There are multiple things that might impact the scp transfer. Some of the things that come to mind include:
- is it possible that there are fragmentation issues. Is there perhaps some link along the path with a small MTU that is causing the network devices to fragment (and possibly reassemble) the packets?
- is it possible that along the path that traffic is being tunneled/encapsulated and de-encapsulated which would impact throughput?
- are there problems that are leading to packet drop and re-transmission of packets?
- is it possible that there are more than one path being used to transmit the data and that some packets are delivered out of order and that re-ordering of the packets is leading to re-transmission of data?
- is it possible that something is causing the server to use a small packet size? Would a larger packet size be more efficient for transmission?
I have experiences the same issue with uploading code from a linux SCP server to ASR1002 router. It does take a long time to copy the image to the flash. I have other linux servers sitting on the same network as the ASR router and it takes less than 20 seconds to copy a 300MB file size. With the ASR router, it takes about 30 minutes to copy the file from the scp server to the ASR flash.
I guess it is normal