SOFTWARE TOOLS for NETWORMlNG/Edited by Olivier Bonaventure

Since November 2001, this column has published short descriptions of freely avaii- able software tools that could he useful for the readers of the magazine, Starting with this issue, we slightly change the format of the column by briefly describing a few tools that can he used to solve a common problem. In this issue, we describe several tools that allow to capture, replay and build packets in a live network. Commebts and suggestions about tools that could be described in this column should he sent by emaii to Olivier Bonaventure (bonaventure@ieee.org).

Olivier Bonaventure Dept. of Computing Sciencebnd Engineering

Universitd Catholiaue de Lonvain (UCL), Belnium . ,

Packet Capture Tools Network researchers and practition-

ers often need to capture and transmit packets on various types of networks. tcpdump [l] was probably one of the first packet capture tools and is still widely used today.

tcpdump is open source and runs on many UNIX variants. Some versions of tcpdump have also been ported to Win- dows [Z]. I t relies on the libpcap library ([3] for UNIX variants, [4] for Windows) to capture raw packets from various types of nctwork interfaces. lihpcap is an open source library that allows the appli- cation using it to select the packets to be captured based on various fields of the data link, network, or transport headers. The packets captured by lihpcap can he analyzed by tcpdump, which contains subroutines to print, in human-readable form, the control information of many protocols of the da t a link, network, transport, and application layers. tcp- dump prints the content of the captured packets in textual format. cthereal [SI is another packet analysis tool that also relies on the lihpcap library. ethereal runs on both UNIX and Windows plat- forms~and provides both text-based and graphical user interface (GU1)-based interfaces. ethereal contains'protocol decoders for many protocols, and new decoders are regularly added. The text- based interface can be used as tcpdump and can also operate in a verbose mode where all the fields of the captured pack- ets are displayed in text or XML format. T h e CUI allows the user to browse through the captured packets. It is possi- ble to define filters to select special pack- ets from the trace.

Packet Replay Tools Packets may he captured for analysis

purposes, but also for performance eval- uation. In this case, it is often important to he able to replay entire packet traces. Various tools exist for this. tcpreplay [6] is open source and works on UNIX vari- ants. I t is able to replay packet traces captured by libpcap. The trace can be replayed at'its captured speed or anoth- e r speed. TCPIvo is another open source

packet replay tool [7]. TCPIvo was designed to achieve high throughput and accuracy. It works on Linux 2.4 or higher on x86-based systems and requires the application of a few kernel patches.

Packet Creation Tools A thi rd common type of packet

manipulation is to generate packets with arbitrary values for several proto- col fields such as IP addresses, but also various flags and sequence numbers of checksum values. Niper [7] is an open source Linux application writ ten in Java. By using the Linux raw sockets, it allows the user to send arbitrary IPv4I IPv6 and TCPIUDP packets. The con- tent of the packets can he defined by using the supplied GUI or via an XML

file. hping [9] is an open source com- mand line application running on many UNIX variants. hping allows the user to gene ra t e arbi t rary IPv4ITCPIUDPI ICMP packets by specifying the con- tents of most fields,in those protocol hzaders. hping also uses lihpcap to cap- tlire t he repl ies s en t by the r emote hosts. lihnet [IO] is an open source pro- gramming library writ ten in C that works on Windows and several UNIX variants. lihnet allows the application to he linked with the library to easily con- struct and send raw packets. lihnet sup- ports various link layers as well as functions t o ease the creation of IPv4I IPv6ITCPI.UDPIDNSIDHCP and RIP, OSPF, or BGP packets.

References [ I ] tcpdump (UNIX): hnp://w.kpdump.org 121 tcpdu'mp (Window): hnp://windump.polito.it 131 libpcap IUNIXI: http://w.tcpdump.org [4] libpcop IWindowJ: hnp://winpcap.plib.it [5] elhereal: h t tp : / /w .e the rwl . com 161 tcpreplay: hnp://tcpreplay.raurceforgenef/ 171 TCPlvo: hnp://w.cse.ogi.edu/ryrl/proieclr/

181 nippr: hnp://?pnrource.elve.v.fi 191 hping: hnp://w.hping.org [IO] libnet: http://WWw.pOcketfoctory.net/

tcpivd

projeds/iibnet/

Wireless networks can impair voice quality by various means, including poor mobile phone quality, voice cumpression and daoompression alg&ms. May. loss or gain in speech levels, noise, aooustic and land- line echo. along with other distortions. GL's Automatad Volce Quality Testing solution provides an effident and portablemeans to quantify these impairments in a unified, 'end-toend" manner featuring:

- Synchronized software for sendinglrecurding voice files * Flexible archiiedurelfeatures for reoording locatins,

parameters, and time stamping MOS for all voice quality standards PAMS, PSQM. PSQM+. PESQ. PESO-LQ Addiional measurements include Mean A d N e Spaech Level, Noise Level, Latency and Clipping

* Results available in real-time or post-processing

Please call or visit wr web site to learn more a b u t GL's other products encompassing Tl/ElfWCC-3/STM-l Testing, CO Switch Simulation. Echo Canceller Testing, and VoiP Simulation and Analysis.

GL Communications Inc. Phone: 301-6704784. Fax: 301-670-9187

E-Mail info@gl.mm . Web: www.gl.mdawqt

IEEE Nerwork * Mayllune 2004 7