Copyright 2011 1 Module 5 TCP/IP (The Transport and Internetworking Layer Protocol) By Dr. Percy Dias
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CCNA 1 Module 11 TCP/IP Transport and Application LayersBy Dr.
Percy Dias
History and Future of TCP/IP
The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions.
Some of the layers in the TCP/IP model have the same name as layers in the OSI model.
Copyright 2011
Internet Layer
The purpose of the Internet layer is to send packets from a network node and have them arrive at the destination node independent of the path taken.
Internet Protocol (IP)
Address Resolution (ARP)
Copyright 2011
Defining a packet and an addressing scheme
Transferring data between the Internet Layer and the Network Access Layer
Routing packets to remote hosts
IP is sometimes referred to as an unreliable protocol
Provides connectionless, best-effort delivery routing of packets
Copyright 2011
*
*
Supporting Reliable Communication
Sending segments from one end host to another end host
Ensuring data reliability provided by sequence numbers and acknowledgments
Ensuring flow control provided by sliding windows
Copyright 2011
Ensure that segments delivered will be acknowledged to the sender
Provide for retransmission of any segments that are not acknowledged
Put segments back into their correct sequence at the destination
Provide congestion avoidance and control
Copyright 2011
Connection-oriented protocol
A protocol either that requires an exchange of messages before data transfer begins or that has a required pre-established correlation between two endpoints
Connectionless protocol
A protocol that does not require an exchange of messages and that does not require a pre-established correlation between two endpoints
Copyright 2011
Connectionless Communication
TCP is connection-oriented, so it requires connection establishment before data transfer begins
For a connection to be established, two hosts must synchronize on each other’s initial sequence numbers (ISNs)
Initial Sequence numbers are actually large random numbers chosen by each host
Connection establishment refers to the process of initializing sequence and acknowledgement fields and agreeing to the port numbers used.
Copyright 2011
TCP uses expectational acknowledgments (Forward Acknowledgment)
Window size determines the amount of data can transmit at one time before receiving an acknowledgment
Larger window sizes increase communication efficiency.
Window field implies the maximum number of unacknowledged bytes allowed outstanding at any instance in time.
Copyright 2011
Copyright 2011
Window Size
TCP window sizes are variable during the lifetime of a connection.
The window “Slides” up and down based on network performance, so it is called sliding window.
Copyright 2011
Acknowledgment
Sender keeps a record of each data packet that it sends and expects an acknowledgment.
Sender starts a timer when it sends a segment, and it retransmits if the timer expires before an acknowledgment (transmission rate should be slowed)
Each Acknowledgement contains a window advertisement that indicates the number of bytes receiver can accept
Copyright 2011
In-Order Delivery
TCP on the receiving computer reassembles data into its original form
The data is put in the correct order
If segments of a file are assembled out-of-order, the file is useless
TCP provides a guarantee of in-order delivery
*
In-Order Delivery
Due to IP routing, a TCP receiver can receive data out of order
If multiple routes exist between a source and a destination, routers can load-balance over several routes
Packets can arrive out of order
*
TCP and UDP Port Numbers
Internet layer delivers data (packets) from one computer to another, but it does not think about which application sent the data or which application on the receiving computer needs the data.
For example, if you have five web-browser windows open, the internet layer delivers the data to the computer, but the transport layer works to ensure that each browser gets the data destined for it and not one of the others.
TCP and UDP use port numbers to pass information to the upper layers
Port numbers use to keep track of different conversations crossing the network at the same time (Enables the receiving computer to know which application to give the data to).
Copyright 2011
Copyright 2011
Port Numbers
In previous slide, the application was assigned a dynamic port number by the host computer
A host typically dynamically allocates port numbers of value 1024 (210) through 65,535 (216 - 1).
When a host starts a new application process, it allocates a dynamic port number that is not already in use by another process.
By each process having its own port number, a PC can have multiple conversations with other PCs (sometimes called multiplexing).
Copyright 2011
Most TCP/IP applications use a client/server model for communications.
Servers cannot use dynamic port numbers because clients must know ahead of time what port numbers servers use.
Numbers below 1024 are considered well-known port numbers.
well-known port numbers are used by Servers, other port numbers used by clients.
Each client on the same host uses a different port number, but a server uses a same port number for all connections.
Well-Know Port Numbers are controlled by Internet Assigned Number Authority (IANA).
Copyright 2011
Client Connecting to Well-Known Port of a Web Server (80)
Copyright 2011
Connection Establishment and Termination
Reliable (Error recovery – consume more bandwidth and use more processing cycles)
Divides outgoing messages into segments
Reassembles messages at the destination station
Copyright 2011
Multiplexing using port numbers
TCP relies on IP for end-to-end delivery of data
At the receiving station, TCP reassembles the segments into a complete message using sequence numbers. TCP must recover data that is damaged, lost or delivered out of order.
Copyright 2011
UDP Protocol
UDP
Connectionless
Unreliable ( No error recovery – use less bandwidth and fewer processing cycle.)
Does not reassemble incoming messages
Uses no acknowledgments
Function
Description
Multiplexing
Function that allows receiving hosts to decide the correct application for which the data is destined, based on the port number
Error recovery (reliability)
Process of numbering and acknowledging data with Sequence and Acknowledgment header fields
Flow control using windowing
Copyright 2011
Networking Fundamentals
Slide 2-4
History and Future of TCP/IP
The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions.
Some of the layers in the TCP/IP model have the same name as layers in the OSI model.
Copyright 2011
Internet Layer
The purpose of the Internet layer is to send packets from a network node and have them arrive at the destination node independent of the path taken.
Internet Protocol (IP)
Address Resolution (ARP)
Copyright 2011
Defining a packet and an addressing scheme
Transferring data between the Internet Layer and the Network Access Layer
Routing packets to remote hosts
IP is sometimes referred to as an unreliable protocol
Provides connectionless, best-effort delivery routing of packets
Copyright 2011
*
*
Supporting Reliable Communication
Sending segments from one end host to another end host
Ensuring data reliability provided by sequence numbers and acknowledgments
Ensuring flow control provided by sliding windows
Copyright 2011
Ensure that segments delivered will be acknowledged to the sender
Provide for retransmission of any segments that are not acknowledged
Put segments back into their correct sequence at the destination
Provide congestion avoidance and control
Copyright 2011
Connection-oriented protocol
A protocol either that requires an exchange of messages before data transfer begins or that has a required pre-established correlation between two endpoints
Connectionless protocol
A protocol that does not require an exchange of messages and that does not require a pre-established correlation between two endpoints
Copyright 2011
Connectionless Communication
TCP is connection-oriented, so it requires connection establishment before data transfer begins
For a connection to be established, two hosts must synchronize on each other’s initial sequence numbers (ISNs)
Initial Sequence numbers are actually large random numbers chosen by each host
Connection establishment refers to the process of initializing sequence and acknowledgement fields and agreeing to the port numbers used.
Copyright 2011
TCP uses expectational acknowledgments (Forward Acknowledgment)
Window size determines the amount of data can transmit at one time before receiving an acknowledgment
Larger window sizes increase communication efficiency.
Window field implies the maximum number of unacknowledged bytes allowed outstanding at any instance in time.
Copyright 2011
Copyright 2011
Window Size
TCP window sizes are variable during the lifetime of a connection.
The window “Slides” up and down based on network performance, so it is called sliding window.
Copyright 2011
Acknowledgment
Sender keeps a record of each data packet that it sends and expects an acknowledgment.
Sender starts a timer when it sends a segment, and it retransmits if the timer expires before an acknowledgment (transmission rate should be slowed)
Each Acknowledgement contains a window advertisement that indicates the number of bytes receiver can accept
Copyright 2011
In-Order Delivery
TCP on the receiving computer reassembles data into its original form
The data is put in the correct order
If segments of a file are assembled out-of-order, the file is useless
TCP provides a guarantee of in-order delivery
*
In-Order Delivery
Due to IP routing, a TCP receiver can receive data out of order
If multiple routes exist between a source and a destination, routers can load-balance over several routes
Packets can arrive out of order
*
TCP and UDP Port Numbers
Internet layer delivers data (packets) from one computer to another, but it does not think about which application sent the data or which application on the receiving computer needs the data.
For example, if you have five web-browser windows open, the internet layer delivers the data to the computer, but the transport layer works to ensure that each browser gets the data destined for it and not one of the others.
TCP and UDP use port numbers to pass information to the upper layers
Port numbers use to keep track of different conversations crossing the network at the same time (Enables the receiving computer to know which application to give the data to).
Copyright 2011
Copyright 2011
Port Numbers
In previous slide, the application was assigned a dynamic port number by the host computer
A host typically dynamically allocates port numbers of value 1024 (210) through 65,535 (216 - 1).
When a host starts a new application process, it allocates a dynamic port number that is not already in use by another process.
By each process having its own port number, a PC can have multiple conversations with other PCs (sometimes called multiplexing).
Copyright 2011
Most TCP/IP applications use a client/server model for communications.
Servers cannot use dynamic port numbers because clients must know ahead of time what port numbers servers use.
Numbers below 1024 are considered well-known port numbers.
well-known port numbers are used by Servers, other port numbers used by clients.
Each client on the same host uses a different port number, but a server uses a same port number for all connections.
Well-Know Port Numbers are controlled by Internet Assigned Number Authority (IANA).
Copyright 2011
Client Connecting to Well-Known Port of a Web Server (80)
Copyright 2011
Connection Establishment and Termination
Reliable (Error recovery – consume more bandwidth and use more processing cycles)
Divides outgoing messages into segments
Reassembles messages at the destination station
Copyright 2011
Multiplexing using port numbers
TCP relies on IP for end-to-end delivery of data
At the receiving station, TCP reassembles the segments into a complete message using sequence numbers. TCP must recover data that is damaged, lost or delivered out of order.
Copyright 2011
UDP Protocol
UDP
Connectionless
Unreliable ( No error recovery – use less bandwidth and fewer processing cycle.)
Does not reassemble incoming messages
Uses no acknowledgments
Function
Description
Multiplexing
Function that allows receiving hosts to decide the correct application for which the data is destined, based on the port number
Error recovery (reliability)
Process of numbering and acknowledging data with Sequence and Acknowledgment header fields
Flow control using windowing
Copyright 2011
Networking Fundamentals
Slide 2-4
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