Hi, I read in the Asterisk Whitepaper, that you can run two cloned servers, one as a primary, one as a backup, and have them automatically failover to the other unit when it crashes, or when you need to restart it. The primary application of course, would be ensuring calls can be made when frequent updates are being handled, or when an update must be restarted on a busy network. The term TDM is banded around too, but from my knowledge, TDM is trunking (probably some clever acronym relating to trunking), and in Asterisk's case, using the IAX protocol. This leads me to the big question; Is there anyway of shifting the load of one Asterisk server to another without breaking or loosing a call? I know that with Survivable Routing (Cisco's big on this), the ISDN interface is actually a router; so the Proxy is just used to decide the destination and LCR functions, and then hands off to a router. This of course, if a Proxy went down, would just prevent new calls from being made, whilst existing calls can continue merrily - until someone switches the Router off, or corrupts the IOS settings :-) At least with Routers, you can configure them to load manager effectively, but how do you backup and load manage Asterisk?? I using SIP, and will be using a bit of SCCP too, so any suggestions would be most grateful!! Regards, Ad.
I simply have 2 asterisk servers and have the clients point to a DNS SVR record for their proxy. The DNS record lists the primary and secondary with preference for the primary. This won't stop calls from being dropped if the primary goes down if you are routing them through the server, but it does ensure that calls placed while the primary is down will still go through. You could do some load management by putting multiple servers in the DNS record and use a DNS server that supports round robin responses. Stephen> -----Original Message----- > From: Adthrawn [mailto:adthrawn@adthrawn.freeserve.co.uk] > Sent: Tuesday, December 30, 2003 12:50 PM > To: asterisk-users@lists.digium.com > Subject: [Asterisk-Users] Backup Proxy & Automatic Failover > > Hi, > > I read in the Asterisk Whitepaper, that you can run two clonedservers,> one as a primary, one as a backup, and have them automaticallyfailover> to the other unit when it crashes, or when you need to restart it. The > primary application of course, would be ensuring calls can be madewhen> frequent updates are being handled, or when an update must berestarted> on a busy network. > > The term TDM is banded around too, but from my knowledge, TDM is > trunking (probably some clever acronym relating to trunking), and in > Asterisk's case, using the IAX protocol. This leads me to the big > question; > > Is there anyway of shifting the load of one Asterisk server to another > without breaking or loosing a call? > > I know that with Survivable Routing (Cisco's big on this), the ISDN > interface is actually a router; so the Proxy is just used to decidethe> destination and LCR functions, and then hands off to a router. This of > course, if a Proxy went down, would just prevent new calls from being > made, whilst existing calls can continue merrily - until someone > switches the Router off, or corrupts the IOS settings :-) > > At least with Routers, you can configure them to load manager > effectively, but how do you backup and load manage Asterisk?? > > I using SIP, and will be using a bit of SCCP too, so any suggestions > would be most grateful!! > > Regards, > Ad. > > _______________________________________________ > Asterisk-Users mailing list > Asterisk-Users@lists.digium.com > http://lists.digium.com/mailman/listinfo/asterisk-users
On Tue, Dec 30, 2003 at 06:49:51PM +0000, Adthrawn wrote:> Hi, > > The term TDM is banded around too, but from my knowledge, TDM is > trunking (probably some clever acronym relating to trunking), and in > Asterisk's case, using the IAX protocol. This leads me to the big > question; >TDM is time division multiplex. It's how phone calls are sliced on digital lines. FDM is frequency domain multiplex : to have two (or more) phone calls on the same wire, you shift the frequencies used for each call. That's similar to the way ADSL can work at the same time as telephone. TDM is far more efficient : you digitalize the phone data (sound), it gets you 8000 bytes per second (64kbps/s). Then, you take a T1 link for instance, you put on it a carrier that allows you to transfer 1536 kbits/s. And you realize that every 8000th of a second, your T1 can transport 24 bytes. This way, every 8000th of a second, you send 24 bytes from 24 simultaneous phone calls. That's TDM. Asterisk (zaptel) does TDM over Ethernet as well : instead of using a sync link such as a T1 or E1, you send multiplexed frames across the Ethernet.> Is there anyway of shifting the load of one Asterisk server to another > without breaking or loosing a call? >No. If you're talking about ISDN, that would mean asking the telco to transfer the call from one span to another, transparently. If you're talking about VoIP, that would mean doing tricky re-routing, which could be nasty if NAT is involved. In any case, that would mean transfering a whole call context as well, like a running AGI script for instance, which is simply not possible.> I know that with Survivable Routing (Cisco's big on this), the ISDN > interface is actually a router; so the Proxy is just used to decide the > destination and LCR functions, and then hands off to a router. This of > course, if a Proxy went down, would just prevent new calls from being > made, whilst existing calls can continue merrily - until someone > switches the Router off, or corrupts the IOS settings :-) >What if the "ISDN router" goes down ?? Asterisk is much more of an ISDN router kind than a proxy kind. Maybe you could try to use SER as a front end ? -- Nicolas Bougues Axialys Interactive
Hi, Would it be possible to use an ISDN router instead of an ISDN card? In addition to the failover issue, I'm also considering running a copy off a Mac OS X machine, and as such I do not have access to ISDN4Linux or CAPI toolsets. The only work-round I can imagine is to use a SIP aware ISDN router (probably a Cisco). Any thoughts? I know Vocal is built in this way (Vocal is owned and funded by Cisco)... Regards, Ad.