Network Simulation Software

Network Simulation SoftwarePacketStorm Communications, Inc. was founded in November 1998 by a group of engineersfrom the prestigious Bell Laboratories.PacketStorm develops, manufactures, and supports high end testing solutions for theInternet Protocol (IP) communications market. PacketStorm is the market leader foradvanced IP Network Emulators with dynamic and traffic conditioning emulation.PacketStorm sells test solutions through a global network of independent representativesand international distributors.ApplicationsEnterprise ApplicationsNew enterprise applications are viewed asstrategic and competitive advantages forbusinesses competing in today’s ultra-competitive markets. Teams of personnel andmillions of dollars are spent on internal facingand client facing applications such as CRM,ERP, etc. Financial institutions and otherindustries are investigating and deploying newtechnologies such as grid computing for thepurpose of giving their business stronger andfaster processing power as well as loweringcosts through shared computer processing.Whether applications are internally developed or customized from existing commercialpackages, the need to thoroughly test for proper operation of features and user volume

usage has been embraced by the Enterprise IT community. Application rollout projectsproceed through the following steps: initial development, unit test, integration test, systemtest, pilot program, and full production. The stakes and costs to fix defects get increasinglyhigher, as the project progresses towards full production.Ultimately, the application is to be deployed to the production environment where a crucialpiece is often overlooked: the impact of the network infrastructure characteristics on theapplication. Typical IT test environments are captive labs, usually relatively close ingeography. Real networks, especially with the current trend of more work being sent off-shore and distributed networking, are global in their reach. Networking departments arewell accustomed to monitoring and trouble shooting network conditions, yet applicationsthat pass all lab tests are still at risk when deployed into the production network.Applications are at risk even when the network is healthy and passing traffic, simplybecause the network characteristics are different from the lab connectivity characteristics.PacketStorm Communications’ network emulators reduce this deployment risk.VoIP Voice over Internet Protocol (VoIP) has made great strides in recent years, and VoIP networks, public and private, are becoming more and more common. However, IP, by its very nature, is an unreliable networking protocol. In its most basic form, IP makes no delivery, reliability, flow control, or error recovery guarantees. As a result, IP mayhave changing delays, packet loss, or deliver packets out of order. When attempting tounderstand and predict the VoIP user experience in pre-deployment planning requires thatreal world and worst-case network conditions be considered. The PacketStorm family ofnetwork emulators addresses these concerns in three ways: product evaluation, pre-deployment testing, and troubleshooting.The above figure illustrates a typical carrier class VoIP system. A traditional phone systemand PBX resides on the customer premise, connected to the PSTN with standard analog orT-1 tie lines. However, once the call is delivered to the PSTN, rather than using traditionalcircuit switching to connect the call to the distant end, the media gateway is responsible forpacketizing the voice into RTP data packets, while the signaling gateways and/orsoftswitches are responsible for translating phone numbers and IP addresses back andforth and routing the call properly. Impairments to the signaling information can cause callset up and tear down problems. Impairments to the RTP voice packets cause voice qualitydegradation.Product evaluation: When choosing a vendor for VoIP network gear deployment,understanding how that equipment will perform is critical. These devices should undergovigorous testing and evaluation in a pre-deployment environment. This is achieved by

using a PacketStorm system to emulate the conditions in the “network cloud”. Voicegateways, Voice gateway controllers, IP-PBX’s, SIP proxy servers, etc should be tested forthe resilience to impaired network conditions. Voice quality can be assessed by inducingdropped packets, packet delays, network jitter, creating duplicate packets, reorderedpackets, etc, and then observing and measuring the voice quality. Call set up and controldevices should also be tested to evaluate their ability to work reliably under these adversenetwork conditions. Multiple vendors’ equipment should be compared side by side forquality and reliablilty in consistent, repeatable, network test conditions to gauge theirperformance prior to selection. Negative network conditions should be steadily applieduntil a product’s ‘breaking point’ is determined. In addition to VoIP specific products, corenetwork devices should also be tested for their Quos capability to ensure that they will beable to prioritize VoIP traffic.VideoVideo over IP applications have soared in popularity over the last five years. Companieshave increased their video conferencing usage as a means to reduce travel expenses, speedup the lead time needed to hold critical meetings, and offer investors access to high levelboard meetings. Traditional phone service providers are rushing to provide video servicesas a way of locking in customers and increasing revenues. Cable TV operators have beensteadily upgrading their analog systems to offer consumers enhanced digital services. All ofthese applications focus on delivering digital video content over data services. As thesevideo services evolve from luxuries and novelties to commodities and everydayexpectations, video IP equipment vendors and service providers are scrambling toestablish themselves as the dominant players in this maturing industry.IP video applications have struggled with two main challenges for high quality videoexperience: the ability to deliver the high bandwidth at an acceptable price and overcomingthe imperfect world of IP networks. Relatively inexpensive DSL and cable modem serviceshave helped to solve some of the high bandwidth issues, but typically the achievedbandwidth is much lower than the published access data rate. New techniques lower thebandwidth requirements needed for quality transmission and compression methods aretwo ways currently being developed to address the bandwidth issue.

In addition to high bandwidth, high quality video must overcome the imperfect world of IPnetworks. There is another very important factor that must be designed for: the imperfectworld of IP networks. Network impairments are expected in IP communications. Networkdelays, dropped packets, traffic congestion, reordered packets, fragmented packets, andduplicated packets are all facts of life in IP communications. Many higher level protocolssuch as TCP are designed with error correction mechanisms to ensure that data is movednearly error free from point to point. TCP dictates that endpoints resend packets whenerrors are encountered, and application delays may incur because of this, but most likelythe correct information will eventually be delivered and the application can operate as itshould. Video streaming and other real time IP applications can’t afford the overhead timeassociated with error correction protocols, and typically rely on UDP protocols. VoIP alsouses UDP protocols, and is subject to similar network impairment problems. Although itcan be an annoying experience to use VoIP service with poor quality, humans can negotiatetheir own ‘error correction’. “Sorry, I didn’t hear that last statement. Could you repeatthat?” IP video does not have the luxury of higher level or human intervention errorcorrection. It is subject to the most demanding endpoint of all; the human eye and humanvisual experience.If uncorrected, dropped packets can cause ‘skips’ in the experienced video. Variablenetwork delays (jitter) can cause the video to appear ‘jerky’ and ‘jumpy’. Data errors cansignificantly delay video quality. The onus now lays on the IP video equipment vendors todesign recovery algorithms that can operate in this environment to reassemble packetsinto a satisfactory video experience for the end user.PacketStorm Communications manufactures the equipment needed to test IP videoapplications and equipment:Repeatable network impairment control: The PacketStorm network emulators provideprecise control and repeatability of the various conditions that will be encountered in WANand LAN data communications networks. Development engineers and QA personal can nowhave a controlled emulated infrastructure to develop and test IP video signal recoverymechanisms, thus ensuring that their equipment will provide a positive experience for theend users. Service providers can also emulate their networks to gauge acceptable limits forerror conditions and then set network alarm thresholds based on these values. For more information please visit http://www.packetstorm.com