cyril7:So each cabinet has 7 GigE links. That means with 196 suscribers they would get 32mb each.
Or 140 lines at 50mbp.
Does that sound right?
No, the ISAM system consists of a host shelf, that can accept upto 7GigE uplinks, this host shelf has 10 downstream GigE links, each extension shelf has a single GigE uplink from the host shelf. Each shell either host or extension can support 4cards x 48 DSL ports = 196.
So the reality is at best 1xGigE per 196 ports or if on a fully maxed out system 7GigE over 1960ports, this works out at 5Mb/s at best or 3.5Mb/s if fully fitted. Obviously Telecom could fit just one GigE to feed the whole 1960 ports, but as I understand it thats not whats provisioned. Exactly what is provisioned is the business of Telecom. So if we presume best case 3.5Mb/s full chat with a 10:1 contention ratio (which is a good business class) giving 35Mb/s (therefore exceeding ADSL2+ full line rate) then there is no reason why Telecoms new ISAM based system cannot provide first class performance.
Excatly what they provide is their business.
Nokia/Seimens and Huwaai gear used by Orcon and Voda give similar levels of access and port density.
Telecom's agreement with previous government was for 80% of users to be cabinetised with FTTN (or was that 80% of lines?) within 5 years and they are progressing on that quite well considering the size of the job. FTTN means fibre to the cabinet, and generally ADSL from the cabinet to the user. Theoretically they could install GPON cards onto the ISAM to connect fibre subscribers if the local fibre co wanted to build a more neutral neighbouring cabinet for other ISPs to use their own splitters. They could not bypass the cabinet for unbundled [ADSL] users who wanted to stay connected to the exchange, since interferance would make the line unstable or unusable (and slow like dialup).
I dont know what actual contention Telecom use, but I suspect around 50:1 on the bigger ISAM nodes if an imaginary 10Mbps target per user was possible. Telecom should have minimum 2 links to each cabinet for redundancy, maybe in a ring or sharing bandwidth at the exchange. For example, if cabinets were fed by 12-strand cables, they might use 2 pairs for the Telecom node and keep the remaining 3 pairs for access seekers. Also worth noting that different fibre technologies need a single strand or a pair.