There is a fixed sender window size. This size determines the number of frames (data link layer's protocol data unit) to be sent simultaneously before receiving an ACK. Window size must be greater than 1. Otherwise, it would reduce to stop and wait protocol.
The word निश्चितः indicates that the number of frames is fixed while transmission. However, it is not an absolute number that is fixed. It may vary in different contexts. सु उपसर्गः is added to indicate this "depending upon context". सुनिश्चितः means well defined according to situation.
If we use only 1 as the window size, then this protocol would be called as stop and wait protocol. अनेकः । कोशः is used to mean packet (network layer PDU). In computer-shrIkAnta, खण्डः is used for both frame and packets. It is ambiguous. To overcome this ambiguity, अधि - उपसर्गः is added to indicate that a packet is encapsulated in a frame. In शब्दकल्पद्रुमः, अधि meaning is given as उपरिभागः (upper portion or outside portion). This meaning perfectly suits the encapsulation meaning. The word अधिभू means master or superior. In apte-1890, अधिः over and above. to place over or at the head. This suits the meaning of overhead. परि - उपसर्गः may also be used as the meaning will be to cover. This needs more thought.
The meaning of transmission is captured by प्रसारः ।
Always policy and mechanism are interlinked in any system. Often, the word protocol is synonymously used with policy which compels us to analyze the nature of protocol of being more close to a policy or a mechanism. In the context of sliding window protocol, the requirement or policy is to transmit multiple frames successfully. The mechanism would be to use sequence numbers, a sliding window and so on. Therefore, although the line between policy and mechanism is blurred in the context of this protocol, we can largely observe that the details of how the policy needs to be implemented are mentioned in the protocol. Therefore, one may argue that this protocol is more close to a mechanism rather than just a policy. The near Sanskrit translation of policy would be नियमः and of mechanism would be विधिः ।
Thank you for observing such potential in this method of defining Sanskrit equivalents for technical terms.
I recall a dictionary specially written for technical terms. https://sanskritdocuments.org/dict/English-Sanskrit_Computer_Dictionary.pdf
This work by Shri. Shrikanta Jamadagni involves huge effort and deserves much appreciation.
Although, such a treatise is already in place, we can always add new terms and their Sanskrit equivalents that are either not found in the existing work or seem like needing a makeover.