gpsr-ns-2.tar.gz

/* * Copyright (c) Xerox Corporation 1997. All rights reserved. * * License is granted to copy, to use, and to make and to use derivative * works for research and evaluation purposes, provided that Xerox is * acknowledged in all documentation pertaining to any such copy or * derivative work. Xerox grants no other licenses expressed or * implied. The Xerox trade name should not be used in any advertising * without its written permission. * * XEROX CORPORATION MAKES NO REPRESENTATIONS CONCERNING EITHER THE * MERCHANTABILITY OF THIS SOFTWARE OR THE SUITABILITY OF THIS SOFTWARE * FOR ANY PARTICULAR PURPOSE. The software is provided "as is" without * express or implied warranty of any kind. * * These notices must be retained in any copies of any part of this * software. */ The script test-suite-intserv.tcl helps runs various measurement based admission control algorithms for controlled-load services in ns. A. FUNCTIONALITY : ------------------ To support controlled load services, there have been essentially 2 pieces of functionality added : 1. End to End signalling mechanism to request a new connection. 2. Enhanced Link Structure. 1.End to End Signalling Mechanism(sa.cc,saack.cc): ------------------------------------------------ A very simple end-to-end signalling protocol(which uses a 3 way handshake) has been implemented to request services. The signalling protocol is sender-initiated wherein the sender sends a "request message"(PT_REQUEST) with the token bucket parameters(r,b).The message goes all the way to the receiver thru the intserv enhanced links. The receiver reverses the "request message" as a "reply message"(PT_REPLY) to the sender. The sender then resends the "reply message" as "confirm message"(PT_CONFIRM) to the receiver. The reply message is needed to indicate to the sender about the successful establishment of connection, after which it may start transmitting data packets. If the reply is a reject, then the source sends the "confirm message" and no more packets. Since, in the ns framework, the reply message traverses through different simple-links than the request message, the confirm message is required to indicate to the signal-support boxes(see below) in the links about the fate of the connection. This is particularly significant for the state of those links which said "yes" to a connection but the connection got rejected on a downstream link. Finally the sender sends a teardown message at the end of the connection. Consequently there are 4 new packet types added : PT_REQUEST PT_REPLY PT_CONFIRM PT_TEARDOWN In addition, a new header type (hdr-resv) (in resv.h) defines fields (for token bucket parameters) for integrated services. 2. Intserv Link : --------------- The SimpleLink structure has been enhanced to look like : ______________________________________ | | | | |Admission| ____|____ ____|____ |-------------|Control | | | | | | | | |Estimator| |Estimator| | |_________| |____1____| |____n____| | | | | ___|___ | | | | | _____ ___|____ _________ _____ _>|Meas- | | | | | | | | | \ | >|urement| | |Delay| __>| Signal |__>|Scheduler|__>|Class-\__| | for |___|_______>|Link | >| Support| >|(Queue) | >|-ifier/ | |class 1| | | >|_____| |________| |_________| |_____/ | |_______| | | | ...... | | | ...... | | |_> _______ | | | >| | | | | |Meas- | | | | |urement|___| | | | for |________| | |class n| | | |_______| | | | |>__________________| > Best Effort traffic ___> indicates packet flow > For supporting controlled load service only, it is assumed that there would be only 2 classes of traffic : controlled load and best effort and so the above link model simplifies to one where there is only 1 measurement and 1 estimator box (tcl/ex/ns-intserv.tcl implements the above link structure). A detailed description of each of the components is as follows : Signal-support(salink.cc): ------------------------- The links need to maintain some transient state about flows requesting service (specifically the link needs to remember its decision for a new flow until it gets the PT_CONFIRM message). Scheduler(simple-intserv-sched.cc): ------------------------------ For controlled load service support, a very simple scheduler queue is implemented as a 2 level service priority queue. Also all signalling control messages are explicitly prevented from drops. Classifier: ---------- Currently, the classifier is a flow-classifier. It treats all traffic with non-zero fid as controlled load traffic and those with zero fid as best effort traffic. Measurement, Estimator and Admission Control Objects: ---------------------------------------------------- The measurement object is a very simple object that measures per-class packets. The Estimator estimates the used bandwidth based on the etimation algorithm in play (which could one of TimeWindow, PointSample or Exponential Average). The admission control object makes an admission control decision based on the load estimate (from the estimator) and the admission control algorithm in play (which could be one of Measured Sum, Hoeffding bounds, Acceptance region-Tangent at Origin or Acceptance region-Tangent at Peak). When a new connection request comes to a link, the signal-support module asks the admission control for a decision which in turn looks at the current load estimate and the new flow parameters. B.USER-LEVEL API : ----------------- To create a int-serv enabled link, use : $ns duplex-intserv-link $n1 $n2 <link bw> <propgn delay> <sched type> <signal-support type> <adc type rel='nofollow' onclick='return false;'> <est type> <service class 1> <service class 1 params>... <service class n) <service class n params> A very simple example of controlled load service class can be found in test-suite-intserv.tcl. This support can be tested by saying something like: % ns tcl/ex/test-suite-intserv.tcl ADC=MS EST=TimeWindow utilization_=0.95 SM=5e3 which would run the test-suite for measured sum admission control with a time-window estimator. The remaining command line params above are specific to the measured-sum algorithm.