Selective repeat protocol, also called Selective Repeat ARQ (Automatic Repeat reQuest), is a data link layer protocol that uses sliding window method for reliable delivery of data frames. Here, only the erroneous or lost frames are retransmitted, while the good frames are received and buffered.
How does a selective repeat protocol work?
In the selective repeat, the sender sends several frames specified by a window size even without the need to wait for individual acknowledgement from the receiver as in Go-Back-N ARQ. In selective repeat protocol, the retransmitted frame is received out of sequence.
How does a sliding window protocol work?
Sliding window protocols are data link layer protocols for reliable and sequential delivery of data frames. In this protocol, multiple frames can be sent by a sender at a time before receiving an acknowledgment from the receiver. The term sliding window refers to the imaginary boxes to hold frames.
How does back n protocol work?
Go-Back-N ARQ is a specific instance of the automatic repeat request (ARQ) protocol, in which the sending process continues to send a number of frames specified by a window size even without receiving an acknowledgement (ACK) packet from the receiver.
Why do we need selective repeat?
Why Selective Repeat Protocol? The go-back-n protocol works well if errors are less, but if the line is poor it wastes a lot of bandwidth on retransmitted frames. An alternative strategy, the selective repeat protocol, is to allow the receiver to accept and buffer the frames following a damaged or lost one.
How is selective repeat better than go back n?
Selective Repeat is far better than Go back N in terms of retransmissions required. Bandwidth requirement is high because even if a single packet is lost, entire window has to be retransmitted. Selective Repeat is better than Go back N in terms of bandwidth requirement.
Why we use sliding window protocol?
Sliding window protocols are used where reliable in-order delivery of packets is required, such as in the data link layer (OSI layer 2) as well as in the Transmission Control Protocol (TCP). They are also used to improve efficiency when the channel may include high latency.
How important is sliding window protocol?
The sliding window provides several benefits: It controls the speed of transmission so that no fast sender can overwhelm the slower receiver; It allows for orderly delivery, as we will show; It allows for retransmission of lost frames, specific retransmission policy depends on the specific implementations.
What is Go-Back-N and Selective Repeat?
Definition. In Go-Back-N if a sent frame is found suspected or damaged then all the frames are retransmitted till the last packet. In Selective Repeat, only the suspected or damaged frames are retransmitted.
What is selective reject technique used for?
Faulty or missing frames or bits are standard errors and to control or check errors requires a unique method, in this case, the Stop-and-wait method, Go-Back-N and Selective Reject are methods that can be used to do so, comparison of time of error checking process with Stop-and-wait method, Go-Back-N and Selective …
What is selective repeat protocol in computer networks?
Selective Repeat Protocol in computer networks is a Sliding Window Protocol. Selective Repeat ARQ or SR Protocol is an implementation of sliding window protocol like Go back N Protocol.
What is Selective Repeat ARQ protocol?
Sliding Window Protocol | Set 3 (Selective Repeat) Receiver stores correct packets until they can be delivered in order to the higher layer. In Selective Repeat ARQ, the size of the sender and receiver window must be at most one-half of 2^m.
What is window size in SR protocol?
Window size should be less than or equal to half the sequence number in SR protocol. This is to avoid packets being recognized incorrectly. If the windows size is greater than half the sequence number space, then if an ACK is lost, the sender may send new packets that the receiver believes are retransmissions.
How does receivereceiver window work?
Receiver window is implemented as a linked list. When receiver receives a new frame, it places the new frame at the end of the linked list. When the received frames are out of order, receiver performs the sorting. Sorting sorts the frames in the correct order. SR protocol requires searching at the sender’s side.
