连接缓冲管理和行程安排forDifferentiated服务(PDF15)简介开始
JoBS: Joint Buffer Management and Scheduling for
Differentiated Services?
J¨org LIEbeherr and Nicolas Christin
Computer ScIEnce Department, University of Virginia, Charlottesville, VA 22904, USA
fjorg, nicolasg@cs.virginia.edu
Abstract. A novel algorithm for buffer management and packet scheduling is
presented for providing loss and delay differentiation for traffic classes at a network
router. The algorithm, called JoBS (Joint Buffer Management and Scheduling),
provides delay and loss differentiation independently at each node, without
assuming admission control or policing. The novel capaBIlitIEs of the proposed
algorithm are that (1) scheduling and buffer management decisions are performed
in a single step, and (2) both relative and (whenever possible) absolute QoS requirements
of classes are supported. Numerical simulation examples, including
results for a heuristic approximation, are presented to illustrate the effectiveness
of the apprOAch and to compare the new algorithm to existing methods for loss
and delay differentiation.
1 Introduction
Quality-of-Service (QoS) guarantees in packet networks are often classifIEd according
to two criteria. The first criterion is whether guarantees are expressed for individual
end-to-end traffic flows (per-flow QoS) or for groups of flows with the same QoS requirements
(per-class QoS). The second criterion is whether guarantees are expressed
with reference to guarantees given to other flows/flow classes (relative QoS), or whether
guarantees are expressed as absolute bounds (absolute QoS).
Efforts to provision for QoS in the Internet in the early and mid-1990s, which resulted
in the Integrated Services (IntServ) service model [3], focused on per-flow absolute
QoS guarantees. However, due to scalaBIlity issues and a lagging demand for
per-flow absolute QoS, the interest in Internet QoS eventually shifted to relative perclass
guarantees. Since late 1997, the Differentiated Services (DiffServ) [2] working
group has discussed several proposals for per-class relative QoS guarantees, e.g., [4,
17].
With the exception of the Expedited Forwarding service [11], proposals for relative
per-class QoS discussed within the DiffServ context define the service differentiation
qualitatively, in the sense that some classes receive lower delays and a lower loss rate
? This work is supported in part by the National ScIEnce Foundation through grants NCR-
9624106 (CAREER), ANI-9730103, and ANI-0085955.
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