Add SCTP SACK Delay parameter

[RafalArciszewski]

Enhancement Proposal

Please consider adding possibility to change SCTP SACK Delay (or other SCTP parameters). Currently our gnb is retransmitting the message after 120ms because SACK was not delivered quick enough.

other parameters I can think of are: heartbit_interval ,rto_initial,rto_min rto_max,max_num_of_ostreams max_num_of_istreams.

[gruyaume]

Hello @RafalArciszewski , thank you for proposing this feature. We'll consider it, but my preference would be for reasonable defaults that work for most people. Most users won't want to play with these knobs.

[RafalArciszewski]

The SCTP config much depends on RTT in the network, number of multihome paths etc.. sto there will always be the need for an "expert mode" :)

I can change sctp_rto_min the gnb config, but what is Ellacore's SACK delay timer default vaule? Is it taken from linux stack?

Below is default template for srsran

https://docs.srsran.com/projects/project/en/latest/user_manuals/source/config_ref.html

srsran config:
    sctp_rto_initial: 120                 # Optional INT. Sets the initial retransmission timeout when creating the SCTP connection.
    sctp_rto_min: 120                     # Optional INT. Sets the minimum retransmission timeout for the SCTP connection.
    sctp_rto_max: 500                     # Optional INT. Sets the maximum retransmission timeout for the SCTP connection.
    sctp_init_max_attempts: 3          # Optional INT. Sets the maximum retransmission attempts for the initial SCTP connection.
    sctp_max_init_timeo: 500              # Optional INT. Sets the maximum retransmission timeout for the initial SCTP connection.
    sctp_hb_interval: 30000               # Optional INT (30000). SCTP heartbeat interval in milliseconds (-1 to use system default).
    sctp_assoc_max_retx: 10               # Optional INT (10). SCTP association max retransmissions (-1 to use system default).
    sctp_nodelay: false                   # Optional BOOLEAN. Setting to true allows the gNB to send SCTP messages as soon as possible without any Nagle-like algorithm. Supported: [false, true].