HubDiscovery » History » Version 4
Alex Afanasyev, 03/05/2014 07:57 AM
| 1 | 3 | Junxiao Shi | # NDN hub discovery procedure |
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| 2 | 1 | Alex Afanasyev | |
| 3 | 3 | Junxiao Shi | 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/). |
| 4 | 1 | Alex Afanasyev | |
| 5 | 3 | Junxiao Shi | ## Overview |
| 6 | 1 | Alex Afanasyev | |
| 7 | 3 | Junxiao Shi | This procedure contains three methods to discover a NDN router: |
| 8 | 1 | Alex Afanasyev | |
| 9 | 3 | Junxiao Shi | 1. Look for a local NDN router by multicast. |
| 10 | This is useful in a home or small office network. |
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| 11 | 2. Look for a local NDN router by DNS query with default suffix. |
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| 12 | This allows network administrator to configure a NDN router for a large enterprise network. |
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| 13 | 3. Connect to the home NDN router according to user certificate. |
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| 14 | This ensures connectivity from anywhere. |
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| 15 | 1 | Alex Afanasyev | |
| 16 | 3 | Junxiao Shi | ## Stage 1: multicast discovery |
| 17 | 1 | Alex Afanasyev | |
| 18 | 3 | Junxiao Shi | ### Request |
| 19 | 1 | Alex Afanasyev | |
| 20 | 3 | Junxiao Shi | The end host sends an Interest over a multicast face. |
| 21 | 1 | Alex Afanasyev | |
| 22 | 3 | Junxiao Shi | Interest Name is `/localhop/ndn-autoconf/hub`. |
| 23 | 1 | Alex Afanasyev | |
| 24 | 3 | Junxiao Shi | ### Response |
| 25 | 1 | Alex Afanasyev | |
| 26 | 3 | Junxiao Shi | A producer app on the HUB answer this Interest with a Data packet that contains TLV-encoded `Uri` block. |
| 27 | The value of this block is the URI for the HUB, preferrably a UDP tunnel. |
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| 28 | 1 | Alex Afanasyev | |
| 29 | 3 | Junxiao Shi | ## Stage 2: DNS query with default suffix |
| 30 | 1 | Alex Afanasyev | |
| 31 | 3 | Junxiao Shi | ### Request |
| 32 | 1 | Alex Afanasyev | |
| 33 | 3 | Junxiao Shi | The end host sends a DNS query that is equivalent to this command: |
| 34 | |||
| 35 | dig +search +short +cmd +tries=2 +ndots=10 _ndn._udp srv |
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| 36 | |||
| 37 | ### Response |
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| 38 | |||
| 39 | The DNS server should answer with an SRV record that contains the hostname and UDP port number of the NDN router. |
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| 40 | |||
| 41 | ## Stage 3: find home router |
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| 42 | |||
| 43 | 4 | Alex Afanasyev | 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 |
| 44 | |||
| 45 | 3 | Junxiao Shi | ### Request |
| 46 | 1 | Alex Afanasyev | |
| 47 | 4 | Alex Afanasyev | 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). |
| 48 | 1 | Alex Afanasyev | |
| 49 | 4 | Alex Afanasyev | If either loading default user identity or converting to DNS format, the phase finishes with error code. |
| 50 | |||
| 51 | 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`. |
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| 52 | 3 | Junxiao Shi | |
| 53 | ### Response |
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| 54 | |||
| 55 | 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. |
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| 56 | |||
| 57 | ## Client procedure |
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| 58 | |||
| 59 | 1. Send a multicast discovery Interest. |
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| 60 | If this Interest got answered, connect to the HUB and abort these steps. |
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| 61 | 2. Send a DNS query with default suffix. |
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| 62 | If this query got answered, connect to the HUB and abort these steps. |
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| 63 | 3. Extract the site-specific part from the default certificate of the user; fail if this cannot complete. |
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| 64 | Send a DNS query to find home HUB. |
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| 65 | If this query got answered, connect to the home HUB. Otherwise, fail. |