My question is in relation to the file transfer protocol SCP. I have a local time sensitive network built. In time sensitive network you can give priority to traffic by vlan tagging and assigning priority 0-7. My question is if you have a saturated network can you vlan tag SCP traffic so that if you transferring very large files then these would get priority?
Depending on your switch models, you may be able to use COS to prioritize different traffic. Remember that VLAN tags are only used on trunk links, which are normally between switches, not to end-devices.
When using QoS, you usually give large file transfers the lowest priority. Typically, you want real-time traffic, such as VoIP, to have the highest priority, then network control protocols, e.g. routing protocols or VoIP control, to have the next highest priority, then normal traffic, and large file transfers the lowest priority.
Layer-2 QoS is usually pretty limited (switches have tiny buffers that are easily overrun, and most business switches will switch at wirespeed). Your biggest QoS bang for the buck is shaping, queuing, and policing on routers, but that only happens when sending traffic from one network to another network.
The first thing you want to look at in you switched layer-2 network is the bandwidth oversubscription ratio. If you have a 1 Gbps traffic flow from one device to another on the same switch, then you have no problem, but if you add a second 1 Gbps flow to the same target device, then you need a connection larger than 1 Gbps to the target device, otherwise you will drop half your traffic, regardless of QoS (QoS cannot create bandwidth, only manage fairness). Between switches, you want to have faster connections than the aggregate of the access connections, but it can get very expensive to have a 1:1 access to distribution bandwidth ratio.