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ehuffman
New Contributor

Does TA-900e support NFAS

That's all - need to know if TA908e/924e supports NFAS

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4 Replies
jayh
Honored Contributor
Honored Contributor

Re: Does TA-900e support NFAS

No. One D-channel per PRI. There are only two PRIs supported anyway, so with NFAS you'd only gain one talk path if it did. If NFAS were supported and you configured a primary and backup D-channel you would still have 46 voice paths so there would be no advantage.

ehuffman
New Contributor

Re: Does TA-900e support NFAS

What if I have a situation where a customer requests NFAS using only a single D-Channel? 

  • NFAS - An ISDN service that allows a single D channel to control multiple PRIs. Using a single D channel to control multiple PRIs allows one B channel on each interface to carry other traffic.
  • 24 B channel interface - A PRI channel group configured to have no NFAS D channel; all the 24 channels are B channels. This particular T1 uses the D channel configured in the primary controller for signaling.
jayh
Honored Contributor
Honored Contributor

Re: Does TA-900e support NFAS


ehuffman wrote:



What if I have a situation where a customer requests NFAS using only a single D-Channel? 


Tell your customer that the TA-900e doesn't support it.

NFAS makes very little sense for a device that only supports only two PRIs delivered over individual T-1 interfaces. If it did support it and the PRI with the D-channel were to fail, it would render the other PRI unusable. Point this out to your customer as a valid reason not to use NFAS here. Using NFAS in this scenario would hurt reliability. 

NFAS is really only useful in much larger deployments such as a T-3 interface with 672 channels spread over 28 T-1s. Here one would typically have two D-channels, one primary and one backup, and could gain 26 B-channel talk paths by doing so. As the TA900e only supports a maximum of two PRIs, and they're on separate physical interfaces, it doesn't scale.

ehuffman
New Contributor

Re: Does TA-900e support NFAS

Got it Jayh - thanks for the explanation.

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