[asterisk-users] is DNS SRV enough for failover?
hi, i'm using DNS SRV for failover, i tried to test shutting the server down, sip client should still register on the other server but it did not. i'm using x-lite which i don't know if it's doing a srv query. does this mean SRV is not enough for failover? if a client has dns caching would this cause a problem? TIA regards nhadie ___ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [asterisk-users] is DNS SRV enough for failover?
Nhadie wrote: > hi, > > i'm using DNS SRV for failover, i tried to test shutting the server > down, sip client should still register on the other server but it did > not. i'm using x-lite which i don't know if it's doing a srv query. > does this mean SRV is not enough for failover? if a client has dns > caching would this cause a problem? SRV records are DNS. DNS is cached. Ergo, SRV records are cached. Ergo, if they are cached excessively - either because the TTL is long, or in defiance of the TTL - it can cause a problem. No, DNS is not a good way to do real-time failover for anything. -- Alex Balashov Evariste Systems Web: http://www.evaristesys.com/ Tel: (+1) (678) 954-0670 Direct : (+1) (678) 954-0671 Mobile : (+1) (706) 338-8599 ___ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [asterisk-users] is DNS SRV enough for failover?
Nhadie wrote: >hi, > >i'm using DNS SRV for failover, i tried to test shutting the server >down, sip client should still register on the other server but it did >not. i'm using x-lite which i don't know if it's doing a srv query. >does this mean SRV is not enough for failover? if a client has dns >caching would this cause a problem? > > No it would not. You should have at least 2 SRV records pointing to your 2 servers. It is ok if your client is caching them if they are not supposed to change. The problem lies in your client. It should realize after a few seconds of trying to register to your main server that it cannot so it should try the next one in line according to your SRV Records. We have deployed thousands of Linksys units configured to query SRV records and they work fine in failover scenarios. I cannot comment on X-Lite. Andres http://www.neuroredes.com >TIA > >regards >nhadie > >___ >-- Bandwidth and Colocation Provided by http://www.api-digital.com -- > >AstriCon 2008 - September 22 - 25 Phoenix, Arizona >Register Now: http://www.astricon.net > >asterisk-users mailing list >To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users > > > ___ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [asterisk-users] is DNS SRV enough for failover?
Andres wrote: > Nhadie wrote: > >> hi, >> >> i'm using DNS SRV for failover, i tried to test shutting the server >> down, sip client should still register on the other server but it did >> not. i'm using x-lite which i don't know if it's doing a srv query. >> does this mean SRV is not enough for failover? if a client has dns >> caching would this cause a problem? >> >> > No it would not. You should have at least 2 SRV records pointing to > your 2 servers. It is ok if your client is caching them if they are not > supposed to change. The problem lies in your client. It should realize > after a few seconds of trying to register to your main server that it > cannot so it should try the next one in line according to your SRV Records. > > We have deployed thousands of Linksys units configured to query SRV > records and they work fine in failover scenarios. I cannot comment on > X-Lite. Hi Sir. This is the result of my query: ~$ host -t SRV _sip._udp.mydomain.com _sip._udp.mydomain.com has SRV record 0 1 5060 sip-1.mydomain.com. _sip._udp.mydomain.com has SRV record 0 3 5060 sip-2.mydomain.com. is that what you meant on having at least 2 SRV record? does this mean i need a UA capable of querying DNS SRV? i know it's not a real failover but at least the UA should still try to register on the other server if it cannot connect. thank you regards, nhadie > > Andres > http://www.neuroredes.com > >> TIA >> >> regards >> nhadie >> >> ___ >> -- Bandwidth and Colocation Provided by http://www.api-digital.com -- >> >> AstriCon 2008 - September 22 - 25 Phoenix, Arizona >> Register Now: http://www.astricon.net >> >> asterisk-users mailing list >> To UNSUBSCRIBE or update options visit: >> http://lists.digium.com/mailman/listinfo/asterisk-users >> >> >> > > > ___ > -- Bandwidth and Colocation Provided by http://www.api-digital.com -- > > AstriCon 2008 - September 22 - 25 Phoenix, Arizona > Register Now: http://www.astricon.net > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: >http://lists.digium.com/mailman/listinfo/asterisk-users > ___ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [asterisk-users] is DNS SRV enough for failover?
>Hi Sir. > >This is the result of my query: > >~$ host -t SRV _sip._udp.mydomain.com > >_sip._udp.mydomain.com has SRV record 0 1 5060 sip-1.mydomain.com. >_sip._udp.mydomain.com has SRV record 0 3 5060 sip-2.mydomain.com. > >is that what you meant on having at least 2 SRV record? >does this mean i need a UA capable of querying DNS SRV? > >i know it's not a real failover but at least the UA should still try to >register on the other server if it cannot connect. > > > Those records look fine. Priority is 0 for both, which is the highest, and the higher one with weight of 3 should be selected most of the times. My guess is your UA is either not doing SRV queries or is not following them in any case. To know if it is actually doing the queries try to sniff the traffic with Wireshark and analyze it. Andres http://www.neuroredes.com >thank you > >regards, >nhadie > > > > > > > > > > > >>Andres >>http://www.neuroredes.com >> >> >> >>>TIA >>> >>>regards >>>nhadie >>> >>>___ >>>-- Bandwidth and Colocation Provided by http://www.api-digital.com -- >>> >>>AstriCon 2008 - September 22 - 25 Phoenix, Arizona >>>Register Now: http://www.astricon.net >>> >>>asterisk-users mailing list >>>To UNSUBSCRIBE or update options visit: >>> http://lists.digium.com/mailman/listinfo/asterisk-users >>> >>> >>> >>> >>> >>___ >>-- Bandwidth and Colocation Provided by http://www.api-digital.com -- >> >>AstriCon 2008 - September 22 - 25 Phoenix, Arizona >>Register Now: http://www.astricon.net >> >>asterisk-users mailing list >>To UNSUBSCRIBE or update options visit: >> http://lists.digium.com/mailman/listinfo/asterisk-users >> >> >> > >___ >-- Bandwidth and Colocation Provided by http://www.api-digital.com -- > >AstriCon 2008 - September 22 - 25 Phoenix, Arizona >Register Now: http://www.astricon.net > >asterisk-users mailing list >To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users > > > ___ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [asterisk-users] is DNS SRV enough for failover?
This is so wrong it's not funny. The caching of DNS SRV records acts in its favor when it comes to failover - the UAs already have the information they need in their resolver cache to perform the failover without having to make another DNS query. The TTL you need to worry about is that of the SIP registration - UAs will typically renew their SIP registration at the half-life of the TTL. A short SIP registration TTL will permit devices which are not actively placing calls to failover more quickly than they otherwise would. Of course, a balance must be struck between short SIP registration TTLs, and the amount of SIP registration traffic this generates. YMMV. CP On Tue, 2008-09-30 at 22:07 -0400, Alex Balashov wrote: > Nhadie wrote: > > hi, > > > > i'm using DNS SRV for failover, i tried to test shutting the server > > down, sip client should still register on the other server but it did > > not. i'm using x-lite which i don't know if it's doing a srv query. > > does this mean SRV is not enough for failover? if a client has dns > > caching would this cause a problem? > > SRV records are DNS. DNS is cached. Ergo, SRV records are cached. > Ergo, if they are cached excessively - either because the TTL is long, > or in defiance of the TTL - it can cause a problem. > > No, DNS is not a good way to do real-time failover for anything. > ___ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
