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Packet Scheduling Algorithm
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- 5IP Network Impairment Level Requirements
- 5.2Impairment Combination Standard Test Cases
- 5.2.1.1.1.1Annex (Normative) – : Description of Discrete Event Simulator
- 5.2.1.1.1.2Annex (Normative) – : C++ Source Code of Discrete Event Simulator
- 5.2.1.1.1.4Annex (Normative) – : Simulator Output
- 5.2.1.1.1.6Annex (Informative) – : User’s Guide
4.7Packet Scheduling AlgorithmCapitalized nouns in the following description refer to objects in the C++ simulator source code. A Packet is driven into the simulation from a PacketGenerator, usually by reading Packets from a PCAP file, and sending them into a Port on a Switch. The Switch receives the Packet, determines where it should go next, and Schedules it for transmission out one of its egress Ports. The egress Port is connected by a Wire to another Switch and the Wire schedules the packet for ingress on the next Switch after the wire’s delay. This process repeats for the entire network topology being simulated and for all packets being simulated. When packets reach their final destination, they are stored in a file for post-analysis. Normative Annex [X], included as an electronic attachment, contains the C++ source code of the simulator. Annex [Y] is a detailed description of the simulator code. 5IP Network Impairment Level RequirementsAn implementation of the network model shall create impairments that conform to the impairment levels specified in this section. 5.1Service Test ProfilesError: Reference source not found represents service test profiles and the applications, node mechanisms and network techniques associated with them. ITU-T Y.1541 uses a similar approach, but a one-to-one mapping to these service profiles may not be possible.
The following three test profiles are used in this IP network model that can be associated with Service Level Agreements (SLA):
These tables represent end-to-end impairment levels, including LAN and access. In Tables 2, 3 and 4, the total packet loss is the sum of the sequential packet loss and random packet loss. Note that service provider SLAs only guarantee characteristics of the core section of the network.
5.2Impairment Combination Standard Test Cases[say how these were chosen so that the simulation results align with the impairment level requirements just described.]
[Explain naming of the test cases. (Les)] [Where do we describe how these test cases can be used? User guide annex?] [somehow fit the spreadsheet here] 5.2.1.1.1.1Annex (Normative) – : Description of Discrete Event SimulatorSimulation Parameter files The parameters for running the simulation are given in a TCL file. The advantage of using TCL as a parameter file format is that it is a well-known file format, and it is extensible so that users can further customize the behavior of the simulation to suit their particular needs. An example of how this helps is that it gives a convenient way to comment out portions of code and to print messages to the screen for information or debugging. [Welch] [Ousterhout] At the very top of a parameter file, the user must include the common support routines from the file tc/common.tcl. source "tc/common.tcl" The first section of the parameter file consists of variable settings using the TCL “set” command. It is no different from setting a normal variable in TCL, except that the names of the variables are specific to the simulator. The example below sets the simulation length to 10 minutes (600 seconds) set SimLengthSeconds [expr 10*60] Note here that a TCL expression is used to make it easy to specify 10 minutes without needing to do the multiplication manually. Next, set the CORE network parameters set NumCoreSW 5 set CORE_Latency 20E-3 set CORE_Speed 1E9
set RLAN_Speed 100E6 Next, set the Remote Access parameters set RACC_SpeedDown 33E6 set RACC_SpeedUp 2E6 set RACC_BER_Fwd 1E-12 set RACC_BER_Rev 1E-12
set CORESW_BufSizeBytes [expr 1*65536] set DSLAM_BufSizeBytes [expr 1*65536] set Firewall_BufSizeBytes 65536 set Modem_BufSizeBytes 65536 The next section of the parameter file specifies the PacketGenerators that read input PCAP files and drive them into the simulation. # ============================================================================================================= # Downstream PCAP Generators # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # Name File Start BW PPM Rand Prio Repeat PIR PBS # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PCAP_Generator PCAPFwdI7 vocal_g729_dir1 2.0 1.0 0.0 0.0 1 -1 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PCAP_Generator PCAPFwdI3 sh_12Mb_cbr_deburst 0.0 0.514 0.0 0.5 2 -1 PCAP_Generator PCAPFwdI5 sh_6Mb_cbr_deburst 10.0 0.260 0.0 0.5 2 -1 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PCAP_Generator PCAPFwdI9 YouTube1080p_Down_nopayload 2.0 0.16 0.0 0.9 7 -1 PCAP_Generator PCAPFwdI10 Hulu480p_Down_nopayload 2.0 0.25 0.0 0.9 7 -1 # -------------------------------------------------------------------------------------------------------------
# Upstream PCAP Generators # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # Name File Start BW PPM Rand Prio Repeat PIR PBS # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PCAP_Generator PCAPRevI3 vocal_g729_dir2 2.0 1.0 0.0 0.0 1 -1 # -------------------------------------------------------------------------------------------------------------
The next section of the parameter file specifies the Packet Monitors that write output PCAP files and “.out” files # ===================================================== # Downstream PCAP Monitors # - - - - - - - - - - - - - - - - - - - - - - - - - - - # - - - - - - - - - - - - - - - - - - - - - - - - - - - PCAP_Monitor PktMonPCAPFwdI7 VoIP1_down # PCAP_Monitor PktMonPCAPFwdI3 HD_8Mbit_cbr PCAP_Monitor PktMonPCAPFwdI5 SD_2Mbit_cbr # PCAP_Monitor PktMonPCAPFwdI9 YouTube_down PCAP_Monitor PktMonPCAPFwdI10 Hulu_down # ----------------------------------------------------- # ===================================================== # Upstream PCAP Monitors # - - - - - - - - - - - - - - - - - - - - - - - - - - - # Name File # - - - - - - - - - - - - - - - - - - - - - - - - - - - PCAP_Monitor PktMonPCAPRevI3 VoIP1_up # -----------------------------------------------------
Note that if a PCAP_Monitor line is commented out or not present, the output files will not be written. This is helpful in situations where only a subset of the output files are needed so that disk space can be saved. The simulation predefines two global variables for use by the TCL code in the parameter file
5.2.1.1.1.2Annex (Normative) – : C++ Source Code of Discrete Event Simulator[electronic attachment] 5.2.1.1.1.3Annex (Normative) – : Packet Capture Files of Interfering Traffic[list file names and sufficient description of each] [electronic attachments] 5.2.1.1.1.4Annex (Normative) – : Simulator Output[list file names. Describe contents of each file.] [electronic attachments] 5.2.1.1.1.5Annex (Informative): ) – Rationale for Network Modelpcap stream selection pcap bit rates access technologies, bit rates, and error rates network topology buffer size (equipment vendor) queuing algorithms 5.2.1.1.1.6Annex (Informative) – : User’s Guide5.2.1.1.1.6.1Emulator Implementation For a specified test case, the simulation produces delay and loss characteristics that can be used in a real-time emulator. The emulator accepts a packet stream under test, and plays out the same stream with packet delays and losses that match the corresponding simulation. An emulator must shape the stream under test to account for the “self-interference” effect. Packets that arrive too close together in time contend for the available bandwidth in the emulated network. The amount of shaping depends on the effective bandwidth available to the stream under test in the given test case. This available capacity is the rate of the access link (the lowest-rate link in the network) less the sum of the rates of the interfering streams at QoS priority the same or higher than the stream under test. [LAN-TO-LAN: Emulator only. Concatenate two core-to-LAN models. Losses add (OR fn). Fixed delays add, but maybe that’s not relevant since...Jitter is a result of adding delays on each half, packet by packet. Interfering streams enter in the core, but it depends on business or residence.] DelayLL = DelaySev1 + DelaySev2 LossLL = LossSev1 “or” LossSev2 BWLL = Min[EBSev1, EBSev2] (EB = Effective BW) 5.2.1.1.1.6.2Practical Use of Test Cases ____________________ Directory: TR-30 -> TR-30.3 -> Public Public -> Ansi/tia-921-b network Model for Evaluating Multimedia Transmission Performance Over the Internet Protocol TR-30 -> Document submitted to Download 182.84 Kb. Share with your friends:
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