is supposed to be
used for (and indeed there is no mention of the type of network).
I know that SLP allows scopes to be defined to help scale to larger
networks, and I was wondering if there was (or could be) an equivalent
with mDNS-SD? My application is a wireless ad-hoc network, so the
question of overhead is an important one.
On Apple's Ethernet network, we typically have around 300 machines all
advertising at least two services, and typically browsing for many
services, and this works out well. We see average multicast traffic
of around 250 packets per minute.
We also have a campus wide wireless network, and typically there can
be around 500 machines, and even this works out well, although packet
count goes up as network latencies increase. I've heard of college
campuses with around 800 machines on a single Ethernet link, and this
starts to cause too much traffic, especially if these campuses are
running older versions of Mac OS X which have less efficient versions
of the mDNS responder.
Hope that helps.
-Marc
On 6/15/06, Lennart Poettering <[EMAIL PROTECTED]> wrote:
On Thu, 15.06.06 17:17, Nicholas Andrews ([EMAIL PROTECTED]) wrote:
> Hello,
>
> I'm interested in how well mDNS-SD scales. I have heard it
described
> as a lightweight protocol, but I've never seen any numbers. At what
> point does it become impractical to use it for service discovery?
According to Apple mDNS scales well for up to 1000 hosts. I don't
know
if they did simulations to prove that claim. And I do not know if
Avahi actually is compatible enough with Bonjour that the claim still
holds. And finally I know nothing about the network technology they
used for that claim (100mbit ethernet, gigabit ethernet, WLAN?).
In short: it's all very vague, the only value we ever heard or read
was 1000 hosts.
A side node: I haven't seen anything about the number of *services*
mDNS scales to. Only *hosts*, which is not really the same.
Lennart
--
Lennart Poettering; lennart [at] poettering [dot] net
ICQ# 11060553; GPG 0x1A015CC4; http://0pointer.net/lennart/
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