Bind 9.2.4 - Load Balancing with SRV

[Mark Andrews]

> Hi DNS Experts,
> 
> I'm looking for some experiences with Bind 9.2.4 and Load Balancing using 
> SRV Records.
> 
> I have the following configuration:
> 
> _ldap._tcp.example.com. 0 IN SRV 1 1 389 oid1.example.com.
> _ldap._tcp.example.com. 0 IN SRV 1 1 3060 oid2.example.com.
> 
> I thought the load between oid1 and oid2 will be distributed evenly (oid1 - 
> 50%; oid2 - 50%), but it is not the case.
> 
> I thought the LDAP Clients will contact the oid servers in the following 
> manner: oid1 -> oid2 -> oid1 -> and so on...
> According to client trace files the load is not evenly distributed, and the 
> clients conntact sometimes repeatedly oid1
> than oid2, and so on,  in no particular oder. Work as designed?
> 
> Best regards,
> Robert 

	Any individual client will contact a individual server with
	a *probability* of 50%.  That does *not* mean that each
	connection will alternate.

	Toss a coin multiple times.  You will not get HTHTHTHTHTHT
	yet the probability of getting a H or a T is 50% and over
	the long term you will a even spread.

	Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org