jerry zhao schrieb: > I want to build a scenrio to emulate video streaming. > my real network topology is: > > A- - - - >B<- - - - -C > The NS was installed on Computer B. > The data rate is relative big(more than 30Mb/s). There is always > warnings " RealTimeScheduler: > warning:slop ... exceed limit ...." > And some packets are lost, but the bandwith is enough to transmit the video > data. > Could anyone tell me if there is a data rate limitation for ns emulate? Any > advice would be appreciated ns-2 defines no limitation. However, ns-2 needs to process data packets almost in real-time and hence is limited by the speed of your hardware / operating system. If you emulate a wired network ns-2 will perform quite well. But for a wireless network performance requirements are much stronger (standard ns-2 will not be able to work at all for wireless networks in most cases). But even if your CPU is fast enough, the operating system can introduce short but significant delays. To avoid them you should try the following: - set ns-2 to run with real-time priority - disable tracing - use a multi-core / CPU system and pin ns-2 to one CPU / core - disable other applications that write to the disk - if you need tracing, buffer output in memory (ram disk)
For high-throughput emulations of wired networks you should consider a different emulator like NIST Net. This should improve your results. Daniel. -- Dr.-Ing. Daniel Mahrenholz rt-solutions.de GmbH Oberländer Ufer 190a D-50968 Köln Web: www.rt-solutions.de rt-solutions.de networks you can trust.
