Credit Windowing extension for DLEP
draft-ietf-manet-credit-window-07

There is ongoing discussion in the WG to add functionality to this draft -- so the authors asked for it to be held.  I'm returning the document to the WG.

There is ongoing discussion in the WG to add functionality to this draft -- so the authors asked for it to be held.  I'm returning the document to the WG.

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Services Operator has completed its review of draft-ietf-manet-credit-window-06. If any part of this review is inaccurate, please let us know.

The IANA Services Operator understands that, upon approval of this document, there are three actions which we must complete.

The IANA Services Operator understands that some of the actions requested in the IANA Considerations section of this document are dependent upon the approval of and completion of registry actions in another document:

draft-ietf-manet-dlep

First, in the DLEP Data Item Values subregistry of the Dynamic Link Exchange Protocol (DLEP) Parameters registry created upon approval of draft-ietf-manet-dlep, three values are to be added to the registry as follows:

Type Code: [ TBD-at-Registration ]
Description: Credit Grant
Reference: [ RFC-to-be ]

Type Code: [ TBD-at-Registration ]
Description: Credit Request
Reference: [ RFC-to-be ]

Type Code: [ TBD-at-Registration ]
Description: Credit Window Status
Reference: [ RFC-to-be ]

Second, in the DLEP Extension Type Values subregistry of the Dynamic Link Exchange Protocol (DLEP) Parameters registry created upon approval of draft-ietf-manet-dlep, ta single new value is to be added to the registry as follows:

Code: [ TBD-at-Registration ]
Description: Credit Windowing
Reference: [ RFC-to-be ]

Third, in the DLEP Status Code subregistry of the Dynamic Link Exchange Protocol (DLEP) Parameters registry created upon approval of draft-ietf-manet-dlep, two values are to be added to the registry as follows:

Code: [ TBD-at-Registration ]
Description: Credit Window Out of Sync
Reference: [ RFC-to-be ]

Code: [ TBD-at-Registration ]
Description: Credit Use Rejected
Reference: [ RFC-to-be ]

The IANA Services Operator understands that these are the only actions required to be completed upon approval of this document.

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is only to confirm what actions will be performed.

Thank you,

Amanda Baber
Lead IANA Services Specialist
PTI

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: "Justin Dean" , manet-chairs@ietf.org, manet@ietf.org, bebemaster@gmail.com, aretana@cisco.com, draft-ietf-manet-credit-window@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Credit Windowing extension for DLEP) to Proposed Standard


The IESG has received a request from the Mobile Ad-hoc Networks WG
(manet) to consider the following document:
- 'Credit Windowing extension for DLEP'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf@ietf.org mailing lists by 2016-11-28. Exceptionally, comments may be
sent to iesg@ietf.org instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract


  This draft describes an extension to the DLEP protocol to provide a
  credit-windowing scheme for destination-specific flow control.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-manet-credit-window/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-manet-credit-window/ballot/


No IPR declarations have been submitted directly on this I-D.

==== AD Review of draft-ietf-manet-credit-window-04 ====

Stan:

Hi!  How are you?

I just finished reading this document.  First of all, thanks for taking this work on!

Please see my comments below.  I think many of the comments (even the Major ones) should be easy to address.  However, I am specially concerned about the actions (terminate) to be taken in some of the cases — which, I think, make DLEP vulnerable.

After you address the Major comments and provide a revised ID, I will want to get a review from the Transport Area, probably in parallel with the IETF Last Call (depending on where we are with the DLEP document).

Thanks!

Alvaro.


Major:

M1. "Credit Use Rejected" Status.  When should this Status be used?  I'm guessing that maybe windowing is not supported (the router understands the feature, but doesn't support it) -- what else?  I suspect that it is up to the receiver to use this status as it sees fit, is that the intent?  If so, please clearly say so.  Are there any well-known reasons that might be beneficial to mention?


M2. Both Sections 8.1. (DLEP Destination Up Message) and 8.2. (DLEP Destination Announce Message) say that "MUST use the value in Credit Grant as the initial value…".  But given that the credit use can be rejected, the "MUST" is misleading.  s/MUST/SHOULD or clarify "…if accepted…"


M3. It is not a requirement that Credit Windows be always implemented in both directions, right?

M3.1. Sections 5. (Operation), 8.3. (DLEP Destination Up Response Message) and 8.4. (DLEP Destination Announce Response Message) all say that after receiving a Credit Grant data item "the receiver MUST respond…with a response message that contains a Credit Grant data item".  However, Section 9.1. (Credit Grant) says that "the receiver MUST respond with a message containing a Credit Window Status data item", which seems to be the right thing.

M3.2. It seems to me that (in 8.3 and 8.4) this text should also talk about the Credit Window Status data item:
M3.2.1. (in the response): "…if the corresponding…message did not contain a Credit Grant…Response message MUST NOT contain a Credit Grant (Section 9.1) data item".
M3.2.2. "receiver of…Response MUST use the received Credit Grant value to initialize…".

M3.3. Related to this point, Section 9.1. (Credit Grant) says that the "Credit Grant data item MAY appear in the DLEP Destination Up, Destination Announce, and Destination Update messages."  No  response messages are listed, which is ok.  I would suggest you stress that those are the only messages which can contain the data item.  Either s/MAY/MAY only, or (even better) s/MAY/MUST only  [I think the "MUST" is ok because the Operation section already talks about not every destination needing credit windowing.]


M4. Credit Window Out of Sync status code.  Both 8.3 and 8.4 say that if a peer "detects a mismatch in the presence or absence of credit window data items…MUST terminate the session".

M4.1. Section 7. (DLEP Status Codes for Credit-Window Extension) says lists the failure mode as "Continue".  Please correct that and make sure that the registration request explicitly tells IANA which range to assign the status codes from.

M4.2. It seems to me that using a "terminate" failure mode may be overkill.  It also seems to me that it would be straight forward to require a Credit Grant data item to be sent after receiving this status code and let the session resync on its own (or send a Credit Grant if the lack of sync is detected locally) — it looks like the potential impact of resetting the session may not be justified for a single stream.  I note in the DLEP spec that even refusing to do something (Request Denied) has a failure mode of Continue.


M5. Section 9.2. (Credit Window Status) says that if the "local credit counts are not synchronized…MAY either…or o Issue a DLEP Destination Down message, to clear credit counts on the session."

M5.1. [nit] was this intended to be a bulleted list?

M5.2. The "MAY" indicates that both actions are optional.  IOW, it says that neither action has to be performed.  If that is so, then how do we get the session back in sync?

M5.3. That second option (Destination Down) could also result in the routing protocol (or anyone else listening to DLEP) to reset their adjacency.  As I mentioned above, this action seems to be too drastic because of the effect.  Or am I missing something?

M5.4. Going back to the "MAY either" part.  When (Why) would an implementation chose not to use the least intrusive option?

M5.5. Given the potential problems with falling out to sync, why is this section not more prescriptive: "It is recommended that implementations issue a DLEP Destination Update with a Credit Window Status data item at a configurable multiple of the DLEP Heartbeat timer…"  Maybe s/recommended/RECOMMENDED


M6. Section 9.3. (Credit Request)

M6.1. "If the corresponding…message for this session did not contain a Credit Grant data item…then receipt of the Credit Request data item MUST be considered as an error by the receiver, requiring termination of the DLEP peer session."  Same comment as before; very disruptive!

M6.2. There's no guidance as to what should be done when receiving a Credit Request.


M7. Section 10. (Security Considerations)

M7.1. "The extension does not introduce any additional threats above those documented in [DLEP]."  I disagree.  The extra opportunities to reset the DLEP session create a potential DoS attack: a peer can (for example) send a Credit Request for any destination not using credits and the whole session is reset, potentially affecting other flows.

M7.2. "The mitigation strategy documented in that document is sufficient to secure operation of this extension."  Neither "mitigation" nor "strategy" show up in the DLEP document — you'll have to be more specific.



Minor:

p1. For ease of tracking, please number the TBD values (for example TBD1, TBD2, etc.) throughout the document to match the requests to IANA.

p2. Section 6 is superfluous, please delete it.

p3. "Descriptions of the data items are included below."  Please put a reference.

p4. The format in Section 9.1. (Credit Grant) shows two "Credit Increment" fields.  From the explanation which indicates a "64-bit quantity), I'm assuming that these are really not 2 independent fields, but one big (64-bits) "Credit Increment" field.  Please fix the figure.
P4.1. The MRW/RRW in the figure in Section 9.2 have the same problem.

p5. I don't think the reference to RFC5578 is needed.  Pointing to another scheme may create confusion.



Nits:

n1. Please expand on first mention: DLEP (in the abstract), RF.

n2. s/Dynamic Link Event Protocol/Dynamic Link Exchange Protocol

n3. s/draft/document

n4. Change the order of the sections putting "Credit Window Data Item Definitions" before "DLEP Data Items for Credit-Window Extension".

(1) What type of RFC is being requested (BCP, Proposed Standard, Internet Standard, Informational, Experimental, or Historic)? Why is this the proper type of RFC? Is this type of RFC indicated in the title page header?

Proposed Standard is appropriate.  There are many years of experience with similar technologies within industry.  The IETF does have experience with similar drafts specifically RFC5578.

(2) The IESG approval announcement includes a Document Announcement Write-Up. Please provide such a Document Announcement Write-Up. Recent examples can be found in the "Action" announcements for approved documents. The approval announcement contains the following sections:

Technical Summary:

This draft describes an extension to the DLEP protocol to provide a credit-windowing scheme analogous to that in RFC5578 for destination-specific flow control.  Credits for data exchange are expressed as two unidirectional windows (Modem Receive Window (MRW) and Router Receive Window (RRW) between the router and modem. A significant difference, due to the differences of how PPPoE (RFC5578) and DLEP operate, is that credits are managed on a destination-specific basis.

Working Group Summary:

This credit extension was originally specified as an optional feature in the base DLEP specification. After an extensive RGtDir review the base DLEP specification was sent back to the WG.  The WG decided that it would clean up the specification if credit windowing was was documented in it's own extension draft; The goal being two fold, stressing that the feature was optional and outlining how future extension drafts to DLEP may be written.

There is strong support within the working group on moving this document forward. Only minor comments regarding prefered alternative credit based winding systems, specifically pause and pfc which this document doesn't preclude others from developing as it's an extension.

Document Quality:

With familiarity of DLEP the specification is easy to read and straightforward.  There is broad support within industry and the Shepard fully expects many of the existing DLEP implementations to support this extension once standardized as there is demand on the customer side.  The document quality was addressed extensively in the RtgDir review and subsequent WG discussions.

Personnel:

Document Shepherd is Justin Dean
Area Director Alvaro Retana
Directorate Reviewer: Lou Burger

(3) Briefly describe the review of this document that was performed by the Document Shepherd. If this version of the document is not ready for publication, please explain why the document is being forwarded to the IESG.

The Shepherd has read the draft document as well as previous non-split versions.  Recent updates (after DLEP document was sent back to the WG and split into two) resolves outstanding issues raised in the RgtDir review.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?

No

(5) Do portions of the document need review from a particular or from broader perspective, e.g., security, operational complexity, AAA, DNS, DHCP, XML, or internationalization? If so, describe the review that took place.

No

(6) Describe any specific concerns or issues that the Document Shepherd has with this document that the Responsible Area Director and/or the IESG should be aware of? For example, perhaps he or she is uncomfortable with certain parts of the document, or has concerns whether there really is a need for it. In any event, if the WG has discussed those issues and has indicated that it still wishes to advance the document, detail those concerns here.

None.

(7) Has each author confirmed that any and all appropriate IPR disclosures required for full conformance with the provisions of BCP 78 and BCP 79 have already been filed. If not, explain why?

Yes.

(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures.

No.

(9) 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 WG as a whole understands and strongly agrees with it moving forward.

(10) Has anyone threatened an appeal or otherwise indicated extreme discontent? If so, please summarise the areas of conflict in separate email messages to the Responsible Area Director. (It should be in a separate email because this questionnaire is publicly available.)

No.

(11) Identify any ID nits the Document Shepherd has found in this document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts Checklist). Boilerplate checks are not enough; this check needs to be thorough.

ID nits was run and there no errors, 2 warnings and one comment.  The warning of note is.
== The document seems to lack the recommended RFC 2119 boilerplate, even if
    it appears to use RFC 2119 keywords.     

(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, media type, and URI type reviews.

A RtrDir review has been performed.

(13) Have all references within this document been identified as either normative or informative?

Yes.

(14) Are there normative references to documents that are not ready for advancement or are otherwise in an unclear state? If such normative references exist, what is the plan for their completion?

No.

(15) Are there downward normative references references (see RFC 3967)? If so, list these downward references to support the Area Director in the Last Call procedure.

No.

(16) Will publication of this document change the status of any existing RFCs? Are those RFCs listed on the title page header, listed in the abstract, and discussed in the introduction? If the RFCs are not listed in the Abstract and Introduction, explain why, and point to the part of the document where the relationship of this document to the other RFCs is discussed. If this information is not in the document, explain why the WG considers it unnecessary.

No.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 5226).

The IANA section clearly specifies which allocations are being requested from those created in the base DLEP draft:
3 "Data Item Type Values"
1 "Extension Type Values"
2 "Status Code Values"

(18) List any new IANA registries that require Expert Review for future allocations. Provide any public guidance that the IESG would find useful in selecting the IANA Experts for these new registries.

None

(19) Describe reviews and automated checks performed by the Document Shepherd to validate sections of the document written in a formal language, such as XML code, BNF rules, MIB definitions, etc.

None.