# Can anyone please help me understand the definition of Store-and-Forward delay from the Kurose and Ross Networking Book?

I have gone through the questions related to store-and-forward and transmission delays but they didn't answer my question. My question is directly related to one of the excerpts in the book (Computer Networking: A Top-Down Approach). Book says:

Store-and-forward transmission means that the switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link. Thus store-and-forward packet-switches introduce a store-and-forward delay at the input to each link along the packet's route. This delay is proportional to the packet's length in bits. In particular, if a packet consists of L bits, and the packet is to be forwarded onto an outbound link of R bps, then the store-and-forward delay at the switch is L/R seconds.

The last line of the above paragraph confuses me as it relates store-and-forward delay to the transmission rate (R bps) of outbound link. As I understand store-and-forward delay is the delay introduced because the switch waits to receive the entire packet before it can be transmitted onto the outbound link. I don't understand how the store-and-forward delay depends on the transmission rate of outbound link. If anything, it should depend on the propagation delay of inbound link (inbound to the switch). What does rate of outbound link has anything to do with switch completely receiving all the bits of the packet?

Can anyone please help me understand this and how my understanding is wrong?

PS: I have read that transmission delay is the time it takes to push the bits of a packet onto an outbound link.

Edited: I read the above definition of transmission delay on wikipedia where it's also stated that transmission delay is same as store-and-forward delay. However, definitions of both seem to vary.

• (What is the propagation delay of inbound link?) Consider the last symbol transmitted. I have read … It would be great if you could tell who originated that and where you came across it - year published welcome. Commented Mar 5, 2022 at 6:10
• @greybeard I read about transmission delay here: en.wikipedia.org/wiki/Transmission_delay. They also consider store-and-forward delay to be the same as transmission delay but their definitions don't seem to be the same to me. Commented Mar 6, 2022 at 17:32