How to configure DSCP ?

[hloudes]

Hello everyone,

Following the latest release of Corosync, the totem.ip_dscp option was introduced. I would like to explore this feature and have implemented it on a 4-node cluster as follows:

I modified the /etc/corosync/corosync.conf file by adding
ip_dscp: 48 to the totem section. After that, I restarted the service because the logs indicated that this setting is not applied on the fly.

Next, I captured packets at the VLAN subinterface, the bridge, and the bond. None of these tcpdump captures showed my DSCP value of 48; strangely, it is set to 4.



Is there any official documentation from Proxmox on how to use DSCP with Corosync?

Thank you in advance.

 

[YaZoal]

Could it be due to the internal bit shift [0]?

ip_dscp This specifies the dscp (differentiated services code point) value to be used in the IP header's type of service (TOS) field according to RFC 2474. Allowed values are 0-63 and symbolic dscp names cs0, cs1, cs2, cs3, cs4, cs5, cs6, cs7, af11, af12, af13, af21, af22, af23, af31, af32, af33, af41, af42, af43 and ef. Value 0 disables the dscp support. Use of TOS field then depends on the used transport. If ip_dscp is set to a value not equal to zero, and an appropriate socket option (IP_TOS) is available, the value is put into the upper six bits of the TOS header field.

Could you test with ip_dscp 12? Remember to increase the config_version [1].

[0] https://manpages.debian.org/unstable/corosync/corosync.conf.5.en.html#ip_dscp
[1] https://pve.proxmox.com/pve-docs/pve-admin-guide.html#pvecm_edit_corosync_conf

 

[hloudes]

Of course, I had already increased the config_version.

I ran the test again with a value of 12. As you can see in the screenshot, Corosync does take the configuration into account, but when I look at my dump, I still see the same thing...