There's a few things going on...
Crashplan on Synology NAS
I blogged about setting DSCP values for Crashplan traffic on a Synology NAS, but in short you can set the TOS or DSCP value of upload traffic using the Crashplan GUI. However, there are some serious bugs in the QoS settings available:
- Setting 'Low' does nothing.
- Setting 'Normal' does nothing.
- Setting 'Reliability' gives a TOS hex value of 0x4 (equivalent to DSCP decimal value of 1).
- Setting 'Throughput' gives a TOS hex value of 0x8 (equivalent to DSCP decimal value of 2).
Worst of all, setting your own 'DSCP decimal value' via the gui, is completely incorrect. What it actually does it set the TOS decimal value instead. So:
- Setting a 'DSCP decimal value' of '40' will actually give you a DSCP value of 10
- Setting a 'DSCP decimal value' of '48' will actually give you a DSCP value of 12
So, it's all pretty screwed up, but you can make it work.
These finding were using a Synology DS415play. I'm assuming you're using the package from PCLoadLetter.co.uk.
Routers
I'm not entirely clear on your setup but ultimately you need to act upon your outgoing traffic at the router. The technicolor router doesn't support QoS at all so forget about that. If you can just use the DDWRT router instead, you could set the QoS on that to de-prioritize DSCP 10 traffic (i.e. you set it to '40' in crashplan), and job done. I' don't have a DDWRT based router, but I have blogged about setting this up on a Draytek Router.
Bridge mode
If we assume you have to keep the Technicolor router connected to the WAN for some reason, you could still use the DDWRT router to perform QOS prioritization, either by putting the Technicolour router in 'bridge' or 'modem' mode (usually the same thing) and then connecting output of that to the WAN port on the DDWRT.
....OR....
Double NAT
Leave the Technicolor router doing normal NAT, and connect the LAN port to the yellow WAN port of the DDWRT router, giving you a 'double NAT' situation. So long as you connect all you lan devices to the DDWRT router, you can largely forget about the Technicolor router upstream. This router can then prioritize all the traffic channelled through it to its WAN port. Its important to realise that anything left connected to the upstream Technicolor router will bypass QOS.