[avahi] scalability of avahi (or mdns-sd in general)

[Marc Krochmal]

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 <lennart at poettering.net> wrote:
>> On Thu, 15.06.06 17:17, Nicholas Andrews (tar.bz2 at gmail.com) 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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