Piggybacking (data transmission)
Encyclopedia
Piggybacking is a bi-directional data transmission
technique in the network layer
(OSI model
). It makes the most of the sent data frames from receiver to emitter, adding the confirmation that the data frame sent by the sender was received successfully (ACK acknowledge). This practically means, that instead of sending an acknowledgement in an individual frame it is piggy-back
ed on the data frame.
used in the OSI model. In the data frame itself, we incorporate one additional field for acknowledgment (called ACK).
Whenever party A wants to send data to party B, it will send the data along with this ACK field. Considering the sliding window here of size 8 bits, if A has received frames up to 5 correctly (from B), and wants to send frames starting from frame 3, it will send ACK6 with the data.
Three rules govern the piggybacking data transfer.
Disadvantages: The receiver can jam the service if he/she has nothing to send. This can be solved by enabling a counter (Receiver timeout
) when a data frame is received. If the count ends and there is no data frame to send, the receiver will send an ACK control frame. The sender also adds a counter (Emitter timeout), if the counter ends without receiving confirmation, the sender assumes packet loss
, and sends the frame again.
Data transmission
Data transmission, digital transmission, or digital communications is the physical transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media...
technique in the network layer
Network layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
(OSI model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
). It makes the most of the sent data frames from receiver to emitter, adding the confirmation that the data frame sent by the sender was received successfully (ACK acknowledge). This practically means, that instead of sending an acknowledgement in an individual frame it is piggy-back
Piggy-back
Piggy-backed is riding on the back of something else. To piggy-back is to ride on someone's back or shoulders or head.-Etymology:...
ed on the data frame.
Working Principle
Piggybacking data transfer is a bit different from Sliding Window ProtocolSliding Window Protocol
A sliding window protocol is a feature of packet-based data transmission protocols. Sliding window protocols are used where reliable in-order delivery of packets is required, such as in the Data Link Layer as well as in the Transmission Control Protocol .Conceptually, each portion of the...
used in the OSI model. In the data frame itself, we incorporate one additional field for acknowledgment (called ACK).
Whenever party A wants to send data to party B, it will send the data along with this ACK field. Considering the sliding window here of size 8 bits, if A has received frames up to 5 correctly (from B), and wants to send frames starting from frame 3, it will send ACK6 with the data.
Three rules govern the piggybacking data transfer.
- If station A wants to send both data and an acknowledgment, it keeps both fields there.
- If station A wants to send just the acknowledgment, then a separate ACK frame is sent.
- If station A wants to send just the data, then the last acknowledgment field is sent along with the data. Station B simply ignores this duplicate ACK frame upon receiving.
Advantages and Disadvantages
Advantages: Improves the efficiencyDisadvantages: The receiver can jam the service if he/she has nothing to send. This can be solved by enabling a counter (Receiver timeout
Timeout (telecommunication)
In telecommunication and related engineering , the term timeout or time-out has several meanings, including...
) when a data frame is received. If the count ends and there is no data frame to send, the receiver will send an ACK control frame. The sender also adds a counter (Emitter timeout), if the counter ends without receiving confirmation, the sender assumes packet loss
Packet loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.-...
, and sends the frame again.