[SIPForum-discussion] Load Balancing in SIP Networks

[Chinar Trivedi]

1. You are confusing Load Balancing with DNS. If you are using a SIP Load
Balancer, it would sit in front of the your SBCs. The DNS lookup should
return Load Balancers' IP address.

Hi Keyur,

I get what you say about LBing with DNS. That is not what we want. DNS
isn't capable to do LBing. DNS will use domain lookups like SRV, NAPTR
Records and that is how we can choose a SBC in a pool of SBCs. What choice
we are facing with here is that what if a Load Balancer is instead used to
work as a DNS and resolving the SBC's IP address.
Is that viable?

Thanks for confirming that the Responses won't break on Layer 3.

You have any idea about stickiness/persistence maintenance for Back end SIP
Servers in IMS like P/I/S-CSCFs?
How is that achieved?

Thanks,
Chinar



On Mon, Oct 21, 2013 at 10:43 PM, Keyur Amin <fossil0681 at yahoo.com> wrote:

> Chinar,
>
> 1. You are confusing Load Balancing with DNS. If you are using a SIP Load
> Balancer, it would sit in front of the your SBCs. The DNS lookup should
> return Load Balancers' IP address.
> 2. Typically, you would want all your new requests to route via the Load
> Balancer. Responses are not required to route via a Load Balancer. No, it
> will not break layer 3.
>
>
> *Thanks,*
> *Keyur Amin*
> ------------------------------
>
> **
>
>
>   On Monday, October 21, 2013 10:44 AM, Chinar Trivedi <
> chinart13 at gmail.com> wrote:
>  Let's us analyze for which all elements in IMS (or any SIP Network for
> that matter) load balancing feature is needed (SBC, P-CSCF, I-CSCF, S-CSCF)
>
> 1. Is Load Balancing (LB) needed for discovering SBC or a UE hitting DNS
> to resolve SBC is needed? As SBC is a Security node in any SIP Network,
> typically what is expected from SBC is NAT, Topology hiding, Call Admission
> Control, etc.
> Having said that, should UE directly be seeing SBC's IP address or should
> UE's query hit a LB to select SBC. If DNS feature is needed, should UE's
> query be hitting DNS for resolving SBC.
> In that case, should LB be acting as DNS or we don't need a LB at all and
> DNS itself should be enough for resolving SBC's IP address and SBC Location.
>
> 2. Is LBing needed only for the forward path or also the reverse path?
> What I understand is LBing is done only in the forward path i.e After every
> SIP element, LB will choose the respective SIP device (P/I/S-CSCF) from a
> pool of multiple SIP elements in actual Registration/ SIP Call. Typically,
> in any SIP Network, the 200 OK Response shouldn't be hitting LB.
>
> If we don't want 200OK or any RESPONSE code messages to hit the SIP
> elements, won't the connection break on Layer 3?
>
> 3. Most important aspect of LBing in SIP Networks is maintaining
> persistence. There are few standard ways of maintaining persistence for
> HTTP Protocols like least response time, Back end Server CPU Load etc. But
> for SIP networks, will it be done on parameters like Call-ID/IMPU or
> multiple parameters should be used. Can we set up multiple rules for LBing
> SIP networks?
>
>
> Let us discuss/analyze. My understanding on above points may be wrong.
> Feel free to correct me.
>
> Thanks,
> Chinar
>
>
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-- 
Chinar D Trivedi,
Master's of Science (MS) in*Telecommunications & Networking*,
School of Information Sciences,
University Of Pittsburgh, PA,
Tel: (412)-916-9496.
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