I’m using Realport on a Digi One SP. Using Wireshark I’ve noticed that the Digi One appears to send some sort of a keepalive to the client (the client is running on Debian). The client responds with a TCP ACK, and that completes the keepalive. This happens every 10 seconds. This happens even if I unplug the Digi One serial cable, so that is why I’m pretty sure this is some sort of a Digi keepalive.
Is there a way to turn this down? The Digi is running over an LTE network and I want to dramatically reduce bandwidth usage. As it is, these keepalives use about 2 MB per day.
edit: Just read in the documentation about this keepalive, and yes indeed this is the cause. The documentation recommends to consider using TCP keepalives instead. I’ve read the section on TCP keepalives, but I’m interested in getting you guy’s take on what would be best practice, considering I’m trying to limit bandwidth usage over the cellular network, but also obviously want the Digi One to be reliable.
edit 2: So I disabled both realport keepalives AND TCP keep alives for fun, but I’m now getting a keepalive every 20 seconds. I understand I probably want TCP keepalives of some sort, but I’m just trying to test the behavior. Below is my config:
Digi One SP Version 82000774_W1 02/16/2016
set config dhcp=off
set config myname=“” domain=“”
set config ip=192.168.10.2 submask=255.255.255.0
set config gateway=192.168.10.1
set config realport=771 sockets=2000 redirect=ignore tbreak=std
set config optimize=throughput
set keys prevcmd=^P nextcmd=^N forwchar=^F backchar=^B
set config boothost=0.0.0.0 bootfile=“” tftpboot=no
set config pmtelnet=off
set config rpexclusive=off
set config rpkeepalives=off
set config cache_dns=on
set ethernet speed=auto duplex=half
set config rarp=on
set config ping-arp=on
set tcpip keepalive_active=off keepalive_idle=02:00:00 keepalive_byte=off
set tcpip probe_cnt=5 probe_interval=30
set tcpip tcp_ttl=64 ip_ttl=64
set tcpip rto_min=100 rto_max=240
set tcpip garp=3600 arp_ttl=1200
set profile range=1 profile=realport
set line range=1 parity=N csize=8 error=ignore
set line range=1 baud=9600 stopb=1 break=ignore inpck=off istrip=off onlcr=off otab=off
set flow range=1 ixon=off aixon=off ixoff=off ixany=off itoss=off altpin=off forcedcd=off
set flow range=1 dtr=off cts=off dcd=off dsr=off
set flow range=1 ri=off
set flow range=1 pre-delay=0 post-delay=0
set flow range=1 rts=off
set keys range=1 xon=^Q xoff=^S xona=^Q xoffa=^S lnext=^V
set port range=1 dev=rp sess=4 termtype=“vt100” edelay=1 auto=off bin=off
set port range=1 uid=none group=none dport=none
set port range=1 dest=none
set port range=1 scriptname=none
set port range=1 keepalive=off flushstchar=default autoservice=default
set port range=1 autodrain=off
set port range=1 idletime=0