Hi Brian,
Could you please explain "each of them retains the
statistical properties of a single Internet"? What are the
properites? Do you mean when the network defines the
Diffserv classes,suppose for AF4 class, they may have
different values for the same parameters such as CIR, EBS?
Or even some of the networks does not have class AF4 but
have class gold, silver, and bronze instead?
Thanks
Yang
On Wed, 29 Oct 2003 12:07:02 +0100
Brian E Carpenter <brc at zurich.ibm.com> wrote:
Another way to look at it is that what diffserv does is
split the network
into several separate networks, but each of them retains
the statistical
properties of a single Internet.
Brian
John Schnizlein wrote:
The simple reason that congestion can occur is that the
TCA
need not limit incoming traffic sufficiently to avoid
it.
The TCA for expedited forwarding is the only one, of
many
traffic classes, that seeks to eliminate potential
congestion,
in order to minimize delay and jitter.
The parameters of other class definitions, assured
forwarding
for example, are intended to mark traffic at different
ingress
rates for different treatment when congestion occurs.
Note
that this anticipates that congestion will occur.
Please recall that the high link utilization in an IP
network
is obtained in large measure because traffic loads are
high
enough to produce occasional congestion. Cooperative
management
of this congestion is the responsibility of
transport-layer
protocols.
John
At 10:43 AM 10/28/2003, Feng Y wrote:
... I wonder why the
overloading or even congestion occurs in diffserv
network.
In diffserv architecture, the “DS ingress node is
responsible for ensuring that the traffic entering the
DS
domain conforms to any traffic conditioning agreement
(TCA)
between it and the other domain to which the ingress
node
is connected” [RFC 2475]. Moreover, “Traffic
conditioning
performs metering, shaping, policing and/or re-marking
to
ensure that the traffic entering the DS domain
conforms to
the rules specified in the TCA, in accordance with the
domain's service provisioning policy”. So what causes
the
overloading or congestion in diffserv? Does anyone
explain
it for me or give me some references. Thanks in
advance.
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IBM
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