APPLICATION AND NETWORK PERFORMANCE - TCP TUNING Alan Bodnar

Agenda Data Communications Advancements Internet Enterprise Applications TCP Protocol Basics TCP Protocol Limitations Bandwidth Delay Product TCP Window Size and Affected Operating Systems TCP Window Size Application and Network Implications TCP and Application Flows TCP and Information Technology Manager Decisions

Data Communication Advancements Wide Area Network Links The speed of wide area network circuits have increased The reliability of wide area network circuits have improved Carriers have expanded globally through international carrier agreements Internet The Internet has global reach Internet gives organizations access to their Customers Internet gives organizations access to their Suppliers Organization Presence

Enterprise Applications High Cost Leverage over a number of business units Global deployments Ten to thousands of WAN network links TCP base application performance becomes critical to the success of the organization TCP Basics Three way handshake Prior to any application data transmission Segment Size Window Size Sequence Number

TCP Limitations Default Window Size High Speed Wide Area Network Links Issues High Latency Networks Issues Bandwidth Delay Product Capacity (bits) = bandwidth (bits/sec) * round trip time (sec) 247,040 bits = 1,544,000 bit/sec * 160(ms) or.16(sec) Optimum window size = 247,040(bits) or 30,880(bytes) 160,000,000 bits = 1,000,000,000 bit/sec * 160(ms) or.16(sec) Optimum window size = 160,000,000(bits) or 20,000,000(bytes)

Actual TCP Bandwidth Throughput TCP Window Size (MAX) / round trip time (sec) = TCP Throughput 65,535(bytes) / 160ms (.16sec) = 409,593(bytes) TCP Throughput = 409,593 (bytes) or 3.28mbps What about links above 160ms? What about links above 3.28mbps?

Affected Platforms Windows Solaris Linux AIX All tunable Application and Network Implications Browser timeouts Application timeouts Data re-entry Retransmission of data Highly utilized device exacerbate issue Network meltdown

TCP and Application Flows First understand network capabilities through BDP Gain an understanding of critical applications TCP Flows via Application Profiling –Segment size –Window size –TCP Turns –Application Turns Management – Better Decision Making Don’t waste money on bandwidth Don’t waste money on hardware Meet business financial goals Meet IT service level agreements

Questions?