Flow Control by Md.Javedul Ferdous East West University
Flow Controlby
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
? ? ? ? ?
Prevent degradation and loss of
efficiency due to overload.
Prevent degradation and loss of
efficiency due to overload.
Deadlock avoidance.
Prevent degradation and loss of
efficiency due to overload.
Deadlock avoidance.
Fair allocation of resources among
competing users.
Prevent degradation and loss of
efficiency due to overload.
Deadlock avoidance.
Fair allocation of resources among
competing users.
Speed matching between the network
and its attached users.
Type of ‘Flow Control’
Stop-and-wait
Type 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
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 and reliable transmission of
messages within each user session and
the efficient sharing of common network
resources by several user sessions
Transport Level
Efficient and reliable transmission of
messages within each user session and
the efficient sharing of common network
resources by several user sessions
Events destination buffer congestion
and overflow is known as transport level
flow control
Problem of ‘Flow Control’
Can’t send too slow or too fast
Problem of ‘Flow Control’
Can’t send too slow or too fast
Too slow
Problem of ‘Flow Control’
Can’t send too slow or too fast
Too slow
wastes time
Problem of ‘Flow Control’
Can’t send too slow or too fast
Too slow
wastes time
Too fast
Problem of ‘Flow Control’
Can’t send too slow or too fast
Too slow
wastes time
can lead to buffer overflow