Thanks. Makes sense.
Jari
On 07.10.2011 06:28, Fred Baker wrote:
On Oct 7, 2011, at 5:25 AM, Jari Arkko wrote:
Question: Yesterday we talked a little bit about what it means for the routing
to be turned on automatically. Prefix assignment based on your delegation from
the ISP is one part of it. What else do we need? Is this just a matter of
making our home router devices have OSPF on by default, and as soon as the
device gets its prefix it will start advertising it in the routing protocol?
For the most part, yes. Most of the parameters that OSPF requires have defaults
specified in the RFC, and while they may or may not be perfect they're not bad.
In managed configurations (SP, Enterprise, etc) folks twiddle the frequency of
Hello messages, with a view to quickly detecting a failure; IIRC, OSPF by
default determines that a neighbor is lost after 4 missed hellos or a link-down
event, so in the worst case this is 50 seconds from the receipt of the previous
successful message. I doubt that's a real issue in residential/SOHO networks.
The other parameters in question include
- the interface prefix itself, which could be derived as in zospf,
- the area number (I'd suggest it default to zero),
- the router ID (a random 32 bit number), and
- security information.
I'd suggest that security information be akin to security on an SSID - pester
the user until he gives you something. zospf may have a comment on security, I
don't recall. The Router ID in IPv4 networks is often one of the IPv4
addresses; for IPv6, it could be derived from a MAC address, a serial number,
or anything else as long as it is unique within the routing domain.
From my perspective, turning on OSPF by default means that the router will not
start actually routing until 40 seconds after it is turned on (OSPF start-up),
and will otherwise mean that it beeps on the LAN every ten seconds; the message
is in the multicast group ALL-OSPF-ROUTERS, which only other routers should be
listening to. By comparison, your favorite 802.1 switch beeps a BPDU on every
interface once per second.
I personally have no issue with OSPF given a rational set of defaults and an
acceptable implementation.
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