LAN Performance Measurements Lab

LAN Performance Measurements Lab Token Ring and Ethernet Name: Date Experiment Performed: Group Members: Lan Performance Lab Ver 1.4, February 2004. - 1 -

Introduction: The goal of this laboratory is for students to gain some first hand experience measuring and observing the performance characteristics of the two LAN technologies, Ethernet and token-ring. The hands-on experience gained in the lab is intended to supplement and reinforce the student's understanding of the operational and performance aspects of the MAC-layer protocols. For student's to benefit from this experience it is essential that they have a basic understanding of IEEE 802.3(Ethernet) and 802.5(Token Ring) specifications. Specific measurements observed in this experiment may vary considerably from commonly held theoretical results. Keep in mind that these popular rules-of-thumb are based upon a number of simplifying assumptions which are not applicable to all environments. For this reason, they should be put in the proper perspective as general guidelines, and not steadfast rules. Furthermore, there are number of limitations to the methodology employed in this lab experiment. Therefore, these results must also be put in the proper perspective. Keep in mind the following limitations to the practical validity of these experiments: (1) packet gap times and (2) frame lengths are deterministic rather than stochastic, (3) the number of stations is small, and (4) the propagation delay for Ethernet and ring latency for token ring are small because the physical network segments are short. These are all significant factors in relation to LAN performance. Furthermore, the traffic generation and monitoring equipment are low-end devices which provide only moderately accurate information and may behave inconsistently under high loads. When analyzing their results, students should keep these factors in mind. They should also attempt to understand why these issues might skew performance measures. Using PC based traffic generators, students will transmit known loads on each network. A range of input loads will be achieved by varying the frame rate and the frame length. To simplify the experiment, configurations will be held constant across all the traffic generators for each experiment. Students will measure the network utilization or throughput, and the time it takes to perform a simple FTP file transfer as the loads are varied. Simple observations should reveal some basic relationships among load, throughput, frame length and delay. Using their understanding of each network's MAClayer protocol, and their understanding of the particular environment they should be able to assess the reasons for the behavior they have observed. Students should understand that it is difficult to compare the performance of Ethernet and token-ring in an absolute sense. But this lab should provide some opportunity to observe relative effects. Students are expected to give some thought as to why the technologies behave differently and when it may be more appropriate to use one versus the other. When considering what they have observed in this lab students should consider the following questions: (1) How performance issues might affect LAN design. (2) What kinds of things might be done to improve LAN performance in an Ethernet or token-ring environment? (3) What should a LAN analyst or engineer look for when assessing LAN performance and design? Lan Performance Lab Ver 1.4, February 2004. - 2 -

Equipment and Setup To be efficient, students will be distributed to two groups. One group works on Ethernet while the other works on Token Ring. Then switch. Please gather all your data during your time-slot before attempting to work out any of the problems. During your assigned lab lecture, the TA will introduce you to the equipment, procedures and concepts needed to complete this lab. There are two parts to this lab. The first part involves performance measurements for 10 Mbps Ethernet. The second part involves a similar set of procedures to measure the performance of a 4-Mbps token-ring. You should verify that the necessary equipment is in place, configured properly and operational before continuing with the lab procedures. Ethernet Configuration Verification: The following is a list of the equipment required for part one of this lab. This equipment should be pre-configured for you before coming into the lab. In general you will not have to worry about the details; they are presented primarily for informational purposes: 8 PC running windows XP 8 Network Interface Cards (NICs). 6 FETEST LanXL - LAN monitoring and traffic generation software. 2 FTP stations, one is FTP server, the other is FTP client. 8 10base-T Ethernet cables linking each PC on the segment to the Hub. 8 RJ45-connectors Table 1: Ethernet Equipment List All the PCs have already been appropriately labeled as traffic generator, or monitor, or FTP server, or FTP clients. Once you have identified the traffic generators, close LanXL and reopen it again. re-boot each machine by powering it off and on. It is important that you perform a cold start because certain software which may have been running causes the network interface to halt when LanXL is run. Procedure-1 Ethernet Traffic Generator and Monitor function Verification: Double click the LanXL icon on windows XP desktop On the LanXL PC which is labeled as "Monitor" 1) Click "Module-> Mode of Operation->" from the main menu, and make sure "capture" and "monitor" are selected 2) Click the start icon on the menu bar Assuming this PC is functioning properly, you should be capturing traffic seen on the Lan Performance Lab Ver 1.4, February 2004. - 3 -

Ethernet segment. However you should not see anything yet because none of the other stations are generating traffic. Next you should test each of the other traffic generators one at a time. Select an un-tested generator: Procedure-2 1) Double click the LanXL icon on windows XP desktop 2) Click "transmit" icon to set it to transmit mode 3) Click detail view icon enter into detail view 4) Click "create/modify transmit buffer icon 5) Click Delete to delete the old settings if it exists. 6) Set the destination address as FFFFFFFF 7) Choose continuous as sending mode 8) Modify packet size and packet gap 9) Click Add 10) Click Load Module 11) Click the start icon on the menu bar At this point the traffic generator should be transmitting Ethernet frames according to its default settings. Check the monitor station to confirm that frames are actually being transmitted. On the monitor PC you should see some indication that frames are being sent by the test traffic generator PC. Hopefully you won't have a problem generating traffic on one PC and monitoring from another. If it is working, stop the traffic generator by clicking "stop" icon. Next you will want to repeat this step with all of the other 5 generator PCs. Procedure-3 Ethernet FTP Verification: Up to now, you have all traffic generators and monitors working. Then, you need to test FTP server and FTP client. Before doing this, you need to stop all the traffic generators. IP address of FTP Server for Ethernet segment 10.1.1.26 And the service is automatically enabled. Start the FTP software on the client machine: Lan Performance Lab Ver 1.4, February 2004. - 4 -

1) Enter DOS mode by clicking Start->run, then type cmd in the "open" field. 2) In the DOS mode, type ftp 10.1.1.26 username: ftpaccess password: ftpaccess 3) Now, you are connected to FTP server. Set file type to Binary by typing the command Binary 4) Get file from FTP server, in the later steps, you need to record the displayed time. get file.exe The file transfer should take about 3 seconds. Note: On the FTP client machine, pressing <F3> will repeat the previous command. You will use this key throughout the lab. Lan Performance Lab Ver 1.4, February 2004. - 5 -

Token-Ring Configuration Verification: The following is a list of the equipment required for part two of this lab. This equipment should be pre-configured for you before coming into the lab. In general you will not have to worry about the details; they are presented primarily for informational purposes: 8 PC running windows XP 8 4/16 Mbps Network Interface Cards (NICs). 6 FETEST LanXL - LAN monitoring and traffic generation software. 2 FTP stations, one is FTP server, the other is FTP client. 1 IBM 8226 token-ring MAU. 8 RJ-45 connectors and twisted cables connecting each PC to the MAU. Table 2: Token-Ring Equipment List You will have 8 PCs for the token-ring experiment: 5 traffic generators, 1 monitor, 1 FTP client and 1 FTP server. All the PCs have already been appropriately labeled as traffic generator, or monitor, or FTP server, or FTP clients. All the NICs had been put into promiscuous mode. Each of the token-ring PCs must be connected to the IBM 8226 MAU via UTP cable. The UTP cable connects to the token-ring NICs and the MAU using RJ-45 type connectors. Procedure-4 Token-Ring Traffic Generator Verification: Monitor setup: Double click the LanXL icon on windows XP desktop On the LanXL PC which is labeled as "Monitor" 1) Click "Module-> Mode of Operation->" from the main menu, and make sure "capture" and "monitor" are selected 2) Click the start icon on the menu bar Assuming this PC is functioning properly, you should be capturing traffic seen on the Token Ring network. Unlike Ethernet, token-ring involves some active management. You should be able to observe captured token-ring monitor frames. Next test each of the traffic generators in turn. Procedure-5 Traffic generator setup: Lan Performance Lab Ver 1.4, February 2004. - 6 -

Select an un-tested generator: Do the same thing step by step as in Ethernet traffic generator setup case which is showed in Procedure-2. At this point the traffic generator should be transmitting Token Ring frames according to its default settings. Check the monitor station to confirm that frames are actually being transmitted. On the monitor PC you should see some indication that frames are being sent by the test traffic generator PC. Hopefully you won't have a problem generating traffic on one PC and monitoring from another. If it is working, stop the traffic generator by clicking "stop" icon. Next you will want to repeat this step with the other generator PCs. The traffic generator should indicate that it is transmitting frames, and you should be able to observe a flurry of capture activity on the network monitor. Procedure-6 Token-Ring FTP Connection Verification: IP address of FTP Server for Token Ring 10.1.1.21 And the service is automatically enabled. Start the FTP software on the client machine: 1) Enter DOS mode by clicking Start->run, then type cmd in the "open" field. 2) In the DOS mode, type ftp 10.1.1.21 username: ftpaccess password: ftpaccess 3) Now, you are connected to FTP server. Set file type to Binary by typing the command Binary 4) Get file from FTP server, in later steps you need to record the displayed time. Remember for normalization compare with Ethernet, this file size is 2.5 times less than the file used in Ethernet case. (Guess why?) get file.exe Lan Performance Lab Ver 1.4, February 2004. - 7 -

Lab Procedures: Part I: Ethernet (IEEE 802.3) Performance Measurements Overview: On a single 10BaseT Ethernet segment there are 6 PCs running LanXL LAN monitoring and traffic generation software. You will configure the 5 traffic generators to generate traffic on the LAN segment by specifying the frame length and the frame inter-arrival time for each iteration of the experiment as specified in the Ethernet configuration charts below. Each configuration imposes a known offered load on the network. The offered load is a function of the frame length, frame inter-arrival time, and the number of stations. For example: Assume the frame length is 1518 octets, the packet gap is 24.2msec and there are 5 stations. First we can calculate the frame rate which is the reciprocal of the packet gap: 41.3 frames per second. Given that each frame is 1518 octets long, we can calculate the load generated by one station as being 1518 x 8 x 41.3 = 501547.2 bps. Since there are 5 stations we have a total load of 5 x 501547.2 = 2507736 bps. Divide this by the capacity of Ethernet which is 10 Mbps and we have a total offered load of 25%. The drop-off varies between PCs and by the particular rate being requested. Therefore the offered loads should be understood as reasonable approximations. Care should be taken not to confuse the term inter-arrival time with inter-frame gap. The IEEE 802.3 standard calls for minimum 9.6us inter-frame gap after the channel has become free before the MAC-layer can initiate a new transmission. This inter-frame gap is enforced at the MAC-layer to meet constraints imposed by the Physical-layer. Interarrival time represents the time between successive MAC-UNITDATA. Request primitives issued by the MAC service user. Keep in mind that the MAC-layer may not be able to service these requests immediately due to on-going network activity. The rate at which these requests are serviced reflects the station's throughput, whereas the rate at which they are made reflects the offered load. In some literature, offered load includes the additional load due to retransmission attempts. Our definition does not include these effects. For each configuration you will estimate the total network utilization by reading utilization from the throughput table on each of the traffic generators and adding them together to get total network utilization. Each of the generators indicates the throughput it is currently achieving. Under light loads, these numbers will be stable and consistent across the network; however as the load increases, these indications will begin to fluctuate considerably due to the effects of contention and collision handling. To record the network utilization you will have to estimate the average value you see and multiply it by 5. Two additional PCs will be used to transfer a file using FTP. The transfer should be done 5 times for each load configuration. Do not to transfer the file while you are determining the utilization. The traffic generated by the file transfer increases the load on the network and thus has a direct impact on the utilization. For light loads the transfer Lan Performance Lab Ver 1.4, February 2004. - 8 -

time stays relatively constant. Under heavy loads it may vary considerably. You should take about 5 readings and calculate an average for each iteration.. There are tables corresponding to each of two sets of experiments. The first uses maximum length Ethernet frames of 1518 octets. The second set uses frame length of 512 octets. You should observe different FTP file transfer performance with same offer load but different packet size on traffic generator (why?). Follow the example procedures detailed following the configuration tables (table 3 and 4) for the first configuration set, and then repeat those procedures for each subsequent configuration. Lan Performance Lab Ver 1.4, February 2004. - 9 -

Ethernet Configuration tables: Packet Size Packet Gap # of Stations Offered Load Utilization FTP File Transfer Time (octets) (msec) (%) (%) (sec) 1518 NA 0 0 0 1518 24.2 5 25 1518 12.1 5 50 1518 8.1 5 75 1518 6.0 5 100 1518 4.0 5 150 1518 3.0 5 200 Table 3: Ethernet - 1518 Octet Frames Packet Size Packet Gap # of Stations Offered Load Utilization FTP File-Transfer Time (octets) (msec) (%) (%) (sec) 512 NA 0 0 0 512 8.20 5 25 512 4.10 5 50 512 2.73 5 75 512 2.05 5 100 512 1.37 5 150 512 1.03 5 200 Table 4: Ethernet - 512 Octet Frames Lan Performance Lab Ver 1.4, February 2004. - 10 -

Ethernet Example Step-by-Step Procedures 1) Ethernet Traffic Generator and Monitor function Verification, refer to Procedure-1 and Procedure-2. 2) Ethernet FTP verification, refer to Procedure-3 3) Stop FTP transfer 4) Stop traffic generator and monitor 5) From FTP client, transfer file from server to client 6) Transfer five times, when finished, record the average time into table3 and table 4. 7) On each traffic generator, set its operation mode as transmitting mode and set the transfer buffer parameters based on table 3 and 4. Refer to Procedure-2. Note: Each of the traffic generators will be configured identically for each run of the experiment. Be sure to confirm that they are the same before you take any measurements. 8) Repeat 7) on each traffic generator. 9) Click start for each traffic generator. 10) Wait for about 15 seconds, click start on the monitor. 11 ) Read the Utilization from the monitor and record it. Note: The total offered load to the network is the sum of the offered load from each of the traffic generators. The total network utilization, which could be seen from monitor, is equal to the sum of the utilization reported by each station. This may become difficult to do as the load increases. Get the best average estimate you can. Determine the utilization and record it in the appropriate place on the Ethernet table. This should be about 20-25% for the experiment corresponding with the first configuration. 12. Connect to FTP server using the Procedure-3. 13. From FTP client, run get file.exe 5 times, and record the average transfer time on the table. 14. Change the traffic generator settings and repeat the procedure from 7 to 13 and record the data. Lan Performance Lab Ver 1.4, February 2004. - 11 -

Part II: Token-Ring (IEEE 802.5) Performance Measurements Overview On a single 4 Mbps token-ring network there are 6 PCs running LanXL network monitoring and traffic generation software. As with the Ethernet experiments, you will configure each of these to generate traffic on the LAN specifying the frame length and the frame inter-arrival rate according to the token-ring configuration table provided below. Each configuration imposes a known offered load on the network. The definition and calculation of offered load is consistent as with the Ethernet, except when dividing to obtain the % of the network's capacity. In this case the aggregate bit rate is divided by 4 Mbps rather than 10 Mbps. A PC is running LanXL in the Capture and Monitor mode. This allows you to observe the traffic on the network and read the total network utilization directly from the monitoring station. The token-ring monitor does not have to be very sophisticated in order to provide this capability; however accurately assessing Ethernet utilization from a monitoring station is far more difficult due to the presence of collisions and retransmissions. For each experiment you will observe and record the total network utilization by reading the average utilization from the Network Utilization window of the monitor PC. Two PCs will be used to transfer a file using FTP. The transfer should be done several times for each load configuration. As with the Ethernet, do not transfer the file while you are determining the utilization. You should take about 5 readings and calculate an average. There are charts corresponding to each of two sets of experiments. The first uses large frame lengths of 1518 octets. The second set uses small length frames of 512 octets. The justification for these choices parallel the explanations given for the Ethernet experiments. Follow the example procedures detailed following the configuration tables for the first configuration set, and then repeat those procedures for each subsequent configuration. Lan Performance Lab Ver 1.4, February 2004. - 12 -

Token-Ring Configuration Charts: Packet Size Packet Gap # of Stations Offered Load Utilization FTP File Transfer Time (octets) (msec) (%) (%) (sec) 1518 NA 0 0 0 1518 60 5 25 1518 30 5 50 1518 20 5 75 1518 15 5 100 1518 10 5 150 1518 7.5 5 200 Table 5: Token-Ring - 1518 Octet Frames Packet Size Packet Gap # of Stations Offered Load Utilization FTP File Transfer Time (bytes) (msec) (%) (%) (sec) 512 NA 0 0 0 512 20.48 5 25 512 10.24 5 50 512 6.83 5 75 512 5.12 5 100 512 3.42 5 150 512 2.56 5 200 Table 6: Token-Ring - 512 Octet Frames Lan Performance Lab Ver 1.4, February 2004. - 13 -

Token-Ring Example Step-by-Step Procedures 1) Token-Ring Traffic Generator and Monitor function Verification, refer to Procedure- 4 and Procedure-5. 2) Token-Ring FTP verification, refer to Procedure-6 3) Stop FTP transfer 4) Stop traffic generator and monitor 5) From FTP client, transfer file from server to client 6) Transfer five times, when finished, record the average time into table5 and table 6. 7) On each traffic generator, set its operation mode as transmitting mode and set the transfer buffer parameters based on table 5 and 6. Refer to Procedure-5. Note: Each of the traffic generators will be configured identically for each run of the experiment. Be sure to confirm that they are the same before you take any measurements. 8) Repeat 7) on each traffic generator. 9) Click start for each traffic generator. 10) Wait for about 15 seconds, click start on the monitor. 11 ) Read the Utilization from the monitor and record it. Note: The total offered load to the network is the sum of the offered load from each of the traffic generators. The total network utilization, which could be seen from monitor, is equal to the sum of the utilization reported by each station. This may become difficult to do as the load increases. Get the best average estimate you can. Determine the utilization and record it in the appropriate place on the Ethernet table. This should be about 20-25% for the experiment corresponding with the first configuration. 12. Connect to FTP server using the Procedure-6. 13. From FTP client, run get file.exe 5 times, and record the average transfer time on the chart. 14. Change the traffic generator settings based on table 5 and table 6 and repeat the procedure from 7 to 13 and record the data. Lan Performance Lab Ver 1.4, February 2004. - 14 -

Part III: Analysis and Questions Students are required to attend a lab session, then complete and hand in the questions on the following pages: Lan Performance Lab Ver 1.4, February 2004. - 15 -

LAN Performance Lab: Analysis and Questions Supplement NAME: The measurement results should be copied from the corresponding tables in your complete lab handout. Please DO NOT turn in the complete handout. Please answer the following questions on a separate piece of paper. If you can, please type your answers. 1. Measurements Please complete the following tables using results you collected in the lab: Lan Performance Lab Ver 1.4, February 2004. - 16 -

Ethernet Configuration tables: Packet Size Packet Gap # of Stations Offered Load Utilization FTP File Transfer Time (octets) (msec) (%) (%) (sec) 1518 NA 0 0 0 1518 24.2 5 25 1518 12.1 5 50 1518 8.1 5 75 1518 6.0 5 100 1518 4.0 5 150 1518 3.0 5 200 Table 3: Ethernet - 1518 Octet Frames Packet Size Packet Gap # of Stations Offered Load Utilization FTP File-Transfer Time (octets) (msec) (%) (%) (sec) 512 NA 0 0 0 512 8.20 5 25 512 4.10 5 50 512 2.73 5 75 512 2.05 5 100 512 1.37 5 150 512 1.03 5 200 Table 4: Ethernet - 512 Octet Frames Lan Performance Lab Ver 1.4, February 2004. - 17 -

Token-Ring Configuration Charts: Packet Size Packet Gap # of Stations Offered Load Utilization FTP File Transfer Time (octets) (msec) (%) (%) (sec) 1518 NA 0 0 0 1518 60 5 25 1518 30 5 50 1518 20 5 75 1518 15 5 100 1518 10 5 150 1518 7.5 5 200 Table 5: Token-Ring - 1518 Octet Frames Packet Size Packet Gap # of Stations Offered Load Utilization FTP File Transfer Time (bytes) (msec) (%) (%) (sec) 512 NA 0 0 0 512 20.48 5 25 512 10.24 5 50 512 6.83 5 75 512 5.12 5 100 512 3.42 5 150 512 2.56 5 200 Table 6: Token-Ring - 512 Octet Frames Lan Performance Lab Ver 1.4, February 2004. - 18 -

2. Required Graphs: You will be required to use MATLAB to plot six graphs as part of the analysis of this lab experiment.. NOTE: MAKE SURE THAT YOU SET THE X AND Y COORDINATES AS INDICATED IN THE LAB, OTHERWISE YOUR GRAPHS WILL BE MARKED WRONG. Label all relevant information on each submitted graph. This includes a title, axis labels and clear indication of the scale on each axis. The dependent variable should be along the vertical axis, the independent variable along the horizontal axis. Graphs: Please complete the following graphs based upon the data you collected in the lab: 3. Questions 1. Graph total offered load (y - axis) versus network utilization (x - axis) for each of the following cases: Ethernet using 1518-octet frames. Ethernet using 512-octet frames. Token-ring using 1518-octet frames. Token-ring using 512-octet frames. 2. Graph network utilization (y - axis) versus file transfer time (x - axis) for each of the following cases: Assume utilization is the independent variable for these graphs. Ethernet using 1518-octet frames. Token-ring using 1518-octet frame. Please provide concise answers to the following questions on an attached sheet. 1. Explain any differences in the Ethernet utilization curves for the two frame sizes tested. 2. What are the advantages and/or disadvantages of using small or large frames on Ethernet? 3. Why does the file transfer time rise so dramatically on the heavily loaded Ethernet network using 1518 byte frames? 4. What can you say about the relative throughput characteristics of Ethernet and token-ring. 5. Explain any differences in delays between lightly loaded token-ring and Ethernet networks. 6. Why do the delay characteristics on the token-ring network remain relatively flat even under heavily loaded conditions? Lan Performance Lab Ver 1.4, February 2004. - 19 -