Author Topic: Linksys SPA-3102  (Read 951 times)

pw44

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Linksys SPA-3102
« on: December 26, 2009, 06:34:41 pm »
Hi,
reading the wikis and users setups, i've found that all uses the SPA-3102 on the internal LinuxMCE network.
Question: is it possible to use the SPA-3102 on the extenal network, making use of the QOS during heavy downloads, i.e. during torrents downloads?
TIA,
Paulo
« Last Edit: December 28, 2009, 11:30:07 pm by pw44 »

trentend

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Re: Linksys SPA-3102
« Reply #1 on: December 29, 2009, 12:44:00 pm »
Use in what way?  For what purpose? How do you mean internal and external network?

The SPA-3102 is a dedicated device, with very specific uses.  It can take an analogue phone signal, and convert it to a VoIP signal (and vica versa) to allow the right software (like, for example, asterisk) to connect to the telephone network.  It can also provide a phone connection point to allow an analogue phone to act as a VoIP extension.

There is some other network hocus pocus in there (like stun traversal), but that is essentially what it should be used for - it is not in any way linked to Linuxmce.  I don't have a linuxmce setup, but I do have asterisk, and I use an SPA-3102 on that asterisk switch (running on a NSLU2).

In telecoms speak the SPA-3102 could (I think) be described as a 1 FXO 1 FXS phone gateway.

pw44

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Re: Linksys SPA-3102
« Reply #2 on: December 29, 2009, 08:37:54 pm »
The SPA-3102 is a dedicated device, and one of it's feature is QOS, shaping packets to privilege the VOIP.
The idea would be connecting the internet port to the adsl modem, the ethernet port to the external nic of the dcerouter, the FXS port to my POTS line and having PAP2T-NA in the internal network (dcerouter internal nic), with the normal telephone and fax devices attached. So, while downloading torrent files, i would have the SPA-3102 QOS assuring voice quality for the VOIP service (not yet in use, but planned in a future, like cheapvoip).
The question was regarding if it's possible to have the SPA-3102 in LinuxMCE and having LinuxMCE using it.
I'm pretty new in this field (VOIP), some questions may sound really stupid, but i want to be sure that what i'm thinking is correct and can be done, before starting to setting it up.... and later discovering that i did it wrong....
TIA.

colinjones

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Re: Linksys SPA-3102
« Reply #3 on: December 29, 2009, 09:19:29 pm »
I'm a bit confused by exactly what you are trying to achieve with this device - connecting to a VoIP provider or connecting Asterisk to a POTS service, it can do either, but your description seems to be attempting both, which doesn't make much sense to me.

Either way, don't be fooled by the QoS features of these devices. For QoS to be effective it must be enforced at every interface between a higher speed network and a lower one - when in-line on your home LAN both sides of the network are most likely the same speed, and so it will not offer any significant benefit over the QoS enforcement that LMCE's core does for VoIP traffic anyway. Moreover, both will not provide the full benefit of QoS unless you setup QoS on your ADSL router as well, anyway!

By all means use this device to connect LMCE's Asterisk system to a POTS provider, but in this configuration QoS is irrelevant, and you don't need to connect the device to the ADSL modem, only to the LMCE network. Or use it as an ATA on the LMCE internal network, to convert an analogue phone into a VoIP phone for LMCE, but in this configuration QoS is even more irrelevant as the core and the modem are doing the prioritisation. If an ATA is what you want, then any old cheap ATA will do for LMCE.

Background: QoS is usually split into 2 parts, marking/colouring and enforcement. The marking process merely uses rules to select particular traffic and set flags the indicate how they should be treated by later devices in the routing path, but doesn't actually perform any prioritisation or other changes to the flows. Enforcement is the actual process of reordering packets to give some priority over others - this can be done based on the flags set during the marking process performed by previous devices (or even the source) or more often based on marking done by the same device as is doing the enforcement.

pw44

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Re: Linksys SPA-3102
« Reply #4 on: December 29, 2009, 10:41:19 pm »
The intention is firstly use only the POTS service, and later, POTS and VoIP with Voipcheap. I do have a POTS service plan, a flat plan with no time limit with a fixed (really low) value for local calls, and it's cheaper than any VoIP provider could offer. For long distance (inland and international) calls i will use Voipcheap, so i will be using POTS and VoIP. The question regarding using this ATA on the external network was merely regarding the QoS when using on a VoIP provider, via ADSL.
So i will need the SPA-3102 for the POTS and VoIP and the other ATA (PAP2T-NA) to distribute the normal analog telephone and fax devices over my home LAN, and my mobile as a wireless extension, using the SIP server from Freebox. Other advantage for me will be having one of the PAP2T-NA travelling with me and giving me a home phone line extension whatever i am (in the office, on trip, etc...)

If in this configuration QoS is irrelevant, i think it's better to use it on the internal network.

Thanks for the detailed explanation.