Re: [Roll] [roll] #5: DODAG
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Re: [Roll] [roll] #5: DODAG
Hi Julien:
In classical terms, an instance really defines a DAG. So if you have
multiple roots then RPL partitions that DAG into a set of
Destination-Oriented DAGs, also called DAG Rooted at a Destination in
the art. All those terms exist with a specific load and the wisdom we
hear from Phil and Dave is not to overload / redefine / restrict those
terms.
The most useful object is the DODAG iteration. A node moves within one
and jump between 2. This is the object for which we should find cool
name. DODAGI is certainly pronounceable by many of us, but it looks a
lot like a WG name in mobility. Any idea?
Cheers,
Pascal
>-----Original Message-----
>From: roll-bounces at ietf.org [mailto:roll-bounces at ietf.org] On Behalf Of
Julien Abeille (jabeille)
>Sent: lundi 9 novembre 2009 11:12
>To: Tim Winter; ROLL WG
>Subject: Re: [Roll] [roll] #5: DODAG
>
>Hi Tim,
>
>My question is: are there DAGs that are not DODAGs in RPL? My feeling
is
>no. Hence I would suppress the DODAG instead of turning all "DAG" into
>"DODAG".
>Best,
>Julien
>
>> -----Original Message-----
>> From: roll-bounces at ietf.org [mailto:roll-bounces at ietf.org] On
>> Behalf Of Tim Winter
>> Sent: samedi 7 novembre 2009 19:55
>> To: ROLL WG
>> Subject: [Roll] [roll] #5: DODAG
>>
>> Hi Julien, WG,
>>
>>
>> roll issue tracker wrote:
>> > #5: DODAG
>> >
>>
--------------------------------+-------------------------------------
>> > --------------------------------+------
>> > Reporter: jpv at ... | Owner: wintert at ...
>> > Type: defect | Status: new
>> > Priority: major | Milestone:
>> > Component: rpl | Version:
>> > Severity: Active WG Document | Keywords:
>> >
>>
--------------------------------+-------------------------------------
>> > --------------------------------+------
>> > * This is currently being discussed by the RPL Author team *
>> >
>> > Email from Julien
>> >
>> > Is there a distinction between DAG and destination
>> oriented DAG. From
>> > what I read I feel all DAGs are destination oriented. If this is
>> > correct I propose to remove the destination oriented DAG concept.
>> >
>>
>>
>> The intent for -05 will be to make the unqualifed use of
>> `DAG' in the text consistent with `DODAG Iteration', as
>> outlined below. So in this use, a `DAG' is a `DODAG'
>> snapshotted by a single sequence number -- a `DODAG
>> Iteration'. There may be cases in -04 where the text reads
>> `DAG' and is in fact referring to `DODAG'- we will be sure to
>> clean these up. Here below is some additional explanation
>> prepared by the author team-
>>
>> Does this help to clarify?
>>
>> Regards,
>>
>> -Tim
>>
>>
>>
>> Instance
>>
>>
>>
>> +----------------------------------------------------------------+
>> |
>> |
>> | (R1) (R2)
>> (Rn) |
>> | / \ /| \ / |
>> \ |
>> | / \ / | \ / |
>> \ |
>> | (A) (B) (M) | (N) ... (X) (Y)
>> (Z) |
>> | /|\ |\ / | |\ | |
>> | |
>> | : : : : : : (O) : : : :
>> : |
>> | / \
>> |
>> | : :
>> |
>> |
>> |
>> | Instance ID
>> |
>> |
>> |
>>
>> +----------------------------------------------------------------+
>>
>> Instance
>>
>>
>> An Instance is a routing topology over an LLN, optimized for a
>> particular objective/application. Discrete Instances may
>> also be set
>> up to offer optimized connectivity to different destinations when
>> appropriate, for example to differentiate a Home Network LLN from
a
>> Utility Network LLN in a smart metering application where
>> a meter may
>> be configured to join both Instances.
>>
>> It consists of one or more Destination Oriented DAGs (DODAGs).
>>
>> It is uniquely identified by an InstanceID.
>>
>> Each instance is operated independently of other instances, and
RPL
>> defines operation over only one instance. Operation among
multiple
>> instances is to be expanded upon in a future revision or companion
>> specification.
>>
>>
>>
>> Destination Oriented DAG (DODAG)
>>
>>
>> +----------------+
>> | |
>> | (R1) | (R2) (Rn)
>> | / \ | /| \ / | \
>> | / \ | / | \ / | \
>> | (A) (B) | (M) | (N) ... (X) (Y) (Z)
>> | /|\ |\ | / | |\ | | |
>> | : : : : : | : (O) : : : : :
>> | | / \
>> | DAGID | : :
>> | |
>> +----------------+
>>
>> DODAG
>>
>>
>> A Destination Oriented DAG is a DAG rooted at a single root node,
>> which is a node with no outgoing edges.
>>
>> In the case where multiple nodes in the LLN coordinate over a
>> backbone and expose the same DAGID (to support the same
>> DODAG), it is
>> conceptually as if there is a single virtual root over the
backbone
>> (not illustrated). In some applications/implementations
>> this may be
>> a desired architecture; in other applications each DODAG
>> may operate
>> with indpendent uncoordinated roots exposing different DAGIDs.
>>
>> A DODAG is uniquely identified over the LLN by the tuple
>> (InstanceID,
>> DAGID).
>>
>> In RPL a node may belong to only one DODAG per Instance at a time.
>>
>>
>>
>> DODAG Iteration
>>
>>
>> +----------------+ +-----------------+
>> | | | |
>> | (R1) | | (R1) |
>> | / \ | \ | / | \ |
>> | / \ | ------\ | / | \ |
>> | (A) (B) | \ | (A) (C) (B) |
>> | /|\ |\ | / | /|\ |\ |
>> | : : : : : | ------/ | : : : : : |
>> | | / | |
>> | Sequence N | | Sequence N+1 |
>> | | | |
>> +----------------+ +-----------------+
>>
>> DODAG Iteration
>>
>>
>> A DODAG Iteration is the DODAG that results from the iterative
>> process that reshapes the DODAG as stimulated by the root. It is
a
>> DAG as constrained by operation of RPL over a fixed
>> Sequence Number.
>>
>> As the root node increments the Sequence Number, different types
of
>> node movement are allowed (e.g. moving `down') and a new DODAG
>> Iteration is formed.
>>
>> A DODAG Iteration is uniquely identified over the LLN by the tuple
>> (InstanceID, DAGID, SequenceNumber).
>>
>>
>>
>> Scope
>>
>> o The scope of an InstanceID is the whole network and it
>> defines an
>> instance
>>
>> o The scope of a DAGID is an instance and it defines a
>> DODAG within
>> that instance
>>
>> o The scope of a Sequence Number is a DODAG and it defines an
>> iteration of that DODAG (DODAG Iteration)
>>
>> o The scope of a rank is a DODAG Iteration and it defines
>> a position
>> of a node within that iteration.
>> _______________________________________________
>> Roll mailing list
>> Roll at ietf.org
>> https://www.ietf.org/mailman/listinfo/roll
>>
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