On Tue, Oct 05, 1999 at 10:06:37AM -0400, Geof Goodrum wrote:
...
> In Alexandria Virginia USA, both the up and downlink rates are currently
> 3Mbps (it's a fiber network). However, @Home is putting in uplink limits
> (128Kbps, I believe) in their service areas to reserve bandwidth for
> shared network residential use. They do not permit Internet server
> applications...
No wonder. Cable-data environment is very much assymmetric
system. Channel capacity is shared, 30 MB (or so) towards
users, and uplink (shared, too) is mere 0.7 kB (or 1/40th)
of the downlink..
If people are just pulling in data (like web-pages), their
uplink traffic is mostly TCP ACKs (40 byte IP packets + MAC-
frame) outwards, but large frames towards themselves. Optimum
performance is likely achievable for data frames of size
40 * (40+30 bytes) = 2800 bytes
which, by the way, is way more than your average 1500 byte
MTU at server Ethernets...
So, even to get maximum performance out of the downlink
capacity, you would need more uplink capacity, or TCP-SACK
feature. (Getting 1/10:th of maximum downlink capacity is
no big deal, IMO. It just tells that there are other limits
before cable downlink. No HTTP proxies at the cable head-end ?)
> ... (the big reason I didn't join up, I was planning to run a web
> server). My parents use it with Win95, and I've found the actual
> downloads do approach 3 Mbps. Very nice.
If I were at cable-data industry, I would not allow running
own servers either - however I would (very likely) have
a web-hotel available for those pages for some moderate
fee (or included in the service base price).
> Geof Goodrum
/Matti Aarnio <[EMAIL PROTECTED]>
-
To unsubscribe from this list: send the line "unsubscribe linux-net" in
the body of a message to [EMAIL PROTECTED]
