The OpenWrt 18.06 series focuses on support for network flow offloading and modernizing the Atheros AR71xx target.
Ok, I try to get into "network flow offloading" later. But is there some more detailed information regarding "modernizing the Atheros AR71xx target."? What does it mean in detail?
I am wondering if I should rather use my Archer C7 instead of the R7800 - if there are massive improvements for the AR71 target?
This mean the ar71xx target get replaced with the ath79 target in the near future...
The ar71xx taget does use c code (mach files) to setup the board / device specific hw and the new ath79 target does use a device tree based description of the hw.
The main bad part in mach files is that the code for every target is included in every image and does eat ram and flash.
With the device tree description it is possible to append only the needed description for the device and does save ram and flash.
Apart from that, to get support for a target upstreamed to the linux code it is necessary to use a device tree based description of the hardware because mach files aren´t accepted anymore in linux source code...
The Archer C7 v2 is already ported to the ath79 target and in the community build section i´ve created "beta" images for some ath79 devices...
I think that it is a leftover placeholder, as ath79 didn't make it to the 18.06 series at all.
Work on ath79 continues in master, but not in 18.06
I don't quite get what you mean with this question. Yes, ath79 will provide flow-offloading for the archer c7 (something that's already present for ipq806x today), but other than that, the r7800 offers vastly faster hardware than any hardware revision of the archer c7.
The r7800 is a 1.7 GHz ARMv7 dual-core SOC with 512 MB RAM and 128 MB flash, without flow-offloading it should be good for 350-400 MBit/s WAN throughput. Software flow-offloading should extend this even further, and there's still the possibility that the two additional 800 MHz NSS cores might provide hardware flow-offloading on top (if that were possible and integrated into OpenWrt master, it should be good for 1 GBit/s linespeed).
The archer c7 is an old 720 MHz mips single-core SOC, offering 128 MB RAM and 16 MB flash. On its own, without flow-offloading, it will top around 150 MBit/s WAN throughput, obviously flow-offloading in ath79 will improve that (and yes, there is also a little improvement to be hoped for with the DSA drivers and potential hardware offloading), but it won't be able to get even close to the r7800.
Both devices are well supported and should continue to work with OpenWrt for quite a while to come, the r7800 is just a massively faster and more current design with more options for future, but if your WAN connection is below ~100 MBit/s and assuming you don't expect much in terms of additional services (SQM, VPN, etc.) the archer c7 should be fine as well.
I think this isn´t true... mips based devices are very good in networking performance... My WDR3600 does reach about 550 MBits (no pppoe) without flow offloading and with flow offloading i get about 920 MBits...
I'm testing with a tl-wdr4300 (so exactly the same device as your tl-wdr3600, except for the 2.4 GHz wlan card) on a 100/40 MBit/s VDSL2 connection with PPPoE. The tl-wdr4300 can cope with that, but when maxing out the connection (no sqm, no active vpn sessions, nothing special except for adblock), there are load spikes that hit the limit of the SOC (idle=0%) and base utilization under load in the upper quarter. That's why I'd put the maximum WAN-to-LAN throughput (with PPPoE) at roughly 150 MBit/s without flow-offloading - depending on your expectations (latencies) you might stretch that a little, but that's around the most I'd be comfortable as 'advertising' for this 560 MHz AR9344 SOC (and yes, in a direct comparison ipq8065/ ng6817 is more snappy), the archer c7 is a bit faster (clocking between 720 (v2, QCA9558) and 750 MHz (v4-5, QCA9563)) which will improve the situation a bit further.
Feels like some people here have some more detailed information - very nice & thanks for your help & answers!
Interesting, how can I learn about that / read about such information?
The device family pages on openwrt.org do not seem to be up to date.
https://openwrt.org/docs/techref/targets/ipq806x (not exist)
https://openwrt.org/docs/techref/targets/ar71xx (don't refer to 79)
Also, ath71 and ath79 seems to be a freely chosen name for a family, I thought it is somehow related to processor / hardware piece names.
Regarding WAN speed: I have rarely experienced more than 5-6 MB/sec on WAN in home networks. Even at work it might be about 30-40 MB / sec with fast servers like at GCP. LAN can be faster / higher ok, but for WAN, I haven't seen lots of that fast servers.
@slh this is why these two models are the same good for me - whereas I got the R7800 as a backup router.
But I also like to be prepared for connection improvements...
I am monitoring the commits logs at git repos, pull requests and the discussions on the developer mailing list.
(ath79 was removed from the 18.06 source repo at the branching, so I find it hard to believe that it would be restored into the branch. Of course, it is possible that it could be backported back after further development in master and included in a later 18.06 service release.)
seems to me, wan-speeds have reached a point where it would be more sensible to express performance in Packets per Second rather than MBit/s?
also it there seems to be a severe performance cost when using pppoe (there are other reports in forums). maybe someone could look into that.
I've updated both a Archer C7 v2 and a WDR4300 v1 to the 18.06 and now 18.06.1 and I feel as if they are less reliable than they were on 17.04. I'm not sure if this is hardware related or not at this point, but since the beginning of August I've had to power cycle them each twice. On 17.04 I think they were power cycled once total.
I'm not sure how to inspect this to clarify, so if anyone has input on how I can do that I would love to hear.
Edit:
Turns out I had an error in my networks DHCP setup. Fixed and will report back if the problems persist.
Yep, have to stick up for our old C7's... I have a 300/30mbit cable connection, and not running anything out of basic router operation, (well, firewall and NAT) I would see speeds of up to 340-350mbit, on eth out, when the cable was in a good mood, running LEDE 17.xx.x. No 0% idle, either, so it could handle more.
With SQM though, that takes things down a notch. 130-140mbits over the eth, maybe 110-120mbits thru the AC WiFi. It will pass a lot more with SQM on, (and at questionable SQM quality) but has to be throttled down to those numbers to stay above 0% idle. So, the ol' girl has a bit more horsepower than you think. 
Think I had 130 days uptime on 17.04, ended by a power failure, not me, so I know what you mean!
Currently, I'm also having issues with 18.06.1, seeming to have higher loads than expected, not able to do half of the above mentioned performance. Not sure what's wrong. Having other odd issues as well, probably try a reflash. Started a thread on that elsewhere, specific to 18.06.1 and C7, loading down and network speed. We've drifted off this thread, though, discussion on that should probably go over to mine.