A few comments on the draft:
1) Support for other realms. Does different realms imply different IP address space? This introduces the problem with overlapped IP address for prefix and also MR HoA.
Each network prefix can be associated to a realm, usually in the form
'organization.example.com'. Besides the routers in customer's own
organization, the prefix list may also include other Mobile Routers,
e.g. Default prefix (0.0.0.0/0) pointing towards Internet gateway
for Internet connectivity, and possible extranets. The realm
information can be used to make policy decisions on the Mobile
Router, such as preferring optimization within specific realm only.
2) For the different realm case (CRs served by different HAs), how does CR’s HA know? This is just another issue with different HAs support. Currently, the draft does say this is out of scope.
In a registration
request, the Mobile Router claims to represent an arbitrary IPv4
network. If the CR has not yet received this information (HoA <->
Network prefix), it SHOULD perform a re-registration to Home Agent to
verify the claim.
3) When there are many MRs, the size of the RRP can be huge. The RO cache has to have all the MRs’ prefixes to work properly (i.e. the last registered MR has the full table). I would propose a more scalable method. Since the HA is aware of the RO-support mode of the MRs for traffic between their networks, HA should notify the MR(s) to trigger Return Routability. In the case of NAT traversal on one MR, HA would tell the right MR to initiate the signaling. It’s also possible that HA facilitate the keying.
4) Clarify the NAT case.
A diagram with more details would be helpful. How does RR work with
CR’s private IPv4 HoA? The CoTI message cannot be routed directed
from MR (using its CoA). It does matter which MR initiates the RR with
the different cases of one side of the MR is behind NAT, or both MRs are behind
the same NAT.
5) Unfortunately this is likely
a common scenario. Just a comment. When HA detects this case, it
may not trigger RO if the new method #3 is used.
If both the Mobile Router and the Correspondent Router are behind
separate NATs, route optimization cannot be performed between them.
Possibilities to set up mutual tunneling when both routers are behind
NAT, are outside the scope of this draft.
6) Different realms may have
overlapped HoA’s.
Due to the fact that the route optimization procedures may occur
concurrently at two Mobile Routers, each working as each other's
Correspondent Router, there may be a situation where two routers are
attempting to establish separate tunnels between them at the same
time. If a router with a smaller Home Address (meaning a normal 32-
bit integer comparison treating IPv4 addresses as 32-bit unsigned
integers) receives a registration request (in CR role) while its own
registration request (sent in MR role) is still pending, the reply
must be deferred until the tunnel initiated by its registration
request is up. This avoids the problem of two separate tunnels
forming concurrently between two Mobile Routers.
7) What happens when both MR
and CR moves at the same time? Maybe some text to cover this?
8) CR cannot initiate RR
in this case.
In the case where Mobile Router is behind NAT (or firewall) and
Correspondent Router is not, the Mobile Router will, when tunnel has
been established, send keepalive messages (ICMP echo requests)
through the tunnel. Until a reply has been received, the tunnel
SHOULD NOT be considered active. Once reply has been received, NAT
mapping is in place and traffic can be sent.
9) HA does not know the same
NAT unless the same CoA address (use explicit language). Different IP
address does not mean it’s not the same NAT.
If Mobile Router and Correspondent Router are behind same NAT from
HA's point of view, it is possible to establish tunnel between them.
10)Generic notification message
could be used by HA to inform the MRs of new MRs/prefixes. Just a
thought.
Kent
