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User Datagram Protocol (UDP) (UDP Operation (Connectionless Service…
User
Datagram Protocol
(UDP)
Process-to-Process Delivery
Type of delivery
Node-to-Node Delivery
Data link layer-delivery of frames between 2 neighboring nodes over a link
Host-to-Host Delivery
Network layer-deliver datagram between 2 hosts
Transport layer function
Process-to-process delivery, the delivery of a packet, part of a message
Client/Server Paradigm
common process-to-process communication
Port Number
At the transport layer, we need a transport layer address (port number) to choose among multiple processes running on the host.
Port number
Internet model Port
0 to 65535 (16 bit integer)
Universal Port
0 to 1023
Ephemeral Port
a port no chosen randomly by the transport layer SW running on the client host
IANA (Internet Assigned Number Authority)
Well-known ports
range: 0 to 1023
Controlled by IANA
Dynamic Port
Range: 49152 to 65535
Ephemeral port
Neither controlled nor registered but can be used as temporary or private port numbers
Registered port
Range: 1024 to 49151
Not assigned and controlled by IANA but can be registered to prevent duplication
Socket Addresses
Combination of IP address and port number
Transport layer needs client socket address and the server socket address
Example
Ip address: 192.168.1.3
Port: 69
Socket address: 192.168.1.3 69
User Datagram
It is UDP packets and have a fixed-size header of 8 bytes
UDP length = IP length - IP header's length
Checksum
3 sections
Pseudoheader
UDP header
Data coming from application layer
Example
Sum
10010110 11101011
Checksum
01101001 00010100
Bits complement
UDP Operation
Multiplexing & Demultiplexing
Multiplexing
many-to-one relationship
Send multiple processes in one channel
Demultiplexing
one-to-many relationship
Transport layer receives datagrams from network layer
Connectionless Service
Packets are not numbered; they may be delayed or connection release
No ACK
Each datagram sent by UDP is an independent datagram
Flow and Error Control
No flow control and no window mechanism except for checksum
Encapsulation and Decapsulation
UDP encapsulates and decapsulates messages in IP datagram
Queuing
Client site
When a process starts it requests a port No from the OS. The client process sends messages to the outgoing queue by using the source port No, specified in the request. UDP removes the messages one by one and after adding UDP header it will deliver them to IP.
Server site
When it starts running, a server asks for incoming and outgoing queues, using its well-known port. When a message arrives for a server. UDP checks to see if an incoming queue has been created for the port number specified in the destination port number field of the user datargram.
Use of UDP
A process that requires simple request-response communication with little concern for flow and error control
Process with internal flow and error control mechanism
Multicasting
Management processing-SNMP
Route updating protocols-RIP
UDP Package
Components
Control-block table
Input queues
Control-block module
Input module
Output module