[103414] in North American Network Operators' Group
Re: latency (was: RE: cooling door)
daemon@ATHENA.MIT.EDU (Frank Coluccio)
Sat Mar 29 21:13:56 2008
From: Frank Coluccio <frank@dticonsulting.com>
To: nanog@merit.edu, Mikael Abrahamsson <swmike@swm.pp.se>
Reply-To: frank@dticonsulting.com
Date: Sat, 29 Mar 2008 20:10:15 -0500
Errors-To: owner-nanog@merit.edu
Please clarify. To which network element are you referring in connection wi=
th
extended lookup times? Is it the collapsed optical backbone switch, or the
upstream L3 element, or perhaps both?
Certainly, some applications will demand far less latency than others. Game=
rs and
some financial (program) traders, for instance, will not tolerate delays ca=
used
by access provisions that are extended over vast WAN, or even large Metro,
distances. But in a local/intramural setting, where optical paths amount to=
no
more than a klick or so, the impact is almost negligible, even to the class=
of
users mentioned above. Worst case, run the enterprise over the optical mode=
l and
treat those latency-sensitive users as the one-offs that they actually are =
by
tying them into colos that are closer to their targets. That's what a growi=
ng
number of financial firms from around the country have done in NY and CHI c=
olos,
in any case.
As for cost, while individual ports may be significantly more expensive in =
one
scenario than another, the architectural decision is seldom based on a sing=
le
element cost. It's the TCO of all architectural considerations that must be=
taken
into account. Going back to my original multi-story building example-- bett=
er
yet, let's use one of the forty-story structures now being erected at Groun=
d Zero
as a case in point:=20
When all is said and done it will have created a minimum of two internal da=
ta
centers (main/backup/load-sharing) and a minimum of eighty (80) LAN enclosu=
res,
with each room consisting of two L2 access switches (where each of the latt=
er
possesses multiple 10Gbps uplinks, anyway), UPS/HVAC/Raised flooring,
firestopping, sprinklers, and a commitment to consume power for twenty year=
s in
order to keep all this junk purring. I think you see my point.=20
So even where cost may appear to be the issue when viewing cost comparisons=
of
discreet elements, in most cases that qualify for this type of design, i.e.=
where
an organization reaches critical mass beyond so many users, I submit that it
really is not an issue. In fact, a pervasively-lighted environment may actu=
ally
cost far less.
Frank A. Coluccio
DTI Consulting Inc.
212-587-8150 Office
347-526-6788 Mobile
On Sat Mar 29 19:20 , Mikael Abrahamsson sent:
>
>On Sat, 29 Mar 2008, Frank Coluccio wrote:
>
>> We often discuss the empowerment afforded by optical technology, but we'=
ve barely
>> scratched the surface of its ability to effect meaningful architectural =
changes.
>
>If you talk to the server people, they have an issue with this:
>
>Latency.
>
>I've talked to people who have collapsed layers in their LAN because they=
=20
>can see performance degradation for each additional switch packets have to=
=20
>pass in their NFS-mount. Yes, higher speeds means lower serialisation=20
>delay, but there is still a lookup time involved and 10GE is=20
>substantionally more expensive than GE.
>
>--=20
>Mikael Abrahamsson email: swmike@swm.pp.se
