DBS: Distributed Benchmark System

Performance Evaluation on VSAT Satellite Link Part I

Various Window Size

• System Structure

  

• Data sheet

    CPU                   Twinhead Subnote(486 33MHz)
    OS                    BSD/OS V2.0.1
    Router                SPARCstation10(SunOS4.1.3)
    TCP Buffer Size         8196byte   (8196octet)
    (Maxmum Window Size)   16384byte  (16384octet)
                           32768byte  (32768octet)
                           65535byte  (66535octet)
                          131072byte (131072octet)
                          196608byte (196608octet)
                          246723byte (246723octet)
    Message Size          1024byte
    Start Time            0.00s
    Number of Send        1000
    

• Sequence Number(Application Level)

  

  You can see TCP Slow-Start functions really slow when it is transfered on the long-delay satellite link.

• Throughput(Application Level)

  

  It seems that TCP Window Scale option works well on the long-delay satellite link. But 7~8 seconds are need to achive maximum throughput.

• Throughput(Application Level)

  

  If your ftp uses window size under 8192byte, you can transfer files only under about 100kbps on satellite link whose round trip time is about 0.5 seconds.

• Congestion Window Size(Kernel Level)