Voice and Video


All our yesterdays... breaking in a new branch architecture for voice

“But do not despise the lore that has come down from distant years; for oft it may chance that old wives keep in memory word of things that once were needful for the wise to know.”
J. R. R. Tolkien, The Fellowship of the Ring

“Facts are stubborn things.”
President Ronald Reagan

New ideas take an age to take root in the voice industry. Which is not to imply we are surrounded by luddites, rather that those inconvenient facts on the ground keep getting in the way of progress. It’s often only at the second or third echo that a concept finds the soil tilled and the sun shining.

Which brings us to new ideas and simpler architectures for voice in the branch office. In the corporate location most susceptible to hardware costs and complexity, we have managed, over the years, to talk ourselves into the most complicated mountain of equipment imaginable: every innovation has caused us to add, and none to subtract from the stack.

But we may finally have arrived at the real architectural breakthrough, the one that will stick and become the model for the next decade. Last month Siemens Enterprise Communications (SEN Group; why not SEC?) announced their OpenScape Voice V4 architecture with OpenScape Branch, and it’s a Good Thing. Not only has Siemens been wise enough to ally itself with Banksy (not the artist, the other one, from StrataCom), but it has taken the plunge and ditched the PSTN interface.

But whence your correspondent’s simmering angst? What’s wrong with the way we have done things for a decade and more? In fact, the simplest required functions for a branch office can be met very easily. A local router or bridge running a secure connection to the corporate data center, carries VoIP streams between IP phones and the central call servers and telephony gateways. A little bit of QoS, perhaps even CAC, maybe a site-to-site VPN, and we are on our way.

But then the traditionalists get hold of the thing, and they wreck it in the name of redundancy (Make no mistake, these thoughts are worthy, well-meaning and contain more than a grain of truth, but they make a dog’s dinner of the network diagram). They worry about what happens if the WAN link fails. Ten years ago we would say:
• Everyone pulls out their cellphones, if they weren’t on them already; and
• If they can’t get data service to the corporate servers and the Internet, they go home and work from there.
But these common-sense observations were inexplicably eschewed by a whole generation of telecom managers. They believed, very honestly believed, that they were required to provide completely reliable communications to these far-flung locations… and they may have been correct, in the prevailing atmosphere.

But look at what’s involved to allow branch telephony to survive a WAN failure:
• A local telephony (PSTN) gateway. This generally means a T1/E1 for larger locations, or analog for smaller ones. Telephony (PSTN) interfaces are painful. Not only does one have to provide a wide choice of hardware, from simple FXO to deviant 4W E&M with inverted R2 signaling right-hand sprocket attachments, but the hardware immediately becomes custom. If one is using a PC chassis, there are plug-in cards, or alternatively one can stack small telephony gateway boxes, but it’s complex and expensive. Then we have to call up the local Telco and order the trunks.
• We also need some local call processing, to complete calls between leader-less IP phones and the local telephony gateways. More complication, configuration, etc, as it requires a stripped-down call server to sit in the background, learn the dial plan and take over when the central-site call server becomes unreachable.
• And to complete the job we may need redundant servers and backup power.
• The telephony gateway, since it’s there, can now be used for local calling and tail-end hopoff. But effort expended in national least-cost routing is surely of limited efficacy in the modern age of telephony?
Hence the addenda consequent to “it’s voice so it has to be redundant” transform a simple multi-service branch router into an expensive collection of boxes and functions.

The solution has been clear for some time, but we needed the time to take stock and assimilate our new surroundings. Assumptions must be changed in two ways:
• Redundancy/Reliability can be relaxed somewhat, or attacked with different tools rather than local-PSTN-for-Internet failure.
• SIP trunking is viable… even this is optional.

Once we have swallowed this assumption, the need for custom hardware disappears, and life becomes wonderfully simple. No redundancy via analog/T1 PSTN. The WAN/Internet path into the branch becomes the only link to the outside world. If the Internet connection drops, we lose communication. (Note that not even local SIP trunking will work through a last-mile Internet failure, the most commonly experienced type of WAN fault.)

Local phones are controlled by central-site call servers over the WAN, or site-site VPN over the Internet. If we want to use tail-end hopoff we can configure local SIP trunking, although this requires a few software elements, an SBC and SIP firewall, more complicated, but potentially useful especially for a multi-national network. And if we want service to continue if the central site call server is unreachable (although the Internet/WAN needs to be up) a local SIP proxy does the job. All these seem to be elements of the Siemens OpenScape Branch solution. I’d add another: Aruba is finding that cellular data is now viable in many places as a backup, or even primary Internet/WAN connection to small branch locations… and it’s as diverse in terms of redundancy as the PSTN.

Since the voice elements are all in software, they can potentially be built into whatever hardware platform is put on-premises: any branch office data equipment with a bit of processing power can do this.

Congratulations to Siemens on breaking the ice with this new branch office voice model. Hopefully this time the concept will take root, and this will very soon become the accepted way to provide branch office voice services.
Search Airheads
Showing results for 
Search instead for 
Did you mean: