Why does HotAdd mode use network?

[readie]

I am investigating some performance issues, and am puzzled by this. When I look at the Bottleneck figures, I am getting
Source 0%
Proxy 21%
Network 94%
Target 99%

I was expecting the Target to be the bottleneck (it's the target iSCSI SAN which is the focus of my investigation at the moment) but in HotAdd mode, why is there any network figure at all? My understanding was that both the source VHD and the target replica VHD are connecting directly to the Veeam Server as VHDs. I can see this happening in VSphere. So what traffic is going over the network?
Does this figure actually refer to the iSCSI network, or what? Looking at the figures (we are getting pathetic 6MB/s at the moment, but we are pretty certain that is down to the change to a different iSCSI SAN) I find it difficult to believe that any network component is running at 94%, even though we are using only 1GB (not10 - yet!).
Thanks for any clues, or explanation to improve my understanding.
Bob

[foggy]

During replication, data read from the source datastore and processed by the source proxy is then transferred to the target proxy to be written to the target datastore. "Network" here refers to the connection between source and target proxy servers. Since (as I can get from your post) you have both source and target proxies deployed on the same server (Veeam B&R console), I would not pay much attention to the value shown for it. The main goal of the bottleneck analysis is to show the weakest point in the chain and in your case it is clearly the write speed to target storage.

[readie]

Thanks. That's clarified.