Finding neighboring mesh nodes

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Assumptions

  • There is at least one mesh node.
  • Meshes are not built through collusion, i.e., each person setting up a node does not do so knowing that others are as well.
  • Mesh nodes are able to broadcast the existence of services they run ("I run a microblog!")
  • Services can be activated on a node (implying that their presence will be announced) or deactivated (implying that their presence will not be announced)
  • Mesh nodes continually listen for announcements of services from neighboring mesh nodeds
  • Mesh nodes maintain directories of services running on neighboring mesh nodes
    • ...except when a service is designed to automatically federate with others of a like type (i.e., announcements of content from one will automatically be incorporated into cached announcements on the node)
  • Clients neither broadcast nor listen for service announcements
    • Smartphones
    • MP3 players
    • Computers not running Byzantium

Existing protocols

  • Avahi/ZeroConf/mDNS
  • Included in Porteus Linux
    • Host can publish running services
    • Host can be informed of services running on other hosts
    • User does not have to specifically configure any of this
    • Host admins may have to configure this
    • Bindings for multiple languages are available
    • Protocol in a nutshell:
      • Ad-hoc DHS over IP multicast (224.0.0.251, port 5353/UDP)
      • Each node has a resource record for each service
        • SRV
        • TXT
        • PTR
        • Types documented in /usr/share/avahi/service-types on Windbringer. File is part of Avahi on all systems.
          • HAS NOTHING TO DO WITH dnsmasq!
    • Resolution is done by the host running an Avahi implementation - broadcast a resolution request to the multicast domain and listen for a response
    • Node needs to have its hostname set (machinename.local)
    • Ignores point-to-point links by default. Add "allow-point-to-point=yes" in avahi-daemon.conf
      • Do mesh interfaces have the POINTTOPOINT flag?
    • wide-area functionality seems relevant to a mesh.
    • deny-interfaces=eth0 in avahi-daemon.conf may be necessary to prevent mDNS traffic from going over gateways.
    • avahi-daemon implements service announcement and listening, and interfaces with Avahi-enabled client apps.
    • avahi-dnsconfd connects to avahi-daemon and keeps track of unicast DNSes detected.
    • Read manage for avahi-daemon.conf!
    • Will need an /etc/avahi/services/foo.service XML file for each service offered by a node.
      • Manpage avahi.service(5) documents all required XML tags.
    • Each mesh node will have a list of all mesh nodes it's heard from in recent memory. This can be used to build the directory of neighboring services.
  • XMPP service discovery
    • Message oriented, based on XML
    • Jabber's protocol.
    • XEP-0030
    • Used for discovering other XMPP entities/services implemented by XMPP servers.
      • Could be used for discovering and federating apps running on other nodes (i.e., distributed microblog).

Notes

  • KDE comes with something called Personal File Server, which allows arbitrary directories to be made available over HTTP(S?). It's Avahi-enabled. KDE is packagedwith Porteus. There's our file dump.
  • avahi-bookmarks allows the user to access HTTP resources with a web browser.
  • nss-mdns should be enabled in /etc/nssswitch.conf.