Subject: [Efficientnd-dt] DAD problems (revision 2)

From: Ole Troan <[email-masked]>
Date: Sun, 23 Mar 2014 11:46:56 +0100

all,

an updated list of DAD problems.

1. Doesn’t detect duplicate L2 addresses in all cases
2. Fails when L2 port is blocked. Host connected to a switch with STP enabled (~50 seconds before traffic is allowed)
3. Fails on multicast unreliable links (collision detection requires two multicast messages to pass through)
4. False positives in case of looped interfaces (solved by enhanced-dad)
5. Introduces delays before an address can be used (Optimistic DAD fixes that rfc4429)
6. Doesn’t deal with partition and joining, since detection is only done on start up.
7. Doesn’t specify what to do in case of collision in the general case. CGA, privacy addresses have their own schemes.
8. Requires all nodes to be awake to defend their address
9. Unclear on what a node should do after L2 events / waking up from sleep
10. DAD is used to build state in the network
11. DAD is used by L2 devices to check if an address is in use (RFC6620)
12. DAD doesn't support multi-link subnets (but the IPv6 architecture doesn't either).

cheers,
Ole