Mailing List Archive: NANOG: users

Larger packets to save power, was: Re: would ip6 help us safeing energy ?

Index | Next | Previous | View Threaded

iljitsch at muada

May 5, 2008, 1:07 AM

Post #1 of 7 (329 views)
Permalink

Larger packets to save power, was: Re: would ip6 help us safeing energy ?

On 5 mei 2008, at 0:57, Adrian Chadd wrote:

> I'd seriously be looking at making current -software- run more
> efficiently
> before counting ipv6-related power savings.

Good luck with that.

Obviously there is a lot to be gained at that end, but that doesn't
mean we should ignore power use in the network. One thing that could
help here is to increase the average packet size. Whenever I've
looked, this has always hovered around 500 bytes for internet traffic.
If we can get jumboframes widely deployed, it should be doable to
double that. Since most work in routers and switches is per-packet
rather than per-bit, this has the potential to save a good amount of
power.

Now obviously this only works in practice if routers and switches
actually use less power when there are fewer packets, which is not a
given. It helps even more if the maximum throughput isn't based on 64-
byte packets. Why do people demand that, anyway? The only thing I can
think of is DoS attacks. But that can be solved by only allowing end-
users to send an average packet size of 500 (or 250, or whatever)
bytes. So if you have a 10 Mbps connection you don't get to send 14000
64-byte packets per second, but a maximum of 2500 packets per second.
So with 64-byte packets you only get to use 1.25 Mbps.

I'm guessing having a 4x10Gbps line card that "only" does 14 Mpps
total rather than 14 Mpps per port would be a good deal cheaper.
Obviously if you're a service provider with a customer that sends 10
Gbps worth of VoIP you can only use one of those 4 ports but somehow,
I'm thinking few people use 10 Gbps worth of VoIP...

Iljitsch

PS. Am I the only one who is annoyed by the reduction in usable
subject space by the superfluous [NANOG]?

_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

iljitsch at muada

May 5, 2008, 9:22 AM

Post #2 of 7 (306 views)
Permalink

Re: Larger packets to save power, was: Re: would ip6 help us safeing energy ? [In reply to]

On 5 mei 2008, at 17:14, Valdis.Kletnieks[at]vt.edu wrote:

>> Obviously there is a lot to be gained at that end, but that doesn't
>> mean we should ignore power use in the network. One thing that could
>> help here is to increase the average packet size. Whenever I've
>> looked, this has always hovered around 500 bytes for internet
>> traffic.
>> If we can get jumboframes widely deployed,

> You don't need jumboframes, you just need to have working Path MTU
> Discovery.
> Or hand-nail your MSS to 1400 or something. But if you don't do
> either of
> those, you basically need to assume that the minimum MTU is 512 or so.

???

Very few people out there use an MTU significantly below 1500 bytes. A
1500-byte MTU will give you an _average_ packet size of ~1000 on long-
lived TCP flows because there is one tiny ACK for every two full size
data segments. (In the other direction, but let's not make things too
complicated right now.) The reason that the average is more like half
that is that on short interactions the last packet is shorter, and of
course there's stuff like gaming, VoIP, DNS that simply uses small
packets.

>> Now obviously this only works in practice if routers and switches
>> actually use less power when there are fewer packets, which is not a
>> given. It helps even more if the maximum throughput isn't based on
>> 64-
>> byte packets. Why do people demand that, anyway?

> Max throughput, or max packets/sec? Max data throughput happens at
> the
> *other* end, with 9K mobygrams...

Right, with 9k packets you only need to send around 13 kpps to fill up
1 Gbps, with 1500 bytes it's some 83 kpps. Helps in overhead, TCP
performance and (potentially) power use.

But someone who is sending a 200 byte packet today isn't going to send
something larger when her MTU is increased from 1500 to 9000 so the
_average_ won't increase by a factor 6.

>> PS. Am I the only one who is annoyed by the reduction in usable
>> subject space by the superfluous [NANOG]?

> Those of us who are *really* annoyed by stuff like that usually cook
> up a procmail recipe to strip it out.. :)

I got my procmail set up so it mostly does what I need right now,
better not mess with it...
_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

mike at reachme

May 5, 2008, 12:56 PM

Post #3 of 7 (305 views)
Permalink

Re: Larger packets to save power, was: Re: would ip6 help us safeing energy ? [In reply to]

> -----Original Message-----
> From: Iljitsch van Beijnum [mailto:iljitsch[at]muada.com]
> think of is DoS attacks. But that can be solved by only allowing end-
> users to send an average packet size of 500 (or 250, or whatever)
> bytes. So if you have a 10 Mbps connection you don't get to
> send 14000
> 64-byte packets per second, but a maximum of 2500 packets per
> second.
> So with 64-byte packets you only get to use 1.25 Mbps.

You have just cut out the VoIP industry, TCP setup, IM or most types of
real-time services on the Internet.

> PS. Am I the only one who is annoyed by the reduction in usable
> subject space by the superfluous [NANOG]?
>

Yes you are the only one. ;)

_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

iljitsch at muada

May 5, 2008, 1:02 PM

Post #4 of 7 (305 views)
Permalink

Re: Larger packets to save power, was: Re: would ip6 help us safeing energy ? [In reply to]

On 5 mei 2008, at 21:56, Mike Fedyk wrote:

>> So if you have a 10 Mbps connection you don't get to
>> send 14000 64-byte packets per second, but a maximum of 2500
>> packets per
>> second. So with 64-byte packets you only get to use 1.25 Mbps.

> You have just cut out the VoIP industry, TCP setup, IM or most types
> of
> real-time services on the Internet.

Of course not. Like I said, as an average end-user with 10 Mbps you
get to send a maximum of 2500 packets per second. That's plenty to do
VoIP, set up TCP sessions or do IM. You just don't get to send the
full 10 Mbps at this size.

_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

niels=nanog at bakker

May 5, 2008, 3:57 PM

Post #5 of 7 (293 views)
Permalink

Re: Larger packets to save power, was: Re: would ip6 help us safeing energy ? [In reply to]

* iljitsch[at]muada.com (Iljitsch van Beijnum) [Mon 05 May 2008, 10:09 CEST]:
> PS. Am I the only one who is annoyed by the reduction in usable
> subject space by the superfluous [NANOG]?

No, and I'm just as annoyed by the (non-McQ) footer with superfluous
information attached to each mail.

On 5 mei 2008, at 17:14, Valdis.Kletnieks[at]vt.edu wrote:
> Those of us who are *really* annoyed by stuff like that usually cook
> up a procmail recipe to strip it out.. :)

That will only lead to duplicates of "Re: " (before and after the tag)
in the Subject, I'm afraid.

-- Niels.

--

_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

nanog at daork

May 5, 2008, 5:07 PM

Post #6 of 7 (289 views)
Permalink

Re: Larger packets to save power, was: Re: would ip6 help us safeing energy ? [In reply to]

On 6/05/2008, at 8:02 AM, Iljitsch van Beijnum wrote:
> Of course not. Like I said, as an average end-user with 10 Mbps you
> get to send a maximum of 2500 packets per second. That's plenty to do
> VoIP, set up TCP sessions or do IM. You just don't get to send the
> full 10 Mbps at this size.

Hmm, I see value in that.

But, good luck trying to convince customers to take a pps limitation
in addition to a Mbps limitation, whether they ever exceed that pps or
not. You /might/ convince them to take a pps limitation only - but if
they want to do 30Mbit (ie 2500pps @ 1500b) then your product needs to
support that.

Maybe you just start calling "10Mbps" "10Mbps, assuming a 500b average
packet size."

Anyway, nice idea in theory - putting more real world limitations in
to sold product limitations - but I don't see it working out with
marketing people, etc. unless someone has been doing it for years
already. It'd be good if the world were all engineers though, huh?

--
Nathan Ward

_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

adrian at creative

May 5, 2008, 6:58 PM

Post #7 of 7 (289 views)
Permalink

Re: Larger packets to save power, was: Re: would ip6 help us safeing energy ? [In reply to]

On Tue, May 06, 2008, Nathan Ward wrote:

> Maybe you just start calling "10Mbps" "10Mbps, assuming a 500b average
> packet size."
>
> Anyway, nice idea in theory - putting more real world limitations in
> to sold product limitations - but I don't see it working out with
> marketing people, etc. unless someone has been doing it for years
> already. It'd be good if the world were all engineers though, huh?

NPE-XXX, anyone?

Adrian

_______________________________________________
NANOG mailing list
NANOG[at]nanog.org
http://mailman.nanog.org/mailman/listinfo/nanog

Index | Next | Previous | View Threaded

Interested in having your list archived? Contact lists@gossamer-threads.com