> On Aug 26, 2018, at 8:12 PM, Ted Lemon <[email protected]> wrote:
>
> The timeout isn't the same for DNSSD Registration Protocol.
Ok, this is a little detailed but let's take what the current draft says and be
explicit about your particular SRP case. I think I am representing SRP
correctly but if not, please correct me.
<srp>
[1. One thing that’s not clear about SRP is if the same host registers more
than one service, does your particular form of UPDATE (which isn’t standard
UPDATE) have to contain the same A and/or AAAA records in both registrations
and if so, what is the server to do about different lifetimes?]
[2. Also, does SRP recommend including PTR records for name registrations of A
& AAAA names? It doesn’t appear to but should it?]
[3. I think you’re going to run into trouble having non-standard UPDATE rules.]
(These are separate discussions about SRP for another forum and if you want to
follow up on these, we should follow up on the dns-sd list.)
</srp>
At the end, I’ll do the more simple case of just A & AAAA records.
Let’s assume 3 clients, all with the same service type (different service types
will have different owner names). We will use _ipp._tcp.example.com as an
example.
Client A sends a registration at time Ta with lease life L1a for PTR, SRV, A,
AAAA, TXT records, lease life L2a for KEY record.
Client B sends a registration at time Tb with lease life L1b for PTR, SRV, A,
TXT records (no AAAA), lease life L2b for KEY record.
Client C sends two different instances of the same service (different instance
names) at time Tc with lease life L1c for PTR, SRV, A, AAAA, TXT records, lease
life L2c for KEY record.
Client A’s UPDATE contains:
_ipp._tcp.example.com PTR p1._ipp._tcp.example.com
p1._ipp._tcp.example.com SRV 0 0 631 p1.example.com
p1._ipp._tcp.example.com TXT paper=A4
p1.example.com A 192.0.2.1
p1.example.com AAAA 2001:db8::1
p1.example.com KEY “key material here"
Client B's UPDATE contains:
_ipp._tcp.example.com PTR p2._ipp._tcp.example.com
p2._ipp._tcp.example.com SRV 0 0 631 p2.example.com
p2._ipp._tcp.example.com TXT paper=A4
p2.example.com A 192.0.2.2
p2.example.com KEY “key material here”
2.2.0.192.in-addr.arpa. PTR p2.example.com.
2.0.0.0.0.0.0.0.0.0.0.0.b8.0d.01.20.ip6.arpa. PTR p2.example.com. (using
bytes instead of nibbles for compactness)
Client C's UPDATE contains two services at the same time with the same lease
lifes:
_ipp._tcp.example.com PTR p3._ipp._tcp.example.com
p3._ipp._tcp.example.com SRV 0 0 631 p3.example.com
p3._ipp._tcp.example.com TXT paper=A4
p3.example.com A 192.0.2.3
p3.example.com AAAA 2001:db8::3
p3.example.com KEY “key material here”
_ipp._tcp.example.com PTR p4._ipp._tcp.example.com
p4._ipp._tcp.example.com SRV 0 0 631 p4.example.com
p4._ipp._tcp.example.com TXT paper=A4
p4.example.com A 192.0.2.4
p4.example.com AAAA 2001:db8::4
p4.example.com KEY “key material here”
The TIMEOUT records on the server would look like the following:
(owner_name TIMEOUT count algorithm expire hash_list, count algorithm expire
hash_list, etc.)
_ipp.tcp.example.com TIMEOUT 1 1 Ta+L1a (#hash for p1._ipp._tcp.example.com PTR
record)
1 1 Tb+L1b (#hash for p2._ipp._tcp.example.com PTR
record)
2 1 Tc+L1c (#hash for p3._ipp._tcp.example.com PTR
record) (#hash for p4._ipp._tcp.example.com PTR record)
p1._ipp._tcp.example.com TIMEOUT 0 0 Ta+L1a
p2._ipp._tcp.example.com TIMEOUT 0 0 Tb+L1b
p3._ipp._tcp.example.com TIMEOUT 0 0 Tc+L1c
p4._ipp._tcp.example.com TIMEOUT 0 0 Tc+L1c
p1.example.com TIMEOUT 2 1 Ta+L1a (#hash for 192.0.2.1 A record) (#hash for
2001:db8::1 AAAA record)
1 1 Ta+L2a (#hash for p1.example.com KEY record)
p2.example.com TIMEOUT 1 1 Tb+L1b (#hash for 192.0.2.2 A record)
1 1 Tb+L2b (#hash for p2.example.com KEY record)
p3.example.com TIMEOUT 2 1 Tc+L1c (#hash for 192.0.2.3 A record) (#hash for
2001:db8::3 AAAA record)
1 1 Tc+L2c (#hash for p3.example.com KEY record)
p4.example.com TIMEOUT 2 1 Tc+L1c (#hash for 192.0.2.4 A record) (#hash for
2001:db8::4 AAAA record)
1 1 Tc+L2c (#hash for p4.example.com KEY record)
2.2.0.192.in-addr.arpa. TIMEOUT 0 0 Tb+L1b
2.0.0.0.0.0.0.0.0.0.0.0.b8.0d.01.20.ip6.arpa. TIMEOUT 0 0 Tb+L1b (using bytes
instead of nibbles for compactness)
So, in general, for any one service registration without PTR records for
addresses, you will create:
3 TIMEOUT records, 2 with a hash and 1 without a hash
or with PTR records for names included, you will create:
5 TIMEOUT records, 2 with a hash and 3 without a hash.
For the simpler case, a host sending a name registration at time Tn for A &
AAAA records with lease lifetime Ln would have an UPDATE that contains:
name_n.example.com A 192.0.2.5
name_n.example.com AAAA 2001:db8::5
5.2.0.192.in-addr.arpa. PTR name_n.example.com.
5.0.0.0.0.0.0.0.0.0.0.0.b8.0d.01.20.ip6.arpa. PTR name_n.example.com. (using
bytes instead of nibbles for compactness)
None of the 3 TIMEOUT records on the server would contain a hash:
name_n.example.com TIMEOUT 0 0 Tn+Ln
5.2.0.192.in-addr.arpa. TIMEOUT 0 0 Tn+Ln
5.0.0.0.0.0.0.0.0.0.0.0.b8.0d.01.20.ip6.arpa. TIMEOUT 0 0 Tn+Ln (using bytes
instead of nibbles for compactness)
Hope this makes things more clear.
Tom
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