Understanding LSP mode

[carlosmcse]

I am newbie to the Avaya VoIP system and i am trying to get a better understanding on how the LSP mode works. This is what we are trying to accomplish. We have multiple office locations world wide. Currently they have their own phone system and if we need to call a office we must dial the entire phone number and the call is connected thru the PSTN network. Our goal is to migrate to VoIP and centralize our phone system. The plan is to use the AVAYA solution on all of our offices and install at out datacenter 2 G650's 2 S8730's CM 5.x and 4 S3500's for VM. For the remote offices we will be installing 2 G450's and 1 S8510 in LSP mode. My understandig (and correct me if i am wrong) is that the office gateways (G450's) will be registered to the datacenter CM's (S8730's), this means that a call coming in to the office Gateway will be answered by the datacenter CM's (S8730's) but since almost all of our offices only have DID's assigned directly to user's extensions (no auto-attendants etc...) the datacenter CM will pass the call to the local office extension then if the call is not answered the VM system (S3500) in the datacenter will answer the call if VM is setup for the extension. If the WAN connection between the remote office and the datacenter is down the local S8510 will take over the calls coming in from the local gateway until the WAN connection is restored. We will have PRI's and PSTN lines for VM routing, my understanding is that if the WAN is down the the local CM is handling the calls for the local office and if the call needs to go to VM the call the local office will make a call to the datacenter system via the PSTN in order to save the VM to the S3500's is this correct?

Sorry for the long message.

 

[FSI]

You need to differentiate between LSP and Media Gateways. Your remote offices need Media Gateways to connect the local trunks (local dialtone). With the WAN up, everything will be centrally controlled by your main S8730 server, however, a call coming in on one of your remote media gateways and answered by a user at the same site will not traverse the WAN, only call control will.

Now add a LSP, which is another server which can take control of media gateways if the link to the main server is down. When a site runs in LSP mode it typically means it became an island, while the LSP knows about the entire (voice-) network it can typically not access anything outside its own location because usually a down WAN link put the thing into LSP mode in the first place. With the WAN down and the remote location in LSP mode, calls between users at the remote site and calls in and out on the local trunks will still work. If your VM is central and relies on the WAN link it will obviously not work. You could send VM calls over PSTN to the main system but depending on your number plan it could be difficult to find the right mailbox for a particular call.

Regards

Frank

 

[t3chhelp]

With the latest Avaya CM release, the dialplan transparency feature will take care of what you are looking for. If the wan were to go down, then the dialplan transparency feature will route call over the PSTN but the call setup time will take a little longer. Contact a local reputable Avaya BP or Avaya direct to discuss, they should be able to give you a better idea.

 

[carlosmcse]

Thanks everyone for your help. What happens if a remote office needs to have a auto-attendant setup? The call comes in thru the local gateway in their office in this case does the call have to go thu the WAN to the centralized ACM system for the Auto-attendant to pickup the call? or is it handled by the local CM that is setup in LSP mode?

My understanding is that everything is handled by the Centralized ACM until there's a WAN failure then the local ACM will take over. I am trying to find a reason why should i centralized or running all offices with their own stanalone system and then using ip trunking to call the other offices, this way there's less WAN traffic.

 

[avayastrongman79]

Just wanted throw another backup feature into the mix, would IGAR come into play in a scenario such as this?

It looks like the need to have a dependable backup link such as a couple of POTS lines or fb lines to create a temporary bridge, could be advantageous.

 

[carlosmcse]

If we decide to go centralized, we would have PRI's and POTS in the local offices. The POTS would be used in case of a PRI outage. The Datacenter would also have multiple PRI's installed only for VM routing thru the PSTN in case of a WAN failure between the remote offices.

But i would like to know the functionality of the inbound call routing if a office uses a auto-attendant when the call comes in thru the local gateway does it travel thru the WAN for the centralized ACM to answer the call? or does the ACM in LSP answers the call?

 

[Mitch672]

carlosmcse,

Not only does the main site process the autoattendant calls, ALL phones & media gateways register to it, and it processes ALL calls ALL of the time, when everything is "normal" (meaning the system is whole, and all WAN links are up and working)

The LSP's ONLY go into service upon a WAN/LAN failure, for the most part the MAIN site processes and handles ALL calls the majority of the time.

If you are in LSP mode, in a WAN failurre condition, and a call arrives on that local remote site, you will not have voice mail or an auto attendant, unless you setup IGAR and DPT (Intergateway Alternative Routing and Dialplan transparancy) those 2 technologies will route the calls via the PSTN (PRI or POTS lines) to the main site, and it would still work, maybe. IGAR and DPT still need a small anount of data bandwidth to be effective as well, since the call information (such as who the call is for, etc) passes via a small amount of data traffic.

Mitch


AVAYA Certified Specialist

 

[carlosmcse]

Thanks for making me understand this LSP mode and call handling. Another question is how does phones know (in case of a WAN failure) to use or register to the local CM? Do you have to tell the phone via the DHCP options as to what the primary and secondary CM? I don't understand how the phone that is registered to the centralized system registers to the local system.

Thanks again for all of your help.

 

[Mitch672]

On the "Ip-Network-Region" form, on page 2, "BACKUP SERVERS(IN PRIORITY ORDER)", you put in the node name of the local LSP(s) you want the phones to register to on connectivity failure, that list is downloaded dynamiclly when the phones register in that IP-Network-Region. You specifically do NOT use DHCP to give out the IPs of LSP's, as that causes a lot of trouble (like phones trying to register to those IP's when the LSP is not active). Communication Manager handles this properly, as long as you have the IP-Network-Regions configured properly.

Mitch


AVAYA Certified Specialist

 

[carlosmcse]

Perfect, thank you for your help. I understand now.