Selective Retransmission Calculator

Selective Retransmission Formula:

\[ Rs = \frac{Nwd \times L}{H \times En + Bwd \times E1 \times Nwd} \]

Number of Word Message Consist (Nwd):

words

Information Bits (L):

bits

Header Bits (H):

bits

Expected Number of Transmission (En):

transmissions

Number of Bits per Word (Bwd):

bits

Expected One Transmission (E1):

transmissions

Selective Retransmission (Rs):

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1. What is Selective Retransmission?

Selective Retransmission also called Selective Repeat ARQ (Automatic Repeat Request), is a data link layer protocol that uses the sliding window method for reliable delivery of data frames.

2. How Does the Calculator Work?

The calculator uses the Selective Retransmission formula:

\[ Rs = \frac{Nwd \times L}{H \times En + Bwd \times E1 \times Nwd} \]

Where:

\( Nwd \) — Number of Word Message Consist (words)
\( L \) — Information Bits (bits)
\( H \) — Header Bits (bits)
\( En \) — Expected Number of Transmission (transmissions)
\( Bwd \) — Number of Bits per Word (bits)
\( E1 \) — Expected One Transmission (transmissions)

Explanation: This formula calculates the selective retransmission efficiency by considering the ratio of information bits to the total transmission overhead.

3. Importance of Selective Retransmission Calculation

Details: Calculating selective retransmission efficiency is crucial for optimizing data transmission protocols, improving network performance, and reducing transmission overhead in communication systems.

4. Using the Calculator

Tips: Enter all required values in the appropriate units. Ensure all values are positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the purpose of selective retransmission?
A: Selective retransmission improves transmission efficiency by only retransmitting lost or corrupted frames rather than all subsequent frames.

Q2: How does selective retransmission differ from go-back-N?
A: Unlike go-back-N which retransmits all frames from the lost one, selective retransmission only retransmits the specific lost or corrupted frames.

Q3: What factors affect selective retransmission efficiency?
A: Frame size, header overhead, transmission success rate, and network conditions all impact the efficiency of selective retransmission protocols.

Q4: When is selective retransmission most beneficial?
A: Selective retransmission is most beneficial in high-error-rate environments or when transmitting large files where retransmitting all subsequent frames would be inefficient.

Q5: What are the limitations of selective retransmission?
A: It requires more complex receiver implementation, increased buffer requirements, and more sophisticated acknowledgment mechanisms compared to simpler protocols.