Seeking advice: POTS for remote office, or 2nd Internet connection

I would first try using g729 for the remote users.
I have a client with about 4 locations and a 1.5 MB SDSL connection where the trixbox is located. The remote phones connect using g729, but use a regular ulaw sip trunk for incoming/outgoing calls (which is not a problem at all.)
Before we had those remote extensions on g729, they would often complain about quality issues. Now they dont. It is very very hard to realize that "voice quality drop" with digium's g729. The first time I tested the phone, I thought g729 didnt install properly but when I went to 'sip show channels' I saw g729 being used.

If g729 isn't an option in the St. Louis office, I guess using POTS would be acceptable.

I am not as experienced as you KodaK by any stretch of the imagination. I can, however say that i have stretched the trixbox around the world and use it daily with very few if any problems outside of the ones generated by my lack of expertise. My apartment is connected to the system remotely thousands of miles away - has a standard dsl (1m down and 500k up) line. I can watch my slingbox tv setup and talk on the phone fine with - no problems with either. ( i am using ulaw for all communications by the way. not the most condensed but certainly clearest to my knowledge. I am pretty sure that a ulaw call will only utilise approx 64kb both ways .)

I have connection to my other place in Europe as well as my place stateside and from time to time connect from Europe to a remote unit in California. My weakest link is only one of the four service providers i use for outside lines and that pings at 120ms. My remote phones often ping at up to 400ms, however when speaking on them (internal to internal) they are clear as a crystal wine glass being jingled by a spoon handle preceeding a toast -- much more clear in fact than a regular pots call (no trixbox system but Bell with normal non cordless phones) between the same two locations (we tested that before installing the voip). When using the high pingtime phones on outside calls, they are usually as good as the providers line.

I do, however use all cisco phones. I have not ever to my recollection had any experience with degradation of call with the exception of having that same one provider improperly configured - which was quickly remedied and of course my fault.

I can not believe, although i understand it is in fact possible, that the internet would be to blame for the poor call quality given that my system provides an extreme case and i test it hard every day of the week - with real use keeping the telemarketers believing that i am actually at home in each place all the time.

If you want to pm me with a number, im abroad now and would be happy to put a call through to you to give you a feel for the clarity from the other side of the world - if that helps.

All remote offices (barring home users) are already connected via VPN, and QoS is already implemented on those links. The problem exists (I believe) in the DMZ, where I'm getting hit with lots of web and email traffic.

I'm not kidding about that. I'm pulling thousands of messages a day across a 3Mb link, and those (nebulous) numbers are only after I reject based on various black lists and pre-greeting traffic and other "HI I AM A SPAM BOT" checks. I reject probably 2/3rds of the mail I'm receiving, and a lot of the legitimate stuff that we do pull in is multi page PDFs with appraisals and rate sheets and the like.

I'd love to host this elsewhere, but when it takes my users longer than 5 seconds to send a 400 page PDF to the mail server it's "slow." Although I suppose I could still have an internal mail server to queue things up, then send it out slowly. Something to think about.

This may look familiar to some people (with a small change):

Internet<-->Telco router<--->border router<-->int phones/computers/etc
                                   |
                                   |
                                   v
                              DMZ:Mail/Web

The link into the border router is saturated because of web and mail (and scp and PPtP and and and. . .) traffic going to the DMZ. It doesn't matter what type of QoS I put there, because I can't control what's coming in only what's going out.

Wrong post

Perhaps I should have also mentioned that we have people using remote extensions to the offices that are softphones that support the iLBC codec. They work better using that codec also. Maybe you would have made the connection then, or perhaps, you already knew that the KS phones didn't support the use of that codec.