RFC 2638 (rfc2638) - Page 2 of 26

A Two-bit Differentiated Services Architecture for the Internet

RFC 2638      Two-bit Differentiated Services Architecture     July 1999


   mechanisms. We propose an architectural framework that permits the
   use of both of these service types and exploits their similarities in
   forwarding path mechanisms. The major goals of this architecture are
   each shared with one or both of those two proposals: keep the
   forwarding path simple, push complexity to the edges of the network
   to the extent possible, provide a service that avoids assumptions
   about the type of traffic using it, employ an allocation policy that
   will be compatible with both long-term and short-term provisioning,
   make it possible for the dominant Internet traffic model to remain
   best-effort.

   The major contributions of this document are to present two distinct
   service types, a set of general mechanisms for the forwarding path
   that can be used to implement a range of differentiated services and
   to propose a flexible framework for provisioning a differentiated
   services network. It is precisely this kind of architecture that is
   needed for expedient deployment of differentiated services: we need a
   framework and set of primitives that can be implemented in the
   short-term and provide interoperable services, yet can provide a
   "sandbox" for experimentation and elaboration that can lead in time
   to more levels of differentiation within each service as needed.

   At the risk of belaboring an analogy, we are motivated to provide
   services tiers in somewhat the same fashion as the airlines do with
   first class, business class and coach class. The latter also has
   tiering built in due to the various restrictions put on the purchase.
   A part of the analogy we want to stress is that best effort traffic,
   like coach class seats on an airplane, is still expected to make up
   the bulk of internet traffic. Business and first class carry a small
   number of passengers, but are quite important to the economics of the
   airline industry. The various economic forces and realities combine
   to dictate the relative allocation of the seats and to try to fill
   the airplane. We don't expect that differentiated services will
   comprise all the traffic on the internet, but we do expect that new
   services will lead to a healthy economic and service environment.

   This document is organized into sections describing service
   architecture, mechanisms, the bandwidth allocation architecture, how
   this architecture might interoperate with RSVP/int-serv work, and
   gives recommendations for deployment.











Nichols, et al.              Informational