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RE: [Diffserv-interest] Re: draft-baker-diffserv-basic-classes-01 .txt
Title: Re: [Diffserv-interest] Re: draft-baker-diffserv-basic-classes-01 .txt
John,
Since
the jitter level is bound by latency, your AF4 service class seems to be
incongruous and can be safely removed from the list. What would
remain appears to be a reasonable grouping of services.
Regards,
Dimitry
Here is my take on the examples you
gave below:
Total of 5 service classes, ever, for any
service:
Control Class: Highest absolute priority. Never used for anything
but control. Period.
EF for TDM-like services such as IP telephony,
circuit em, and possibly (depending on your attitude) interactive video
services. Engineered such that it is never oversubscribed under even the most
extreme conditions. Yields low latency and jitter.
AF4 for
latency-sensitive (but not particularly jitter-sensitive) traffic such as
unidirectional audio-video streaming, TV broadcast, etc. Jitter is buffered by
end systems. Also available for people who want to pay through the nose for
transactional data service (banks may). Very conservatively engineered w.r.t.
CIR... Should never block.
AF1 for guaranteed CIR services with some
(but not much) delay sensitivity, such as SNA, VPN, etc. This class - even CIR
- will typically be oversubscribed, based on statistical analysis of network
traffic.
BE for everything else - Best Effort internet services, etc.
No distinction between "standard" and "low priority". This is both. BE
is subject to complete blocking under extreme conditions, but these conditions
should almost never occur with proper network engineering. In fact, the apps
that use it should not even know when they are blocked even for several
seconds, since they are totally elastic. Service providers will price and
differentiate based on their performance on this class as well as the others.
If someone is intense about blocking, they can pay to up their service to AF1
or even AF4.
Why do you need more? All services can be addressed using
these basic classes, plus policy-based tweaks on policers and shapers and
queuing systems (WFQ or CBQ). If a customer wants a better quality than is
"typical" of a particular service, they can pay to bump up a class (except to
the control class). CIR on EF and AF4 will not be oversubscribed. The payback
from excessive attention to detail in management is negligible at best. Any
problems that occur will be due to failure to properly engineer the network
bandwidth or access policies.
Please explain to me why I am
wrong.
j
From: Jozef Babiarz <babiarz@nortelnetworks.com>
Date:
Sun, 02 Nov 2003 16:52:18 -0500
To: Brian E Carpenter
<brc@zurich.ibm.com>, "John H. Shuler"
<johnshuler@mac.com>
Cc:
diffserv-interest@ietf.org
Subject: RE: [Diffserv-interest] Re:
draft-baker-diffserv-basic-classes-01 .txt
Brian E Carpenter wrote:
John, I guess your comment refers to the draft so I changed the subject.
If you want to be sure the authors see your comments, you might want
to
write to them directly. My reactions inserted below.
Brian
"John H. Shuler" wrote:
>
> Why make a distinction between "Standard Service Class" and "Low
Priority
> Data"?
There is a kitchen sink aspect to this draft
that worries me. Rather than
starting simple, with three or four generic
service classes, the authors
have chosen to present the union of a number
of diffserv deployment models.
I think that risks confusing operators by
giving them too much complexity
to choose from.
[[Joe] The draft
tries to address the service differentiation that is needed in carriers and
enterprise networks including access networks. I agree that network
administrators both in carrier and enterprise should start off with only the
service differentiation level (service classes) that are required for their
business. Let me provide some examples that I worked on so that you can
understand why we have defined the number of service classes.
Carriers
wanted to use IP technology for provide telephony service, plus provide IP VPN
service with CIR as well basic Internet connectivity service. This scenario
can be address by configuring the network using the following service classes
define in the draft.
- Standard service class for Internet connectivity
- High Throughput Data service class of IP VPN and collection of network
data for billing
- Telephony service class for VoIP and signaling between
voice gateways
- Network Control service classes for routing, etc.
This simple example used four of the defined service classes.
A different operator is deploying the services listed above plus new
multimedia IP services like desktop video conferencing to go along with
telephony, instant massaging plus other "workflow" applications.
This
operator needs:
- Standard
- High Throughput Data
- Low Latency
Data
- Multimedia Conferencing
- Telephony
- Network Control
Another operator has plans to offer broadcast TV service,
pay-per-view, telephony, two different SLAs for IP VPN services and basic
Internet connectivity. They will need:
- Standard
- High Throughput
Data
- Low Latency Data
- Multimedia Streaming
- Telephony
-
Network Control
A large enterprise is currently configuring their
network to support the flowing service classes (using the drafts terminology).
Most location will have a subset of services available with migration to
network wide service transparency in the future.
- Standard
- High
Throughput Data
- Low Latency Data
- Multimedia Streaming
-
Multimedia Conferencing
- Telephony
- Network Control
-
Administration
I can go through more scenarios that I have come across
over the years.
I agree that two or three user service classes is what
many operators start off with, however they are not always the same three and
they always like to know how they can evolve in the future.]
Regards,
Joe.
Jozef Babiarz
QoS and Network Architecture
Nortel Networks
email: babiarz@nortelnetworks.com
Tel: (613) 763-6098 ESN:393-6098