Your SlideShare is downloading. ×
T Tcp
Upcoming SlideShare
Loading in...5

Thanks for flagging this SlideShare!

Oops! An error has occurred.

Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

T Tcp


Published on

Unit 3 Of ACN

Unit 3 Of ACN

Published in: Technology, Education

  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

No notes for slide


  • 1. TCP performance problem 1
    • Standard TCP imposes two performance problems for transaction-oriented communication.
    • First, a TCP connection is opened with a "3-way handshake", which must complete successfully before data can be transferred.
    • The 3-way handshake adds an extra RTT (round trip time) to the latency of a transaction.
  • 2. 3 way handshake
  • 3. TCP performance problem 2
    • The second performance problem is that closing a TCP connection leaves one or both ends in TIME-WAIT state for a time 2*MSL
      • where MSL is the maximum segment lifetime (defined to be 120 seconds).
    • A new connection cannot be opened until the TIME-WAIT delay expires
  • 4. TCP close (connection termination)
  • 5. The TIME-WAIT State
    • The TIME-WAIT state is required for two main reasons.
      • The first is to provide enough time to ensure that the ACK is received by the other device, and to retransmit it if it is lost.
      • The second is to provide a “buffering period” between the end of this connection and any subsequent ones. If not for this period, it is possible that packets from different connections could be mixed, creating confusion.
    • The standard specifies that the client should wait double a particular length of time called the maximum segment lifetime (MSL) before finishing the close of the connection.
  • 6. TCP performance problem 3
    • Transaction rate:
      • the 16-bit port space limits the rate to 2**16/240 transactions per second
      • more practically, an excessive amount of kernel space would be occupied by TCP state blocks in TIME-WAIT state.
  • 7. Solutions for TCP performance problems
    • T/TCP solves these two performance problems for transactions, by
      • (1) bypassing the 3-way handshake (3WHS)
      • (2) shortening the delay in TIME-WAIT state.
  • 8. Bypassing the Three-Way Handshake
    • T/TCP introduces a 32-bit incarnation number, called a "connection count" (CC)
    • A distinct CC value is assigned to each direction of an open connection
    • A T/TCP implementation assigns monotonically increasing CC values to successive connections that it opens actively or passively
  • 9. TCP Accelerated Open (TAO)
    • A T/TCP server keeps a cache containing the last valid CC value
    • If an initial <SYN> segment from a particular client host carries a CC value larger than the corresponding cached value, the <SYN> segment must be new and can therefore be accepted immediately
    • Otherwise it executes a normal 3WHS
  • 10. new TCP options
    • CC – for bypassing 3WHS
    • CC.NEW
      • Receiving a CC.NEW causes the server to invalidate its cache entry and do a 3WHS
    • CC.ECHO
      • When a server sends a <SYN,ACK> segment, it echoes the connection count from the initial <SYN> in a CC.ECHO option, which is used by the client to validate the <SYN,ACK> segment.
  • 11. TCP Accelerated Open Client Server CC[A] = X SYN, data1, CC=x SYN, ACK(data1), data2, CC=y, CC.ECHO=x CC[A] = X0 X>X0, TAO OK
  • 12. Minimal TCP transaction Client Server CC[A] = X SYN, data1, FIN, CC=x SYN,ACK(FIN),data2,FIN,CC=y,CC.ECHO=x CC[A] = X0 X0>X, TAO OK ACK(FIN),CC=x closed Syn-sent Time-wait Listen Closed Close-wait
  • 13. Truncation of TIME- WAIT Client Server CC[A] = X SYN, data1, FIN, CC=x SYN,ACK(FIN),data2,FIN,CC=y,CC.ECHO=x CC[A] = X0 X0>X, TAO OK ACK(FIN),CC=x closed Syn-sent Time-wait Listen Closed Close-wait SYN,data3, FIN, CC=z Syn-sent