Specification of the Controlled-Load Network Element Service (RFC2211)
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
This memo specifies the network element behavior required to deliver Controlled-Load service in the Internet. Controlled-load service provides the client data flow with a quality of service closely approximating the QoS that same flow would receive from an unloaded network element, but uses capacity (admission) control to assure that this service is received even when the network element is overloaded.
Network Working Group J. Wroclawski
Request For Comments: 2211 MIT LCS
Category: Standards Track September 1997
Specification of the Controlled-Load Network Element Service
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
This memo specifies the network element behavior required to deliver
Controlled-Load service in the Internet. Controlled-load service
provides the client data flow with a quality of service closely
approximating the QoS that same flow would receive from an unloaded
network element, but uses capacity (admission) control to assure that
this service is received even when the network element is overloaded.
This document defines the requirements for network elements that
support the Controlled-Load service. This memo is one of a series of
documents that specify the network element behavior required to
support various qualities of service in IP internetworks. Services
described in these documents are useful both in the global Internet
and private IP networks.
This document is based on the service specification template given in
. Please refer to that document for definitions and additional
information about the specification of qualities of service within
the IP protocol family.
2. End-to-End Behavior
The end-to-end behavior provided to an application by a series of
network elements providing controlled-load service tightly
approximates the behavior visible to applications receiving best-
effort service *under unloaded conditions* from the same series of
network elements. Assuming the network is functioning correctly,
these applications may assume that:
- A very high percentage of transmitted packets will be
successfully delivered by the network to the receiving end-nodes.
(The percentage of packets not successfully delivered must closely
approximate the basic packet error rate of the transmission
- The transit delay experienced by a very high percentage of the
delivered packets will not greatly exceed the minimum transmit
delay experienced by any successfully delivered packet. (This
minimum transit delay includes speed-of-light delay plus the fixed
processing time in routers and other communications devices along
To ensure that these conditions are met, clients requesting
controlled-load service provide the intermediate network elements
with a estimation of the data traffic they will generate; the TSpec.
In return, the service ensures that network element resources