End-to-End QoS
Reliance on a particular link-layer technology to deliver QoS is fundamentally flawed.
TCP/IP is the “common bearer service,” the most common denominator in today’s Internet.
Partial-path QoS mechanisms introduce distortion of the data flow and are ineffectual.
Notes:
It is also unrealistic to attempt to provide end-to-end QoS in the Internet with any particular link-layer technology, such as ATM, since a packet in flight between a source and destination may traverse any number of link-layer transport media types (e.g. Ethernet, point-to-point serial links).
This is where the “most common denominator” philosophy comes into play. Since the “common bearer service” in the Internet is the TCP/IP protocol suite, this is the natural place to do traffic differentiation.