Subject: [Roll] Link & Node Cost Criteria in the protocol-survey Document

From: Ian Chakeres <[email-masked]>
Date: Tue, 10 Feb 2009 10:16:39 -0500

I have been discussing the Link & Node Cost Criteria with the authors
to understand whether DYMO passes, fails, or ?s.

During this discussion I examined the protocol-survey document text,
and it lead me to questions. To help clear up these question, I've
brought the issue to the list.

Here is the relevant text from the protocol-survey document.

"""
4.5.  Link and Node Cost

  These two criteria specify how a protocol chooses routes for data
  packets to take through the network.  Classical routing algorithms
  typically acknowledge the differing costs of paths and may use a
  shortest path algorithm to find paths.  This is a requirement for low
  power networks, as links must be evaluated as part of an objective
  function across various metric types, such as minimizing latency and
  maximizing reliability [I-D.ietf-roll-indus-routing-reqs].

  However, in low power networks it is also desirable to account for
  the cost of forwarding through particular routers.  Applications
  require node or parameter constrained routing, which takes into
  account node properties and attributes such as power, memory, and
  battery life that dictate a router's willingness or ability to route
  other packets.  Home routing requirements note that devices will vary
  in their duty cycle, and that routing protocols should prefer nodes
  with permanent power [I-D.ietf-roll-home-routing-reqs].  The urban
  requirements note that routing protocols may wish to take advantage
  of differing data processing and management capabilities among
  network devices [I-D.ietf-roll-urban-routing-reqs].  Finally,
  industrial requirements cite differing lifetime requirements as an
  important factor to account for [I-D.ietf-roll-indus-routing-reqs].
  Node cost refers to the ability for a protocol to incorporate router
  properties into routing metrics and use node attributes for
  constraint-based routing.

  A "pass" indicates that the protocol contains a mechanism allowing
  these considerations to be considered when choosing routes.
"""

My understanding of the above text indicates that a routing protocol
will receive a "pass" if it can take link & node costs into
perspective when making routing decisions. For example, the routing
protocol should be capable of avoiding nodes with low battery power,
or more highly utilizing nodes with more energy remaining, or choose
paths with more memory (buffers), or take advantage of some special
abilities to route others' packets.

Given my understanding of this text I believe  DYMO should receive a
"pass", since DYMO is capable of performing route selection based on
many criteria by manipulating the dimension-less distance metric. For
example, myself and others have used spec complaint DYMO
implementations and biased route selection to avoid nodes with low
energy.

If your thoughts on this topic agree with mine, please chime in.

If your thoughts differ, please chime in - and I'd ask you to please
suggest changes to the protocol-survey text to clarify the
requirements more succinctly and help me understand why DYMO might not
be able provide sufficient flexibility.

Thanks.
Ian Chakeres