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TCP/IP Transport &
Application Layers
Semester 1 – Module 11
Module Objectives:
Describe the functions of the TCP/IP transport layer
Describe flow control
Explain how a connection is established between peer systems
Describe windowing and acknowledgment
Identify and describe transport layer protocols
Describe TCP and UDP header formats
Describe TCP and UDP port numbers
List the major protocols of the TCP/IP application layer
Provide a brief description of the features and operation of well-known TCP/IP
applications
TCP/IP Transport Layer
- Segmentation of upper-layer application data
- Establishment of end-to-end operations
- Transportation of segments from one end
host to another
- Flow control provided by sliding windows
- Reliability provided by sequence numbers
and acknowledgments
Flow Control
• Flow control ensures that a source host
does not overflow the buffers in a
destination host by allowing the source
and destination hosts to communicate
Session establishment, maintenance, and termination
- establish a connection-oriented session between
similar applications at the application layer
- connection is established and the transfer of
data begins after all synchronization has
occurred
- Manages connection by using indicators, such
as “not ready” or ready”
- Terminates connection when all data is done
being sent.
Windowing
• Data packets must
be delivered to the
recipient in the
same order in which
they were
transmitted to have
a reliable,
connection-oriented
data transfer
Acknowledgement
• Reliable delivery
guarantees delivery
through a data link to
another device without
duplication or data loss
• Positive acknowledgment
requires an ACK when
the data is received by
the destination
UDP
- The following protocols use UDP:
- The following are the definitions of the fields in the UDP
segment:
- Source port – Number of the port that sends data
- Destination port – Number of the port that receives data
- Length – Number of bytes in header and data
- Checksum – Calculated checksum of the header and data fields
- Data – Upper-layer protocol data
TCP and UDP Port Numbers
- Both TCP and UDP use port numbers to pass information to the upper layers.
- Port numbers are used to keep track of different conversations that cross the network at the same time
- Numbers below 1024 are considered well-known ports numbers.
- Numbers above 1024 are dynamically-assigned ports numbers.
- Registered port numbers are for vendor-specific applications. Most of these are above 1024.
- Port Numbers to know:
- FTP – 20 and 21
- HTTP – 80
- Telnet – 23
- SMTP – 25
- DNS – 53
- TFTP - 69
DNS
• system used on the Internet for translating
names of domains and their publicly advertised
network nodes into IP addresses
• Examples of dns extensions:
- .us – United States
- .uk – United Kingdom
- .edu – educational sites
- .com – commercial sites
- .gov – government sites
- .org – non-profit sites
- .net – network service
FTP and TFTP
• FTP is a reliable, connection-oriented
service that uses TCP to transfer files
between systems that support FTP.
• TFTP is a connectionless service that
uses User Datagram Protocol (UDP).
• Small and easy to implement
SMTP
• Email servers communicate with each
other using the Simple Mail Transfer
Protocol (SMTP) to send and receive mail
SNMP
- The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices
- An SNMP managed network consists of the following three key components: - Network management system (NMS) – NMS executes applications that monitor and control managed devices. The bulk of the processing and memory resources required for network management are provided by NMS. One or more NMSs must exist on any managed network. - Managed devices – Managed devices are network nodes that contain an SNMP agent and that reside on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be routers, access servers, switches, and bridges, hubs, computer hosts, or printers. - Agents – Agents are network-management software modules that reside in managed devices. An agent has local knowledge of management information and translates that information into a form compatible with SNMP
