HubDiscovery » History » Revision 5
Revision 4 (Alex Afanasyev, 03/05/2014 07:57 AM) → Revision 5/8 (Alex Afanasyev, 03/05/2014 08:35 AM)
# NDN hub discovery procedure When an end host starts up, or detects a change in its network environment, it MAY use this procedure to discover a local or home NDN router, in order to gain connectivity to [the NDN research testbed](http://named-data.net/ndn-testbed/). ## Overview This procedure contains three methods to discover a NDN router: 1. Look for a local NDN router by multicast. This is useful in a home or small office network. 2. Look for a local NDN router by DNS query with default suffix. This allows network administrator to configure a NDN router for a large enterprise network. 3. Connect to the home NDN router according to user certificate. This ensures connectivity from anywhere. ## Stage 1: multicast discovery ### Request The end host sends an Interest over a multicast face. Interest Name is `/localhop/ndn-autoconf/hub`. ### Response A producer app on the HUB answer this Interest with a Data packet that contains TLV-encoded `Uri` block. The value of this block is the URI for the HUB, preferrably a UDP tunnel. ## Stage 2: DNS query with default suffix ### Request The end host sends a DNS query that is equivalent to this command: dig +search +short +cmd +tries=2 +ndots=10 _ndn._udp srv ### Response The DNS server should answer with an SRV record that contains the hostname and UDP port number of the NDN router. ## Stage 3: find home router This stage assumes that user has configured default certificate using http://ndncert.named-data.net/ as described in http://redmine.named-data.net/attachments/download/23/CertificationArchitecture.pptx ### Request The end host loads the default user identity (e.g., ``/ndn/edu/ucla/cs/afanasev``) and converts it to DNS format (see https://github.com/named-data/ndnx/blob/master/csrc/util/ndn-name-dnsifier.py as a reference implemenation). (To get default identity: ``KeyChain::getDefaultIdentity()`` method in ndn-cpp-dev library.) If either loading default user identity or converting to DNS format, the phase finishes with error code. The end host sends a DNS query for an SRV record of name `_ndn._udp.` + user identity in DNS format + `_homehub._autoconf.named-data.net`. ### Response The DNS server should answer with an SRV record that contains the hostname and UDP port number of the home NDN router of this user's site. ## Client procedure 1. Send a multicast discovery Interest. If this Interest got answered, connect to the HUB and abort these steps. 2. Send a DNS query with default suffix. If this query got answered, connect to the HUB and abort these steps. 3. Extract the site-specific part from the default certificate of the user; fail if this cannot complete. Send a DNS query to find home HUB. If this query got answered, connect to the home HUB. Otherwise, fail.