[LINK] NBN is FTTH
Paul Brooks
pbrooks-link at layer10.com.au
Thu Apr 9 12:08:13 AEST 2009
George Bray wrote:
> Paul, thanks for your figures and that article link.
>
> Are FTTP tails generally configured as symmetric pipes in existing
> scenarios (Japan/Korea)? Is a bridged interface by definition
> symmetric?
>
No, and not really - the bridge itself might be symmetric (a standard
ethernet port), but the bandwidth back upstream to the network is u
sually less.
See Chunhwa Telecom's FTTx rates for one point-example of services
offered in Korea at the moment:
http://www.cht.com.tw/CHTFinalE/Web/Personal.php?CatID=898
"2. The download/upload speeds for this service are 3M/768K, 10M/2M,
50M/3M, 100M/5M."
I was a bit disappointed when I saw this - the upstream connection
should be expected to be greater than this, and there is nothing
preventing an operator providing symmetric service options - again, in
the GPON technology I outlined earlier, the downstream link is 2.5 Gbps
shared, the upstream PON link is half that - 1.25 Gbps or so - so I
can't see a technical reason why upstream:downstream ratios need to be
worse than 1:2.
In fact, if half the downstream capacity is tied up with television and
other one-way traffic (channel-change signals upstream are negligable)
then 1:1 symmetric links for data should be achievable - it appears to
be a product marketing issue, not a technical issue that makes these
plans so asymmetric.
> And do you think we can expect multicast to be enabled across the
> entire net? Is IPv6 multicast in production use these days, or just
> where I've seen it being tested in academia?
>
I'm sure the operator may use multicast to distribute its own PayTV
services and thinsg like that, but enabling multicast for the general
subscriber might be stretch, unless service providers can successfully
lobby the RuddTelecom engineers that it is required in order to fulfill
the objective of open-access for all service providers, as the efficient
method of enabling multiple competing PayTV service providers and
multimedia education service providers.
Paul.
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