[nm-wg] Re: [I2G2-Proto] NMWG schema comments (mainly about IPv6 and multicast)

[Joe Metzger]

Dan Gunter wrote:

>>> COMMENT #3
>>> ----------
>>> Just a question. I don't understand InterfaceContent in nmwgtopo.rnc
>>>
>>> There is ipAddress and ifAddress. What is the difference? I guess 
>>> ipAddress is the address used to reach the router while ifAddress is 
>>> configured on the monitored interface? Maybe we should make that more 
>>> explicit?
>>>
>>
>> The ipAddress more or less the address of the chassis; it is an 
>> administrative address that may be running some form of management 
>> software.  The ifAddress is the particular address of an interface.  
>> We have kept both as a courtesy to implementation designers; this may 
>> prevent a forced lookup of an address saving valuable time and effort.
>>
> huh? if it's the "administrative" address, you should call it that. But 
> I don't see this as generally applicable. Let caching be handled by the 
> implementation.
> 
> I would think that what you need is the interface name/index and 
> addresses. Given the note below, organized as a list of (address, 
> interface name) pairs, where either or both can be repeated. Imitating 
> the brilliant representation of traceroute :-)

Dan,
It is not a caching issue.  It is that ifName & IP Address are not
sufficent to uniquely identify an interface in all cases.

IP addresses are not guaranteed to be unique.  Interface names are not unique.
For example, we have plans to deploy around 4 different DNS servers
using anycast. All will have the same IP address. All the different router
interfaces connected to the different servers will have the same IP address.
It is possible that they could all be on ge-1/0/0.  The name of the
router or chassis is required to distinguish between the connection to a
DNS server in California vs one in New York.

I think this concept is generally applicable.  Especially if you consider
deployment in networks that use nat or private address space where you
could have lots of collisions, not just a couple per network.


--Joe

> 
> 
> -Dan
> 
>>>
>>> COMMENT #4
>>> ----------
>>> Note an interface in IPv6 has by nature several IPv6 addresses. I 
>>> mean unicast addresses here. There are link-local addresses (often 
>>> only one derived from physical interface address) and one or more 
>>> global unicast addresses.
>>> It is I think necessary that ifAddress in InterfaceContent of 
>>> nmwgtopo.rnc becomes a vector instead of just a single element? I 
>>> guess we should display as well the link-local address... maybe 
>>> having some type for it like "IPv6-LL")
>>>
>>
>> We have only briefly dealt with ipv6 issues in the schemas, and we do 
>> hope to encompass more features in the future.  It is possible to have 
>> a 'list' element in a schema, although i am unsure of what 
>> ramifications (if any) it would bring to the current design.  This is 
>> something we should consider.
> 
> 
>>
> 
>