Traffic Shaping (Part 1)

Transcription

1 Lab 2a Traffic Shaping (Part 1) Purpse f this lab: In this lab yu will build (prgram) a netwrk element fr traffic shaping, called a leaky bucket, that runs ver a real netwrk. The traffic fr testing the leaky bucket will be the Pissn, VBR vide, and LAN traffic traces frm Lab 1. Nte: Lab 2b will be a cntinuatin f this lab. Sftware Tls: The prgramming fr this lab is dne in Java and requires the use f Java datagrams. What t turn in: Turn in a reprt with yur answers t the questins in this lab, including the plts, hard cpies f all yur Java cde, and the annymus feedback frm. Versin 1 (January 27, 2007) Versin 2 (January 28, 2011) Jörg Liebeherr, All rights reserved. Permissin t use all r prtins f this material fr educatinal purpses is granted, as lng as use f this material is acknwledged in all derivative wrks.

2 Table f Cntent Table f Cntent 2 Preparing fr Lab 2a 2 Cmments 2 Part 1. Prgramming with Datagram Sckets and with Files 3 Part 2. Traffic generatrs 5 Part 3. Leaky Bucket Traffic Shaper 7 Feedback Frm fr Lab 2a 13 Preparing fr Lab 2a This lab requires netwrk prgramming with Java datagram sckets. There is an infrmative and shrt tutrial n Java datagrams is available at: Java datagram sckets use the UDP transprt prtcl t transmit traffic. The relatinship between Java datagrams and the UDP prtcl is described in: Cmments Quality f plts in lab reprt: This lab asks yu t prduce plts fr a lab reprt. It is imprtant that the graphs are f high quality. All plts must be prperly labeled. This includes that the units n the axes f all graphs are included, and that each plt has a header line that describes the cntent f the graph. Feedback: T be able t imprve the labs fr future years, we cllect data n the current lab experience. Yu must submit an annymus feedback frm fr each lab. Please use the feedback frm at the end f the lab, and return the frm with yur lab reprt. Extra credit: Cmplete the ptinal Part 4 fr 10% extra credit. Java: In the Unix lab, the default versin f the Java installatin is relatively ld. T access a mre recent versin use the cmmand: Cmpiling: /lcal/java/jdk1.5.0_09/bin/javac Running: /lcal/java/jdk1.5.0_09/bin/java ECE 466 LAB 2A - PAGE 2 J. Liebeherr

3 Part 1. Prgramming with Datagram Sckets and with Files The purpse f this part f the lab is t becme familiar with prgramming Datagram sckets and with writing Java prgrams that read and write data t/frm a file. The prgrams prvided in this part intend t ffer guidance fr the prgramming tasks needed later n. Exercise 1.1 Prgramming with datagram sckets Cmpile and run the fllwing tw prgrams. The prgram Sender.java transmits a string t the receiver ver a datagram scket. The prgram Receiver.java displays the string when it is received. Sender.java Receiver.java imprt java.i.*; imprt java.net.*; public class Sender { public static vid main(string[] args) thrws IOExceptin { InetAddress addr = InetAddress.getByName(args[0]); byte[] buf = args[1].getbytes(); DatagramPacket packet = new DatagramPacket(buf, buf.length, addr, 4444); DatagramScket scket = new DatagramScket(); scket.send(packet); } } imprt java.i.*; imprt java.net.*; public class Receiver { public static vid main(string[] args) thrws IOExceptin { DatagramScket scket = new DatagramScket(4444); byte[] buf = new byte[256]; DatagramPacket packet = new DatagramPacket(buf, buf.length); System.ut.println("Waiting..."); scket.receive(packet); String s = new String(p.getData(), 0, p.getlength()); System.ut.println(p.getAddress().getHstName() + ": " + s); } } Cmpile the prgrams. Start the receiver by running java Receiver. Assuming that the receiver is running n a hst with IP address , start the sender by running: java Sender My String The receiver prgram shuld nw display the string My String. Repeat this exercise, with the difference, that yu run the sender and receiver n tw different hsts. ECE 466 LAB 2A - PAGE 3 J. Liebeherr

4 Exercise 1.2 Reading and Writing data frm a file Dwnlad the Java prgram ReadFileWriteFile.java. The prgram reads an input file "data.txt" which has entries f the frm I P B The file is read line-by-line, the values in a line are parsed and assigned t variables. Then the values are displayed, and written t a file with name utput.txt. Run the prgram with the VBR vide trace frm Lab 1 as input. The vide trace is available at: Mdify the prgram s that it cmputes and displays the average size f the fllwing frame types: I frames; P frames; B frames. ECE 466 LAB 2A - PAGE 4 J. Liebeherr

5 Part 2. Traffic generatrs The gal in this part f the lab is t build a traffic generatr that emulates realistic traffic surces. The traffic generatr is driven by a traffic trace file, i.e., ne f the trace files frm Lab 1. The entries in the file permit t determine the size f transmitted packets and the elapsed time between packet transmissins. Fr each entry in the trace file, the traffic generatr creates a UDP datagram f the indicated size and transmits the datagram t the traffic sink. The traffic sink recrds time and size f each incming datagram, and writes the infrmatin int a file. The scenari is depicted in the figure belw. In this part f the lab, yu will build a traffic generatr fr the trace files with Pissn traffic. In Part 3, yu wrk with the Bellcre trace file. In Part 4, yu use the VBR vide traffic. Exercise 2.1 Traffic Generatr fr Pissn traffic Write a prgram that is a traffic generatr fr the cmpund Pissn traffic surce (see Lab 1, Exercise 1.4) and that transmits the traffic using Java datagrams t a traffic sink. The traffic sink has t be prgrammed as well. A trace fr the cmpund Pissn surce is available at URL The file has the frmat: SeqN Time (in µsec) Size (in Bytes) This results in a cmpund Pissn prcess with packet arrival rate λ = 1250 packets/sec, and the packet size has an expnential distributin with average size 1/µ =100 Bytes. ECE 466 LAB 2A - PAGE 5 J. Liebeherr

6 The traffic generatr reads each line frm the trace file, re-scales the values, and transmits a UDP datagram packet using the fllwing cnsideratins: The size f the transmitted datagram is equal t the (re-scaled) packet size value; The time f transmissin is determined frm the (re-scaled) time values. (The first packet shuld be transmitted withut delay). Exercise 2.2 Build the Traffic Sink Write a prgram that serves as traffic sink fr the traffic generatr frm the previus exercise. The requirements fr the traffic sink are as fllws: Read packets frm a specified UDP prt; Fr each incming packet, write a line t an utput file that recrds the size f the packet and the time since the arrival f the previus packet (Fr the first packet, the time is zer). Test the traffic sink with the traffic generatr frm Exercise 2.1. Exercise 2.3 Evaluatin Run experiments where yu transmit traffic frm the traffic generatr t the traffic sink. Evaluate the accuracy f the traffic generatr by cmparing the entries in the trace file (at the traffic generatr) t the results written t the utput file (at the sink). Use at least 10,000 data pints fr yur evaluatin. Prepare a plt that shws the difference f trace file and the utput file. Fr example, yu may create tw functins that shw the cumulative arrivals f the trace file and the utput file, respectively, and plt them as a functin f time. Try t imprve the accuracy f the traffic generatr. Evaluate and graph yur imprvements by cmparing them t the initial plt. Exercise 2.4 Accunt fr packet lsses. Packet lsses may ccur due t bit errrs, buffer verflws, cllisins f transmissins, r ther reasns. Packet lsses are less likely if bth the sender and the receiver are n the same machine. The UDP prtcl des nt recver packet lsses. Indicate in yur plts frm the evaluatin any packet lsses. Lab Reprt: Prvide discussins and graphs as requested in Exercise 2.3 and Exercise 2.4. ECE 466 LAB 2A - PAGE 6 J. Liebeherr

7 Part 3. Leaky Bucket Traffic Shaper In this part f the lab, yu familiarize yurself with a reference implementatin f a Leaky Bucket. The implementatin f the leaky bucket (in Java) and dcumentatin fr using the implementatin is available at: ucket In the next lab (Lab 2b) yu will mdify the surce cde f the implementatin. Right nw, the bjective is t run the cde f the reference implementatin, but withut a need t mdify the prvided surce cde. A leaky bucket traffic shaper with burst size LB max and rate r is shwn in the figure. Tkens are fed int the bucket at rate r. N mre tkens are added if the bucket cntains LB max tkens. Data can be transmitted nly if there are sufficient tkens in the bucket. T transmit a packet f L bytes, the bucket must cntain at least L tkens. If there are nt sufficient tkens, the packet must wait until there are enugh tkens in the bucket. The maximum size f the buffer is B max. Initially, the leaky bucket is full and the buffer is empty, i.e., LB(t) = LB max bytes and B(t) = 0 bytes. Nte that L shuld nt be smaller than the maximum packet size. The leaky bucket fr this Lab receives data frm a traffic generatr n a UDP prt and transmits the utput t a traffic sink, specified in terms f a an IP address and a UDP prt. This is illustrated belw. ECE 466 LAB 2A - PAGE 7 J. Liebeherr

8 An implementatin f the Leaky bucket fr packet sizes with a variable length is sketched in the fllwing figure. The traffic generatr (TG) generates packets that are transmitted t the Leaky Bucket, which sends the packets t the traffic sink (TS) after applying a shaping plicy. The leaky bucket is cmprised f fur cmpnents: Bucket Receiver (BR), Bucket Sender (BS), the Tken Bucket, and a Buffer. Upn arrival t the leaky bucket, packets are handled by BR which stres packets int the buffer r sends them ut immediately. The Buffer wrks as a FIFO queue with limited capacity and hlds packets until they can be send. The Tken Bucket generates tkens at a given rate (r) and hlds up t LB max tkens. BS takes packets ut f buffer and sends them when enugh tkens are available. The reference implementatin f the Leaky Bucket implements the abve functins, but which is missing details n the methd fr updating the value f LB and fr cmputing the time t* fr waking up the Bucket Sender. This implementatin is prvided by the package LeakyBucket, which cnsists f fur Java classes: Class LeakyBucket Creates the cmpnents f the leaky bucket and starts BR, BS, and TkenBucket in different threads. An instant f LeakyBucket is created with the fllwing parameters: ECE 466 LAB 2A - PAGE 8 J. Liebeherr

9 inprt UDP Prt number, where BR expects arriving packets. utaddress - IP address t which BS sends packets. utprt UDP prt number t which BS sends packets maxpacketsize - Maximum size f packet that can be prcessed. buffercapacity - Capacity f buffer in bytes (B max ). bucketsize Maximum number f tkens in leaky bucket (LB max ). bucketrate - Tken generating rate in tkens/sec (r). filename - Name f file, where arrival times are recrded. Buffer Thread safe implementatin f a FIFO buffer that is meant t be used in prducer/cnsumer scenari. This buffer stres packets that must nt exceed MAX_PACKET_SIZE and has inherent capacity f MAX_VALUE packets. The capacity f the buffer can be specified explicitly in bytes. The buffer has methds fr adding packets t the tail f the buffer and remving packets frm the head f the buffer, peeking at the first packet (withut remving it), and querying the currently ccupied buffer size (in terms f packets r bytes). LeakyBucketReceiver (BR) Waits n a specified UDP prt fr incming packets. When a packet arrives, it recrds its arrival time, size, buffer backlg (B), and the number f tkens in the bucket (LB) t a file. A received packet is prcessed in the fllwing way: if (buffer_is_empty && nt(sendinginprgress) && enugh_tkens_available) cnsume tkens; send packet; else add packet in buffer; Whether a transmissin is in prgress is checked by reading the SendingInPrgress variable f BucketSender. Nte that BucketReceiver and BucketSender never send at the same time, since BucketReceiver nly transmits when the buffer is empty. If a packet cannt be added t the buffer, e.g., because the buffer is full, the packet is drpped and an errr message displayed. LeakyBucketSender (BS) Remves packets frm buffer and transmits them t a specified address (IP address and UDP prt), when there are enugh tkens. The prcedure fr transmissin is as fllws: If (buffer_is_nt_empty) if (enugh_tkens) cnsume tkens; sendinginprgress = true; remve packet frm buffer; send packet; sendinginprgress = false; else get expected time when there will be enugh tkens; sleep fr this time; ECE 466 LAB 2A - PAGE 9 J. Liebeherr

10 else wait fr packet t arrive t buffer; // buffer wakes up BS when packet arrives TkenBucket This class updates the cntent f the tkens in the tken bucket. A tken bucket is created with tw parameters size and rate, where size is the maximum cntent f the tken bucket (LB max ), rate is the tken generatin rate in tkens per secnd (r). Other classes can request the TkenBucket abut the cntent f the tken bucket, and can request t remve tkens frm the bucket. The fllwing requests are available: getntkens: Returns number f tkens in bucket. remvetkens(x) : Request t remve X tkens frm the bucket. The methd returns false if there are less than X tkens in the bucket. getwaitingtime(x): Returns the waiting time (in nansecnds) until bucket has X tkens. Nte that there is n guarantee that there will be enugh tkens at the returned time (smene else may have remved tkens). Exercise 3.1 Running the reference implementatin f the Leaky Bucket Yur task is t execute the reference implementatin f the leaky bucket s that it receives packets frm yur implementatin f the traffic generatr frm Part 2, and send packets t yur versin f the traffic sink. The transmissins between traffic generatr, leaky bucket, and traffic sink use UDP datagrams. The size and timing f packet transmissins by the traffic generatr is dne as described in Part 2. Upn each packet arrival, the leaky bucket regulatr writes a line t an utput file that recrds the size f the packet and the time since the arrival f the last packet (Fr the first packet, the time is zer). Als recrded are the number f tkens (LB) in the leaky bucket and the backlg in the buffer (B) after the arrival f the packet. In yur implementatin, the traffic sink, the Leaky Bucket, and the traffic generatr must be started separately as independent prcesses. The fllwing cde segment shws hw yu start the LeakyBucket f the reference implementatin in a prcess. The implementatin assumes that the class LeakyBucket is in a subdirectry with name LeakyBucket : imprt LeakyBucket.LeakyBucket; public class Main { ECE 466 LAB 2A - PAGE 10 J. Liebeherr

11 } public static vid main(string[] args) { // listen n prt 4444, send t lcalhst:4445, // max. size f received packet is 1024 bytes, // buffer capacity is 100*1024 bytes, // leaky bucket has tkens, rate 5000 tkens/sec, and // recrds packet arrivals t bucket.txt). LeakyBucket lb = new LeakyBucket(4444, "lcalhst", 4445, 1024, 100*1024, 10000, 5000, "bucket.txt"); new Thread(lb).start(); } Exercise 3.2 Evaluate the reference implementatin fr the Pissn traffic file Cnsider the transmissin f Pissn traffic frm Exercise 2.3. Prepare a single plt that shws the cumulative arrival functin as a functin f time f: The data f the trace file (as read by the traffic generatr); The arrivals at the leaky bucket; The arrivals at the traffic sink. Prvide a secnd plt that shws the cntent f the tken bucket and the backlg in the Buffer as a functin f time. Exercise 3.3 Evaluate the reference implementatin fr the Ethernet and Vide Tracefiles Repeat the evaluatin fr the vide traffic trace and the Ethernet trace file that were used in Lab 1, and which are available at: Vide trace file: Ethernet traffic: There are a few things t nte: The frmat f the trace files fr the Vide and the Ethernet traffic is described in the descriptin f Lab 1. ECE 466 LAB 2A - PAGE 11 J. Liebeherr

12 Fr the vide trace file, the size f a vide frame may exceed the maximum size f a datagram, and yu need t send the frame in multiple datagrams. Lab Reprt: Prvide the surce cde fr yur surce cde fr Exercise 3.1. D nt include the surces fr the traffic generatr and traffic sink. Als, d nt include surce files f the reference implementatin. Fr Exercises 3.2 and 3.3, prvide the set f plts and include a descriptin f the plts. ECE 466 LAB 2A - PAGE 12 J. Liebeherr

13 Feedback Frm fr Lab 2a Cmplete this feedback frm at the cmpletin f the lab exercises and submit the frm when submitting yur lab reprt. The feedback is annymus. D nt put yur name n this frm and keep it separate frm yur lab reprt. Fr each exercise, please recrd the fllwing: Part 1. Prgramming with Datagram Sckets and with Files Part 2. Traffic generatrs Difficulty (-2,-1,0,1,2) -2 = t easy 0 = just fine 2 = t hard Interest Level (-2,-1,0,1,2) -2 = lw interest 0 = just fine 2 = high interest Time t cmplete (minutes) Part 3. Leaky Bucket Traffic Regulatr Please answer the fllwing questins: What did yu like abut this lab? What did yu dislike abut this lab? Make a suggestin t imprve the lab. ECE 466 LAB 2A - PAGE 13 J. Liebeherr