Pause Frames

[adairw]

Noticed tonight that on the trunk port of a WS-12 there are a few hundred thousand TX pause frames that have gathered in two days of up time. This trunk port carries the management VLAN's for the AP's and the Customer traffic VLAN's to and from the mikrotik router.
The router shows the exact same number of RX pause frames.

So the switch is telling the router to slow down, right? for the switch to do that wouldn't/shouldn't it need to be receiving pause frames from the AP's? I checked all eight of the AP's port stats on the WS and none of them show any RX pause frames.
Six of the eight AP's are RM5-Ti's, linked up and 1Gb and showing flow control is enable. The uplink port to the router is also 1Gb/Full with flow control enabled, as indicated by the switch.

What gives?

Here is the only "gotcha". The entire network is routed. BUT we use VPLS tunnels for the customer traffic back to the core.
So I've always been confused about where that leaves us in the pause frame game. Technically it's layer 2 from the CPE to the Core. But the we use port isolation and split horizon bridging on the tik to only let traffic flow between the customer and the core. not between customer and customer, etc. So there is no routed interface to stop the pause frames until it gets to the core.
When I look at the back haul to the core (this site is one hop out over a exalt g2 11ghz link), there is a WS on both sides. neither side of the link show pause frames either TX or RX. The ports on the switch show the radio doesn't have flow control turned on. in fact neither does the router on the port facing that radio in the core. (the MPLS router)

There is another leg of the network I was watching that has the exact same setup, WS on both sides, G2 11Ghz link in the middle and flow control is on everything. This site is only running VLANS between it and the core. The backhaul shows lots of RX and TX pause frames but nothing on the AP ports.

I'm confused.

[sirhc]

The pause frames will not be on the AP port but will be on the port facing the router.

The port facing the router should have Tx Pause Frames as the switch is telling the router to slow down. The router should have Rx pause frames.

We talked about this many times, do a search for pause frames here on the forums.

But the packets going to the AP over run the AP port buffers and the switch sends a Tx Pause frame to the router which you will see on the port facing the router not the port the AP is plugged into it.

Read this entire thread: viewtopic.php?f=17&t=671&hilit=pause+frame

[sirhc]

You can also go watch this video and I discuss pause frames in pretty good depth and how I deal with them as far as separating bachhaul ports from AP ports

https://www.youtube.com/watch?v=8JvBEAD4MFM

[adairw]

Thanks Chris.
I've read most of it and watched the video. Maybe I need to go refresh.