This document discusses transport layer protocols like TCP and UDP. It explains that TCP provides reliable, in-order delivery of streams of bytes through mechanisms like packet sequencing, acknowledgments, retransmissions, and flow control. UDP is a simpler protocol that just sends datagrams without these reliability features. It also describes how TCP establishes connections using a three-way handshake and how it closes connections using FIN and ACK packets.

1. PAPER NAME : COMPUTER NETWORKS
STAFF NAME : MISS.S.MANIMOZHI .MCA,M.phil,phd.,
CLASS : III BCA A
SEMESTER : VI
UNIT : IV
TOPIC : TRANSPORT PROTOCOLS

3.  Lightweight statement between development
 Avoid slide and delays of planned, steadfast
liberation.
 Send messages to and collect them from a opening.
SRC port DST port
checksum length
DATA

4.  philosophy original transport-layer military
 (De)multiplexing
 detect bribery
 Consistent liberation
 Flow control
 Transport-layer protocol in the Internet
 User Datagram Protocol (UDP)
 Transmission Control Protocol (TCP)

5.  Application layer
 Announcement for explicit applications
 E.g., HyperTextTransfer Protocol (HTTP), FileTransfer
Protocol (FTP), Network NewsTransfer Protocol (NNTP)
 Transport layer
 Statement between processes (e.g., socket)
 Relies on network layer and serve the application layer
 E.g.,TCP and UDP
 Network layer
 Logical announcement between nodes
 Hides details of the link knowledge.
 E.g., IP

6. Dispatcher: break application
messages into segment
and pass to network
Receiver: reassembles
segments into messages,
passes to submission several
transport protocol available to
application.
Internet:TCP and UDP
application
transport
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physicalnetwork
data link
physical

7.  Datagram messaging service (UDP)
 No-frills conservatory of “best-effort” IP
 Unswerving, in-order liberation (TCP)
 Connection set-up
 Discarding of dishonored packets
 Re transmission of lost packets
 Flow control
 blockage control (next lecture)
 Other services not available
 Delay guarantee
 Bandwidth guarantee
7

8.  superior direct over what information is sent and when
 As soon as an application process write into the socket
 … UDP will drape up the in sequence and force the package
 No setback for connection assembly
 UDP just blast away without any formal preliminaries
 … which avoid originate any superfluous delays
 No connection shape
 No section of buffers, limit, sequence #s, etc.
 … making it easier to lever many active regulars at once
 little packet star transparency
 UDP title is only eight-bytes long
8

9.  compact disk stream
 Retransmitting lost/dishonored packets is not
valuable.
 By the occasion the packet is retransmitted, it’s
too late.
 E.g., telephone calls, video conferencing, gaming
9
“Address for www.cnn.com?”
“12.3.4.15”

10. 10
Host A
Host B

11. 11
Host A
Host B
TCP Data
TCP Data
Segment sent when:
1. Segment full (Max Segment Size),
2. Not full, but times out, or
3. “Pushed” by application.

12. TCP Data
TCP Data
TCP
HDR
TCP
HDR
ISN (initial sequence number)
Sequence
number = 1st
byte ACK sequence
number = next
expected byte

13.  Correspondent set a rest to wait for an ACK
 Too little: bushed retransmissions
 Too extended: intense delays when packet missing
 TCP sets fracture as a profession of the RTT
 Envisage ACK to pull in after an RTT
 … plus a fudge feature to report for queue
 But, how does the sender know the RTT?
 Can resolution the RTT by examination the ACKs
 Downy estimate: keep a supervision regular of the RTT
▪ EstimatedRTT = a * EstimatedRTT + (1 –a ) * SampleRTT
 Compute timeout:TimeOut = 2 * probable RTT

14. RTT: gaia.cs.umass.edu to fantasia.eurecom.fr
100
150
200
250
300
350
1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106
time (seconnds)
RTT(milliseconds)
SampleRTT Estimated RTT

15.  Stop-and-wait is inefficient
 Only oneTCP segment is “in flight” at a time
 Especially bad when delay-bandwidth product is
high
 Numerical example
 1.5 Mbps link with a 45 msec round-trip time
(RTT)

16.  Allow sender to get ahead of the receiver
 … though not too far ahead
Sending process Receiving process
Last byte ACKed
Last byte sent
TCP TCP
Next byte expected
Last byte written Last byte read
Last byte received

17.  Closing the connection
 Finish (FIN) to close and receive remaining bytes
 And other host sends a FIN ACK to acknowledge
 Reset (RST) to close and not receive remaining bytes
time
A
B

18.  Distribution a FIN:
close()
 course is complete
sending data via the
hole
 course appeal to
“close()” to close the
hole
 OnceTCP has sent all of
the terrific bytes…
 … thenTCP send a FIN
 in receipt of a FIN: EOF
 Process is reading data
from the socket
 Eventually, the
enterprise to read
returns an EOF

19. Source port Destination port
Sequence number
Acknowledgment
Advertised windowHdrLen Flags0
Checksum Urgent pointer
Options (variable)
Data
Flags: SYN
FIN
RST
PSH
URG
ACK

20.  Three-way handshake to establish connection
 Host A sends a SYN (open) to the host B
 Host B returns a SYN acknowledgment (SYN ACK)
 Host A sends an ACK to acknowledge the SYN ACK
A B
Each host tells
its ISN to the
other host.

21.  Transport protocols
 Multiplexing and demultiplexing
 Sequence numbers
 Window-based flow control
 Timer-based retransmission
 Checksum-based error uncovering