[Serusers] Global Failover Server

Fri Jul 7 15:13:51 CEST 2006

Correct me if I'm wrong, but since SER is capable to handle tens or hundreds
of thousands of SIP messages per second, why not cut this number down to
thousands and compose a HA and Redundancy solution combining some stateless
proxy in front of a bunch of servers using cache based (like in 2 - MySQL
cluster, p.ex.)? The stateless proxy could have some local replication (two
peers: one active and one inactive) sharing a common IP (registered on SRV)
for HA, and the geographic issue could be achieved with a complete
replication of this set.

The down-point in this approach is that in a geographic switch there is no
guarantee that the clusters would be totally consistent between the two
sets. The fall can (and Murphy says it will) occur just before, or in the
middle, a big replication DB operation. But if You can accomplish that than
I see this as a good solution.

Comments?

Edson.

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From: serusers-bounces at lists.iptel.org
[mailto:serusers-bounces at lists.iptel.org] On Behalf Of Greger V. Teigre
Sent: sexta-feira, 7 de julho de 2006 06:49
To: G.Jacobsen
Cc: seruser List
Subject: Re: [Serusers] Global Failover Server

Yes, but this depends on your deployment setup and policies. Obviously, you
cannot support all features with all UAs. Three-way conferencing for
example. There's no guarantee that REFER and NOTIFYs work for three random
UAs from different vendors. There are still too many bugs around. So, you
need to say: If you have this and that UA, you will probably not get
three-way conferencing.  Not much difference from saying: If you have this
and that UA, you may experience service outages.

There are several ways of creating server-side redundancy and scalability.
Unfortunately, none are trivial. There are three I have heard have been
successfully used in large-scale setups:
1. Cacheless usrloc with a mysql cluster as back-end DB combined with
implementation of the Path header (to find the registrar of a given UA). No
replication across servers
2.  Multiple SER registrars, each with a standalone, local DB and where SIP
is used to replicate registrations.  By storing replications from a peer in
a location_peer1 table and then lookup using this table, you can route
INVITEs to the registrar being able to pinhole the NAT in front of a given
UA
3. Each SER is connected to a single mysql DB cluster as in #1, but since
usrloc also is in memory (cacheless usrloc is not used), replication is done
between the SER servers and save_memory() is used to store the location only
in memory (the registrar updates the cluster with save())

Each of these three can be combined with either:
a. call-id sticky front-end load balancer (commercial or modified LVS) 
b. DNS SRV
c. Linux HA creating two and two peers

Only b) combined with either 1) or 3) or 2+c) can give geographic, client
and server-side redundancy and scalability.

Scalability and redundancy is sort of a pet project of mine... I would like
to see a simple, clear-documented and code-supported setup that satisfies
most common requirements. Currently I'm leaning against #2 (which actually
can be implemented in vanilla SER 0.9.x, but would be easier and better with
built-in support). I'm thinking about a setup where two and two servers are
peers to eachother using Linux HA. Both servers would have one active SER
instance and one inactive ready for taking over for the peer.

I have posted this overview to:
http://www.iptel.org/drupal/failover_redundancy_and_scalability_overview

See also:
http://www.iptel.org/drupal/ser/wishlist

g-)
G.Jacobsen wrote: 

Samuel,

Do you happen to know what percentage of UAs out there are really
"Compliant" UAs ?

My impression so far regarding SRV DNS records is that they are
theoretically a nice feature but unfortunately almost useless since one
needs to cater for those non-compliant UAs anyway. I would love to be
convinced of the contrary.

Can anyone supply real usage figures regarding compliant/non-compliant UAS ?

TIA

Gerry

-----Original Message-----
From: serusers-bounces at lists.iptel.org
[mailto:serusers-bounces at lists.iptel.org]On Behalf Of samuel
Sent: Donnerstag, 6. Juli 2006 14:52
To: Ritesh Jalan
Cc: seruser List
Subject: [Bulk] Re: [Serusers] Global Failover Server

Look at RFC 3623.
Cofigure two SRV entries in your DNS, one pointing to the UAS SERver and
another to the UK server. "Compliant" UAs will try to contact the other
proxy upon failure of their current one.

Samuel.

2006/7/5, Ritesh Jalan <ritesh.j at net4.in>: 

Hi All

Pls. guide me how can we implement failover on SIP Server located globally,
Like one server in USA another in UK. 

Ritesh Jalan 
Mobile: 91-9818616329 
MSN: ritesh_jalan at hotmail.com 

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