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Spirent TestCenter: What is the relationship between Connections and Transactions in the ALP Load Profile?

  • Application Layer Protocol Load Profiles
    • Traffic Type
    • Connections vs Transactions
  • Connections 
    • Denotes a TCP connection. Defines the number of simultaneous network connections generated. This setting generates enough load to reach and sustain the desired number of open TCP connections.
    • An open connection does not necessarily have nonstop activity. Observe the time it takes a TCP connection to complete, the time to SYN/ACK, and the number of successful versus failed transactions at a specified number of open TCP connections. (Many Transactions within a Connection to keep data flowing for the length of the time period specified as the steady state within the profile.)
    • The maximum connections is determined by the height of the load profile.
  • Transactions 
    • Defines the number of simultaneous transactions generated. This specification generates and maintains enough load to reach an outstanding number of active transactions, such as HTTP GETs or FTP Puts in progress.
    • There can be multiple Transactions in a single Connection.
    • A single transaction contain one file requests.
      • The number of transactions is controlled by the Max Pipeline Dept, Max Request Per Client, Max Transactions Per Server.
    • Once all the transactions for the Connection has been completed, new Connections and transactions will take place and continue until the end of the test.
    • For Example if I have 30 connections and my Max Pipeline Depth, Max Request Per Client, Max Transactions Per Server are set at 10, after 10 transactions of a connection are completed a new connection will be made and another 10 transactions will take place.
      • Pipeline = Number of unacknowledged requests that the HTTP client will allow at any given time. Once this number is reached, the client will wait to receive a response (acknowledgement) before sending another request. 
        • Increasing Pipeline cannot be higher than the Max Transactions Per Server since or rather will not have any affect since it will be limited by that parameter.
      • Max. Transactions Per Server  = maximum number of transactions between a single client and server.
      • Max Requests Per Client = maximum number of requests from a single client.
      • Server setting "Max Request Per Client" should be equal to or greater than the Client setting "Max Transactions Per Server"
        • If Client sends more transactions then the Server setting of "Max Request Per Client" then the extra transactions will be aborted.
  • Example: A single TCP Connection showing 10 transactions with Pipeline of 8.
    • We see that 8 request (GETs) are sent first to wait for an ACK before sending the next two.

Product : Spirent TestCenter,Raw TCP,HTTP,ALP