Presentation (1) (1).pptx
- 2. TEAM MEMBERS • Sanjay.k • Saran.s • Somansankara.p.r • Vishnuprasanth.b
- 3. AGENDA: • INTRODUCTION • DATA RATES • LATENCY • JITTER • PACKET LOSS • LARGE WINDOW • LIMITTED TRANSMITT
- 4. Introduction The current internet draftfor TCP over 2.5G/3G wireless networks (Inamura,2002) describes a profile for optimizing TCP over today’s and tomorrow’s wirelessWANs such as GSM/GPRS, UMTS, or cdma2000.The focus on 2.5G/3G for transport of internet data is important as already morethan 1 billion people use mobile phones and it is obvious that the mobile phone systemswill also be used to transport arbitrary intern et data
- 5. DATA RATES • Data rates of today’s 2.5G systems are 10–20 kbit/suplink and 20–50 kbit/s downlink, 3G and future 2.5G systems will initially offerdata rates around 64 kbit/s uplink and 115–384 kbit/s downlink. To supportmultiple users within a radio cell, a scheduler may have to repeatedly allocate anddeallocate resources for each user. This may lead to a periodic allocation andrelease of a high-speed channel
- 6. LATENCY • Forward error correction (FEC) and interleaving let the round trip time(RTT) grow to several hundred milliseconds upto some seconds. The currentGPRS standard specifies an average delay of less than two seconds for thetransport class with the highest quality
- 7. JITTER • Wireless systems suffer from large delay variations or ‘delay spikes’.Reasons for sudden increase in the latency are: link outages due to temporal lossof radio coverage, blocking due to high-priority traffic, or handovers. Handoversare quite often only virtually seamless with outages reaching from some 10ms(handover in GSM systems) to several second
- 8. PACKET LOSS • Packets might be lost during handovers or due to corruption. Butdue to link-level retransmissions the loss rates of 2.5G/3G systems due tocorruption are relatively low. However, recovery at the link layer appears as jitterto the higher layers
- 9. Based on these characteristics, (Inamura, 2002) suggests the followingconfiguration parameters to adapt TCP to wireless environments • LARGE WINDOWS TCP should support large enough window sizes based on the bandwidth delay product experienced in wireless systems. A larger initial windowof 2 to 4 segments may increase performance particularly for short transmissions
- 10. Limited transmit This mechanism, defined in RFC 3042 is an extension of FastRetransmission/Fast Recovery and is particularly useful when small amounts ofdata are to be transmitted (standard for, e.g., web service requests