Network Working Group J. Babiarz Internet-Draft X-G. Liu Intended status: Informational Nortel Expires: January 9, 2008 July 8, 2007 Simulations Results for 3sM draft-babiarz-pcn-explicit-marking-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 9, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document describes the simulation setups and results for testing the Three State PCN Marking approach. Simulations done to date, demonstrate that the three state PCN marking approach has certain ability to support admission control and flow termination of real- time application flows at the congestion point of the PCN-enabled network. The real-time traffic used in the simulation covers voice and video traffic with large and small number of flows. Babiarz & Liu Expires January 9, 2008 [Page 1] Internet-Draft Simulations Results for 3sM July 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology used in this Document . . . . . . . . . . . . 4 1.2. Overview of Three State PCN Marking Approach . . . . . . . 5 2. General Description of the Simulation Setup . . . . . . . . . 5 2.1. Traffic Sources . . . . . . . . . . . . . . . . . . . . . 6 2.2. Multiple PCN Nodes . . . . . . . . . . . . . . . . . . . . 7 2.3. Traffic Control . . . . . . . . . . . . . . . . . . . . . 8 3. Performance of 3sM . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Performance of Flow Termination . . . . . . . . . . . . . 8 3.1.1. Large Number of Flows in a Single Domain . . . . . . . 9 3.1.2. Small Number of Flows in a Single Domain . . . . . . . 11 3.1.3. Large Number of Flows in a Multi Domain . . . . . . . 12 3.1.4. Discussion of Parameter Settings . . . . . . . . . . . 13 3.2. Performance of Admission Control . . . . . . . . . . . . . 14 3.2.1. Simulation Results for Admission Control . . . . . . . 16 4. Simulation Results Prior to 68th IETF . . . . . . . . . . . . 18 4.1. Simulation Setup for Voice Traffic . . . . . . . . . . . . 19 4.2. Large Number of Voice Flows . . . . . . . . . . . . . . . 20 4.3. Small Number of Voice Flows . . . . . . . . . . . . . . . 21 4.4. Large Number of Voice Flows with Packet Loss . . . . . . . 23 4.5. Small Number of Voice Flows with Packet Loss . . . . . . . 24 4.6. Corner Voice Cases Studied . . . . . . . . . . . . . . . . 25 4.7. Simulation Setup for Video Traffic . . . . . . . . . . . . 25 4.8. Excess Load Marking Algorithm Used in Simulation . . . . . 27 5. Security Considerations . . . . . . . . . . . . . . . . . . . 28 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 7. Informative References . . . . . . . . . . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 Intellectual Property and Copyright Statements . . . . . . . . . . 31 Babiarz & Liu Expires January 9, 2008 [Page 2] Internet-Draft Simulations Results for 3sM July 2007 1. Introduction In a PCN-enabled network, each link is configured with an admissible rate (AR). When the PCN traffic rate on a link exceeds its AR, the corresponding PCN node re-marks all PCN packets on this link with an "admission-stop" (AS) codepoint. The PCN egress nodes analyze the packet markings, and if sufficiently many packets are AS-marked within an ingress-egress aggregate, signal "admission-stop" for this aggregate to the appropriate admission control entity to stop admitting flows belonging to this aggregate so as to avoid the PCN traffic rate to exceed AR. When the PCN egress nodes stop receiving AS-marked packets, they signal "admission-continue" after some time to allow admitting flows from the blocked aggregate. Similarly, a supportable rate (SR) is configured for each link in a PCN-enabled network. When the current PCN traffic rate on a link exceeds its SR, the corresponding PCN node re-marks some of the PCN packets on this link with an "excess-traffic" (ET) codepoint. The PCN egress nodes pass the marking information to the appropriate flow termination entity (e.g. at the respective PCN ingress nodes) to terminate flows in order to reduce the PCN traffic rate of the SR- overloaded link below its SR. The reader is referred to [I-D.eardley-pcn-architecture] for details. The purpose of this document is to evaluate the performance of the proposed three state PCN marking (3sM) [I-D.babiarz-pcn-3sm] approach. We provide an overview of the simulations setup and the results of testing that were carried out. Simulation demonstrate that the three state PCN marking (3sM) approach has certain ability to support admission control and flow termination of real-time application flows at the congestion point of the PCN-enabled network. The simulation is based on modeling the real-time traffic of voice, both constant bit rate and variable bit rate with silence suppression, and variable rate MPEG-4 like video with large and small number of flows. The preliminary key findings of the simulation are: o Both the AR- and SR-meters are able to be adjusted to provide the desired traffic control to a certain degree, i.e., limiting the traffic in the network within some tolerance level for the test cases. o The setting of the two meters are usually not sensitive or can be set proportional to the traffic load (BW and number of flows) in the test cases. o The effectiveness of the AR-meter and AS-marker is similar for a single bottleneck node and a number of bottleneck nodes. (the SR- meter and ET-marking has not been tested for this scenario, it is Babiarz & Liu Expires January 9, 2008 [Page 3] Internet-Draft Simulations Results for 3sM July 2007 on the to do list.) o The precise control of mixed VBR traffic for admission control is difficult with small number of flows, as expected additional mechanism may be needed. o Flow termination using the proposed SR-metering and ET-marking: * Is independent of the number of flows at the congestion point or in an ingress-egress aggregate, works equality well on small and large links. * Works over a large range of network RTTs. * Works well with packet loss. * The desired setting for "s" marking slow-down parameter can be determined based on a given formula. * ET-marking identifies flows that are routed on overloaded paths, therefore when multiple paths exist in a network the edge nodes or explicitly informed which flows should be terminated. * ET-marking is proportional to the level of overload, the higher the overload the more packets are marked. * ET-marking has an exponential decay property. 1.1. Terminology used in this Document Since the terminology for this work is evolving, we provide a brief explanation of terms used in this document and the referenced simulation results. Preemption = flow termination SR = Supportable Rate = Preemption Threshold Preemption Level = traffic above this rate is marked as excess. Same as Supportable Rate. ET-marking = PM flag = explicit marking of packet to indicated excess load. In the simulation, the router sets both ECN bits to "11" in the IP header. Preemption Time = round-trip-time (RTT) in the network + processing time of termination of a flow. This is how long it Babiarz & Liu Expires January 9, 2008 [Page 4] Internet-Draft Simulations Results for 3sM July 2007 takes before a marked flow to stops sending packets. "s" slow-down marking factor = pcn_px = represents marking a packet every "x" bytes of excess rate. AR = Admissible Rate AS-marking = Admission Stop-marking = marking to indicated that additional new flows should be blocked. 1.2. Overview of Three State PCN Marking Approach For AR metering, the proposed approach defines an AR-meter and AS- marker based on a token bucket (TB) with threshold marking. The TB has a bucket of size TB.size which is continuously filled with tokens at rate TB.rate. The AR-meter and AS-marker consider only packets that are not ET-marked. When a non-ET-marked PCN packet arrives, it is re-marked to "AS" if the fill state of the bucket (TB.fill) in tokens is smaller than its size (packet.size) in bytes; otherwise, the fill state is reduced by packet.size tokens and if the fill state is then smaller than the marking threshold (TB.threshold), the packet is also re-marked to "AS" while if the fill state is then larger than or equal to the marking threshold, the packet is not re-marked. For SR metering, the proposed approach defines an SR-meter and ET- marker based on a token bucket with tail marking and marking frequency reduction (see Appendix A for explanation). The TB has a bucket of size TB.size which is continuously filled with tokens at rate TB.rate. When a non-ET-labelled PCN packet arrives, it is re- marked with "ET" if the fill state of the bucket (TB.fill) in tokens is smaller than its size (packet.size) in bytes and "s" additional tokens are added to the bucket; otherwise, the fill state is reduced by packet.size tokens. The slow-down parameter "s" reduces the marking frequency of the mechanism. If an ET-marked packet arrives, the TB's fill state is also incremented by "s". 2. General Description of the Simulation Setup The simulation model used in our experiments consists of the traffic sources, the PCN-enabled network nodes, and the traffic control loop (admission control and flow termination entities) Figure 1. Babiarz & Liu Expires January 9, 2008 [Page 5] Internet-Draft Simulations Results for 3sM July 2007 +-------------------------------------+ | Block/start admission or flow | | termination signal with time lag | V | +-----------+ +---------------+ +---------+ | | | | | | | Traffic | | PCN Node | | Traffic | | Sources | ===>| with |===>| Control | | | | AR/SR Meter & | | | +-----------+ | Marker | +---------+ | | +---------------+ Figure 1: PCN Marking Simulation Model 2.1. Traffic Sources The traffic source model can generate voice or video flows (calls) according to the Poisson arrival process with a given arrival rate. A Poisson arrival can contain one or more flows. The arrival batch size is a random variable with a given mean batch size. To model the reroute events in the network, the traffic source model can also generate flows at scheduled time points and/or within scheduled short time intervals. The model also allows some flows to start together, e.g., a voice flow plus a video flow. Each flow has a random life-span (holding time) with a given mean holding time. During its life time, a flow periodically generates packets based on a given codec and packetization scheme such as G.711 for voice over IP. Depending on the type of application and codec used in simulation, the packets from a flow can have fixed or variable sizes, and the inter-arrival time between the packets can be fixed or variable. To model the applications such as G.711 with silence suppression, the packet generation of a flow can be described by an ON-OFF process with given mean ON and OFF periods. With an ON-OFF flow, the packet can only be generated in the ON-period of the flow. An ON-OFF flow may start in either the ON or OFF state. When a flow starts, it can delay the generation of its first packet for some random time up to a given time limit, say 10 seconds. This delay is used for modeling the media delay of the call setup process for telephony application. To avoid unrealistic synchronization effects in the network, in any case, the start of the first packet from a flow is always randomized within a given small time interval after the flow start time, which is independent of the media delay. Babiarz & Liu Expires January 9, 2008 [Page 6] Internet-Draft Simulations Results for 3sM July 2007 The generation of packets for different flows are independent of each other. There can be mixed types of flows in the network. Each flow belongs to a given traffic aggregate with a fixed route crossing the network. Different types of flows can be in the same traffic aggregate. When modeling flow admission control, after a flow starts, the traffic source model will check if the traffic aggregate is blocked for admission. If the aggregate is blocked, any new flows will immediately be turned off (blocked) without generating any packet. The blocking of a traffic aggregate for admission will not affect the existing flows of the aggregate. When modeling flow termination, the traffic source model may receive signals for terminating particular flows. Upon receiving the flow termination signal, the affected flow will immediately be turned off, stopping generating of packets. 2.2. Multiple PCN Nodes For multiple PCN nodes simulations, we use a "parking lot" model with n nodes in tandem. A traffic aggregate uses a given segment of the n-node tandem to cross the network, i.e., its traffic will enter the network at node i and exit the network at node j (1<=i<=j<=n), where all the nodes in the segment are consecutively numbered. The node is configured with queue size and a given service rate or link bandwidth. The queue can be configured to have finite or unlimited buffer size. When a PCN packet arrives at a node, before entering the queue, the packet is metered by the AR-meter and/or SR- meter and re-marked if needed. The AR-meter and SR-meter are modeled using the example pseudo codes provided in [I-D.babiarz-pcn-3sm]. After AR- and/or SR-metering, the packet enters the queue to be forwarded or is discarded if the queue is full. After forwarding, the packet will proceed to the next node or exit the network, depending on the definition of its traffic aggregate. The packet travel between nodes is instant. Upon exiting the network, the packet will be checked by the traffic control for its PCN marking and then destroyed. Based on the PCN marking of the packet, the traffic control will decide if it needs to signal the traffic model for a given type of traffic control: block new flow, restart admission of a particular traffic aggregate and/or terminate a particular flow. The signal to the traffic source model will experience certain delay or round-trip-time (RTT). The RTT can be modeled as a fixed time for all the flows or different RTT per Babiarz & Liu Expires January 9, 2008 [Page 7] Internet-Draft Simulations Results for 3sM July 2007 each flow. (Term RTT signifies the delay between generating a packet and receiving the corresponding traffic control feedback at the traffic source. But, in our model, RTT does not include any queueing delay experienced by the packet.) 2.3. Traffic Control In the simulation for admission control, the "block admission signal" will be sent whenever the traffic control sees an "AS" marking in the packet. The receiver (ingress) of the signal controls admission of all new flows within the aggregate and the same route. If the traffic aggregate is currently not blocked, the receiving of the block admission signal will trigger a "stop blocking timer" with a preset timeout. At timeout, the traffic control will check if there is one more block admission signal sent for the traffic aggregate during the timeout period, and if so, it will restart the timer. This process will repeat until there is no block admission signal sent for the traffic aggregate in the past timeout period. At this time, the traffic control will send the start admission signal for the traffic aggregate to allow it to admit flows into the network from now on. In the simulation for flow termination, a flow termination signal will be sent to the traffic source model for each ET-marked packet. Since SR is by definition greater than AR, a flow termination signal will also generate a block admission signal to the related traffic aggregate if admission control is being modeled at the same time. For more details of the simulation setup, see the case description sections in this document. 3. Performance of 3sM In this section we discuss the simulations results that where performed in time for 69th IETF meeting. Graphical results of the simulations can be viewed at http://standards.nortel.com/pcn/3sM-Simulation-1.pdf [SIM1-07]. See also Section 4 for simulations results that where done prior to 68th IETF meeting. 3.1. Performance of Flow Termination The following simulations were performed to measure how long it takes for the defined mechanism in 3sM to reduce the aggregate traffic after condition where significant overload of PCN traffic occurred on a link (like after fast reroute of traffic due to link failure). Babiarz & Liu Expires January 9, 2008 [Page 8] Internet-Draft Simulations Results for 3sM July 2007 The simulation setup emulates a condition where all PCN traffic is rerouted instantaneously from the failed link on to a good link that was at 50% or 100% of supportable rate (SR). The rerouted PCN traffic from the failed link is equivalent to SR of the remaining link, so that after reroute the load on the link is 150% and 200% of SR. Simulations were done with CBR and variable rate silence suppressed voice traffic sources. Our traffic generation model produces many individual flows that represented one of the codecs. Results are recorded for the following codec mix: o G.711CBR = G.711 with 20ms packetization time CBR, (200 bytes packets sent every 20ms) o 3VBR+CBR = 4 different code mix. 3 codecs running silence suppression per ITU-T P.56, G.711 at 20ms (200 byte packets), G.711 at 10ms (120 byte packets) and G.729 at 20ms (60 byte packets). And one dual-rate codec that sends packets at constant rate, 360 byte packets every 20ms. Each of the codec types generates approximate 20% of SR traffic measured as a rate. Note, that there is significantly more number of G.729VBR flows than flows generated by the dual-rate codec. The traffic mix for 3VBR+ CBR produces a 15 to 1 bandwidth ratio; the highest flow rate is 15 times bigger than the lowest rate within the mix for this simulation. 3.1.1. Large Number of Flows in a Single Domain For these simulations, it was assumed that the RTT within a single domain would be less than 50ms, therefore we simulated with 50ms as the RTT. However, normally RTT between different ingress-egress nodes will very, therefore typical results would produce shorter delays than the corner case that we simulated using 50ms for delay after marking for flow termination. Large number of flows, equates approximately 500 to 4,250 flows depending on the codec mix used to generate SR of 40 Mbps. Parameter setting: o Token bucket of the meter was configured to be 50,000 bytes in size o Supportable Rate = 40.0 Mbps o FT-marking reduction factor "s" was set to 1064 bytes. The table in Figure 2 summarizes the results of how long it took to Babiarz & Liu Expires January 9, 2008 [Page 9] Internet-Draft Simulations Results for 3sM July 2007 terminate the excess traffic form 200% of SR to SR. Also we provide the measured traffic rate and variation after flow termination was completed. The rate of remaining traffic was measured over 12 second period and results are recorded in table below as average, maximum, minimum and the variances. ------------------------------------------------------------------ | | % Overload, time in sec. | Bandwidth in Mbps | |----------+---------------------------+---------------------------| | Traffic | 150% | 125% | 110% | 100% | AVG | Max | Min | Var | |----------+------+------+------+------+------+------+------+------| | G.711CBR | 0.15 | 0.20 | 0.25 | 0.50 | 40.0 | 40.0 | 40.0 | 0 | |----------+------+------+------+------+------+------+------+------| | 3VBR+CVR | 0.15 | 0.20 | 0.30 | ~2 | 38.9 | 41.7 | 36.7 | 5.00 | ------------------------------------------------------------------ Figure 2: Overload at 200% of SR with "s" set to 1064 bytes The table in Figure 3 summarizes the results with FT-marking reduction factor "s" set to 2064 bytes. ------------------------------------------------------------------ | | % Overload, time in sec. | Bandwidth in Mbps | |----------+---------------------------+---------------------------| | Traffic | 150% | 125% | 110% | 100% | AVG | Max | Min | Var | |----------+------+------+------+------+------+------+------+------| | G.711CBR | 0.15 | 0.30 | 0.45 | 1.20 | 40.0 | 40.0 | 40.0 | 0 | |----------+------+------+------+------+------+------+------+------| | 3VBR+CVR | 0.20 | 0.35 | 0.85 | ~3 | 38.9 | 41.8 | 36.3 | 5.52 | ------------------------------------------------------------------ Figure 3: Overload at 200% of SR with "s" set to 2064 bytes The table in Figure 4 summarizes the results of how long it took to terminate the excess traffic form 150% of SR to SR with "s" set to 2064 bytes. ------------------------------------------------------------------ | | % Overload, time in sec. | Bandwidth in Mbps | |----------+---------------------------+---------------------------| | Traffic | 150% | 125% | 110% | 100% | AVG | Max | Min | Var | |----------+------+------+------+------+------+------+------+------| | G.711CBR | - | 0.20 | 0.35 | 1.05 | 40.0 | 40.0 | 40.0 | 0 | |----------+------+------+------+------+------+------+------+------| | 3VBR+CVR | - | 0.20 | 0.40 | ~2 | 38.7 | 41.6 | 35.4 | 6.30 | ------------------------------------------------------------------ Figure 4: Overload at 150% of SR with "s" set to 2064 bytes Babiarz & Liu Expires January 9, 2008 [Page 10] Internet-Draft Simulations Results for 3sM July 2007 3.1.2. Small Number of Flows in a Single Domain For these simulations, it was assumed that the RTT within a single domain would be less than 50ms, therefore we simulated with 50ms as the RTT. However, normally RTT between different ingress-egress nodes will very, therefore typical results would produce shorter delays than the corner case that we simulated using 50ms for delay after marking for flow termination. Small number of flows equates approximately 10 to 30 flows depending on the codec mix used to generate SR of 0.8 Mbps. Parameter setting: o Token bucket of the meter was configured to be 10,000 bytes in size o Supportable Rate = 0.8 Mbps o FT-marking reduction factor "s" was set to 1064 bytes. The table in Figure 5 summarizes the results of how long it took to terminate the excess traffic form 200% of SR to SR. Also we provide the measured traffic rate and variation after flow termination was completed. The rate of remaining traffic was measured over 12 second period and results are recorded in table below as average, maximum, minimum and the variances. ------------------------------------------------------------------ | | % Overload, time in sec. | Bandwidth in Mbps | |----------+---------------------------+---------------------------| | Traffic | 150% | 125% | 110% | 100% | AVG | Max | Min | Var | |----------+------+------+------+------+------+------+------+------| | G.711CBR | 0.20 | 0.25 | 0.30 | 0.40 | 0.80 | 0.80 | 0.80 | 0 | |----------+------+------+------+------+------+------+------+------| | 3VBR+CVR | 0.25 | 0.35 | 0.40 | ~2 | 0.74 | 1.07 | 0.50 | 0.57 | ------------------------------------------------------------------ Figure 5: Overload at 200% of SR with "s" set to 1064 bytes The table in Figure 6 summarizes the results with FT-marking reduction factor "s" set to 2064 bytes. Babiarz & Liu Expires January 9, 2008 [Page 11] Internet-Draft Simulations Results for 3sM July 2007 ------------------------------------------------------------------ | | % Overload, time in sec. | Bandwidth in Mbps | |----------+---------------------------+---------------------------| | Traffic | 150% | 125% | 110% | 100% | AVG | Max | Min | Var | |----------+------+------+------+------+------+------+------+------| | G.711CBR | 0.30 | 0.40 | 0.60 | 0.65 | 0.80 | 0.80 | 0.80 | 0 | |----------+------+------+------+------+------+------+------+------| | 3VBR+CVR | 0.30 | 0.35 | 0.45 | ~4 | 0.74 | 1.05 | 0.51 | 0.54 | ------------------------------------------------------------------ Figure 6: Overload at 200% of SR with "s" set to 2064 bytes 3.1.3. Large Number of Flows in a Multi Domain For these simulations, it was assumed that the RTT in a multi domain network would be less than 200ms, therefore we simulated with 200ms as the RTT. However, normally RTT between different ingress-egress nodes will very, many flows would have shorter than 200ms RTT, therefore typical results would produce shorter delays than the corner case that we simulated using 200ms for delay after marking for flow termination. Large number of flows equates approximately 500 to 4,250 flows depending on the codec mix used to generate SR of 40 Mbps. Performance results for RTT of 800ms can be found in [SIM-07]. Parameter setting: Token bucket of the meter was configured to be 50,000 bytes in size Supportable Rate = 40.0 Mbps FT-marking reduction factor "s" was set to 4064 bytes. The table in Figure 7 summarizes the results of how long it took to terminate the excess traffic form 200% of SR to SR. Also we provide the measured traffic rate and variation after flow termination was completed. The rate of remaining traffic was measured over 12 second period and results are recorded in table below as average, maximum, minimum and the variances. Babiarz & Liu Expires January 9, 2008 [Page 12] Internet-Draft Simulations Results for 3sM July 2007 ------------------------------------------------------------------ | | % Overload, time in sec. | Bandwidth in Mbps | |----------+---------------------------+---------------------------| | Traffic | 150% | 125% | 110% | 100% | AVG | Max | Min | Var | |----------+------+------+------+------+------+------+------+------| | G.711CBR | 0.45 | 0.65 | 0.90 | 1.6 | 40.0 | 40.0 | 40.0 | 0 | |----------+------+------+------+------+------+------+------+------| | 3VBR+CVR | 0.45 | 0.75 | 1.7 | ~4 | 38.9 | 42.3 | 36.1 | 6.24 | ------------------------------------------------------------------ Figure 7: Overload at 200% of SR with "s" set to 4064 3.1.4. Discussion of Parameter Settings Token bucket sizes: The size of the token bucket filters out short term rate variations. Normally, larger token bucket is need for highly variable traffic. The draw back of configuring token bucket too big is that it will delay the start of FT-marking (flow termination). "s" FT-marking reduction factor: The "s" parameter controls how often packets are marked when in overload. SR-meter measures traffic that is in excess of SR and FT-marker marks a packet ever "s" bytes of excess traffic. FT- marking is proportional to the overload, the higher the overload the higher the number of packets get FT-marked. In our simulations we used the following equation to compute the value for "s"; average rate of a flow * RTT * 2 = s; we used the rate of G.711 at 20ms CBR codec for the average rate in the calculations. Making "s" too small leads to over flow termination due to the delay in the response. A flow is terminated RTT after it is marked. As observed in simulations, this flow termination mechanism has exponential decay property and to prevent over termination, the period between ET-marking when PCN traffic rate is one flow above SR needs to be greater than 2 * RTT. Making "s" too big leads to longer termination time. The "s" parameter has the biggest impact on how fast or slow excess traffic is reduced. Babiarz & Liu Expires January 9, 2008 [Page 13] Internet-Draft Simulations Results for 3sM July 2007 RTT - total delay for termination of flows (network + ingress and egress processing delays.) Since PCN is a responsive mechanism, node meters traffic and ET- mark packets indicate the traffic is in excess of SR, the time that it take for the indication that flow needs to be terminated and the reduced load on to the overloaded link is what we call RTT. RTT has direct impact on how fast the overload condition can be eliminated. 3.2. Performance of Admission Control The purpose of the simulation experiments with admission control is to test the ability of the AR-meter and AS- marker of 3sM to support admission control in a PCN-enabled network and to observe the behavior of the AR-meter and AS-marker as a function of its settings and the traffic and network environments. For this purpose, we have performed the following preliminary simulation tests: o Erlang-B Test: test if the AR-meter and AS-marker can support admission control similarly to the Erlang blocking system for CBR traffic at a single node. o Overload Protection Test: test the above with 2x base load and everything else being the same. o Multiple-congested-node Test: test the performance of the AR-meter and AS-marker configured for a single node applies to a three- identical congestion-node environment with CBR traffic of 2x base load; traffic aggregate A1: route 1->2->3. o Cross-traffic Test: similar to the above, with additional CBR traffic aggregates from different routes carried in the ("parking- lot") network, where the aggregate traffic at each node with cross-traffic is increased proportionally to the combined load; 2 traffic aggregates are used, A1: route 1->2->3 with 2x base load, A2: route 2->3->4 with base load. o VBR Test: test the performance of the AR-meter and AS-marker configured for Erlang-B Test applied to VBR traffic at a single node, where the AR is set proportionally to the expected data rate of the aggregate traffic sources. o Traffic Mix Test: similar to the above, with combined VBR/CBR traffic served by the single node. Babiarz & Liu Expires January 9, 2008 [Page 14] Internet-Draft Simulations Results for 3sM July 2007 In all the above cases, the following settings are used unless otherwise indicated. Traffic settings: o the base load defined as the number of the targeted flows to be carried by the system, N, where N=10 for small load (S), N=50 for medium load (M), and N=200 for large load (L); o a Poisson arrival rate of Y=45*N flows (calls) per hour per base load: i.e., Y=450 flows/hour for small load (S); Y=2250 flows/hour for medium load (M); Y=9000 flows/hour for large load (L); o a batch size of 1 flow per arrival; o the mean holding time of 1 minute for each flow; o the maximum media delay of 10 seconds; o CBR traffic data rate of 80 kbps per flow with a fixed packet size of 200 bytes (corresponding to G.711 with 20 milliseconds of frame time for voice over IP); o VBR traffic with exponentially distributed ON and OFF periods with mean ON period of 1.004 seconds and mean OFF period of 1.590 seconds (corresponding to a voice codec with silence suppression); o the traffic mix with 3 types of flows, each with N/3 flows: type 1 flow: G.711/20ms VBR (data rate 31 kbps); type 2 flow: G.711/10ms VBR (data rate 37.2 kbps); type 3 flow: G.729/20ms VBR (data rate 9.3 kbps); o all the packets entering the system to be PCN marked. AR-meter settings: o AR=TB.rate=the data rate of the base load times (N-1)/N; o TB.size=20K bytes; o TB.thershold=10K bytes Admission control setting: o stop blocking timer timeout = 1 second; o RTT=50 milliseconds, fixed for all flows. Babiarz & Liu Expires January 9, 2008 [Page 15] Internet-Draft Simulations Results for 3sM July 2007 Network node settings: o link BW = 2 x the data rate of the traffic load seen at a link; o unlimited buffer size , identical for all the nodes. Simulation settings: o the initial number of the flows activated equal to the Poisson arrival rate in flows per hour x mean holding time in minutes /60; o the warm-up period of 99 seconds; o the observation period of 120 seconds; o the observation interval of 50 milliseconds; o simulation result measurement based on averaging 10 independent samples, each with 120-seconds worth of statistics collected in simulation. 3.2.1. Simulation Results for Admission Control Babiarz & Liu Expires January 9, 2008 [Page 16] Internet-Draft Simulations Results for 3sM July 2007 Blocking BW Data Rate Worst Probability Utilization (Mbps) Overshoot S M L | S M L | S M L | S M L ------------------------------------------------------------------ Erlang-B 12% 0.3% 0% | 62% 72% 73% | 0.5 2.9 11.8 | 0% 4% 0% Test (Erlang-B Theoretical 10% 1% 0% | 75% 75% 75% | 0.6 3 12) ------------------------------------------------------------------ 2x Overload Protection 37% 32% 40% | 80% 93% 97% | 0.6 3.7 15.6 |16% 20% 17% Test ------------------------------------------------------------------ Multiple- congestion- * * * | 80% 93% 97% | 0.6 3.7 15.5 | * * * node Test (2x overload) ------------------------------------------------------------------ Cross- Traffic * * * | 80% 95% 97% | 0.6 3.8 15.5 | * * * Test (2x overload) ------------------------------------------------------------------ VBR Test 7% 4% 1% | 51% 71% 77% | 0.16 1.1 4.8 | 0% 0% 0% (Erlang-B Theoretical 10% 1% 0% | 75% 75% 75% | 0.24 1.2 4.7) ------------------------------------------------------------------ Traffic Mix 20% 11% 0.2% | 58% 71% 72% | 0.14 0.9 3.8 | 0% 0% 0% Test (Erlang-B Theoretical 10% 1% 0% | 75% 75% 75% | 0.19 0.96 3.8) ------------------------------------------------------------------ *: not summarized at the time of preparing this draft; but they look similar to the corresponding 2x Overload Protection Test results. Observations o For CBR traffic, the AR-meter and AS-marker can support blocking performance similar to what is expected form Erlang blocking system for small to large loads; as expected, the performance of small load is not as good as for larger loads. o Protection for 2x provisioned BW with CRR traffic: worst case: <=20% overshoot for small to large loads. o For the multiple congestion node and traffic crossing scenarios, the AR-meter and AS-marker can provide similar protection to the single node for small to large loads; this is expected since the control is based on the average rate in all the cases. Babiarz & Liu Expires January 9, 2008 [Page 17] Internet-Draft Simulations Results for 3sM July 2007 o Similar behaviors of the AR-meter and AS-marker are observed for VBR and mixed traffic; as expected, the AR-meter and AS-marker will need different settings for VBR/mixed traffic than those for CBR traffic to improve performance. The AR-meter and AS-marker settings used in the simulation are chosen from a number of different settings. With different AR-meter and AS- marker settings, the simulation results can be different in terms of the number of flows carried by the system, the blocking probability, BW utilization, overshoot, control reaction time, etc. This behavior of the AR-meter and AS-marker suggests that the AR-meter and AS- marker has certain ability to assist the admission control to limit traffic load in the system to the desired level. All the results shown in the above have considered the impact of the media delay. Without the media delay, the performance of the simulation is expected to improve according to our preliminary tests. Conclusions o AR meter parameters can be adjusted to provide the following desired behaviors: (1) admit traffic to the expected data rate; (2) reduce over-/under-shoot to some degree; (3) change reaction time to some degree; (4) be applicable to a variety of traffic characteristics and multiple congested-node network with cross- traffic. o Limitations observed: (a) difficult to avoid over-/under-shoot for large media delay; (b) difficult to avoid over-/under-shoot for VBR/mixed traffic with small load. 4. Simulation Results Prior to 68th IETF This section captures the simulation work that was done prior to 68th IETF meeting. Documented are explanation of our simulation setup and results. Detailed explanations and graphed results from the simulations can be viewed in [SIM-07] (http://standards.nortel.com/pcn/Simulation_EPCN.pdf). In Section 4.1 we provide a brief explanation of the simulations setup that was used to test flow termination of constant and variable rate (silence superseded) voice traffic, Section 4.2 to Section 4.6 discusses results of the voice-related simulation, and Section 4.7 briefly discusses the preliminary video-related simulation results. All the simulations were performed using the token bucket algorithm documented in Section 4.8. Note: Since the terminology for this work is evolving, we provide a Babiarz & Liu Expires January 9, 2008 [Page 18] Internet-Draft Simulations Results for 3sM July 2007 brief explanation of terms used in the simulation results. Preemption = flow termination Preemption Threshold = Supportable Rate Preemption Level = traffic above this rate is marked as excess. Same as Supportable Rate. PM flag = explicit marking of packet to indicated excess load. In the simulation, the router sets both ECN bits to "11" in the IP header. Preemption Time = RTT + processing time of termination of a flow. This is how long it takes before a marked flow stops sending packets. pcn_px = represents marking a packet every "x" bytes of excess rate. pcn_tb = token bucket depth. In our simulations, we graphically show architectural performance comparison criteria for: o Convergence time in response to a step overload. o Convergence time in response to multiple steps of overload. o Convergence time in response to packet loss. 4.1. Simulation Setup for Voice Traffic Our simulations were done using OPNET see simulation results at [SIM-07] (http://standards.nortel.com/pcn/Simulation_EPCN.pdf). Pages 2 through 6 [SIM-07] provide details of the simulation setup: o Pages 2 and 3 [SIM-07] describe simulation setup. The source traffic generator (SRC) block produces flows and each flow has a flow ID, with each flow sending packets at its codec configured rate. Start time of packets between flows is asynchronous, representing different sources. Codec mix and number of flows enabled is programmable. o Pages 4 and 5 [SIM-07] describe characteristics of the 4 voice codecs used in the simulations and explanation of two methods used to simulate fail in the network to cause flow termination (preemption) to be invoked. During a failure, 100% of additional Babiarz & Liu Expires January 9, 2008 [Page 19] Internet-Draft Simulations Results for 3sM July 2007 traffic is introduced on to the path (router that is performing metering and marking of packets). The additional load was introduced using two models. The first failure emulates a fast reroute, were all traffic is switched instantaneously. The second failure on the graph (occurring at 500 time intervals, or approximately 25 seconds in the simulation) represents a condition where reroutes takes some time. We configured the simulation so that 80% of new traffic is added within 1 second and the remaining 20% within additional 5 seconds. Our simulations generated a traffic mix ratio of up to 15 to 1 for voice. The highest sending rate is 15 times the smallest. 4.2. Large Number of Voice Flows First we provide simulation results when there are many flows at the congestion point (internal router), 500 to 4,250 flows depending on codec mix used. The violet trace on the graphs shows the number of flows that are sending packets. o The preemption marking threshold is set to 40Mbps, so when traffic exceeds this rate packets are marked every "x" bytes of excess rate. o The forwarding rate is configures such that there is no packet loss in these simulations. See Section 4.4 for results with packet loss. o We simulated with pcn_px = 2,064, 4,064 and 8,064 bytes sizes as well with preemption time set to 50ms, 200ms and 800ms to see the impact these parameters had on rate and behavior of flow termination (preemption). See page 7 [SIM-07] (http://standards.nortel.com/pcn/Simulation_EPCN.pdf) for more details. Pages 8 through 20 [SIM-07] show the simulation results. The left side of graph shows aggregate bandwidth. The bottom of the graph indicates time scale in 0.05 seconds resolution or 3 seconds between vertical dashed lines. The right side of the graph shows number of active flows (flows that are sending packets). The violet trace shows number of active flows. The orange trace shows aggregated transmitted rate that egresses the congested router. The blue trace shows aggregated transmitted rate that is flowing into the router. Note: The blue trace is only visible when there is packet loss. In simulations where there is no packet loss the orange trace over- writes the blue. Observations for large (500 - 4,250) number of flows with no packet loss: Babiarz & Liu Expires January 9, 2008 [Page 20] Internet-Draft Simulations Results for 3sM July 2007 o The shorter the preemption time, the faster overload condition is restored back to supportable rate. o The smaller the pcn_px value (packet marked every "x" bytes of excess traffic), the faster the overload condition is restored back to supportable rate. o Packets where marked and flows where terminated when ever excess rate exceeded by pcn_px bytes the supportable rate. o The marking and flow termination (preemption) produced exponential decay behavior. When excess rate was high meaning many flows needed to be terminated, the marking was frequent but as excess load decreased so did the marking and flow termination frequency. Produce a stable behavior for both constant rate and silence suppressed voice traffic. o Flow termination (preemption) of traffic generated by constant bit rate codecs is faster than when silence suppression was used since the model that we used to generate VBR voice had an exponential distribution that generated mean on period of 1 second and mean off period of 1.59 seconds (40 on / 60 off). o With VBR voice, during reroute condition some active flows were in silence mode (not sending any packets during off period that had exponential distribution) as can be observed by rounded peak for active flows during link failure. Therefore the total load was not presented instantaneously. o The defined token bucket measurement method, marked higher rate flows more aggressively then lower rate flows. See page 15 [SIM-07] for details. This can also be observed that with mixed codec the number of flows that can be supported after link fail is higher then before. 4.3. Small Number of Voice Flows Here (on slides 21 to 28) we provide simulation results when there are small numbers of flows at the congestion point (internal router), 10 to 80 depending on codec mix used. The violet trace on the graphs shows the number of flows that are sending packets. o The preemption marking threshold is set to 800Kbps, so when traffic exceeds this rate packets are marked every "x" bytes of excess rate. o The forwarding rate is configured such that there is no packet loss in these simulations. See Section 4.5 for results with Babiarz & Liu Expires January 9, 2008 [Page 21] Internet-Draft Simulations Results for 3sM July 2007 packet loss. o We simulated with pcn_px = 2,064 and 8,064 bytes sizes as well with preemption time set to 50ms, 200ms and 800ms to see the impact these parameters had on rate and behavior of flow termination (preemption). See page 21 [SIM-07] for more details. Pages 22 through 28 [SIM-07] show the simulation results when there are a low number of flows at the congested router. Observations for small (10 - 80) number of flows with no packet loss: o The shorter the preemption time, the faster overload condition is restored back to supportable rate. o The smaller pcn_px value (packet marked every "x" bytes of excess traffic), the faster the overload condition is restored back to supportable rate. o Packets where marked and flows where terminated when ever excess rate exceeded by pcn_px bytes the supportable rate. o When excess rate was high meaning many flows needed to be terminated, the marking was frequent but as excess load decreased so did the marking and flow termination frequency. Produce a stable behavior for both constant rate and silence supersede voice traffic. o Flow termination (preemption) of traffic generated by constant bit rate codecs is faster than when silence suppression was used since the model that we used to generate VBR voice had an exponential distribution that generated "mean on period" of 1 second and "mean off period" of 1.59 seconds (40 on / 60 off). o With VBR voice, during reroute condition some active flows were in silence mode (not sending any packets during off period that had exponential distribution) as can be observed by rounded peak for active flows during link failure. Therefore the total load was not presented instantaneously. o The defined token bucket measurement method, marked higher rate flows more aggressively then lower rate flows. See [SIM-07] page 28 for details. This can also be observed that with mixed codec the number of flows that can be supported after link fail is higher then before. The explicit marking behavior produced similar results when the number of constant rate and variable rate (silence suppressed) voice Babiarz & Liu Expires January 9, 2008 [Page 22] Internet-Draft Simulations Results for 3sM July 2007 flows was small or high. These simulation results would indicated that for voice traffic this marking approach works independently of number of flows at the congestion point. 4.4. Large Number of Voice Flows with Packet Loss Now (see slides 29 to 38) we analyze the impact of packet loss has on the explicate marking approach when there are many flows at the congestion point (internal router), 500 to 4,250 depending on codec mix used. The violet trace on the graphs shows the number of flows that are sending packets. o The preemption marking threshold is set to 40Mbps, so when traffic exceeds this rate packets are marked every "x" bytes of excess rate. o The forwarding rate is configures to 48Mbps (introducing up to 40% packet loss) or 40Mbps (introducing up to 50% packet loss). 50% packet loss occurs when forwarding rate of service class = supportable rate (or preemption level), current traffic level is at supportable rate and 100% of additional traffic is added to simulate traffic being switch or rerouted due to failure in the network. o We simulated with pcn_px = 8,064 bytes sizes as well with preemption time set to 200ms and 800ms to see the impact these parameters had on rate and behavior of flow termination (preemption). See page 29 [SIM-07] for more details. Pages 30 through 38 [SIM-07] show the simulation results. Observations for large (500 - 4,250) number of flows with up to 40% and 50% packet loss: o As can be observed the flow termination behaved is similar to when there was no packet loss, except that when there is packet loss the time it takes to terminate sufficient number of flows to the supportable rate (preemption threshold) takes longer. This is because some of the marked packets are lost. o We also observed that over preemption can occur see page 31 [SIM-07] for CBR (G.711 at 20ms) only traffic when pcn_px value of 8.064 bytes is used with preemption time of 800ms. Increasing pcn_px or decreasing preemption time will remove the over preemption condition for this traffic mix. o This packet marking and flow termination approach works well even under high packet loss conditions. Babiarz & Liu Expires January 9, 2008 [Page 23] Internet-Draft Simulations Results for 3sM July 2007 4.5. Small Number of Voice Flows with Packet Loss Now we analyze the impact of packet loss has on the explicate marking approach when there are a small number of flows at the congestion point (internal router), 10 to 80 depending on codec mix used. The violet trace on the graphs shows the number of flows that are sending packets. o The preemption marking threshold is set to 800Kbps, so when traffic exceeds this rate packets are marked every "x" bytes of excess rate. o The forwarding rate is configures 960Kbps (introducing up to 40% packet loss) and 800Kbps (introducing up to 50% packet loss). 50% packet loss occurs when forwarding rate of service class = supportable rate (or preemption level), current traffic level is at supportable rate and 100% of additional traffic is added to simulate traffic being switch or rerouted due to failure in the network. o We simulated with pcn_px = 8,064 bytes sizes and preemption time set to 800ms to see the impact these parameters had on rate and behavior of flow termination (preemption). See page 39 [SIM-07] for more details. Pages 40 through 43 [SIM-07] show the simulation results when there are a low number of flows with up to 40% and 50% packet loss at the congested router. Observations for small (10 - 80) number of flows with up to 40% and 50% packet loss: o As can be observed the flow termination behaved is similar to when there was no packet loss, except that when there is packet loss the time it takes to terminate sufficient number of flows to the supportable rate (preemption threshold) takes longer. o We also observed that over preemption can occur see page 40 [SIM-07] for CBR (G.711 at 20ms) only traffic when pcn_px value of 8.064 bytes is used with preemption time of 800ms. Increasing pcn_px or decreasing preemption time will remove the over preemption condition for this traffic mix.. o This packet marking and flow termination approach works well even under high packet loss conditions. Babiarz & Liu Expires January 9, 2008 [Page 24] Internet-Draft Simulations Results for 3sM July 2007 4.6. Corner Voice Cases Studied Now we want to look at some corner cases where this method starts to breakdown. We looked at the configuration of parameters that caused the following conditions: o Over termination (preemption) of flows. This condition occurs when pcn_px parameter is too small for the time that it takes to terminate a flow (total preemption time). This condition is noticeable when there is CBR only traffic flowing through the router. Increasing pcn_px therefore slowing down flow termination can eliminate any possibility of over terminating flows. This is a parameter that can be configured by the network administrator. See simulation results [SIM-07], pages 45-48 of examples of this condition. o Synchronization of packet marking. This conditional occurs for CBR fixed packet size traffic at metering point and when pcn_px is an even multiple of payload packet size, e.g., packet size = 200 bytes and pcn_px = 2,000 bytes. Page 49 [SIM-07] shows that synchronization of marking condition. However, this undesirable behavior does not break the mechanism, but it takes longer to terminate flows. o Preemption takes to long. This condition can be created if pcn_px is configured to be x times larger than need. Page 50 [SIM-07] shows the impact of setting pcn_px 2x bigger then needed. 4.7. Simulation Setup for Video Traffic In this section, we briefly discuss the preliminary video-related simulation results; for details, see pages 51-65 [SIM-07] (http://standards.nortel.com/pcn/Simulation_EPCN.pdf). The video simulation is based on the same token bucket algorithm as the voice simulation discussed in the previous sections. The main differences between our video simulation and voice simulation are the traffic source model and the selection of the pcn_tb and pcn_px values. In the video simulation, the traffic source model is based on the video model proposed by [Maglaris-88], which has the following properties: o a constant frame rate of F frames per sec (a fixed time interval between frames), Babiarz & Liu Expires January 9, 2008 [Page 25] Internet-Draft Simulations Results for 3sM July 2007 o a constant number of P pixels per frame, o a random number of bits per frame calculated using the number of compressed bits per pixel in the n-th frame modeled by a first- order autoregressive Markov process. In our simulation, the packetization of the bits is modeled as follows, o the MTU of the video packet is 1356 bytes, including 40 bytes of the IP header; o only the positive bits calculated from the above video model can generate packets; o the first 1316*8 bits of the total bits of a frame is packed into the first MTU-sized packet; the second 1316*8 bits is packed into the second MTU-sized packet; this is done until all the bits are packed; the last packet likely smaller than MTU contains all the remainder bits plus the 40-byte IP header; o the packets generated from a frame are sent to the network one by one at the end of the time interval of 1/F seconds with a per- packet serialization time of (packet size / link speed); o when a source starts, the first frame is generated at a random time point in the 1/F-sec time interval. In our current video simulation, only a single type of video source is used for generating video flows, which has an expected average data rate of 400Kbps. The following flow settings are considered, similarly to those voice settings, where T is relative to the end of the simulation warm-up period, o Small sources with preemption threshold BW = 4Mpbs: start with 8 flows, add 10 flows at T = 3 sec; add another 10 flows at T = 24 sec; o Medium sources with preemption threshold BW = 40Mpbs: start with 80 flows, add 100 flows at T = 3 sec; add another 100 flows at T = 24 sec; o Large sources with preemption threshold BW = 200Mpbs: start with 400 flows, add 500 flows at T = 3 sec; add another 500 flows at T = 24. The simulation was run with these flow settings for three RTT (flow termination) times of 50, 200, and 800ms and four token bucket- Babiarz & Liu Expires January 9, 2008 [Page 26] Internet-Draft Simulations Results for 3sM July 2007 marking interval combinations, o (pcn_tb = 400KB; pcn_px = 200KB); o (pcn_tb = 200KB; pcn_px = 100KB); o (pcn_tb = 300KB; pcn_px = 200KB); o (pcn_tb = 250KB; pcn_px = 50KB). In all the simulation runs, the forwarding rate of the router is set as two times the preemption threshold BW, and the buffer has unlimited space (i.e., there is no packet loss). We have the following observations from the simulations, o video flow preemption is achievable and behaves similarly to what is observed in the voice simulations; o the tested token bucket-marking interval combinations are similarly effective across the flow settings and RTT cases with combination (pcn_tb = 400 KB; pcn_px = 200 KB) seemingly the most stable; o It is difficult to measure the over-/under-preemption error, as offered traffic is constantly changing. However, we believe that (pcn_tb = 400 KB; pcn_px = 200 KB) provide more consistent results then (pcn_tb = 250 KB; pcn_px = 50 KB) parameter settings. 4.8. Excess Load Marking Algorithm Used in Simulation Below is the pseudo code of a token bucket algorithm that was used in our simulations for metering and marking for flow termination (preemption) of flows. This is an example of an metering and preemption marking function that would reside in PCN capable routers. Configuration parameters are per DSCP: pcn_pt = traffic rate at preemption threshold in bits per second pcn_tb = the size of token bucket in bytes for detection that preemption threshold is exceeded pcn_px = the measurement of excess rate, (sets ECN=11 every "x" bytes of excess traffic) Definition of terms used in the algorithm: Babiarz & Liu Expires January 9, 2008 [Page 27] Internet-Draft Simulations Results for 3sM July 2007 delta_t is the time since the processing of the previous packet for this token bucket pktLen is the length of the packet being processed in unit of bytes Initialization of local variables: tokenCountP = pcn_tb //initialize token bucket to max. pcn_pt_B = pcn_pt / 8 //change preemption rate to bytes per second Preempt_Level_Metering_Marking routine, with length of current packet as input: Preempt_Meter ( pktLen) { tokenCountP = tokenCountP + (delta_t * pcn_pt_B) //this adds tokens to token bucket tokenCountP = Min (tokenCountP, pcn_tb) //keeps tb from growing pass full tokenCountP = tokenCountP - pktLen //subtracts tx bytes from bucket if (tokenCountP < = 0) //when tb becomes empty or negative { Set ECN = 11 //preemption mark packet, (Set ECN bits = 11) tokenCountP = tokenCountP + pcn_px //add "x" tokens to token bucket } return } // End of Preempt_Meter(). Figure 9 5. Security Considerations Not applicable for this draft. 6. Acknowledgements The authors would like to thank the Dave McDysan for review of 00 version of this document and for his suggestions to make it more complete. Babiarz & Liu Expires January 9, 2008 [Page 28] Internet-Draft Simulations Results for 3sM July 2007 7. Informative References [I-D.babiarz-pcn-3sm] Babiarz, J., "Three State PCN Marking", draft-babiarz-pcn-3sm-00 (work in progress), July 2007. [I-D.eardley-pcn-architecture] Eardley, P., "Pre-Congestion Notification Architecture", draft-eardley-pcn-architecture-00 (work in progress), June 2007. [Maglaris-88] Maglaris et al, "Performance Models of Statistical Multiplexing in Packet Video Communications, IEEE Transactions on Communications 36, pp. 834-844", July 1988. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001. [SIM-07] Liu, X-G. and J. Babiarz, "Simulation Results for Explicit PCN Marking and Flow Termination (http://standards.nortel.com/pcn/Simulation_EPCN.pdf)", February 2007. [SIM1-07] Liu, X-G. and J. Babiarz, "Simulation Results for Three State PCN Marking for Admission Control and Flow Termination, http://standards.nortel.com/pcn/3sM-Simulation-1.pdf", July 2007. Authors' Addresses Jozef Z. Babiarz Nortel 3500 Carling Avenue Ottawa, Ont. K2H 8E9 Canada Phone: +1-613-763-6098 Email: babiarz@nortel.com Babiarz & Liu Expires January 9, 2008 [Page 29] Internet-Draft Simulations Results for 3sM July 2007 Xiao-Gao Liu Nortel 3500 Carling Avenue Ottawa, Ont. K2H 8E9 Canada Phone: +1-613-763-7516 Email: xgliu@nortel.com Babiarz & Liu Expires January 9, 2008 [Page 30] Internet-Draft Simulations Results for 3sM July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Babiarz & Liu Expires January 9, 2008 [Page 31]