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Sonco · Guest

I have always heard that a 10mb network should be on a hundred mb backbone.
is there any drawbacks to having everything on 100mb.

we are talking about 5 servers, 4 switches and about 60 workstations.

any comments ?

Alan J. Flavell · Guest

On Sun, 30 Jan 2005, Sonco wrote:

Walter Roberson · Guest

In article <364hcuF4th9aqU1@individual.net>, Sonco <sonbo@comcast.net> wrote:
:I have always heard that a 10mb network should be on a hundred mb backbone.

Not really. The key factor is that your backbone needs to be fast
enough to handle the traffic being put over it without undue buffering
and delays. That's really only something that you can determine through
traffic measurements.

:we are talking about 5 servers, 4 switches and about 60 workstations.

That doesn't really give us much feel for the extent to which the
server-to-server or server-to-workstation traffic is taxing the
existing equipment. For example, if those are streaming media servers
and you are doing video production, you should probably be going right
to gigabit, but if you are just doing a little light email then
you might not stress even a 10 Mb/s backbone.

In our network, which is roughly 4 times as large as yours,
our measurements show that most of the users would barely notice
if we were to drop them and their switches down to 10 Mb/s.
There is, though, one user on one port of one of the switches who
is producing more data than the rest of the users combined: that one
user should have a gigabit port and gigabit backbone to the server.

Other than that, our traffic is fairly localized, with the greatest
portion of the user traffic occuring within one [server] room. User
traffic tends to be rather "bursty" and it can be difficult to
find the right balance of cost and necessity. If one user
saturates their local link 1% of the time, do they need an upgrade?
10%? 30%? 80%? You can't place any hard numbers, because it depends
on how the user is using the network: if that user can start a
transfer and then work productively while the transfer is occuring,
as long as the transfer finishes within a few hours, then a slow
connection might be good enough -- but if you have a researcher
who is interacting strongly with a computer model, then the
difference between 5 minutes and 30 seconds can be very important.

Our experience is that the activity which most greatly taxes our
network is the [automated] backups. If you have enough data stored
then even if only a fraction of it changes each day, doing
a full backup can easily keep your network links saturated
for 6 or more hours. After a point of growth, those backups
aren't going to finish overnight or even over the weekend,
and the backup traffic is going to start interfering with user
traffic: by the time you reach a terabyte or so, you might find
that you are designing your network around the backups
rather than around the user traffic.
--
*We* are now the times. -- Wim Wenders (WoD)

Alan J. Flavell · Guest

On Sun, 30 Jan 2005, Walter Roberson wrote:

James Knott · Guest

Alan J. Flavell wrote:

jpd · Guest

Begin <ctj55g$9tj$1@canopus.cc.umanitoba.ca>
On 2005-01-30, Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:

Al Dykes · Guest

In article <3670g5F4uacnkU1@individual.net>,
jpd <read_the_sig@do.not.spam.it.invalid> wrote:

Fred Marshall · Guest

If that's all there is to it then you might ask yourself a few questions:

Is the 10Mb network there so that it will intentionally limit the data rate
from any client to the backbone? Why?

Compared to 10Mb, if everything is 100Mb, will that necessarily increase the
volume of data? Probably not. It would only increase the peak data rate -
and reduce the time accordingly. Thus reduce the possibility of collisions.

Depending on the topology of the servers and switches there should be less
opportunity for collisions anyway - until multiple workstations vie for
service on the same server.

Ask this: why would it matter if the network elements limit data rate to
10Mb on the clients or if network loading limits data rate to <100Mb on
occasion?

Hints:
If the traffic is such that the 10Mb clients are limited to less than 10Mb
on occasion then having them faster won't help on those occasions.
Otherwise, there is the opportunity for the clients to get faster service if
they are configured at 100Mb.

If there are clients that will immediately query the servers after receiving
each prior server response then they would burn up bandwidth. That would be
an unfortunate design but may well exist. In this case having slower
clients could be helpful.

I imagine that the "conventional wisdom" goes like this:

"If you have 60 clients that will all be served by a backbone then it's a
good idea for the backbone to be faster than the individual clients"
This is all well and good IF:
- The clients already exist
- The slower speed at the clients is acceptable
- The clients don't already exist and having higher speed at the clients is
more expensive
- The clients will use more bandwidth if it's available (as the pathological
case above).
However, IF:
- The network doesn't already exist.
- Cost is pretty much independent of speed
- There is no pathological behavior
- Faster at the clients is better
Then having everything as fast as possible could be a good idea.

I'm not suggesting anything but that you ask yourself some questions about
these things. I'm sure others will provide you with better guidance.

Fred

"Sonco" <sonbo@comcast.net> wrote in message
news:364hcuF4th9aqU1@individual.net...

Robert Redelmeier · Guest

Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:

Walter Roberson · Guest

In article <ctllao$jqq$1@panix5.panix.com>, Al Dykes <adykes@panix.com> wrote:
:In article <3670g5F4uacnkU1@individual.net>,
:jpd <read_the_sig@do.not.spam.it.invalid> wrote:
:>Begin <ctj55g$9tj$1@canopus.cc.umanitoba.ca>
:>On 2005-01-30, Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:
:>> There is, though, one user on one port of one of the switches who
:>> is producing more data than the rest of the users combined: that one
:>> user should have a gigabit port and gigabit backbone to the server.

:>I'd start with putting him on netnanny or something suitably annoying
:>to see if that doesn't reduce the traffic to something reasonable. :-)

As the OP of that statement, I can say that it would not be an
appropriate solution to the situation.

:How are you measuring your network ?

Well, since you ask, I have Fluke's Network Inspector monitoring
all of the switches and producing 5-minute trend graphs. I also
sometimes turn on MRTG and watch the graphs for awhile. More often
though, I record the packet counters and examine the packet volumes
along the various links, cross-correlating from each end of the
link to avoid making mistakes.

:You've got to give us more information before I'll say that your
:requirement exceeds a plain 100Mb full duplex switched network. It's
:a no-braiener to make the server-switch connection a Gbe interface,
:but beyond that you need to do some work to understand what your
:bottleneck is. The physical plant has lots to do with the design. If
:you're in one building with a few floors then pulling a run from the
:main equipment room to a switch on each floor gives you a colapsed
:backbone for not a lot of money.

We have a building with 4 floors and two "wings", with a traditional
star topology to a basement LAN router. One of the two wings is
within the 100 meter copper limit, but due to the way the cross-connect
between the wings run, the switches in the other wing are near or
exceed the 100 m limit, so those have fibre to the core router.
Fibre was also installed on the other side for future expansion, with
all the fibre terminating in that basement room.

:Pulling fibre is a no-brainer and
:100Mb to each floor may be enough and save the price of a an expensive
:Gbe switch in the center, but a couple years from now when you need it
:it will be an easy upgrade path, and cheaper.

Our measurements show we need the "expensive Gbe switch" anyhow, in
order to keep up with our backups -- we've just gone from ~ 1 TB
of storage to ~12 TB of storage capacity [not all used yet!!]
The question was whether it would be best to install a managed gigabit
switch in the wing where only one user is producing a great amount
of data. Our conclusion was that it would be cheaper to pull
copper [and fibre too since most of the cost is in the labour
of putting the cables into the trays] over to our mini-NOC where
we intend the new core router to live.

:"more traffic than the rest of the network, combined" is meaingless
:for the purposes of this discussion

I didn't say "than the rest of the network combined", I said
"than the rest of the users combined". There's a difference.

:unless you give us numbers.

The one user produces ~50 gigabytes per day, usually 6 days a week,
250-350 Gb per week total. Assuming 50% transfer efficiency
[allowing for overheads and architectural limitations as you
get towards gigabit], that is half a working day of continuous
data transfer at 100 Mb/s. By way of comparison, all of our other
servers combined [other than the one the above user data is stored on]
backed up this morning into 437 Gb of tape. If you need more exact
numbers, such as number of packets and bytes transfered per port, then
I can supply several months worth of that information in ~5 minute
increments, but it would be a bit of a nuisance to extract it in
detail out of the database it is in.

Personally though, I don't think it'd be productive to dig up the
details. I monitored the system carefully before making decisions
about which portions needed upgrading and which did not. You should not,
though, neglect the influence of power politics: if my measurements show
that an entire subdepartment could easily fit into 10 Mb/s whilst
a different subdepartment is overflowing 100 Mb/s, the first
subdepartment will tend to feel that it is owed a network upgrade
when the second gets one...

:also suggests that that you have a small # of machines since the
:larger the base the harder it is for one machine to exceed the
:aggregate unless he's very different, such as the only diskless
:workstation, or does daily full backups to the servfer.

Look@Lan tells me I have 324 different devices intermittantly on the
network. Over 600 devices are assign IP addresses, but they
don't all necessarily get used in the same month. We probably
average close to 4 networked devices per person.

:It would be worth the time to see if he's got a virus or spyware.
:Then you should try to understand his business and what makes him
:special.

You ass-u-me'd that I don't understand his business and what makes him
special. I have a fairly good idea of what makes him special.

:I would, before I asked for the money got Gbe. If the
:netowrk connection isn't his bottleneck then there is no reason to
:spend money on him.

:A desktop machine generating enough data for a 100MB/sec net
:connection to be a bottleneck is a rare thing in business.

Again you have ass-u-me'd. You failed to look at my email address
and take a step such as visiting our web site. We aren't -in-
business: we are public sector biomedical research.

For what it's worth, the user is involved in Proteomics and is,
if I recall correctly, doing automated DNA sequence analysis.
The rate of data production swamps our previous high-point
of projects having to do with Functional Imaging of the Brain
in MRI machines, a typical run of which was only 1/2 Gb.
--
I don't know if there's destiny,
but there's a decision! -- Wim Wenders (WoD)

Walter Roberson · Guest

In article <86vLd.25867$iC4.24061@newssvr30.news.prodigy.com>,
Robert Redelmeier <redelm@ev1.net.invalid> wrote:
:Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:
:> There is, though, one user on one port of one of the switches who
:> is producing more data than the rest of the users combined:

:Sniffer time! What is all that traffic?

:Is the user running some non-standard software that syncs a
:lot (MS FastIndex?), or is s/he infected with a virus?

Non-standard perhaps, but not that syncs a lot, and no virus is
involved. The user is running a high-speed scientific instrument.
The other scientific instruments in the building do not produce
data nearly as quickly.
--
Those were borogoves and the momerathsoutgrabe completely mimsy.

Robert Redelmeier · Guest

Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:

Hansang Bae · Guest

Sonco wrote:

glen herrmannsfeldt · Guest

Fred Marshall wrote:

(snip)

J. Clarke · Guest

Fred Marshall wrote:

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