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.