What is your PBX or CTI solution without an interface to the outside world. One can use VoIP but there are still a lot of systems going the traditional route and connecting to a Telco either via Analog (POTS) or a T1/PRI/E1. With Asterisk the two main solutions to do this are an internal PCI card or an external Gateway device. Both options will make and receive calls from the telco but which one is better?
I’ll cut to the chase and say PCI cards should not be recommended for High Availability solutions. They can still have their place in a system without HA and where costs are a major factor, but the decision to use them should be made with their limitations in mind.
Using a Gateway device, such as Patton or Audiocodes, provides the following benefits over an internal card:
- Multiple telephony servers can connect to a single gateway. Which is important for the next two items.
- With multiple servers connected to a single gateway in a HA solution calls will be routed to the active server(s).
- Load balancing done at the gateway level in a high volume centers to distributed calls across servers.
- Independence from a single server. If a specific server needs to be rebooted or taken offline for maintenance a gateway will keep working.
- Location of telco demarc can be independant of telephony system. This can be in a different room, floor, building or even country. Just be careful of lag causing issues. But given the proper connections can allow moving the IP PBX system into the cloud while still supporting traditional telco trunks.
- In a mixed trunk environment of VoIP and traditional telco connections the Gateway can abstract this so the IP PBX’s configuration is similar for all trunks.
- Scaling up only requires adding a new gateway and a configuration change to the telephony system which minimizes downtime and risk. Mainly due to avoiding the need to open the system to install new cards.
Considering the above it is hard to see the case for a PCI card, especially in an HA solution. They may still have their place elsewhere but I’ll be recommending a VoIP Gateway going forward.
Any comments on PRI to Ethernet bridges? How do unified communications solution provider like Shoretel or Mitel compare against Asterisk based solutions? Do they offer HA and redundancy through similar techniques?
I’ve used and seen redphone’s PRI Ethernet bridge used a few times before, those are a step better than an internal card but I would still prefer a VoIP gateway on it’s own. The redphone required specific modules and configuration done at a lower level than a SIP trunk to a VoIP Gateway or SIP Provider needs.
For Shoretel, Mitel, and others.. they can offer similar HA and redundancy to solutions with Asterisk in the backend. The issue is an Asterisk solution can mean so many different things. However it’s a good idea for a future post to make that comparison. It’ll take some digging to figure out what each solution/system really provides in terms of HA/Redundancy, see: //asterisk-acd.com/2014/08/20/the-differences-in-call-survival-and-call-recovery/ for case where a term is not always clear.