RFC 2990 (rfc2990) - Page 2 of 24

Next Steps for the IP QoS Architecture

RFC 2990            Next Steps for QoS Architecture        November 2000


       3.12 QoS Deployment Logistics ..........................  17
    4. The objective of the QoS architecture ..................  18
    5. Towards an end-to-end QoS architecture .................  19
    6. Conclusions ............................................  21
    7. Security Considerations ................................  21
    8. References .............................................  22
    9. Acknowledgments ........................................  23
   10. Author's Address .......................................  23
   11. Full Copyright Statement ...............................  24

1. Introduction

   The default service offering associated with the Internet is
   characterized as a best-effort variable service response.  Within
   this service profile the network makes no attempt to actively
   differentiate its service response between the traffic streams
   generated by concurrent users of the network.  As the load generated
   by the active traffic flows within the network varies, the network's
   best effort service response will also vary.

   The objective of various Internet Quality of Service (QoS) efforts is
   to augment this base service with a number of selectable service
   responses.  These service responses may be distinguished from the
   best-effort service by some form of superior service level, or they
   may be distinguished by providing a predictable service response
   which is unaffected by external conditions such as the number of
   concurrent traffic flows, or their generated traffic load.

   Any network service response is an outcome of the resources available
   to service a load, and the level of the load itself.  To offer such
   distinguished services there is not only a requirement to provide a
   differentiated service response within the network, there is also a
   requirement to control the service-qualified load admitted into the
   network, so that the resources allocated by the network to support a
   particular service response are capable of providing that response
   for the imposed load.  This combination of admission control agents
   and service management elements can be summarized as "rules plus
   behaviors". To use the terminology of the Differentiated Service
   architecture [4], this admission control function is undertaken by a
   traffic conditioner (an entity which performs traffic conditioning
   functions and which may contain meters, markers, droppers, and
   shapers), where the actions of the conditioner are governed by
   explicit or implicit admission control agents.

   As a general observation of QoS architectures, the service load
   control aspect of QoS is perhaps the most troubling component of the
   architecture.  While there are a wide array of well understood
   service response mechanisms that are available to IP networks,



Huston                       Informational