No session timeout

To allow clients to permanently connect with legacy medical applications and systems that do not have keepalive or auto-reconnect features, the session timeout can be set to never for firewall services, policies, and VDOMs.

The options to disable session timeout are hidden in the CLI.

To set the session TTL value of a custom service to never:
config firewall service custom
    edit "tcp_23"
        set tcp-portrange 23
        set session-ttl never
To set the session TTL value of a policy to never:
config firewall policy
    edit 201
        set srcintf "wan1"
        set dstintf "wan2"
        set srcaddr "all"
        set dstaddr "all"
        set action accept
        set schedule "always"
        set service "TCP_8080"
        set logtraffic disable
        set session-ttl never
        set nat enable
To set the session TTL value of a VDOM to never:
config system session-ttl
    set default never
    config port
        edit 1
            set protocol 6
            set timeout never
            set start-port 8080
            set end-port 8080
To view a session list with the timeout set to never:
# diagnose sys session list

session info: proto=6 proto_state=01 duration=9 expire=never timeout=never flags=00000000 sockflag=00000000 sockport=0 av_idx=0 use=3
class_id=0 ha_id=0 policy_dir=0 tunnel=/ vlan_cos=0/255
state=log may_dirty f00
statistic(bytes/packets/allow_err): org=2290/42/1 reply=2895/34/1 tuples=2
tx speed(Bps/kbps): 238/1 rx speed(Bps/kbps): 301/2
orgin->sink: org pre->post, reply pre->post dev=18->17/17->18 gwy=
hook=post dir=org act=snat>
hook=pre dir=reply act=dnat>
pos/(before,after) 0/(0,0), 0/(0,0)
misc=0 policy_id=9 auth_info=0 chk_client_info=0 vd=1
serial=00000b27 tos=ff/ff app_list=0 app=0 url_cat=0
sdwan_mbr_seq=0 sdwan_service_id=0
rpdb_link_id = 00000000 ngfwid=n/a
dd_type=0 dd_mode=0
npu_state=0x000001 no_offload
no_ofld_reason:  disabled-by-policy
total session 1