The Foundry solution (ServerIron) is not BGP based. It is a DNS-based solution that uses a round-trip-time metric (calculated based on TCP syn/ack from client to server by the ServerIron on a per connection basis). The two down-sides of a DNS based solution are both caused by the fact that client source IPs are not contained in the request that comes from the client DNS resolver: 1] persistant connections must be managed on each real server. 2] client's whose IP is not within the same netblock (defaults to /20, tuneable) as DNS resolver do not get the benefit of RTTmetrics. Peter At 6:10 PM -0400 7/5/00, Dmitri Krioukov wrote:
the major disadvantage of the foundry (bgp) solution is longer prefix injection.
the major problem with the dns-based solutions is that they're not topology-aware (-> suboptimal routing). attempts to make dns smart lead to rather awkward reverse pinging configurations and proprietary protocols running between load balancers. (there was also rfc2052 by paul vixie but it required modification of dns clients.)
there is also the "triangle data flow" solution, which is broken by cef...
i'm in the process of preparing an overview of the available techniques along with introduction of a new one, which solves a lot of headaches. it requires a feature set that is not available on any of the currently existing lb platforms, hence, for testing, i had to develop one using open source (i chose linux to make it fast (it had almost all bits in place -- check http://www.linuxvirtualserver.org/)). -- dima.
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of tony bourke Sent: Wednesday, July 05, 2000 2:11 PM To: Jeremiah Kristal Cc: nanog@merit.edu Subject: Re: bad idea?
actually, Foundry has a global solution based on BGP, check them out.
There is a load-balancing mailing list, which addresses such issues.
http://vegan.net/lb is the info to sign up.
Tony
On Wed, 5 Jul 2000, Jeremiah Kristal wrote:
Given a small, globally routable netblock to be used for front-end web servers, and a strong aversion for using DNS for any type of load balancing, would it be reasonable to build two identical servers farms with the same public IP addresses and rely on the BGP sessions with the hosing providers to remove one advertisement in the event of a problem? I've been looking at ways to ensure that the webservers are always available, short of building a network connecting hosting facilities.
Jeremiah being a customer stinks
-------------- -- ---- ---- --- - - - - - -- - - - - - - Tony Bourke tony@vegan.net