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5.1 Explain Transport Layer Protocols - Coggle Diagram
5.1 Explain Transport Layer Protocols
Explain transport layer responsibilities
and protocols.
Transport Layer Responsibilities
Tracking the Conversation
Segmentation
Identifying the Application
Role of Transport Layer
Responsible for establishing a
temporary communication
session between two
applications and delivering data
between them.
Link between the application
layer and the lower layers that
are responsible for network
transmission.
Conversation Multiplexing
Segmenting the data into smaller chunks enables many different
communications to be multiplexed on the same network.
Transport Layer Reliability
TCP/IP provides two transport layer
protocols:
Transmission Control Protocol
(TCP)
◦ Considered reliable which
ensures that all of the data
arrives at the destination.
◦ Additional fields needed in
header which increasessize
and delay.
TCP Three Responsibilities:
▪ Numbering and tracking data segments
▪ Acknowledging received data
▪ Retransmitting any unacknowledged data
after a certain period of time
User Datagram Protocol (UDP)
◦ Does not provide for reliability.
◦ Fewer fields and is faster than
TCP.
Use UDP for less overhead and to
reduce possible delays.
Best-effort delivery (unreliable)
No acknowledgment
Similar to a non-registered letter
The Right Transport Layer Protocol for the Right
Application
TCP - databases, web
browsers, and email clients
require that all data that is
sent arrives at the
destination in its original
condition.
UDP - if one or two
segments of a live video
stream fail to arrive, if
disruption in the stream,
may not be noticeable to
the user.
Differentiate the characteristic of
Transmission Control Protocol (TCP) and
User Datagram Protocol (UDP) protocols
TCP Features
Establishing a Session
◦ Connection-oriented protocol
◦ Ensures the application is ready to receive the data
◦ Negotiate the amount of traffic that can be forwarded at a given time
Reliable Delivery
◦ Ensuring that each segment that the source sends arrives at the destination
Same-Order Delivery
◦ Numbering & Sequencing the segments guarantees reassembly into the proper order
Flow Control
◦ Regulate the amount of data the source transmits
UDP Features
Data is reconstructed in the order that is received.
Any segments lost are not resent.
No session establishment.
Does not inform sender of resource availability.
Identify TCP and UDP application
Applications that use TCP
HTTP
FTP
SMTP
Telnet
Applications that use UDP
DHCP
DNS
SNMP
TFTP
VolP
IPTV
Explain port number groups
Port Numbers
Source Port
◦ Originating application port
that is dynamically generated
by sending device
◦ Example: Each separate HTTP
conversation is tracked based
on the source ports.
Destination Port
◦ Tell the destination what
service is being requested
◦ Example: Port 80 web services
are being requested
Socket Pairs
▪ Source and destination
port placed in segment
▪ Segments encapsulated in
IP packet
▪ IP and port number =
socket
▪ Example: 192.168.1.7:80
▪ Sockets enable multiple
processesto be
distinguished
▪ Source port acts as a
return address
Port Number Groups
▪ Well-known Ports (Numbers 0 to 1023) - These numbers are reserved for
services and applications.
Registered Ports (Numbers 1024 to 49151) - These port numbers are assigned
by IANA to a requesting entity to use with specific processes or applications.
▪ Dynamic or Private Ports (Numbers 49152 to 65535) - Usually assigned
dynamically by the client’s OS and used to identify the client application during
communication.
Explain TCP Three-way Handshake
TCP Three-way Handshake Analysis
The three-way handshake:
◦ Establishes that the destination device is
present on the network.
◦ Verifies that the destination device has
an active service and is accepting
requests on the destination port number
that the initiating client intends to use.
◦ Informs the destination device that the
source client intends to establish a
communication session on that port
number.
TCP Reliability – Ordered Delivery
Sequence numbers are assigned
in the header of each packet.
Represents the first data byte of
the TCP segment.
During session setup, an initial
sequence number (ISN) is set -
represents the starting value of
the bytes.
As data is transmitted during
the session, the sequence
number is incremented by the
number of bytesthat have been
transmitted.
Missing segments can then be
identified.
TCP Flow Control – Window Size and
Acknowledgments
▪ In the figure, the source is
transmitting 1,460 bytes of
data within each segment.
▪ Window size agreed on
during 3-way handshake.
▪ Typically, PC B will not wait
for 10,000 bytes before
sending an
acknowledgment.
▪ PC A can adjust its send
window as it receives
acknowledgments from PC
B.
TCP Flow Control – Congestion Avoidance
Congestion causes
retransmission of lost TCP
segments
▪ Retransmission of segments
can make the congestion
worse
▪ To avoid and control
congestion, TCP employs
several congestion handling
mechanisms, timers, and
algorithms
▪ Example: Reduce the number
of bytes it sends before
receiving an acknowledgment
UDP Low Overhead versus Reliability
▪ UDP not connectionoriented
▪ No retransmission,
sequencing, and flow
control
▪ Functions not
provided by the
transport layer
implemented
elsewhere
UDP Datagram Reassembly
UDP reassembles data
in order received and
forwards to application
Application must
identify the proper
sequence