I really did not intend to be banging on about VSAT again this time.  I was considering a debate on interconnect fees (flavour of the year at the moment), unbundling the local loop or VoIP. Then I set about challenging the statements the guys here had made to me that a VSAT network can be cheaper than one using Diginet.  The gauntlet was thrown down as it were and in the process of batting emails back and forth, I began to see what they were on about.

Now I have to confess to having taken them at their word (they have honest faces around here) but having a niggling feeling that they'd botched the figures somewhere or had been quoting an extreme example which was unfairly in VSAT's favour.  You see, in all the years I've been in the telecoms game, VSAT has been this sort of “last resort” / “robust but niche” / “hellishly expensive” way of getting bits from A to Z, with Z usually in some exotic location like Zanzibar.  The thought of considering VSAT as a viable option to Diginet when rolling out the Storm VoIP network just never entered my head when I worked for them and was tasked with finding a Diginet alternative.  I probably would have laughed in your face had you suggested it then.  We played with VoIP over ADSL, VoIP over WiFi, VoIP over Sentech's BizNet Xpress (brilliant, but for the provider's inability to support it), never VoIP over VSAT. 

We should have seriously considered using VSAT.

Now it obviously depends on how many nodes you have (the more the merrier) and what traffic you are planning on sending over the links.  Voice & Data on the same line provides planning challenges.  Once you've settled on the VoIP codec you're going to use, you have to determine how many simultaneous calls (in and out-bound) you want to be able to handle on each link, what the minimum throughput is you need for the data at any one time, and which applications must stand aside for voice and critical data.  For the Storm VoIP service, we then committed to a Diginet line size, waited months for the install and prayed we did not have to upgrade in a hurry if ever. 

With VSAT, its nothing like that – you can upgrade links easily, specify Committed Information Rates (CIR) and Quality of Service (QoS) etc. which can then easily be changed.  But the kicker, the real kicker, is that all your links can be planned as one bundle, aggregating it all at the Earth Station, and anyone who has planned networks knows that the more handsets you have per PBX or “downstream” data clients coming into your PoP, the more efficiently you can use your “upstream” bandwidth through careful use of what is sometimes called “oversell” or “contention” - heck, we even plan telephone exchange capacity this way!  Umoya have effectively used oversell or contention ratios of 30:1 for some networks, but then the voice traffic has been low and sporadic and data bursty.  As an ISP, Storm used a ratio of 3:1 downstream:upstream for corporate voice and data traffic and we found we never had customer links “flatline”.

So you plan for all your sites as if they were one large site with one PBX and many handsets, and aggregate all your site data needs.  Bandwidth usage ends up about as efficient as you can get!

ps. I tested VoIP over a DOUBLE hop VSAT connection yesterday – not too shabby at all – if Isaac had not told me he was calling from a VoIP phone and over two hops, I'd have thought it was GSM.

How's this for size?:

10 sites, 128kbps/site, contention ratio of only  5:1

or 20 sites, 512kbps, contention ratio of 10:1.

or even

8 sites, 128kbps/site, contention ratio of only 3:1 nets you a 20% savings at the end of 4 years

You have to be committed for a reasonable period, but depending on your needs, this could be a very good option.

OK, time out - I swear I won't blog about VSAT next time!

regards
Dave