<There are two different products - jetstream and jetstart. Jetstream, telecom (well except a couple of ISP's - if there are still any that do) provide the bandwidth - so it is simply routed to global gateway/the internet. For
jetstart the data flows from ipnet to your ISP then to the internet.>

Correct so far

<Its fairly obvious that its a good idea to do accounting at the earliest possible opertunity. In the case of jetstream that happens to be the DSLAM's (Digital subscriber line access multiplexor) or whatever the new buzword names they give the new alcatel units are (the brain fails me at 10pm on a friday night). Which is quite simply the device you connect to at the exchange.>

Sorry but the DSLAM is just an ATM multiplexer with DSL line interfaces. As such it doesn't know about IP therefore can't count packets or bits (it could count ATM cells). DSLAM is the generic term, Alcatel call them ASAM's - ATM Subscriber Access Multiplexer. Traffic counting is done by the RAN (Remote Access Node) or BRAS (Broadband Remote Access Server) depending on the school you went to. The RAN is where the ATM and PPP is terminated and therefore the IP is accessible again.

<For Jetstart - your ISP can't start counting data until it has flowed to it - so it occurs a bit further down the line.>

<So Jetstream is accounted based on the line (the actual physical port - sorta) that you connect to the exchange with. Hence if you use somebody else's jet*stream* login it will be charged against you. I even vaguely remember a conversation from a few years back about the DSLAMS counting data at layer2 - meaning it also counts the ATM frames or cells (whatever the layer 2 encoding for PPP over ATM is - read up on the OSI model if you have no idea what I'm talking about). Although I don't remember the outcome of that conversation - if anybody can remember I'm interested to know.>

Memory must be playing tricks, anyway it is wrong. Traffic is counted at layer 3 as above

<However - with jet*start* the accounting is based on data flowing through your ISP with a particular IP address - so you can use your login when staying at your mate's place and have it charged to your account. ISP's can count data as they wish>

<So there is one of two possible outcomes when a user becomes uncapped.
1) One or more radius servers stuffed up along the way and it now thinks you have a jetstream line and routes the data through telecom - but telecom doesn't keep your accounting info because you shouldn't have a jetstream line - so no data flows through your ISP and telecom isn't counting. Wooohooo to anybody this happens to ;) (jk guys).>

As Telecom doesn't bill Jetstart on usage they don't use the records collected. It is up to the ISP to cap as they fit (and record the throughput themselves).

<2) The 128K ratelimiting at your exchange decides to lose it's mind. So data is still flowing to your isp, and I suppose isp's don't do their own ratelimiting on the incoming data, because its theoretically completely unnecessary (the data should already be ratelimited) and very heavy on router 'horsepower'. In this situation you would be getting a semi-unlimited speed (depending how good your isp is :P) but it would still be flowing
through your ISP - so adding to your bill.>

Rate limiting is done by the RAN which isn't at the exchange. You get a full rate line but the back-end ATM for your circuit gets limited out of (and into) the RAM at ATM.

<There - clear as mud? Please feel free to correct me - I'm not exactly completely up to speed on nz ISP best practises - but I think that's the guts of it.>

<Also a thing to note is that when a jetstart line is first installed/enabled/whatever apparently it is full speed jetstream until the next / 2nd time you login. I've heard of people keeping their linux routers up for a while to take advantage of this :).>

Generally not true (but can happen) - mostly you are 'forced' to log-in again by dropping the PPP in the middle of the night - only if you new, this is done selectively.

These are only my views rah rah rah....

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Disclaimer: This e-mail contains my personal views and is sent in good faith for the general education of the recipient. These views are not to be construed as the official view of my employer.
Cheers
Wayne
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