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.

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.