Flow Control

by

MD. JAVEDUL FERDOUS

EAST WEST UNIVERSITY

Flow Control

Flow control is the process of managing

the rate of data transmission between two

nodes to prevent a fast sender from

outrunning a slow receiver. It provides a

mechanism for the receiver to control the

transmission speed, so that the receiving

node is not overwhelmed with data from

transmitting node.

So why need it

? ? ? ? ?

The Reasons

Prevent degradation and loss of

efficiency

The Reasons

Prevent degradation and loss of

efficiency

Deadlock avoidance.

The Reasons

Prevent degradation and loss of

efficiency

Deadlock avoidance.

Fair allocation of resources among

competing users.

The Reasons

Prevent degradation and loss of

efficiency

Deadlock avoidance.

Fair allocation of resources among

competing users.

Speed matching between the network

and its attached users.

Types of ‘Flow Control’

Types of ‘Flow Control’

Stop-and-wait

Types of ‘Flow Control’

Stop-and-wait

Sliding Window

Stop-and-wait

Fundamental technique to provide

reliable transfer under unreliable packet

delivery system

Stop-and-wait

Fundamental technique to provide

reliable transfer under unreliable packet

delivery system

Simplest form of flow control

Stop-and-wait

Fundamental technique to provide

reliable transfer under unreliable packet

delivery system

Simplest form of flow control

Inefficiencies when sending longer

transmissions

Stop-and-wait

Sliding Window

Technique for controlling transmitted

data packets between two network

computers where reliable and sequential

delivery of data packets is required.

Sliding Window

Technique for controlling transmitted

data packets between two network

computers where reliable and sequential

delivery of data packets is required.

Best utilized when the buffer size is

limited and pre-established.

Sliding Window

Technique for controlling transmitted

data packets between two network

computers where reliable and sequential

delivery of data packets is required.

Best utilized when the buffer size is

limited and pre-established.

Better Performance.

Sliding Window

Levels of Flow Control

Levels of Flow Control

Hop Level

Levels of Flow Control

Hop Level

Entry-to-Exit Level

Levels of Flow Control

Hop Level

Entry-to-Exit Level

Network Access Level

Levels of Flow Control

Hop Level

Entry-to-Exit Level

Network Access Level

Transport Level

Hop Level

Prevent store and forward buffer

congestion and its consequences

Hop Level

Prevent store and forward buffer

congestion and its consequences

Maintain a smooth flow of traffic

between two neighboring nodes In a

computer network

Entry-to-Exit Level

Implement as a protocol between the

source and destination switch

Entry-to-Exit Level

Implement as a protocol between the

source and destination switch

Protect the exit node from congestion

Network Access Level

Throttle external inputs based on

measurements of internal network

congestion.

Transport Level

Efficient & reliable transmission and

sharing of common network resources

by several user sessions

Transport Level

Efficient & reliable transmission and

sharing of common network resources

by several user sessions

Events destination buffer congestion

and overflow is known as transport level

flow control

Problems of ‘Flow Control’

Can’t send too slow or too fast

Problems of ‘Flow Control’

Can’t send too slow or too fast

wastes time

Problems of ‘Flow Control’

Can’t send too slow or too fast

wastes time

can lead to buffer overflow

Thank You