Re: [OSPF] Stephen Farrell's No Objection on draft-ietf-ospf-prefix-link-attr-12: (with COMMENT)

["Acee Lindem (acee)" <[e-mail]>]

Hi Stephen, 

On 8/19/15, 11:51 AM, "Stephen Farrell" <[e-mail]> wrote:

>Stephen Farrell has entered the following ballot position for
>draft-ietf-ospf-prefix-link-attr-12: No Objection
>
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>COMMENT:
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>- The opaque ID field descriptions in sections 2 and 3 read a
>little oddly to me. What happens if someone decides to use up
>ID=0? Does that mean they can't overwrite that value until
>much later maybe? 

Since it is only to provide uniqueness for opaque LSAs of the same type
originated by the same router, there is no consequence of using 0.


>And what if a whole bunch of routers choose
>the same value (because it's configured or hard-coded)? I
>think you need a bit more text on that. And with only 24 bits
>the probability of a collision if you just pick randomly isn't
>that low, so I'm not sure if random selection is a good plan
>here either. (How often will a new one of these be seen?)

The scope of the Opaque ID is only the originating router so each has its
own number space.  

>
>- Do these opaque values get forwarded widely? If so, then I
>guess they may provide a covert channel. I didn't see that
>mentioned in the security considerations of RFC5250. Is it
>mentioned elsewhere? If not, is it worth a mention here?
>(Probably not, but thought I'd ask.)

Unlike unused protocol fields, it is not really covert since it is a part
of the OSPF LSA ID and is viewable in OSPF OAM and logs. Since it is just
a number, one could, however, set it arbitrarily.


>
>- Thanks for section 5. Nice to see. (Makes me wonder what
>those implementations do with the opaque ID though:-)

The Opaque ID is just used as a key for LSAs.

Thanks,
Acee


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