An upper bound model for TCP and UDP throughput in IPv4 and IPv6

Transcription

1 ARTICLE IN PRESS Joural of Network ad Computer Applicatios 31 (2008) A upper boud model for TCP ad UDP throughput i IPv4 ad IPv6 Eric Gamess, Ria Suro s Cetral Uiversity of Veezuela, Escuela de Computació, Caracas, Veezuela Received 10 July 2007; received i revised form 21 November 2007; accepted 26 November 2007 Abstract Due to the shortage of public IPv4 addresses, the IETF has developed a ew versio of the Iteret Protocol called IPv6. May istitutios all over the world had already started the migratio to IPv6. Sice this migratio has to be doe slowly, the first step is the coexistece of the two protocols (IPv4 ad IPv6) for some years. Oe importat issue for IPv6 to gai acceptace, is its performace i eduser applicatios. Hece, due to the availability of a variety of IPv6 implemetatios o differet operatig systems, it is importat to evaluate the performace of the differet IPv6 stacks, ad compare it to the oe show by IPv4. I this paper, we preset a upper boud model to compute TCP ad UDP throughput for IPv4 ad IPv6, i a full-duplex poit-to-poit coectio. Our model ca be used for ay variat of Etheret techology (10, 100, ad 1000 Mbps). To validate this model, we did experimets ad compared the maximum theoretical throughput with the experimetal oes. Experimets were doe with Widows XP SP2, Solaris 10, ad Debia 3.1, which are very popular operatig systems. The results show that 10 Mbps Etheret techology is already very mature, sice it gave performace very close to the maximum theoretical throughput. Experimets with FastEtheret (100 Mbps) show a TCP ad UDP throughput close to the maximum theoretical throughput, especially for large payload. I the case of GigaEtheret (1000 Mbps), experimetal results are ot far from the maximum throughput for large TCP ad UDP payload. However, for small TCP ad UDP payload, the differeces betwee our model (the maximum throughput) ad the experimets are importat. These differeces should sigificatly decrease with the release of faster techology (processors ad RAM). r 2008 Elsevier Ltd. All rights reserved. Keywords: IPv4; IPv6; Bechmarks; TCP throughput; UDP throughput; Performace evaluatio; Etheret Correspodig author. Tel.: addresses: egamess@kuaimare.cies.ucv.ve (E. Gamess), rsuros@ucv.ve (R. Surós) /$ - see frot matter r 2008 Elsevier Ltd. All rights reserved. doi: /j.jca

2 586 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Itroductio Due to its rapid ad uexpected growth, the Iteret is facig serious problems i the last few years. Lack of adequate IPv4 address space may be slowig dow the developmet of the Iteret ad ew applicatios. Several proposals have bee developed ad implemeted to solve these problems. A popular solutio to the IPv4 address shortage is Network Address Traslatio (NAT) (Srisuresh ad Egevag, 2001) which cosists of hidig etworks with private IPv4 addresses behid a NAT-eabled router with few public IPv4 addresses. As traffic passes from the private etworks to the Iteret, the source address i each packet is traslated o the fly from the private addresses to the public addresses by the NAT-eabled router. Similarly, the destiatio address i each packet for icomig traffic is traslated by the NAT-eabled router. However, NAT is a partial solutio sice it has drawbacks. Hosts behid a NAT-eabled router do ot have true edto-ed coectivity ad caot participate i some Iteret protocols. Services that require the iitiatio of coectios from the Iteret ca be disrupted. Aother solutio to the problem of the shortage of public IPv4 addresses that faces the Iteret cosists to migrate to the ew versio of the Iteret protocol (Davies, 2002; Deerig ad Hide, 1998; Popoviciu et al., 2006), called IPv6, or the coexistece betwee both protocols (Blachet, 2006). IPv6 fixes a umber of problems i IPv4, such as the limited umber of available IPv4 addresses. IPv6 has a 128-bit address, while IPv4 has a 32-bit address. IPv6 also adds may improvemets to IPv4 i areas such as routig ad etwork autocofiguratio. I recet years, IPv6 has received sigificat attetio from researchers, educatioal istitutios, software vedors, ad ed users. All moder operatig systems (Widows 2003/XP/Vista, Liux, Mac OS, AIX, Solaris, FreeBSD, etc.) support IPv6. For may applicatios, the overhead itroduced by the operatig system over the etwork performace is critical. However, oly a few works had bee preseted to evaluate the performace of IPv6 at the operatig system level. Ettika (2000) ad Ettika et al. (2000) aalyzed IPv6/IPv4 performace usig simple applicatios (pig ad FTP). They used computers with FreeBSD ad KAME 1 IPv6 protocol stack to simulate routers. They reported latecy usig the pig utility, ad throughput usig the FTP applicatio. Zeadally ad Raicu (2003) evaluated IPv6/IPv4 performace o Widows 2000 (Microsoft IPv6 Techology Preview for Widows 2000) ad Solaris 8. They coected two idetical workstatios usig a poit-to-poit coectio ad reported results such as throughput, roud-trip time, CPU utilizatio, socket-creatio time, ad cliet server iteractios, for both TCP ad UDP. They used packets ragig from 64 to 1408 bytes. Their experimetal results show that IPv6 for Solaris 8 outperform IPv6 for Widows 2000, while IPv4 outperform IPv6 for TCP ad UDP for both operatig systems. Zeadally et al. (2004) evaluated IPv6/IPv4 performace o Widows 2000, Solaris 8, ad RedHat 7.3. The authors experimetally measured throughput of TCP ad UDP, latecy, CPU utilizatio, ad web-based performace characteristics. Mohamed et al. (2006) evaluated IPv6/IPv4 performace o Widows 2003, FreeBSD 4.9 ad RedHat 9. They measured throughput, roud-trip time, socket-creatio time, TCP-coectio time, ad umber of coectios per secod i three differet test-beds. The first test-bed cosisted of a sigle computer ad commuicatio was limited to processes ruig i this computer usig the loopback iterface. I the secod test-bed, two computers were coected 1

3 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) through a Etheret hub. The Etheret hub was replaced by a router i the third test-bed. They used packets ragig from 1 byte up to the limits of a IP packet (which is typically aroud 65,535 bytes). Shiau et al. (2006) evaluated IPv6/IPv4 performace i two differet scearios. I the first sceario, they coected two idetical computers usig a poit-topoit coectio. I the secod sceario, the two idetical computers were each coected to a real large-scale etwork eviromet (Taiwa Advaced Research ad Educatio Network) through a Cisco 3750 GB switch, ad a Cisco 7609 router. Fedora Core II was the operatig system of the two computers. The authors reported results such as throughput, roud-trip time, packet loss rate, for both TCP ad UDP. Noe of these previous works compares the experimetal results for TCP ad UDP throughput to the maximum possible throughput. I this paper, we preset a upper boud model for TCP ad UDP throughput for IPv4 ad IPv6 over Etheret. We also setup a test-bed ad make ow our measuremet of TCP ad UDP throughput for IPv4 ad IPv6 o differet operatig systems (Widows XP SP2, Solaris 10, ad Debia 3.1). We compare the experimetal throughput results to the maximum theoretical throughput to validate our model. The rest of this paper is orgaized as follows. Sectio 2 discusses some cocepts of Etheret, IPv4 ad IPv6 that are fudametal to ifer our upper boud model for TCP ad UDP throughput. Sectio 3 presets the upper boud model for TCP ad UDP throughput. Sectio 4 describes our experimets to evaluate the TCP ad UDP throughput, ad compare the experimetal results with the theoretical maximum. Sectio 5 cocludes the paper. 2. IPv4 ad IPv6 over Etheret Our upper boud model for TCP ad UDP throughput is limited to Etheret for a fullduplex poit-to-poit coectio. Etheret is the most widely available LAN techology. Differet badwidth for Etheret had bee proposed ad developed. The 10 Mbps Etheret variat (10Base2, 10Base5, 10BaseT) was the domiat techology of LAN a few years ago. Due to the immese demad for high-speed etworkig, it has become almost obsolete ad is replaced by 100 Mbps Etheret (FastEtheret) ad 1000 Mbps (GigaEtheret). Fig. 1 shows a Etheret frame. The frame is composed of a header ad a trailer. The header has three fields (destiatio address, source address, ad type) ad is 14 bytes log. The trailer has oe field () with a legth of 4 bytes. The payload of Etheret has a miimum legth of 46 bytes ad a maximum legth of 1500 bytes, also called the MTU (maximum trasmissio uit). If a higher layer protocol (such as IP) provides a packet that is smaller tha 46 bytes, paddig must be doe by Etheret to complete the miimum Etheret data legth. The physical layer adds a header to the frame before sedig it through the trasmissio medium. This header cosists of two fields called preamble ad start frame delimiter (SFD). Destiatio Address Source Address Type Iformatio (Data) Etheret II payload 6 bytes 6 bytes 2 bytes 46 to 1500 bytes 4 bytes Fig. 1. Etheret frame.

4 588 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) The preamble is a 56-bit (7 bytes) patter of alteratig 1 ad 0 bits, which allows devices o the etwork to easily detect a ew icomig frame ad sychroize their clock with the clock of the sedig device. The SFD is a 8-bit value ( ) that separates the preamble of a Etheret frame from the begiig of the data-lik header. Also, betwee two cosecutive Etheret frames, a idle period kow as the iter frame gap (IFG) must be preset. The miimum IFG is a 96 bit times, that is the time it take to trasmit 96 bits (12 bytes) of raw data o the medium. I half-duplex Etheret, collisios ca occur ad statios must retrasmit the frame. The timig of retrasmissio is typically cotrolled usig a retrasmittig algorithm such as a biary expoetial backoff (BEB) algorithm. The BEB algorithm geerally specifies 2 as a commo small costat factor by which the time betwee makig retrasmissio attempts is icreased for each subsequet attempt. I fullduplex ad switched Etheret, there are o collisios, so there is o use of a BEB algorithm. Fig. 2 shows the IPv4 header as defied i Postel (1981a). Sice the header has a variable legth (depedig o optios), the field Iteret header legth (IHL) is used to specify its legth. IHL is a field of 4 bits ad must be multiplied by 4 to compute the actual legth of the IPv4 header i bytes. The miimum header legth is 20 bytes (IHL ¼ 5), ad represets a IPv4 packet without optios. Total Legth (16 bits) is the total legth of the packet (IPv4 header legth+ipv4 data legth). This field allows the legth of a IPv4 packet to be up to 65,535 bytes (icludig the header). That is, up to 65,515 bytes (65,515 ¼ 65,535 20) for IPv4 data i a packet without optios. Fig. 3 shows the header of IPv6 as defied i Deerig ad Hide (1998). The header legth is fixed to 40 bytes. So the field IHL defied i IPv4 was elimiated i IPv6. The field Total Legth defied i IPv4 is ow amed Payload Legth. Payload Legth represets the legth of the IPv6 optio headers ad IPv6 data (the legth of the rest of the packet that follow the IPv6 header). That is, Payload Legth does ot iclude the legth of the IPv6 header (40 bytes). So a IPv6 packet ca have up to 65,535 bytes of data whe it does ot have optios. I the trasport layer, TCP (Postel, 1981b) ad UDP (Postel, 1980) are the mai protocols. TCP guaratees reliable ad i-order delivery of data from seder to receiver. TCP is used by may applicatios such as file trasfer protocol (FTP), hyper text trasfer protocol (HTTP), secure shell (SSH), ad simple mail trasfer protocol (SMTP). Fig. 4 shows the TCP header. Without optios, it is 20 bytes log. Table 1 shows the maximum umber of bytes that ca be icluded i a TCP segmet as data (TCP payload). UDP does ot provide the reliability ad orderig that TCP does. Datagrams may arrive out of order, appear duplicated, or go missig without otice. Without the overhead of checkig whether every datagram actually arrived, UDP is faster ad more efficiet for may lightweight or time-sesitive purposes. UDP is used by may applicatios such as trivial file Versio IHL Type of Service Total Legth Idetificatio 0 D M Fragmet Offset F F Time To Live Protocol Header Checksum Source Address Destiatio Address Fig. 2. IPv4 header.

5 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Versio Traffic Class Flow Label Payload Legth Next Header Hop Limit Source Address (128 bits) Destiatio Address (128 bits) Fig. 3. IPv6 header Source Port Destiatio Port Sequece Number Ackowledgmet Number Data Offset Reserved U A P R C S G K H R S S Y T N F I N Widow Checksum Urget Poiter Fig. 4. TCP header. Table 1 Maximum data i TCP segmet (bytes) Network protocol Maximum IPv4/IPv6 data size TCP header legth Maximum data i TCP segmet IPv4 65, ,495 IPv6 65, ,515 trasfer protocol (TFTP), simple etwork maagemet protocol (SNMP), ad dyamic host cofiguratio protocol (DHCP). Fig. 5 shows the UDP header. It is always 8 bytes log. Table 2 shows the maximum umber of bytes that ca be icluded i a UDP datagram as data (UDP payload). 3. Upper boud model for TCP ad UDP throughput To compute the roud trip time (RTT), we must cosider: (1) the processig time, (2) the trasmissio time, ad (3) the propagatio time. The processig time is the overhead itroduced by the seder ad the receiver to hadle the frame for trasmissio ad receptio. The trasmissio time is the amout of time the seder takes to emit all bits ito medium. It ca be calculated by dividig the umber of bits by the badwidth. The propagatio time is the amout of time it takes a bit to traverse the lik. It ca be

6 590 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Source Port UDP Legth (UDP Header + UDP Payload) Destiatio Port Checksum (UDP Header + UDP Pseudo Header + UDP Payload) Fig. 5. UDP header. Table 2 Maximum data i UDP datagram (bytes) Network protocol Maximum IPv4/IPv6 data size UDP header legth Maximum data i UDP datagram IPv4 65, ,507 IPv6 65, ,527 calculated by dividig the legth of the medium by its propagatio speed (propagatio speed depeds o the physical medium). Let call ratio() the ratio of the umber of TCP (or UDP) payload bytes to trasmit over the miimum umber of bytes ecessary for the trasmissio. I the followig subsectios, we give the formula of ratio() for TCP with IPv4, TCP with IPv6, UDP with IPv4, ad UDP with IPv6. represets the umber of TCP (or UDP) payload bytes to trasmit Ratio of TCP with IPv4 For reasos of space, we will oly preset the steps to compute this ratio for a sigle TCP segmet. I the best case, the IPv4 header ad the TCP header will both be 20 bytes log (whe there are o optios). Sice the Etheret MTU is 1500 bytes, the maximum TCP data i oe segmet is 1460 bytes (1460 ¼ ). Also, for small values of (1pp5), paddig will be ecessary to fulfill the miimum Etheret data size (46 bytes). So we ca divide the trasmissio of oe TCP segmet i two cases: First case: IfA{1,2,3,4,5,6}, Etheret paddig will be ecessary. So to sed bytes of TCP data (TCP payload), the miimum umber of ecessary bytes is IFG 12 bytes Preamble 7 bytes SFD 1 byte Etheret 18 bytes IPv4 20 bytes TCP 20 bytes Data bytes Paddig 6 bytes Total 84 bytes The for this case, ratioðþ ¼ 84 :

7 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Secod case: IfA{6, y, 1460}, o Etheret paddig is ecessary. So to sed bytes of TCP data (TCP Payload), the miimum umber of ecessary bytes is IFG 12 bytes Preamble 7 bytes SFD 1 byte Etheret 18 bytes IPv4 20 bytes TCP 20 bytes Data bytes Total +78 bytes The for this case, ratioðþ ¼ þ78. We ca show that the ratio of TCP with IPv4 ca be geeralized to ay value of. We do ot have to deal with fragmetatio, sice TCP will segmet the data (TCP payload) accordigly to the MTU of Etheret. The geeral formula is If app6+1460a the ratioðþ ¼ 84 þ 1538E½ð 1Þ=1460Š. If app a the ratioðþ ¼ þ 78 þ 78E½ð 1Þ=1460Š, where E(x) is the fuctio that returs the iteger portio of the argumet specified (x) Ratio of TCP with IPv6 I this case, we do ot have to deal with Etheret paddig sice IPv6 header is 40 bytes log ad TCP header is 20 bytes log. So the miimum legth of a TCP segmet i IPv6 is 60 bytes, which is greater tha the miimum 46 bytes of data for Etheret. We do ot have to worry about fragmetatio, sice TCP will segmet the data (TCP payload) accordigly to the MTU of Etheret. We ca show that the geeral formula is ratioðþ ¼ þ 98 þ 98E½ð 1Þ=1440Š Maximum theoretical throughput of TCP with IPv4 ad IPv6 The maximum theoretical throughput of TCP will be obtaied betwee two hypothetical devices, coected by a full-duplex poit-to-poit lik, that have a processig time of 0 s. That is, devices where the overhead itroduced by the seder ad the receiver to hadle the frame for trasmissio ad receptio is 0 s. Eve if such devices do ot exist, the maximum theoretical throughput of TCP is very useful sice it ca be compared to the real throughput of TCP for IPv4 ad IPv6. Usig a full-duplex poit-to-poit lik suppress collisios ad radom access for retrasmissio due to the BEB algorithm.

8 592 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) TCP Throughput (Mbps) IPv4 IPv TCP Payload (bytes) Fig. 6. Maximum theoretical throughput of TCP for IPv4 ad IPv6 (Mbps). For a FastEtheret etwork (100 Mbps), the maximum theoretical throughput of TCP i a poit-to-poit coectio ca be calculated by multiplyig the correspodig ratio (see Sectio 3.1 for IPv4 ad Sectio 3.2 for IPv6) by the badwidth. Fig. 6 shows the maximum theoretical throughput of TCP for IPv4 ad IPv6 with a TCP data (TCP payload) betwee 1 ad 5000 bytes. We ca observe that the maximum theoretical throughput of TCP for IPv4 (upper curve) is superior to the oe show by IPv6 (lower curve). This small differece (lower tha 5% for a payload greater tha 300 bytes) is due to the header of IP (20 bytes i IPv4 ad 40 bytes i IPv6). From Fig. 6, we ca ifer that the maximum theoretical throughput of TCP for IPv4 icreases with the size of the TCP data from 1 to 1460 bytes. For 1461 bytes, this maximum theoretical throughput fall dow ad starts to icrease agai util a TCP data of 2920 bytes log. This patter will appear every 1460 bytes. Let us give a explaatio of this behavior. To sed TCP data with a legth less tha or equal to 1460 bytes, a sigle TCP segmet is ecessary. The first fall dow is due to the use of a secod TCP segmet to sed the required TCP data (1461pp2920). The secod fall dow is due to the use of a third TCP segmet to sed the required TCP data (2921pp4380), ad so o. The maximum of the fuctio is ratioð1460þ100 ¼ ratioð2920þ100 ¼¼ :92 Mbps: 769 So, Mbps is the maximum throughput of TCP with IPv4 for ay legth of TCP data usig FastEtheret. The maximum theoretical throughput of TCP for IPv6 shows a similar behavior tha the oe show by IPv4. The fall dow is every 1440 bytes. The maximum of the fuctio is ratioð1440þ100 ¼ ratioð2880þ100 ¼¼ :63 Mbps: 769 So, Mbps is the maximum throughput of TCP with IPv6 for ay legth of TCP data usig FastEtheret Ratio of UDP with IPv4 UDP with IPv4 is a little more complex tha TCP sice UDP does ot segmet as TCP do. So, fragmetatio will be held i the etwork layer by IPv4. The UDP header has a

9 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) fixed legth of 8 bytes. So, the first frame ca carry up to 1472 bytes of UDP data that is, 1500 (MTU of Etheret) mius 20 bytes of IPv4 header, mius 8 bytes of UDP header. The subsequet frames ca carry up to 1480 bytes sice they do ot iclude the UDP header. Also, paddig will be doe i the last fragmet whe ecessary to fulfill the miimum requiremet of 46 bytes for Etheret data. So the geeral formula for UDP with IPv4 is If 1pp18 the ratioðþ ¼ 84. If 18pp1472 the ratioðþ ¼ þ 66. If app a the ratioðþ ¼ 1622 þ 1538E½ð 1473Þ=1480Š. If app a the ratioðþ ¼ þ 124 þ 58E½ð 1473Þ=1480Š. Accordig to Table 2, users that call fuctio sedto (Steves et al., 2003) ca sed up to 65,507 bytes of UDP data with oe call of the fuctio. Sice UDP does ot segmet the UDP data, IPv4 will fragmet the data if ecessary. Fig. 7 shows how a UDP data of 3020 bytes will be set over Etheret if user makes a uique call to fuctio sedto. Aswe ca see, IPv4 will fragmet the UDP data i three fragmets of 1472, 1480, ad 68 bytes. The iformatio ecessary to hadle fragmetatio is icluded i the IPv4 header through the use of four fields (Idetificatio, DF, MF, ad Fragmet Offset) as depicted i Fig. 2. That is, o extra optios are eeded i IPv4 to hadle fragmetatio. Aother possibility to sed 3020 bytes of UDP data is through three calls of fuctio sedto to elimiate fragmetatio. Users sed 1472, 1472, ad 76 bytes i each call of the fuctio. Fig. 8 shows how the 3020 bytes of UDP data will be set over Etheret i this case. Users ca sed UDP data of ay legth (p to 65,507 bytes) by makig a uique call to fuctio sedto with the complete data, or by dividig the origial data ito smaller portios to be set by differet calls to the fuctio. However, the UDP throughput will be better with a uique call tha with several calls, sice the UDP header is set oly oe time with a uique call, while it is set may times with several calls. So the formula of the ratio 7 bytes 1 14 bytes 20 bytes 8 bytes 1472 bytes 4 bytes Preamble SFD Etheret Header IPv4 Header UDP Header 7 bytes 1 14 bytes 20 bytes 1480 bytes 4 bytes Preamble SFD Etheret Header IPv4 Header 7 bytes 1 14 bytes 20 bytes 68 bytes 4 bytes Preamble SFD Etheret Header IPv4 Header Fig. 7. Sedig 3020 bytes of UDP data i oe call (IPv4).

10 594 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) bytes 1 14 bytes 20 bytes 8 bytes 1472 bytes 4 bytes Preamble SFD Etheret Header IPv4 Header UDP Header 7 bytes 1 14 bytes 20 bytes 8 bytes 1472 bytes 4 bytes Preamble SFD Etheret Header IPv4 Header UDP Header 7 bytes 1 14 bytes 20 bytes 8 bytes 76 bytes 4 bytes Preamble SFD Etheret Header IPv4 Header UDP Header Fig. 8. Sedig 3020 bytes of UDP data i three calls (IPv4). of UDP with IPv4 preseted i this sectio is boud to a uique call of the fuctio sice we are preseted a upper boud model for the UDP throughput i this paper Ratio of UDP with IPv6 If the UDP data is big eough, fragmetatio will be held i the etwork layer by IPv6. Accordig to Deerig ad Hide (1998), fragmetatio must be doe by the seder. That is, itermediate devices such as routers are ot allowed to fragmet a packet i IPv6. The iformatio ecessary to hadle fragmetatio is icluded as a optio i a extesio header. This extesio header is 8 bytes log. Accordig to Table 2, users that call fuctio sedto ca sed up to 65,527 bytes with oe call of the fuctio. Fig. 9 shows how a UDP data of 3020 bytes will be set over Etheret if the user makes a uique call to fuctio sedto. As we ca see, IPv6 will fragmet the UDP data i three fragmets of 1440, 1448, ad 132 bytes. I this case, the geeral formula for UDP with IPv6 is If 1pp1452 the ratioðþ ¼ þ 86. If 1453pp2892 the ratioðþ ¼ If X2893 the ratioðþ ¼ þ 180. þ 266 þ 86E½ð 2893Þ=1448Š. Aother possibility to sed 3020 bytes of UDP data is through three calls of fuctio sedto to elimiate fragmetatio. Users sed 1452, 1452, ad 116 bytes i each call of the fuctio. Fig. 10 shows how the 3020 bytes of UDP data will be set over Etheret i three calls. Tryig to avoid fragmetatio will lead to a better UDP throughput that makig a uique call to fuctio sedto (eve though the users must divide the UDP data i small chuk ad make the correspodet call). For this reaso, we also give the geeral formula for UDP with IPv6 i this case. Depedig of their programmig styles, users must

11 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) bytes 1 14 bytes 40 bytes 8 bytes 8 bytes 1440 bytes 4 bytes Preamble SFD Etheret Header IPv6 Header Fragmet Header UDP Header 7 bytes 1 14 bytes 40 bytes 8 bytes 1448 bytes 4 bytes Preamble SFD Etheret Header IPv6 Header Fragmet Header 7 bytes 1 14 bytes 40 bytes 8 bytes 132 bytes 4 bytes Preamble SFD Etheret Header IPv6 Header Fragmet Header Fig. 9. Sedig 3020 bytes of UDP data i oe call (IPv6). 7 bytes 1 14 bytes 40 bytes 8 bytes 1452 bytes 4 bytes Preamble SFD Etheret Header IPv6 Header UDP Header 7 bytes 1 14 bytes 40 bytes 8 bytes 1452 bytes 4 bytes Preamble SFD Etheret Header IPv6 Header UDP Header 7 bytes 1 14 bytes 40 bytes 8 bytes 116 bytes 4 bytes Preamble SFD Etheret Header IPv6 Header UDP Header Fig. 10. Sedig 3020 bytes of UDP data i three calls (IPv6). compute the maximum theoretical UDP throughput for IPv6 with the appropriate ratio: ratioðþ ¼ þ 86 þ 86E½ð 1Þ=1452Š Maximum theoretical throughput of UDP with IPv4 ad IPv6 The maximum theoretical throughput of UDP will be obtaied betwee two hypothetical devices, coected by a full-duplex poit-to-poit lik, that have a processig time of 0 s. That is, devices where the overhead itroduced by the seder ad the receiver to hadle the frame for trasmissio ad receptio is 0 s. Eve if such devices do ot exist, the maximum theoretical throughput of UDP is very useful sice it ca be compared to the real throughput of UDP for IPv4 ad IPv6. Usig a full-duplex poit-to-poit lik suppress collisios ad radom access for retrasmissio due to the BEB algorithm. For a FastEtheret etwork (100 Mbps), the maximum theoretical throughput of UDP i a poit-to-poit coectio ca be calculated by multiplyig the correspodig ratio (see Sectio 3.4 for IPv4 ad Sectio 3.5 for IPv6) by the badwidth. Fig. 11 shows the maximum theoretical throughput of UDP for IPv4 ad IPv6 with a UDP data (UDP payload) betwee 1 ad 5000 bytes. We ca observe that the maximum theoretical throughput of UDP for IPv4 (upper curve) is superior to the oe show by IPv6 (lower curve). This small differece (lower tha 5% for a payload greater tha 300 bytes) is due to the header of IP (20 bytes i IPv4 ad 40 bytes i IPv6).

12 596 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) UDP Throughput (Mbps) IPv4 IPv UDP Payload (bytes) Fig. 11. Maximum theoretical throughput of UDP with fragmetatio for IPv4 ad IPv6 (Mbps). The maximum theoretical throughput of UDP for IPv4 icreases with the size of the UDP data from 1 to 1472 bytes. For 1473 bytes, this maximum theoretical throughput fall dow ad starts to icrease agai util a UDP data of 2952 bytes log. For 2953 bytes, this maximum theoretical throughput fall dow ad starts to icrease agai util a UDP data of 4432 bytes log. This patter will appear every 1480 bytes. Let us give a explaatio of this behavior. To sed UDP data with a legth less tha or equal to 1472 bytes, a sigle UDP datagram is ecessary. The first fall dow is due to the use of a secod UDP datagram to sed the required UDP data (1473pp2952). The secod fall dow is due to the use of a third UDP datagram to sed the required UDP data (2953pp4432). The maximum theoretical throughput of UDP for IPv6 shows a similar behavior tha the oe show by IPv4. The fall dow is every 1448 bytes. 4. Experimets As recommeded i Brader (1991) ad Brader ad McQuaid (1999), we setup a testbed cosisted of two idetical PCs coected by a poit-to-poit lik (see Fig. 12). Both PCs were equipped with a dual AMD Optero 246 (2 GHz), 2 GB of RAM, a 72 GB hard drive, ad a full-duplex 10/100/1000 Mbps PCI Etheret adapter. I each PC, we made three partitios o the hard disk ad istalled Widows XP SP2, Solaris 10, ad Debia 3.1. We did our ow bechmarks usig the C programmig laguage to measure the throughput ad the roud-trip time for TCP ad UDP. The bechmarks are based o the cliet/server model. Basically, a message (TCP segmet or UDP datagram) of a fixed legth is exchaged betwee the server ad the cliet a umber of times. We took a timestamp before ad after the iterchage. The differece of the timestamps is divided by the umber of time the message was set ad received to get the average roud-trip time. The experimet was repeated to get cosistet measuremets. I Widows, we compiled the source code with a free C compiler called Dev-C beta This compiler is based o the GNU gcc compiler. For Solaris, we used gcc compiler versio For Debia, we compiled usig gcc compiler versio that came i the distributio

13 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Poit-to-Poit IPv6/IPv4 IPv6/IPv4 Fig. 12. Test-bed. Table 3 TCP throughput for IPv6 (10 Mbps) Widows Solaris Debia Maximum , , , , ,000, Table 3 shows the TCP throughput of IPv6 for the three operatig systems (experimetal TCP throughput) whe the PCI Etheret cards are i 10 Mbps mode i the two computers. (first colum) represets the size of the TCP payload (TCP data) i bytes. I the last colum, we put the maximum theoretical throughput that was computed usig the ratio defied i Sectio 3.2. For most values of the data sizes, Widows shows the best TCP throughput. Also, it is oticeable that the throughput show by the three operatig systems is very close to the maximum theoretical throughput. Table 4 shows the TCP throughput of IPv6 for the three operatig systems whe the PCI Etheret cards are i 100 Mbps mode i the two computers. Widows ad Debia have a similar throughput. For small TCP data, Solaris has the lowest TCP throughput. However, Solaris exceeds the other two operatig systems for large TCP data. Table 5 shows the TCP throughput of IPv6 for the three operatig systems (experimetal TCP throughput) whe the PCI Etheret cards are i 1000 Mbps mode i the two computers. Debia outperforms the other two operatig systems. For small TCP data, Solaris has the lowest TCP throughput. However, Solaris has a performace similar to Debia for large TCP data. To compare the experimetal throughput with the maximum theoretical throughput, Table 6 gives the percet of the actual throughput agaist the maximum throughput for Widows with the three Etheret speeds. We choose Widows sice it is the most widely used operatig systems i the world. The results show that 10 Mbps Etheret techology is already very mature, sice it gave performace very close to the maximum theoretical throughput. FastEtheret (100 Mbps) is ot far from the maximum throughput, especially for TCP data greater tha 1000 bytes. GigaEtheret (1000 Mbps) is far from the maximum theoretical throughput for small TCP data. However, GigaEtheret shows good results for large TCP data.

14 598 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Table 4 TCP throughput for IPv6 (100 Mbps) Widows Solaris Debia Maximum , , , , ,000, Table 5 TCP throughput for IPv6 (1000 Mbps) Widows Solaris Debia Maximum , , , , ,000, Table 6 TCP Throughput for IPv6 (Widows) 10 Mbps (%) 100 Mbps (%) 1000 Mbps (%) , , , , , , ,000,

15 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Fig. 13 represets the TCP throughput of IPv4 whe the PCI Etheret cards are i 100 Mbps mode i the two computers for the three operatig systems. Also, the maximum theoretical throughput (which was computed usig the ratio defied i Sectio 3.1) is added to the graphics as a referece. For most values of the data sizes (TCP payload), Debia shows the best throughput. For values of the TCP payload greater tha 2000 bytes, the results show by the experimets are close to the maximum. Fig. 14 represets the UDP throughput of IPv4 whe the PCI Etheret cards are i 100 Mbps mode i the two computers for the three operatig systems. Also, the maximum theoretical throughput (which was computed usig the ratio defied i Sectio 3.4) is added to the graphics as a referece. For most values of the data sizes (UDP payload), TCP Throughput (Mbps) UDP Throughput (Mbps) Widows Solaris Debia Maximum TCP Payload (bytes) Fig. 13. TCP throughput for IPv4 (100 Mbps). Widows Solaris Debia Maximum UDP Payload (bytes) Fig. 14. UDP throughput for IPv4 (100 Mbps)

16 600 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Debia shows the best throughput. For small values of the data size, Solaris has the smallest throughput, but it equals or exceeds the other two operatig systems for large values. For values of the UDP payload greater tha 2000 bytes, the results show by the experimets are close to the maximum. Fig. 15 represets the UDP throughput of IPv6 whe the PCI Etheret cards are i 100 Mbps mode i the two computers for the three operatig systems. Also, the maximum theoretical throughput (which was computed usig the ratio defied i Sectio 3.5) is added to the graphics as a referece. For most values of the data sizes (UDP payload), Debia shows the best throughput. For small values of the data size, Solaris has the smallest throughput, but it equals or exceeds the other two operatig systems for large values. For values of the UDP payload greater tha 2000 bytes, the results show by the experimets are close to the maximum. Table 7 represets the TCP ad UDP throughput with IPv4 ad IPv6 for Widows usig FastEtheret. We choose Widows sice it is the most widely used operatig systems i the world. These results show that IPv4 throughput is over IPv6 throughput for both, UDP Throughput (Mbps) Widows Solaris Debia Maximum Table 7 TCP ad UDP throughput i Widows (100 Mbps) UDP Payload (bytes) Fig. 15. UDP throughput for IPv6 (100 Mbps) TCP (IPv4) TCP (IPv6) UDP (IPv4) UDP (IPv6) , , , , ,000,

17 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) TCP ad UDP. However, the differece is small ad is due to the IP header (20 bytes i IPv4 ad 40 bytes i IPv6). Similar results were obtaied for the other two operatig systems (Solaris 10 ad Debia 3.1). 5. Coclusio ad future work I this paper, we have developed a upper boud model for TCP ad UDP throughput i IPv4 ad IPv6 over Etheret betwee two devices coected by a full-duplex poit-topoit lik. We also wrote some bechmarks usig the C programmig laguage to compute experimetally the TCP ad UDP throughput of IPv4 ad IPv6. The experimets that we did over importat operatig systems (Widows XP SP2, Solaris 10, ad Debia 3.1) show that 10 Mbps Etheret is a very mature techology, sice the experimetal results are very close to the results of our model. FastEtheret (100 Mbps) experimetal results gave performace close to the maximum theoretical throughput, especially for TCP ad UDP data greater tha 2000 bytes. GigaEtheret (1000 Mbps) is close to the maximum throughput for large TCP ad UDP payload. However, for small TCP ad UDP payload, the differeces betwee our model (the maximum throughput) ad the experimets are importat. We suppose that these differeces should sigificatly decrease with the release of faster techology (processors ad RAM). I geeral, our experimets show that the IPv4 throughput is a little smaller that its equivalet i IPv6. This is due to the differece i the IP headers (20 bytes for IPv4 ad 40 bytes for IPv6), eve if IPv4 has to compute the checksum, which was elimiated i IPv6. The throughput show by Debia ad Widows XP are most of the time very similar. Solaris has a smaller throughput for small TCP ad UDP data, but most of the times it outperforms Widows XP ad Debia for large TCP ad UDP data. For future work, we pla to improve our model for 1000 Mbps Etheret, by takig ito accout the processig time. We also pla to exted our upper boud model to coectios that are ot poit-to-poit, that is coectios that iclude oe or more itermediate switches or routers. We also wat to further ivestigate the performace of trasitio mechaisms (Nordmark ad Gilliga, 2005) such as 6to4 (Carpeter ad Moore, 2001) ad Teredo (Huitema, 2006), which costitute a ecessary step toward IPv6 s full deploymet. Refereces Blachet M. Migratig to IPv6: a practical guide to implemetig IPv6 i mobile ad fixed etworks, 1st ed. Wiley; Brader S. Bechmarkig termiology for etwork itercoectio devices. RFC 1242, July Brader S, McQuaid J. Bechmarkig methodology for etwork itercoect devices. RFC 2544, March Carpeter B, Moore K. Coectio of IPv6 domais via IPv4 Clouds. RFC 3056, February Davies J. Uderstadig IPv6, 1st ed. Microsoft Press; Deerig S, Hide R. Iteret protocol, versio 6 (IPv6) specificatio. RFC 2460, December Ettika K. IPv6 dual stack trasitio techique performace aalysis: KAME o FreeBSD as the case. Techical report. Faculty of Iformatio Techology, Multimedia Uiversity, Jala Multimedia; October Ettika K, Gopi K, Takefumi Y. Applicatio performace aalysis i trasitio mechaism from IPv4 to IPv6. IWS2000, Japa; February Huitema C. Teredo: Tuelig IPv6 over UDP through Network Address Traslatios (NATs), RFC 4380, February 2006.

18 602 ARTICLE IN PRESS E. Gamess, R. Surós / Joural of Network ad Computer Applicatios 31 (2008) Mohamed S, Buhari M, Saleem H. Performace compariso of packet trasmissio over IPv6 etwork o differet platforms. IEE Proc Commu 2006;153(3): Nordmark E, Gilliga R. Basic trasitio mechaisms for IPv6 hosts ad routers. RFC 4213, October Popoviciu C, Levy-Abegoli E, Grossetete P. Deployig IPv6 etworks, 1st ed. Cisco Press; Postel J. User datagram protocol. RFC 768, August Postel J. Iteret protocol. RFC 791, September 1981a. Postel J. Trasmissio cotrol protocol. STD 7, RFC 793, September 1981b. Shiau W, Li Y, Chao H, Hsu P. Evaluatig IPv6 o a large-scale etwork. Comput Commu 2006;29(16): Srisuresh P, Egevag K. Traditioal IP etwork address traslator (traditioal NAT). RFC 3022, Jauary Steves R, Feer B, Rudoff A. Uix etwork programmig: the sockets etworkig API. Addiso-Wesley Professioal, 3rd ed., October Zeadally S, Raicu I. Evaluatig IPv6 o widows ad solaris. IEEE Iteret Comput 2003;7(3):51 7. Zeadally S, Wasseem R, Raicu I. Compariso of ed-system IPv6 protocol stacks. IEEE Proc Commu 2004; 151(3):