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Re: [DNA-BOF] Example of 'IP neighbourhood' instead of 'L3 link' incharter.
Hi Greg!
Please find some comments, suggestions, and nits in-line.
On Fri, 9 Jan 2004, Greg Daley wrote:
|When an IP node detects or suspects that its underlying link
|layer (L2) connectivity has or may have undergone a change, it
|needs to check whether its IP layer (L3) configuration and
|connectivity are still valid or have changed. In the case that
|the L3 connectivity has changed, the node needs to reconfigure
|and may need to initiate mobility procedures, such as sending
|Mobile IP binding updates. Changes in an L2 connection do not
|necessarily mean that there has been change in L3 connectivity.
It's clear what "detects" mean: a(n error) message from the layer
below. But what does "suspect" mean?
What about replacing "link layer (L2) connectivity" with "link
layer binding"? Do we actually need "IP layer (L3) configuration
*and* connectivity". Why isn't "configuration" enough?
Suggested text:
When an IP node detects (or suspects?) a change in its link layer
[connectivity|binding] it needs to check whether its IP
configuration is still valid. Changes in link layer
[connectivity|binding] may force a node to modify its IP
configuration by initiating mobility procedures such as sending
Mobile IP updates [RFC 3344]. However, in many cases, link layer
changes do not necessitate IP reconfiguration.
|For the purposes of detecting network attachment, an IP
|neighbourhood is defined by the range within which IP packets may
|be sent without resorting to forwarding. In other words, a
|neighbourhood is the range where a given IP configuration is
|valid.
s/defined by/defined as/
I'm not very comfortable with defining this new term: IP
neighborhood
|In IPv6, the IP layer configuration information includes the set
|of valid unicast addresses[RFC2462, RFC3315], the DAD status of
|the addresses[RFC2462], valid routing prefixes[RFC2461], set of
|default routers[RFC2461], neighbor and destination
|caches[RFC2461], multicast listener (MLD) state[RFC2710]. The
|current IPv6 stateless and stateful autoconfiguration procedures
|may take a fairly long time due to delays associated with Router
|Discovery and Duplicate Address Detection processes.
s/[RFC/ [RFC /
s/DAD/Duplicate Address Detection/ (acronym not defined)
s/ processes//
|In some wireless technologies, the link layer state and events
|may not be accurate and unambiguous from the IP point of view.
Well, are they at least unambiguous from the LL point of view?
s/may not be accurate and unambiguous/may be ambiguous/
|For example, a host may be able to see a base station but still
|be unable to deliver or receive IP packets within the IP
|neighborhood. Similarily, a hardware indication that a radio link
|is up does not necessarily mean that all link layer
|configuration, such as authentication or virtual LAN connectivity
|has been completed. Therefore detecting network attachment
|requires not only change detection but IP layer connectivity
|testing.
What does "see a base station" mean? Sense its presense at the LL?
s/Similarily/Moreover/
s/authentication or virtual LAN/authentication and virtual LAN/
Does "In sum, detecting network attachement requires not only
detection of link layer [connectivity|binding] changes, but also
determining whether IP reconfiguration is needed."
read better than
"Therefore detecting network attachment requires not only change
detection but IP layer connectivity testing."?
|The purpose of the DNA working group is to define standards track
|and BCP documents that allow hosts to detect their IP layer
|configuration and connectivity status quickly, proposing some
|optimization to the current specifications that would allow a
|host to reconfigure its IPv6 layer faster than today.
Suggested text:
The purpose of the DNA working group is to produce Standards Track
and BCP documents that describe how hosts can quickly determine
the validity of their IP configuration, and propose optimizations
to current specifications allowing for faster IPv6
reconfiguration.
|Initiation of neighbourhood change detection procedures can be
|achieved either through reception of messages at the IP layer or
|through indications from other layers. The working group will
|produce a document that contains a catalogue of the indications
|available from a number of link layer technologies.
Is the following problem relevant to the WG? Assume that a user is
at an outdoors cafe which offers 802.11 connectivity at $x/min.
After a while, Mr. Nice Guy turns on his free-to-all wireless
access point allowing anyone to share his broadband connection.
Shouldn't the user be informed of the offering and permitted to
switch to the free AP?
|The working group will define best current practice for nodes
|making use of existing L3 and L2 information for detecting
|network attachment.
|
|The working group will define a set extensions to the
s/a set/a set of/
|current IPv6 configuration protocols [RFC2461, 2462, possibly
|RFC3315] that allow the nodes to discover whether L3
|configuration or connectivity may have changed more reliably and
|easily than today.
(again "L3 connectivity")
|
|?In order to detect network attachment, it is important
|?to be able to send and receive IP packets, even if the
|?IP neighbourhood has changed. The DNA WG will develop
|?a system which allows use of an IPv6 addresses without
|?the latency cost of the traditional DAD [RFC2462].
|?Such a system may allow the transfer of user data
|?while neighbourhood change detection and DAD
|?procedures are in progress.
|
|The DNA WG will not define new procedures or APIs
|related to link layers.
IMO, the paragraph is redundant and restrictive, but I agree with
an earlier of your posts about the possibility of initiating a
different/follow-up WG.
<snip>
|Aug 2004: Submit Goals for Detecting Network Attachment
| in IPv6 as informational.
s/informational/Informational/
|
|Aug 2004: Submit Best Current Practice for Detecting
| Network Attachment in IPv6 as BCP
|
|Aug 2004: Submit Existing Link Layer Hints Catalogue as
| informational.
s/informational/Informational/
|
|?Aug 2004: Submit IPv6 DAD Optimization Goals as
|? informational.
s/informational/Informational/
Kudos for your excellent work!
Best regards,
Kostas
__________________________________________________________________
Kostas Pentikousis www.cs.stonybrook.edu/~kostas