Subject: [mif] Issue: message size for communicating the default route? draft-ietf-mif-dhcpv6-route-option-04

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Mar 2012 14:27:07 +0200

Dear participants in MIF WG,

Currently draft-ietf-mif-dhcpv6-route-option-04 specifies that when
communicating a default route, the minimal message size (RT_PREFIX
option absent) is 46 bytes (Next Hop Option 20bytes, Route Prefix Option
26bytes).

Sometimes the draft says this Route Prefix Option may be absent for
default routes, thus total length could be 20bytes.

But it is not clear when could it be absent.  Section 4.1 says "Default
route is configured using RT_PREFIX option that specifies ::/0 route,
included as suboption in NEXT_HOP."

and section 5 says "Server MAY send a single NEXT_HOP without any
RT_PREFIX suboptions or with RT_PREFIX that contains ::/0 to indicate
available default route."

I query opinions from the WG about this.

Alex

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From: Tomek Mrugalski <[email-masked]>
Date: Wed, 28 Mar 2012 09:09:29 +0200

> option absent) is 46 bytes (Next Hop Option 20bytes, Route Prefix Option
Please re-read the draft, section 5.2. Note that prefix field itself is
variable and its size depends on prefix-length. You seem to be
interested in low-capability devices. Assuming you use route option to
configure just default route, Route Prefix option is 10 bytes long, so
the total is 30, not 46 bytes.

> default routes, thus total length could be 20bytes.
The ability to skip Route Prefix Option used to be allowed, but that is
not the case anymore. As I mentioned, there is still text that was
missed during the last series of updates and it will be removed in -05.

Tomek

---

From: Alexandru Petrescu <[email-masked]>
Date: Fri, 30 Mar 2012 14:35:41 +0200

> the total is 30, not 46 bytes.

The total could be even smaller (20bytes?) if only one option were used, 
not two (nexthop+routeprefix).

Alex

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