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Re: QoS for ADSL customers
- From: Sean Donelan
- Date: Wed Nov 30 10:16:56 2005
On Wed, 30 Nov 2005, Joe Shen wrote:
> To Kim's situation, IP packet header based (or access
> interface based) traffic classification is pratical.
> If application based traffic classification is
> required, tools from sandvine or packeteer may have to
> be sitted between ERX1440 and Cisco7609. IMHO, ISP
> network should NOT trust any TOS/DSCP set by their
> customers; so, classifying and (re)tagging must be
> done in PE or BRAS. On the other hand, anti-spoofing
> configuration must be enabled in ERX1440 or 7609.
> Anyway, I don't trust current router's ability on
> content based traffic delivery.
The problem with waiting until the PE or BRAS to do the classification is
most access providers use traffic aggregation in the access network (e.g.
ATM/DSL, Cable, WiFi, etc). This means the interfaces on the BRAS or PE
are oversubscribed and the access network interface will experience
inbound cell/frame drops.
If you don't trust the router's ability, imagine a dslam's ability to do
it at the ATM layer.
Some networks let users tag their traffic, other networks re-tag all
traffic according the network's policies. At the moment it seems to be a
business decision. But the result is users shouldn't expect unmangled
TOS/DSCP bits over the Internet. Coordinating the IP layer QOS with the
access network/physical layer QOS is a bit of a challenge.