Representing Multi-Value Time in Mobile Ad Hoc Networks (MANETs)
draft-ietf-manet-timetlv-08

[Ballot comment]
My position is largely the same as Ron's.

I have not seen any arguments for why it needs to be this complex. However, I don't think it will harm the internet and thus do not think it is appropriate to hold a discuss on this case. I

[Ballot comment]
I am voting ABSTAIN.  I too, find the document and its design choices very confusing.  I can't see why a *general-purpose* duration type would necessarily need to work this way.  I find there are some choices in the design that are bad for general interoperability.  It may be that those choices could be justified for certain use cases and in a protocol more limited than MANET, but I just can't see it for general-purpose time typing.

[Ballot comment]
I'm still dubious of the complexity of creating a new custom 8-bit
floating point number format rather than just using a simple 32-bit
integer or a 32-bit IEEE floating point number.  However, at least the
motivation for doing so is documented in the document.

[Ballot comment]
I'm still dubious of the complexity of creating a new custom 8-bit
floating point number format rather than just using a simple 32-bit
integer.  However, the motivation for doing so is now well-justified in
the document.

[Ballot comment]
As with others, I find this design the Wrong Thing (tm).  If you can afford the overhead of a TLV in your protocol you surely do not need to bit bum values down to 8 bits.

The range of times they can represent is 1 to 64 seconds times some magic constant with some arbitrary variable degree of precision. Magic constants are always bad news unless you have a protocol to negotiate them and even then they are bad news.

They could quite reasonably take a slice out of the middle of the NTP format. If they were to use say two bytes of seconds and one byte of fractional seconds that would give them 18 hours in 4ms accuracy. If they make the structure a nice round 4 bytes you get 6 months in 4ms accuracy, and that has got to be enough for any application that I can think of without needing some global magic number.

[Ballot comment]
After some discussion with the authors, I agree that this level of complexity is required if you are going to try to convey that amount of information in only 8 bits.

I support Lars' objection, that the TLV should be simplified at the cost of a few more bits. However, I won't stand in the way of this draft and change my position to ABSTAIN.

[Ballot comment]
After some degree of discussion with the authors, I support Lars' objection, that the TLV should be simplified at the cost of a few more bits. However, I won't stand in the way of this draft and change my position to ABSTAIN.

[Ballot comment]
I share some of the same concerns as Jari. The document doesn't need a tutorial by any means, but a little bit of context around why such a complicated time format is needed would be helpful. I question whether this is truly necessary, and whether again the "make it general for any purpose" pendulum has swung a bit too far again here. A little bit of explanation would be helpful.

[Ballot discuss]
This discuss is along the same lines as Chris Newman's ABSTAIN. The authors generate a new mechanism for representing time, but they never explain the following:

- why are we constrained to 8 bits
- if all MANET nodes must have the same value C, why is it included in the calculation?
- what granularity is required (seconds, milliseconds?)
- what high and low values must be represented

If some of this was in the document and I missed it, I apologize in advance. The document was very difficult to read.

[Ballot discuss]
This discuss is along the same lines as Chris Newman's ABSTAIN. The authors generate a new mechanism for representing time, but they never explain the following:

- why are we constrained to 8 bits
- since all systems need to use the same value of C, why not mandate 0
- what granularity is required (seconds, milliseconds?)
- what high and low values must be represented

If some of this was in the document and I missed it, I apologize in advance. The document was very difficult to read.

[Ballot discuss]
This discuss is along the same lines as Chris Newman's ABSTAIN. The authors generate a new mechanism for representing time, but they never explain the following:

- why are we constrained to 8 bits
- since all systems need to use the same value of C, why not mandate 0
- what granularity is required (seconds, milliseconds?)
- what high and low values must be represented

If some of this was in the document and I missed it, I apologize in advance. The document was very difficult to read.

[Ballot discuss]
The functionality that this draft specifies is good and
needed.

However, I had difficulty in reading this specification. My main
issue is that it has been made so general that in many
places it is hard to understand what the actual rules about
the TLV are.

Some examples:

> A Time TLV may be a packet, message or address block TLV.

This is the only place in the document that mentions packet TLV.
However, according to packetbb (that I have just glanced at so far)
packet, message, and address block TLVs appear to be separate
entities. If you really intended to allow the Time TLV to be
used as a Packet TLV, perhaps you need specify this in more
detail. Otherwise, you can change the quoted text to include
only message and address block TLVs.

What is needed to resolve the Discuss: please explain this in
more detail.

> IANA is requested to assign the same numerical value to the message
> TLV and address block TLV types with the same mnemonic.

So, you have two different entities with different names, but
they have the same mnemonic and code points. Confusing. I wonder
if one entity which is simply used in different contexts would
work better, or if the packetbb structure does not allow this,
just define clearly separate entities with separate names and
code points (but possibly the same format).

Or maybe you have gone too far in the definitions; you could
have just defined the format and allowed other MANET documents
employ the time format in the definition of specific TLVs. That
way it would have been very clear what kind of requirements
apply (e.g., how many times are needed, what the times apply
to, etc.) I am not convinced that messages and address blocks
are the only things that ever need time values in the MANET
space.

What is needed to resolve the Discuss: please explain exactly
what you mean, or change the definitions so that there is
no ambiguity.

>  = {}*

Parsing this format requires knowning the length. You get the
length from the TLV header. Perhaps obvious, but stating this
would have made reading the document easier for me.

What is needed to resolve the Discuss: please explain this in
more detail.

> In a multivalue Time TLV, each single value subfield of the
> multivalue Time TLV is defined as above.  Note that [1] requires that
> each single value subfield has the same length (i.e. the same value
> of n) but they need not use the same values of  to .

I do not understand how you differentiate between a single value and
multiple values. For instance, if there are three values then the
number of octets is odd, which is also true for single values.

What is needed to resolve the Discuss: please explain this in
more detail.

> A VALIDITY_TIME TLV is an address block TLV that defines the validity
> time of the addresses to which the TLV is associated.  After this
> time the receiving node MUST consider the addresses to no longer be
> valid (unless these are repeated in a later message). 

What addresses? See also the last paragraph of my IANA comment above.

What is needed to resolve the Discuss: please explain this in
more detail.

[Ballot comment]
What makes it hard to read this spec is that the definitions are
almost, but not entirely, free of context. A set of addresses is
a context for some statement about them. Your specification defines
the format of the statement about time, but does not fully define
what objects (addresses) it applies to. You could also have chosen
between including the object in question in the format or leaving the
object to the definition of whoever uses this format.

Let me compare this definition to something that we've done in the
RADIUS, Diameter, or MIB spaces. Typically, there's a definition
of a datatype (such as integer, time, utf8 string or even a filter
definition). Separate from these we have definition of attributes
or MIB objects that employ these datatypes. Those definitions
give the context and rules how to interprete the values. The datatype
definitions are simply for data items, void of any context such as
what this integer/time/string would relate to. Something to consider
here?

Here's what idnits had to say:

The document seems to lack the recommended RFC 2119 boilerplate, even if
it appears to use RFC 2119 keywords -- however, there's a paragraph with
a matching beginning. Boilerplate error?

[Ballot discuss]
The functionality that this draft specifies is good and
needed.

However, I had difficulty in reading this specification. My main
issue is that it has been made so general that in many
places it is hard to understand what the actual rules about
the TLV are.

Some examples:

> A Time TLV may be a packet, message or address block TLV.

This is the only place in the document that mentions packet TLV.
However, according to packetbb (that I have just glanced at so far)
packet, message, and address block TLVs appear to be separate
entities. If you really intended to allow the Time TLV to be
used as a Packet TLV, perhaps you need specify this in more
detail. Otherwise, you can change the quoted text to include
only message and address block TLVs.

> IANA is requested to assign the same numerical value to the message
> TLV and address block TLV types with the same mnemonic.

So, you have two different entities with different names, but
they have the same mnemonic and code points. Confusing. I wonder
if one entity which is simply used in different contexts would
work better, or if the packetbb structure does not allow this,
just define clearly separate entities with separate names and
code points (but possibly the same format).

Or maybe you have gone too far in the definitions; you could
have just defined the format and allowed other MANET documents
employ the time format in the definition of specific TLVs. That
way it would have been very clear what kind of requirements
apply (e.g., how many times are needed, what the times apply
to, etc.) I am not convinced that messages and address blocks
are the only things that ever need time values in the MANET
space.

>  = {}*

Parsing this format requires knowning the length. You get the
length from the TLV header. Perhaps obvious, but stating this
would have made reading the document easier for me.

> In a multivalue Time TLV, each single value subfield of the
> multivalue Time TLV is defined as above.  Note that [1] requires that
> each single value subfield has the same length (i.e. the same value
> of n) but they need not use the same values of  to .

I do not understand how you differentiate between a single value and
multiple values. For instance, if there are three values then the
number of octets is odd, which is also true for single values.

> A VALIDITY_TIME TLV is an address block TLV that defines the validity
> time of the addresses to which the TLV is associated.  After this
> time the receiving node MUST consider the addresses to no longer be
> valid (unless these are repeated in a later message). 

What addresses? See also the last paragraph of my IANA comment above.

[Ballot comment]
Let me compare this definition to something that we've done in the
RADIUS, Diameter, or MIB spaces. Typically, there's a definition
of a datatype (such as integer, time, utf8 string or even a filter
definition). Separate from these we have definition of attributes
or MIB objects that employ these datatypes. Those definitions
give the context and rules how to interprete the values. The datatype
definitions are simply for data items, void of any context such as
what this integer/time/string would relate to. Something to consider
here?

Here's what idnits had to say:

The document seems to lack the recommended RFC 2119 boilerplate, even if
it appears to use RFC 2119 keywords -- however, there's a paragraph with
a matching beginning. Boilerplate error?

[Ballot discuss]
The functionality that this draft specifies is good and
needed.

However, I had difficulty in reading this specification. My main
issue is that it has been made so general that in many
places it is hard to understand what the actual rules about
the TLV are.

Some examples:

> A Time TLV may be a packet, message or address block TLV.

This is the only place in the document that mentions packet TLV.
However, according to packetbb (that I have just glanced at so far)
packet, message, and address block TLVs appear to be separate
entities. If you really intended to allow the Time TLV to be
used as a Packet TLV, perhaps you need specify this in more
detail. Otherwise, you can change the quoted text to include
only message and address block TLVs.

> IANA is requested to assign the same numerical value to the message
> TLV and address block TLV types with the same mnemonic.

So, you have two different entities with different names, but
they have the same mnemonic and code points. Confusing. I wonder
if one entity which is simply used in different contexts would
work better, or if the packetbb structure does not allow this,
just define clearly separate entities with separate names and
code points (but possibly the same format).

Or maybe you have gone too far in the definitions; you could
have just defined the format and allowed other MANET documents
employ the time format in the definition of specific TLVs. That
way it would have been very clear what kind of requirements
apply (e.g., how many times are needed, what the times apply
to, etc.) I am not convinced that messages and address blocks
are the only things that ever need time values in the MANET
space.

>  = {}*

Parsing this format requires knowning the length. You get the
length from the TLV header. Perhaps obvious, but stating this
would have made reading the document easier for me.

> In a multivalue Time TLV, each single value subfield of the
> multivalue Time TLV is defined as above.  Note that [1] requires that
> each single value subfield has the same length (i.e. the same value
> of n) but they need not use the same values of  to .

I do not understand how you differentiate between a single value and
multiple values. For instance, if there are three values then the
number of octets is odd, which is also true for single values.

> A VALIDITY_TIME TLV is an address block TLV that defines the validity
> time of the addresses to which the TLV is associated.  After this
> time the receiving node MUST consider the addresses to no longer be
> valid (unless these are repeated in a later message). 

What addresses? See also the last paragraph of my IANA comment above.
What makes it hard to read this spec is that the definitions are
almost, but not entirely, free of context. A set of addresses is
a context for some statement about them. Your specification defines
the format of the statement about time, but does not fully define
what objects (addresses) it applies to. You could also have chosen
between including the object in question in the format or leaving the
object to the definition of whoever uses this format.

[Ballot discuss]
The Security Considerations section is inadequate.  It needs to be noted that the format does
not support any of the security services (authentication, integrity, confidentiality).  Provisioning
such services, if required, is left to the designers of any protocol that uses this format.  In
particular, authenticating the source of the TLV and the integrity of the contents would seem
important to *any* protocol that uses this TLV.  Otherwise, substitution attacks would cause
the reciever to trust out-of-date information, reject current information as stale, etc.
(On the other hand, confidentiality may not always be required.)

[Ballot discuss]
Section 6:

  The  field of a single value Time TLV is specified, using the
  regular expression syntax of [1], by:

In my opinion the stated reference does not define a working language for expressing syntax. It for example lacks precedence rules and has no words about usage of any type of parantheses despite them being used.

[Ballot discuss]
The document is depending on draft-ietf-manet-packetbb which is already the object of a number of DISCUSSes arounf the justification and efficiency of the multi-message format. I believe these need to be solved first before this document is approved.

I am also concerned about the null content security considerations section. I would expect that at least authentication considerations and possible attacks resulting in the modification or non-delivery of the time TLVs be mentioned together with references to the security measures to prevent these. I would hold this part of the DISCUSS until a security review is posted, or the issue is covered by one of the Security ADs.

[Ballot comment]
I agree with the gen-art reviewer that the concept of "distance" is not well-explained. I'm also questioning why it makes sense to specify a relatively complex construct such as distance-dependent time in a generic TLV format - is this really common enough across MANET protocols so that it needs to be specified generically? (I've never seen it used for any other protocol.)

Finally, Chris raises a good point - it's unclear why a new fixed-point format is the right thing here, especially since it can only be understood if one knows what "C" is in use. Burning a few more bits and eliminating "C" seems to be the right tradeoff.

[Ballot discuss]
The functionality that this draft specifies is good and
needed.

However, I had difficulty in reading this specification. My main
issue is that it has been made so general that in many
places it is hard to understand what the actual rules about
the TLV are.

Some examples:

> A Time TLV may be a packet, message or address block TLV.

This is the only place in the document that mentions packet TLV.
However, according to packetbb (that I have just glanced at so far)
packet, message, and address block TLVs appear to be separate
entities. If you really intended to allow the Time TLV to be
used as a Packet TLV, perhaps you need specify this in more
detail. Otherwise, you can change the quoted text to include
only message and address block TLVs.

> IANA is requested to assign the same numerical value to the message
> TLV and address block TLV types with the same mnemonic.

So, you have two different entities with different names, but
they have the same mnemonic and code points. Confusing. I wonder
if one entity which is simply used in different contexts would
work better, or if the packetbb structure does not allow this,
just define clearly separate entities with separate names and
code points (but possibly the same format).

Or maybe you have gone too far in the definitions; you could
have just defined the format and allowed other MANET documents
employ the time format in the definition of specific TLVs. That
way it would have been very clear what kind of requirements
apply (e.g., how many times are needed, what the times apply
to, etc.) I am not convinced that messages and address blocks
are the only things that ever need time values in the MANET
space.

>  = {}*

Parsing this format requires knowning the length. You get the
length from the TLV header. Perhaps obvious, but stating this
would have made reading the document easier for me.

> In a multivalue Time TLV, each single value subfield of the
> multivalue Time TLV is defined as above.  Note that [1] requires that
> each single value subfield has the same length (i.e. the same value
> of n) but they need not use the same values of  to .

I do not understand how you differentiate between a single value and
multiple values. For instance, if there are three values then the
number of octets is odd, which is also true for single values.

> A VALIDITY_TIME TLV is an address block TLV that defines the validity
> time of the addresses to which the TLV is associated.  After this
> time the receiving node MUST consider the addresses to no longer be
> valid (unless these are repeated in a later message). 

What addresses? See also the last paragraph of my IANA comment above.
What makes it hard to read this spec is that the definitions are
almost, but not entirely, free of context. A set of addresses is
a context for some statement about them. Your specification defines
the format of the statement about time, but does not fully define
what objects (addresses) it applies to. You could also have chosen
between including the object in question in the format or leaving the
object to the definition of whoever uses this format.

Let me compare this definition to something that we've done in the
RADIUS, Diameter, or MIB spaces. Typically, there's a definition
of a datatype (such as integer, time, utf8 string or even a filter
definition). Separate from these we have definition of attributes
or MIB objects that employ these datatypes. Those definitions
give the context and rules how to interprete the values. The datatype
definitions are simply for data items, void of any context such as
what this integer/time/string would relate to. Something to consider
here?

[Ballot comment]
Here's what idnits had to say:

The document seems to lack the recommended RFC 2119 boilerplate, even if
it appears to use RFC 2119 keywords -- however, there's a paragraph with
a matching beginning. Boilerplate error?

[Ballot discuss]
Eric Gray wrote a fairly critical Gen-ART Review, but there has
  not been a response to it.  The review can be found at:

    http://www.alvestrand.no/ietf/gen/reviews/
    draft-ietf-manet-timetlv-04-gray.txt

  While I do not expect the authors to agree with all of the concerns
  that are raised, I do expect to see a response to these Last Call
  comments.

[Ballot comment]
I saw no discussion in this document justifying the complexity of
creating a new custom 8-bit floating point number format rather than
just using a simple 32-bit integer.

IANA Last Call comments:

[ Note: The registries defined by draft-ietf-manet-packetbb-11.txt
do not contain elements for Type Extension or Description. Either
that document or this document needs to be adjusted accordingly. ]

Action 1 (Section 9.1):

Upon approval of this document, the IANA will make the following
assignments in the "MANET Parameters" registry located at
http://www.iana.org/assignments/TBD
sub-registry "Message TLV Types"

Type Name Reference
------ -------------------- ------------------------
TBD1 VALIDITY_TIME [RFC-manet-timetlv-04]
TBD2 INTERVAL_TIME [RFC-manet-timetlv-04]



Action 2 (Section 9.2):

Upon approval of this document, the IANA will make the following
assignments in the "MANET Parameters" registry located at
http://www.iana.org/assignments/TBD
sub-registry "Address Block TLV Types"


Type Name Reference
------ -------------------- ------------------------
TBD3 VALIDITY_TIME [RFC-manet-timetlv-04]
TBD4 INTERVAL_TIME [RFC-manet-timetlv-04]


We understand the above to be the only IANA Actions for this
document.

PROTO Write-up

1. Have the chairs personally reviewed this version of the
Internet Draft (I-D), and in particular, do they believe this I-D is
ready to forward to the IESG for publication?

Yes the chairs have reviewed this document, and we believe that it is
ready to go to the IETF for publication.

2. Has the document had adequate review from both key WG members
and key non-WG members? Do you have any concerns about the depth or
breadth of the reviews that have been performed?

Yes the I-D has been adequately reviewed.

3. Do you have concerns that the document needs more review from a
particular (broader) perspective (e.g., security, operational
complexity, someone familiar with AAA, etc.)?

We do not have any particular concerns regarding additional
required reviews for this document.

4. Do you have any specific concerns/issues with this document
that you believe the ADs and/or IESG should be aware of? For example,
perhaps you are uncomfortable with certain parts of the document, or
have concerns whether there really is a need for it. In any event, if
your issues have been discussed in the WG and the WG has indicated it
that it still wishes to advance the document, detail those concerns
in the write-up.

No contentious issues were raised during WG discussion on this
document.

5. How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?

The three main WG protocol documents contain a reference to this
I-D. That is, NHDP, DYMO, and OLSRv2 all utilize the TLV format and
types specified in this document.

6. Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarize the areas of conflict in separate
email to the Responsible Area Director.

There was no WG conflict regarding this document.

7. Have the chairs verified that the document adheres to all of
the I-D Checklist items ?

Yes the document adheres to the I-D checklist items.

8. Is the document split into normative and informative
references? Are there normative references to I-Ds, where the I-Ds are
not also ready for advancement or are otherwise in an unclear state?
(note here that the RFC editor will not publish an RFC with normative
references to I-Ds, it will delay publication until all such I-Ds are
also ready for publication as RFCs.)

Yes the references are split into normative and informative
references.

9. What is the intended status of the document? (e.g., Proposed
Standard, Informational?)

Proposed Standard.

10. For Standards Track and BCP documents, the IESG approval
announcement includes a write-up section with the following sections:

* Technical Summary

This document specifies the syntax of a PacketBB (publication
requested) TLV for representing time. It also defines two TLV types
that conform to the TimeTLV representation.

* Working Group Summary

This document contains information that was originally in OLSRv2. It
was pulled out and generalized, since it is applicable to many MANET
WG protocols. It is an integral component of NHDP, OLSRv2, and DYMO.

* Protocol Quality

The TimeTLV format was architected to represent a wide range of time
values. The necessity and flexibility of the format is demonstrated
by the two TimeTLV type instances specified in this document.