RoE and the control channel
Folks,
We had some initial discussion way back on the control channel associated with the RoE traffic. My initial proposal was to reserve one RoE packet type for the control messages. These control messages would carry TLVs instead of a data blob and be interleaved in between "normal" RoE packets carrying sample data.
The use cases for the control channel would be e.g. negotiating parameters during the link setup, carrying auxiliary data/information along with the antenna carriers and doing periodic data path measurements (whatever that then would be). I would assume the spec to have a minimal set of TLVs defined, e.g. for native RoE link setup and CPRI mapper purposes. Some TLVs would just be containers, since we e.g. have no idea (and will not go there) how antenna carrier related control data is structured or functions.
It is expected that the size available for a periodic control packet is small (see example below). That implies we should then think of a way to interleave TLVs over multiple packets. Here I would copy-with-pride the recent solution that was done for interleaving attributes over multiple RADIUS packets ;)
I have also thought about optional opaque control field in the header (a flag would indicate its presence). However, I am not really a great fan of such since it would mean a varying size header etc.
Comments/thoughts?
- Jouni
-- additional stuff --
A quick _example_ calculation/arrangement (assuming 8x 20MHz carriers, 10G link, 256 bytes payload and 802.1Q support), the control channel would have ~660Mbps bandwidth. A control packet is sent every 8x Tc so I am essentially queuing 8 packets to gain space for additional data (~172 bytes worth per packet). If I need to send longer control packets I would need pre-emption support or queue more or interleave my data over multiple packets.
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Jouni Korhonen, CTO Office, Networking, Broadcom Corporation
O: +1-408-922-8135, M: +1-408-391-7160