Good day bind experts -
Please can anyone advise the best way to optimize named's UDP timeout settings for caching-only local resolver usage over a slow network link - I can't seem to find any in the Bv9ARM document specifically describing how named implements UDP re-transmits - please could someone point me at the right pages or place to look, besides the source code, which I am reading now, if there are any ? My problem is that at home my whole internet goes through one 100M CAT-6 ethernet cable to a GSM 3G/4G modem (90% 3G WCDMA) , it seems no more than about 128 kilobyte/sec download & less upload bandwidth is available, whenever my browser decides to download something large (like a JavaScript blob) , then DNS requests start timing out, the browser keeps re-issuing its requests, and similar nasty feedback situations occur when the GSM modem's DHCP lease expires and it has to re-setup its NAT for the ethernet link, so all UDP requests time out for about 10 seconds, building up quite a backlog. I have tried playing around with named.conf settings: resolver-retry-interval 8; resolver-retry-time 32; max-retry-time 32; but they don't seem to help - I still get a 'DNS freeze' situation for about 10-30 seconds when the GSM modem renegotiates its DHCP lease, during a yum / dnf 'update', during large browser downloads or stream playing ... My Linux v5.12.17 (Fedora-34) x86_64 box runs named 9.6.18 from the Fedora RPM, and hosts a Windows 10 VM, which is quite a chatty DNS user, and runs a hostapd instance through which traffic from a local network of 3 Android mobile phones use as their default data connection, which also use the laptop's DNS server, and send SIP voice traffic through my company's SIP server which I maintain , so the Linux box does NAT for the Windows VM and for the Android mobile clients, the laptop named instance serves authorative zones for my localhost, local VMs and DMZ Android Mobile phone units, and ALL hosts, including the windows host, use BIND named running on the Linux laptop gateway, which is the default route endpoint for all hosts, and which has a 'forwarders { ... };' clause in named.conf containing my Cellular Network provider's DNS server IP addresses . These remote Cellular DNS servers can respond very slowly at peak internet usage times. It is nice to be able to see all packets from the android mobile phones with tcpdump, and to be able to receive the voice traffic that they send to our cloud SIP server (which I can see being NAT-ed), and the SIP server sends back, which get NAT-ed to the Windows VM Dispatcher and audio playback GUI running on the laptop which I also maintain . My BIND named server also implements an RBL blacklist kindly made available as a hosts file, which I convert to a Response Policy Zone file, at https://someonewhocares.org/hosts . DNSSEC is also enabled by default. My named.conf has a clause: allow-query { localhost; 192.168.W.0/24; 192.168.M.0/24; 192.168.V.0/24; }; where W is Windows VM network, M is mobile device network, and V is my corporate L2TP/IPSEC VPN network, also doing NAT, and one 'localhost-resolver' "View" with match-clients { /* same as above */ } ; and recursion yes; This setup works great on a normal office LAN , where there are multiple hops to the internet available, but not on my home slow single ethernet connection to the whole ethernet, through a modem that must peridically renegotiate a DHCP lease. When the modem renegotiates its DHCP lease every hour, I typically have to restart named and hostapd . I just want named to notice that the response times to the forwarders are increasing , and to increase its number of UDP re-transmit attempts and timeout time (time between attempts ) accordingly, and vice versa (decrease them back to defaults when forwarder responsiveness improves). Before I start hacking the named udp.c server code , please could anyone advise if there are ways through configuration settings to adjust the named UDP re-transmit timeout & number of attempts strategy for slow networks ? I can't believe there aren't any ? Thanks in advance for any informative replies, Best Regards, Jason Vas Dias _______________________________________________ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users