Re: [RE] Overprovisioning (was Re: [RE] CE applications)
I agree that overprovisioning is not a viable solution for a network
that is expected to always work.
On the other hand, I think there is no convincing argument that why the
existing layer2/3 QoS will not solve the need.
If the ONLY objective of the Residential Ethernet is to achieve BOUNDED
latency/jitter and bandwidth guarantees for the real-time applications,
then a combination of admission control, ingress traffic/rate shaping,
and some types of priority queuing can solve this problem WITHOUT
overprovisioning. The issue of cost can be quickly resolved by volume
production of chips incorporating the QoS features. The QoS management
complexity can be resolved by enhancing automated provisioning protocol
like DHCP.
Things are different, if the objective of Residential Ethernet include
(as I mentioned before)
- constant, sub-millisecond latency for real-time traffic
- zero jitter for real-time traffic
- zero packet loss for real-time traffic
Such objectives will be very difficult, if not impossible, to achieve
with only a combination of admission control, ingress traffic/rate
shaping, and priority queuing. I think this group need to highlight
these objectives in order to justify works for enhancement of layer 2
protocols by some iso/sync-chronous schemes.
Henry
-----Original Message-----
From: owner-stds-802-3-re@IEEE.ORG [mailto:owner-stds-802-3-re@IEEE.ORG]
On Behalf Of Michael D. Johas Teener
Sent: Wednesday, September 01, 2004 10:36 AM
To: STDS-802-3-RE@listserv.ieee.org
Subject: [RE] Overprovisioning (was Re: [RE] CE applications)
There are two clear problems with overprovisioning.
1) No matter what level you set your network/interconnect, a reasonable
number of applications will cause queuing somewhere in the system
(transmit buffers, receive buffers, network (switch/router) buffers).
The behavior of these queues *must* be defined or the customer will be
unhappy.
1a) For example, when I was at Apple they thought the 1Gbyte/sec
speed of the HyperTransport interconnect was so "over provisioned" that
they did not test some interesting cases, and ran into serious buffer
overflow problems that could only be solved by throttling some much
slower speed interfaces.
(The G4/PCI-based PowerBook that I'm using has better FW800 performance
than the G5/HyperTransport PowerMac that has so much better internal
data rates.)
1b) Another example is the fun that the enterprise people are having
now with queue overflows and lost performance in 1G and 10G SANs and
cluster connections. The bandwidth is *clearly* adequate, but the
traffic models cause all kinds of queuing problems.
2) Overprovisioning costs $. 1G is *a lot* more expensive that 100M. I
can
*easily* integrate the 100M PHY into a larger part ... The cost of
integrating the 1G PHY into CE-type LSI is significant. ... And, yes, it
will get to a reasonable level in the not too distant future, but by
that time the uses of 1G bandwidths will be high enough that the queuing
problems in (1) above will show their ugly heads, and you will need 10G
to avoid them ... And we are back to the $ problem.
So ... I think we should try to aim towards something that will *always*
work and not count on the *probability* that the consumer won't do
anything to cause queuing problems. Let's fix the problem and not
pretend it doesn't exist.
On 9/1/04 10:05 AM, "Gross, Kevin" <kevin.gross@CIRRUS.COM> wrote:
> Excuse me for responding to my own post but I'd also like to point out
> the overprovisoning solution to this scenario.
>
> Current home-class servers are challenged to saturate even a 100Mbit
> link with intelligent data. Even if neither the server nor client
> bandwidth were a bottleneck, bandwidth delay product issues inherent
> in TCP would likely slow down your file transfer and leave plenty of
room for the streams.
>
> At 1Gbit, the network is clearly overprovisioned and would work fine
> even without 802.1Q.
--
-----------------------------------------------------------
Michael D. Johas Teener - Mike@Teener.com PGP ID 0x3179D202
23 Acacia Way, Santa Cruz, CA 95062-1313
+1-831-247-9666, fax +1-831-480-5845
------------------- www.teener.com ------------------------