NS service

1. About

TL;DR

The Domain Name System (DNS) is the naming system used to identify computers reachable through the network. It maps human-friendly domain names to the numerical IP addresses computers need to locate each other.

Note: The NS service consists of authoritative nameservers only, for recursive resolvers see DNS service instead.

2. Systems

2.1 Frontend

FQDN IPv6 IPv4
ns.bfh.info
ipv6.ns.bfh.info
ipv4.ns.bfh.info

2.2 Backend

Warning
Always use the frontend DNS record

Never use the backend nodes directly:

  • backend may change without notice at any time (e.g. IP addresses, DNS records, configuration, etc.)
  • backend has no legacy support or grace periods, changes are implemented instantly
  • backend can be rebootet without notice at any time
  • backend access will soon be restricted

FQDN IPv6 IPv4
node1.ns.bfh.info 2a07:6b40::21 147.87.0.21
node2.ns.bfh.info 2a07:6b40::22 147.87.0.22
node3.ns.bfh.info 2a07:6b40::23 147.87.0.23
node4.ns.bfh.info 2a07:6b40::24 147.87.0.24
FQDN IPv6 IPv4
ns.bfh.info 2a07:6b40::20 147.87.0.20
node1.proxy.ns.bfh.info 2a07:6b40::26 147.87.0.26
node2.proxy.ns.bfh.info 2a07:6b40::27 147.87.0.27
node3.proxy.ns.bfh.info 2a07:6b40::28 147.87.0.28
node4.proxy.ns.bfh.info 2a07:6b40::29 147.87.0.29
FQDN IPv6 IPv4
mdns.bfh.info 2a07:6b40::100 147.87.0.100
node1.mdns.bfh.info 2a07:6b40::101 147.87.0.101
node2.mdns.bfh.info 2a07:6b40::102 147.87.0.102
FQDN IPv6 IPv4
ddns.bfh.info 2a07:6b40::110 147.87.0.110
node1.ddns.bfh.info 2a07:6b40::111 147.87.0.111
node2.ddns.bfh.info 2a07:6b40::112 147.87.0.112

3. Features

3.1 Protocols

  • DNS (UDP/TCP) on port 53 (frontend and backends)

  • DNS over TLS on port 853 (frontend only)

  • DNS over HTTPS on port 443 (frontend only)

3.2 ACLs

  • queries are accepted from everywhere

  • zone transfers for all local zones are accepted from 2a07:6b40::/29, 147.87.0.0/16 and 10.0.0.0/8 only, everything else is denied (!= drop)

  • DDNS is accepted from dhcp.bfh.info nodes and Microsoft Active Directory

3.3 TTL, Cache

  • global TTL of 1m for all zones

  • queries to frontend are not cached on purpose

  • queries to frontend for own zones are not cached on purpose and are directly forwarded to NS servers

3.4 Forwarding

  • forwarded queries to authoritative backend are based on least outstanding connection count

3.5 Details

  • both frontend and backends use SO_REUSEADDR and SO_REUSEPORT

  • DNS cookies are renewed every 24h, bad cookies are set to (until enabling RRL) no query being slipped

4. Backlog

4.1 Legacy

  • 2023: remove node{5,6}.ns.bfh.ch (carrying bfh.ch zone only)

  • 2023: add node{5,6}.ns.bfh.info (carrying all zones)

4.2 Features

  • 2023: autoincrement serial on mdns.bfh.info

  • 2023: moving dnsdist webfrontend behind apache with ldap auth

  • 2023: restricting backend subnet access to frontend and management only

  • 2023: verify if enabling auto_reverse (#576) on mdns.bfh.info is a good idea

  • 2023: static rate limiting

  • 2023: enabling DNSSEC

  • 2023: anycasting ns.bfh.info

  • ????: benchmarking

4.3 Known issues

  • no known issues