I would reword that slightly. Melinda Shoer has been known to suggest
that RSVP might be used as a firewall traversal mechanism, implying
that a NAT/Firewall might be interested in the protocol even though
it is "middleware" more than "router".
It does mean, however, "if you receive this message, you may
determine that you are interested in its contents under a stated
configuration", and it does not mean "you must act as if you are
interested".
On Nov 2, 2005, at 2:29 PM, John Spence wrote:
I believe I see the distinction. The Router Alert is of
particular interest to routers, not all intermediate nodes, and
it includes "extra" information about the contents of the packet
(outside the Router Alert Option or indeed other options in the
H-B-H header).
A H-B-H extension header says "look at the options and perform
them", and the Router Alert is a "hint" saying there may be even
more interesting stuff in the packet - besides just the options -
that requires the router's attention.
Spence
(hi Brian)
-----Original Message-----
From: Brian McGehee [mailto:[EMAIL PROTECTED]
Sent: Wednesday, November 02, 2005 9:48 AM
To: 'John Spence'; 'Fred Baker'
Cc: [email protected]
Subject: RE: Question about the need for a "Router Alert
Option" (RFC 2711)within a Hop-By-Hop Option Extension Header
(RFC 2460) ...
I like to think of it like this.
A Router alert is a messaging saying "Hey Routers. You MIGHT
be interested in the body(payload. Other ext headers) of this
packet"
A HBH is a message saying "Hey ALL NODES in transit. You MUST
look in the HBH and do what it says"
Hope that helps... (hi john)
-Brian
http://consult.tavian.com/
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of John Spence
Sent: Tuesday, November 01, 2005 7:31 PM
To: 'Fred Baker'
Cc: [email protected]
Subject: RE: Question about the need for a "Router Alert
Option" (RFC 2711)within a Hop-By-Hop Option Extension Header
(RFC 2460) ...
Sorry - that fired too fast.
RFC 2711 also references RFC 2460, so it was built for the
H-B-H extension header. Also, if you look at RFC 3810
(MLDv2), it also references the Router Alert Option and says:
All MLDv2 messages described in this document MUST be sent
with a link-local
IPv6 Source Address, an IPv6 Hop Limit of 1, and an
IPv6 Router Alert option [RFC2711] in a Hop-by-Hop Options
header. (The Router Alert option is necessary to cause
routers to examine MLDv2 messages sent to IPv6 multicast
addresses in which the routers themselves have no
interest.)
So, I still don't understand the Router Alert Option, but I
see a number of places where it is referenced.
[[Spence]]
________________________________
From: John Spence [mailto:[EMAIL PROTECTED]
Sent: Tuesday, November 01, 2005 7:25 PM
To: 'Fred Baker'
Cc: '[email protected]'
Subject: RE: Question about the need for a "Router Alert
Option"
(RFC 2711) within a Hop-By-Hop Option Extension Header (RFC
2460) ...
Thanks for the quick reply. The Router Alert Option (RFC
2711) is dated October 1999. It says "This memo describes a new
IPv6 Hop-by-Hop Option type ", so the Router Alert is designed
for the H-B-H Extension header.
----------------------------------------------------
John Spence, CCSI, CCNA, CISSP
Native6, Inc.
IPv6 Training and Consulting
[EMAIL PROTECTED]
(wk) 206-682-0275
www.native6.com
----------------------------------------------------
________________________________
From: Fred Baker [mailto:[EMAIL PROTECTED]
Sent: Tuesday, November 01, 2005 6:48 PM
To: John Spence
Cc: [email protected]
Subject: Re: Question about the need for a
"Router Alert Option" (RFC 2711) within a Hop-By-Hop Option
Extension Header (RFC 2460) ...
one of them sounds like it is redundant. I
think the Router Alert predated the HBH header...
On Nov 1, 2005, at 6:04 PM, John Spence wrote:
Hello;
If the H-B-H
extension header means "all intermediate nodes must look in
here for options to process", why is the "Router Alert" option
needed?
As I read the text of the two RFCs, the Router Alert Option is
redundant - just including a H-B-H header means "intermediate
nodes must look at this packet even if it is not addressed to
them", which seems to be the same meaning as Router Alert.
I must be missing
something. Can someone provide a quick answer, or a pointer to
the answer so I can research it myself?
Thanks very much.
John Spence
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