[Roll] Review of draft-ietf-roll-urban-routing-reqs-01

Dear WG,

As discussed in Dublin, the plan is to try to Last Call all the
application-specific routing requirements document before end of September.
Thus, please provide your detailed comments as soon as possible.

Let me start my co-chair review with the Urban WSNs Routing Requirements,
since (with the exception of the Mobility issue) the document is fairly
stable. Comments are not by order of importance by in chronological order.

Abstract
#######
s/ for a wireless ROLL solution to be useful the protocol(s) ought to be
energy-efficient, scalable, and autonomous/ the routing solution ought to be
energy-efficient, scalable and autonomous.

JP> You may want to use a different word than ³Autonomous². Do you refer to
the ³self configuration² property ?

Section 1
#######
* ³Section 6 discusses the routing requirements for networks comprising
   such constrained devices in a U-LLN environment.  These requirements
   may be overlapping requirements derived from other application-
   specific requirements documents or as listed in
   [I-D.culler-rl2n-routing-reqs].²

JP> Please remove this reference (ID abandoned) and insert reference to
http://www.ietf.org/internet-drafts/draft-ietf-roll-home-routing-reqs-02.txt
, 
http://www.ietf.org/internet-drafts/draft-ietf-roll-indus-routing-reqs-01.tx
t and 
http://www.ietf.org/internet-drafts/draft-martocci-roll-commercial-routing-r
eqs-00.txt.

* s/ Section 7 provides an overview of security considerations/ Section 7
provides an overview of routing security considerations

Section 2
########

* S/ ROLL: Routing over Low power and Lossy networks/ ROLL: Routing Over Low
power and Lossy networks

* Schedule:  An agreed execution, wake-up, transmission, reception,
         etc., time-table between two or more field devices.
The definition is a little bit too vague. If used in the generic sense, no
need to add it to the terminology section. Otherwise, it ought to be more
specific.

Section 3.1.1
###########
* S/ pre- planned location/ pre-planned location

* What you refer to as a repeater is in fact a router. What I would suggest
here is to reword this paragraph to indicate that some nodes are simple
routers whereas other nodes are routers and also perform sensing/actuating
task. Insert this paragraph after the Actuators and Sensors paragraphs.

* ³Actuators may generally be mobile but are likely to be static in the
majority of near-future roll-outs²: seems a bit contradictory. Don¹t you
want to simply say that in a near-future the majority will be static?

* ³Similar to the access points, actuator nodes do not suffer from any
long-term resource constraints.² what about battery-operated actuators ?

Section 3.1.4
###########
* ³pollution data, such as polluting gases (SO2, NOx, CO, Ozone),
 heavy metals (e.g.  Mercury), pH, radioactivity, etc;² => please expand
acronym when first used.

* ³These meters will be capable of
   advanced sensing functionalities such as measuring quality of
   service, providing granular interval data, or automating the
   detection of alarm conditions.²
You may want to more accurately define the term ³quality of service² since
as you know, we used that term of other purposes in IETF documents.

* In addition they may be capable of
   advanced interactive functionalities such as remote service
   disconnect or remote demand reset.² => in this case, they are also acting
as actuators.

Section 3.2 
#########

* s/ between one other/between each other

* ³The network MUST be capable of supporting the organization of
   a large number of sensing nodes into regions containing on the order
   of 10^2 to 10^4 sensing nodes each.²
JP> Thanks to make this ³MUST² routing-specific and move it to the
requirements section.

Section 3.3
#########

* RFID: expand acronym (Radio Frequency IDentification) and add to the
terminology section

* s/battery-powered nodes/battery powered nodes
³Sensor nodes are capable of forwarding data.² In other words, they can act
as routers. No need to repeat this here.

Section 3.4
#########

* ³2.  packet errors due to medium access control;² JP> It is not really
³packet error² here.

* Some available protocols may cause packets of neighbouring nodes to
collide and hence cause a link outage.² JP> You may want to be more specific
³Some² ?

* ³if ISM bands are to be used.  For instance, if the 2.4GHz ISM band is
   used to facilitate communication between U-LLN nodes, then heavily
   loaded WLAN hot-spots become a detrimental performance factor
   jeopardizing the functioning of the U-LLN.²
JP> Please expand acronym when first used and add to the terminology section
(ISM, WLAN, ...)

* Don¹t you want to say a few words about the varying BER leading to
potentially even higher packet error loss ratio?

Section 4.1
#########

* ³Pre-programmed MAC²: expand acronym

* ³the autonomous organization² => self-organizing?

* ³For example, nodes in urban sensor nodes SHOULD be able to:² => Several
of the requirements that follow are nor routing specific. You may either
want to change the SHOULD for a ³should² or just focus on the routing
aspects and move them to the routing requirements section.

* ³o  Dynamically compute, select and possibly optimize the (multiple)
      path(s) that will be used by the participating devices to forward
      the traffic towards the actuators and/or the access point
      according to the service-specific and traffic-specific QoS,
      traffic engineering and security policies that will have to be
      enforced at the scale of a routing domain (that is, a set of
      networking devices administered by a globally unique entity), or a
      region of such domain (e.g. a metropolitan area composed of
      clusters of sensors).²
JP> You list important and stringent requirements here. Do you really need a
routing algorithms capable of computing a path on a per QoS/service
specific/... Basis ?

Section 4.2
#########

* ³After the initialization phase and possibly some operational time,
   new nodes may be injected into the network as well as existing nodes
   removed from the network.  The former might be because a removed node
   is replaced or denser readings/actuations are needed or routing
   protocols report connectivity problems. ³
JP> Just to avoid any mis-interpretation when referring to routing problem,
you mean that it may be desirable to inject to node because connectivity is
not sufficient (lack of enough redundant path, ...) and not because of a
routing issue per say.

* ³Differentiation
   SHOULD be made between node disappearance, where the node disappears
   without prior notification, and user or node-initiated disassociation
   ("phased-out"), where the node has enough time to inform the network
   about its removal.²
JP> Again this is not a routing requirement. Unless you refer to the ability
for the routing protocol to advertise to the rest of the network that it
will be removed in order for the other node to re-compute their path and
avoid traffic disruption (e.g. Similarly to what we do with the ISIS
overload bit for example.) Is it what you mean ? If so, please clarify and
move the routing requirement (SHOULD in capital letter to the routing
requirement section).

* ³The protocol(s) hence SHOULD support the pinpointing of problematic
routing areas²
JP> Could you clarify what you mean by ³pinpointing² since it could be
interpreted in many ways?

* The following section also requires some clarification  you wrote:
³Furthermore, to inform the
   access point(s) of the node's arrival and association with the
   network as well as freshly associated nodes about packet forwarding
   schedules, roles, etc, appropriate (link state) updating mechanisms
   SHOULD be supported.²
JP> Are you explicitly requiring a Link State routing protocol or a routing
protocol that provides information about link states or ... ?
Note that a requirement document should stay solution agnostic and stay
focus on the requirement. Is you requirement that any node needs to have
visibility on other node characteristics with no attempt of aggregation?

Section 4.3
#########

* ³The protocol(s) hence MUST support a large number of highly
   directional unicast flows from the sensing nodes or sensing clusters
   towards the access point or highly directed multicast or anycast
   flows from the nodes towards multiple access points.²
JP> I think that what you mean is that the routing protocol MUST be
optimized for Multipoint-to-Point traffic patterns (from sensors/actuators
to Sink). As written, it is not clear whether you refer to it as a routing
requirement ?
This in fact what you wrote in section 6.5: ³To this end, the routing
protocol(s) SHOULD support and utilize the fact of highly directed traffic
flow to facilitate scalability and parameter constrained routing.²

* s/ More generally, entire routing areas may be avoided at e.g. night but
heavily used during the day when nodes are scavenging from sunlight/ More
generally, entire routing areas may be avoided (e.g. at night) but heavily
used during the day when nodes are scavenging from sunlight.
JP> Doesn¹t this translate to the requirement for time-based routing (some
form of policy routing) ?

Section 4.4
#########

³However, they are not very stringent where
   latencies SHOULD simply be sufficiently smaller than typical
   reporting intervals²
JP> This is certainly true but not a routing requirement but a data plane
requirement unless you refer to the ability to support QoS aware routing
where each node may want to be able to compute different paths depending on
the traffic requirements?

* Move ³U-LLN network devices SHOULD support unicast and multicast routing
capabilities² to the routing requirement section. You may want to leave the
sentence here (without a SHOULD).

* You use the term ³anycast² that has been discussed in the past, in
particular in the context of the Home routing requirement document. I would
suggest to define this term in the document, refer to RFC4291 or RFC1546,
...

Section 4.5
#########

* ³An alarm is likely being
   registered by a plurality of sensing nodes where the delivery of a
   single alert message with its location of origin suffices in most
   cases.²
Then you provide the example of toxic gas level. This is one example where
it might be desirable not to perform data aggregation/fusion and get
multiple copies of the same message from different source to perform
³triangulation² and better localize the incident.

* ³Routing within urban sensor networks SHOULD require the U-LLN nodes
   to dynamically compute, select and install different paths towards a
   same destination, depending on the nature of the traffic.  From this
   perspective, such nodes SHOULD inspect the contents of traffic
   payload for making routing and forwarding decisions:

JP> This clarifies my previous question; you do refer to ability to compute
different paths (with different characteristic). Note that the path
selection process performed by the sender and potentially routers along the
path is not strictly speaking a routing requirement.
Move this requirement to the requirement section.

* ³for example, the analysis of the traffic payload SHOULD be derived into
aggregation
   capabilities for the sake of forwarding efficiency.²
JP> Can you clarify what you mean here?

* ³Delays and latencies are
   important; however, again, deliveries within seconds SHOULD suffice
   in most of the cases.²
JP> Clearly not a routing requirement!

Section 5
########

* ³The network SHOULD take into consideration that different application
   traffic may require different priorities when traversing the network,
   and that some traffic may be more sensitive to latency.²
JP> If by priorities you mean different routes with different
characteristics then this is fine and already covered. If you refer to
packet marking to provide different QoS in the data plane, this is not a
routing requirement.

* ³An U-LLN SHOULD support occasional large scale traffic flows from
   sensing nodes to access points, such as system-wide alerts. ³ and ³A node
MUST be able to send its own alerts toward an access
   point while continuing to forward traffic on behalf of other devices
   who are also experiencing an alert condition.  The network MUST be
   able to manage this sudden large traffic flow.²
JP> Not routing requirements. Unless ... You require the ability to compute
multiple paths and use all of them (symmetrical or asymmetrical routing ???)
to spread out the traffic and limit network delays ?

* You make an interesting reference to Smart Grid and DR/DSM. That said, you
wrote ³The network SHOULD support internetworking, while giving attention to
security implications of interfacing, for example, a home network with a
utility U-LLN.²
JP> Don¹t you mean that the routing protocol must be able to potentially
interact via potential route redistribution with other routing protocol used
in the Internet, should these two protocols not be identical ?

Section 6
#########

* S/Current urban roll-outs are composed of sometimes more than a hundred
nodes/ Current urban roll-outs are composed of sometimes more than one
hundred nodes

* ³ The routing protocols(s) SHOULD support the organization of a large
number of nodes into regions of to-be-specified size.²
JP> It will be difficult (or too easy ;-)) to be compliant with that SHOULD
with a to-be-specified size. Or did you mean ³configurable² ?

* ³To this end, the routing protocol(s) MUST support parameter
   constrained routing, where examples of such parameters (CPU, memory
   size, battery level, etc.) have been given in the previous paragraph.²
JP> Please use the term ³node constrained based routing²

* ³For the latter, the protocol(s) MUST support multi- and
   any-cast addressing.  The protocol(s) SHOULD also support the
   formation and identification of groups of field devices in the
   network.²
JP> You may want to more accurately define the term ³anycast²

* ³ To mandate fully interoperable implementations, the routing
   protocol(s) proposed in U-LLN MUST support different devices and
   underlying technologies without compromising the operability and
   energy efficiency of the network.²
JP> This requires clarification here. Do you mean that the routing protocol
MUST support node constrained based routing? If so, it is already stated
above. The support of different L1/L2 is a given (route over).

* Section 6.8, as written, is not related to routing but data plane. Let me
be more specific:

* ³To this end, the routing protocol(s) SHOULD support minimum latency
   for alert reporting and time-critical data queries.²
JP> The support of minimum latency path (data plane !) or the support for
different metric path (control plane) ?

* ³For regular data
   reporting, it SHOULD support latencies not exceeding a fraction of
   the smallest reporting interval.  ³
JP> Not a routing requirement. Even if you are referring to a bound on the
total path metric (the metric reflecting the delay in this case), this is an
implementation issue.

* ³Due to the different latency requirements, the routing protocol(s) SHOULD
support the ability of dealing with different latency requirements.  The
routing protocol(s) SHOULD also support the ability to route according to
different metrics (one of which could e.g. be latency).²
JP> yes these are routing requirements although I would suggest to remove
the first sentence, the requirement being captured in the second sentence.

Section 7
#########

* ³As every network, U-LLNs are exposed to security threats that MUST be
addressed.²
JP> You cannot put a MUST here unless you list the routing security threats.

* s/ potential security threats/ potential routing security threats => JP>
Please use the term ³routing security² in place of ³security² throughout the
section. 

* ³U-LLN networks SHOULD support mechanisms to preserve the
   confidentiality of the traffic that they forward.  The U-LLN network
   SHOULD NOT prevent an application from employing additional
   confidentiality mechanisms.²
JP> I do agree with the requirement but this is not a routing requirement.
Could you focus on the routing security issues ? Or are you referring to the
routing traffic confidentiality ? This is what you do right after:
³ The U-LLN MUST be protected against attempts to inject false or
   modified packets.  For example, an attacker SHOULD be prevented from
   manipulating or disabling the routing function by compromising
   routing update messages.  Moreover, it SHOULD NOT be possible to
   coerce the network into routing packets which have been modified in
   transit.  To this end the routing protocol(s) MUST support message
   integrity.²
JP> I do not see any reference to the type of routing attacks that could be
performed on such networks because of the typical P2MP traffic pattern,
extensive use of wireless links, ...
JP> What I would suggest is to re-focus on the routing security issues with
the Security expert that will get appointed.

Reference section
###############

The current reference section reads:
11.2.  Informative References

   [I-D.brandt-roll-home-routing-reqs]
              Brandt, A., "Home Automation Routing Requirement in Low
              Power and Lossy Networks",
              draft-brandt-roll-home-routing-reqs-01 (work in progress),
              May 2008.

JP> Please update to draft-ietf-roll-home-routing-reqs and add the reference
to draft-ietf-roll-indus-routing-reqs

   [I-D.culler-rl2n-routing-reqs]
              Vasseur, J. and D. Cullerot, "Routing Requirements for Low
              Power And Lossy Networks",
              draft-culler-rl2n-routing-reqs-01 (work in progress),
              July 2007.

JP> This one can be removed.

Last comment: please check that you expand acronyms when first used.

Thanks.

JP.