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Go and read G.993.2; I've got the 12/2011 version to hand. Table 6-1 in the copy I've got shows the profile parameters and the bandplan parameters. For Profile 17a, the MBDC (the aggregate data rate a Profile 17a compliant device must support) is 100 Mbit/s.
Gone and re-read.
My copy of the document (same version) tells me that MBDC stands for "Minimum Bi-directional Net Data Rate Capability". So it really refers to a minimum capability of hardware. Not a maximum capability, and certainly not a maximum possibility.
Later on, the spec has this to say:
The bidirectional net data rate capability is the maximum value of the bidirectional net data rate that the VTU can support.
The required minimum bidirectional net data rate capability (MBDC) is the minimum value of the bidirectional net data rate that a VTU compliant with a profile shall be capable of supporting.
I understand the first part of that paragraph to mean: A VTU has a maximum BNDR that it can cope with, as a consequence of the power of the hardware it is designed with. This is the highest capability of the device.
I understand the second part of the paragraph to mean that, for a VTU to be considered as compatible with any particular profile, its maximum BNDR must be above the MBDC value. In this case, for profile 17a, a VTU must be able to shift 100Mbps at minimum to qualify. No specification of what the maximum BNDR can be.
So that doesn't mean that profile 17a itself - the band plan in use - is limited to carrying an aggregate of 100Mbps. Just that devices might be the limiting factor.
Eircom's testing has been done using bandplan 998ADE17 with Profile 30a devices; it uses the same frequency spectrum as BT do in the UK, but Profile 30a devices must support 200 Mbit/s MBDC.
So you agree that when the network runs as profile 17a, it doesn't present a 100Mbps aggregate limitation - that only happens when you have a weedy, minimum-spec CPE modem.
Presumably, you also agree that CPE devices can be more powerful than the minimum needed to qualify as being "profile 17a" capable. And that they don't need to be actually running profile 30a to make use of the that extra power. And that such a beefy modem can run in "profile 17a" mode, alongside a beefed-up network, and work at an aggregate speed of above 100Mbps.
Combine a beefy, above-minimum-capability DSLAM running profile 17a, with a beefy, above-minimum-capability modem running a matching profile 17a, and you get aggregate speeds above 100Mbps. Ergo profile 17a, per se, does not present an aggregate speed limitation.
That certainly seems to be the case for Eircom.
Whatever hardware they used during testing of vectoring, they continued to leave subscribers on the same F1000 modem - there was no new modem dispatched when profiles were upgraded.
The Eircom F1000 modem, aka the Zyxel VMG8324-B10A, seems to synchronize happily at an aggregate of over 122mbps (102.4/20.5). Yet Zyxel's own specs for the VMG8324 don't mention capability for profile 30a.
http://www.zyxel.com/uk/en/products_services/vmg8324...
Zyxel themselves think that profile 17a has maximums of 100 down combined with 50 up.
http://www.zyxel.com/solutions/solution_detail_20101...
Or should we tell them they needn't bother?
Eircom's testing has been done using bandplan 998ADE17 with Profile 30a devices; it uses the same frequency spectrum as BT do in the UK, but Profile 30a devices must support 200 Mbit/s MBDC.
I should emphasise that we know that the only difference such a CPE device can make is that it brings additional power. Neither end is actually working in the profile 30a mode, shown by plenty of screenshots over on boards.ie where the modem reports both profile 17a and the 100/20 speeds.
IIRC, profile 30a doesn't support US0 either ... yet we see US0 as part of those same screenshots.
I also have a recollection of vendors reporting that profile 30a - where there are 3,500ish tones spaced at 8.6kHz - isn't vectoring-compatible with profile 17a in the same bundle.