Re: [RE] Is anything special required??

["Tuck, Fred" <Fred.Tuck@xxxxxxxxxxxx>]

Hugh:

 

You are right.  For some reason I was thinking that the 1GB link is half duplex.  With full duplex there is no problem.

 

Fred Tuck

EchoStar Data Networks

 

-----Original Message-----
From: Hugh Barrass [mailto:hbarrass@cisco.com]
Sent: Thursday, May 05, 2005 7:16 PM
To: Tuck, Fred
Cc: STDS-802-3-RE@LISTSERV.IEEE.ORG
Subject: Re: [RE] Is anything special required??

 

Fred,

Just a nit-pick:

8 x 100Mb links cannot oversubscribe a 1 x 1Gb uplink. That type of  10:1 provisioning has been used for many years for dumb satellites feeding into smarter hubs (you have to watch out for the downlinks though :-).

Hugh.

Tuck, Fred wrote:

All:

Let me throw out a few assumptions that will be typical in a home

environment.  I don't think over-provisioning will always work in these

areas.  Some of these may seem a little contrived but as I pointed out in an

email a couple of months ago we have to be very liberal in our data rate

assumptions for home environments.  Trick modes, large HD file transfers,

and new minimal compressed HDV and other formats will easily consume 10s if

not 100s of Mb/sec of bandwidth each.  

Assumptions / Realities of home market.

1.       Multiple switches:  Users are going to have clusters of AV equipment

interconnected with switches that will then be connected to a whole home

switch.  Total bandwidth over a single switch can exceed 1Gb (8 100t ports

full duplex = 1.6Gbs) If all of this traffic is going to another switch it

requires a link of greater than 1Gbs.  Does anyone expect that we will be

able to do 10G Ethernet links in a home environment?

2.       Switches connected by something other than Ethernet:  There will be

other network environments in the home that use existing coax such as MoCA.

These will be used as backbone links and they will run at lower data rates.

We must interoperate with these other networks and they will have QOS and BW

reservation.  This is necessary because many people will be unwilling or

unable to run cat5 or other new wiring within their home.  In some places

like Florida, where there is a lot of cement block construction, it is

almost impossible to run new wiring.

3.       Gigabit links:  Some people have suggested that in a year or so that

all new links will be 1Gb.  This works fine if one is going to a single

switch with a full bandwidth backplane.  The above problems still exist when

you go to multiple switches or hybrid environments.

4.       Properly engineered LANs:  Over-provisioning works when you know

what your application environment and data rates are going to be.  Or you

can build an environment where the switch interconnects can handle all of

the backplane traffic between two switches.  I do not believe that you can

guarantee either of these things in a home environment.

5.       There will be multiple HD TVs in homes.  17 inch LCDs easily handle

HD resolution.  Even 14 inch displays in laptops and portable players have

1280 x 768 resolution.

6.       People will be making very large data transfers 10s of GB.  Large

directories of Multi Mega pixel photos, HD home videos, and transfers to

portable devices.  Multiple servers or DVRs in a home.  Etc... 

Fred Tuck

EchoStar Data Networks

-----Original Message-----

From: owner-stds-802-3-re@IEEE.ORG [mailto:owner-stds-802-3-re@IEEE.ORG] On

Behalf Of David V James

Sent: Thursday, May 05, 2005 12:13 PM

To: STDS-802-3-RE@LISTSERV.IEEE.ORG

Subject: Re: [RE] Is anything special required??

Arthur,

I do not agree that the term "over provisioned" is an abstract quantity.

If a 100Mbps network can carry the traffic with bandwidth allocation

then a gigabit network will be over-provisioned.

Does this mean that your definition of overprovisioned is 10%?

I'm not trying to say that 10% is good or bad, just trying to

nail down a specific counterproposal for consideration.

Without a specific number, its hard to respond intelligently.

As an extreme example, 1% may make things more deterministic,

but 1% might be an unacceptable limitation in the marketplace. 

Do you disagree on those goals, or on the conclusions

we have reached, based on those goals?

Can we safely assume that the disagreement was in goals,

specifically 75% vs 10% of link utilization for RE traffic?

Since one can't affect non-RE stations, such as server-to-PC

data transfers, I suppose the 10% would only apply to RE

traffic restrictions. Is this the intent of your proposal?

Respectfully,

DVJ

-----Original Message-----

From: owner-stds-802-3-re@IEEE.ORG

[mailto:owner-stds-802-3-re@IEEE.ORG]On Behalf Of Arthur Marris

Sent: Thursday, May 05, 2005 12:17 AM

To: STDS-802-3-RE@LISTSERV.IEEE.ORG

Subject: Re: [RE] Is anything special required??

David,

For some of us, the goals are to allow time-sensitive

traffic to occupy 75% of the bandwidth on 100Mb/s links,

with no other loading or topology constraints. This is

a bit easier to deal with, since the abstract quantities

of "over provisioned" and "would notice" are better

quantified and therefore measurable/provable.

I do not agree that the term "over provisioned" is an abstract quantity.

If a 100Mbps network can carry the traffic with bandwidth allocation

then a gigabit network will be over-provisioned.

While the preceding goals, there do seem to be a few

special subscription and pacing requirements.

Do you disagree on those goals, or on the conclusions

we have reached, based on those goals?

I think the goal at this time should be to identify the needs and

requirements of various CE applications in terms of throughput, latency,

jitter, loss etc and see what enhancements need to be made to Ethernet

(if any) to address these. I think Denis said something similar in a

previous message.

Arthur.