Preserving Topology Confidentiality in Inter-Domain Path Computation Using a Path-Key-Based Mechanism
RFC 5520

Received changes through RFC Editor sync (changed abstract to 'Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (TE) Label Switched Paths (LSPs) may be computed by Path Computation Elements (PCEs). Where the TE LSP crosses multiple domains, such as Autonomous Systems (ASes), the path may be computed by multiple PCEs that cooperate, with each responsible for computing a segment of the path. However, in some cases (e.g., when ASes are administered by separate Service Providers), it would break confidentiality rules for a PCE to supply a path segment to a PCE in another domain, thus disclosing AS-internal topology information. This issue may be circumvented by returning a loose hop and by invoking a new path computation from the domain boundary Label Switching Router (LSR) during TE LSP setup as the signaling message enters the second domain, but this technique has several issues including the problem of maintaining path diversity.

This document defines a mechanism to hide the contents of a segment of a path, called the Confidential Path Segment (CPS). The CPS may be replaced by a path-key that can be conveyed in the PCE Communication Protocol (PCEP) and signaled within in a Resource Reservation Protocol TE (RSVP-TE) explicit route object. [STANDARDS-TRACK]')

[Ballot comment]
Section 6 is well written and includes extremely useful operational and manageability information. I do not believe however that the usage of 2119-style kewwords is necessary in sub-section 6.2, as that section makes requirements about the content and impmentation of the informational model defined in other documents.

[Ballot discuss]
As Hilarie Orman said in her SecDir Review, this document is confusing
  to security folks.  Naming the identifiers, which are used to preserve
  confidentiality, "keys" makes the term "path key expansion" especially
  jarring to security folks.  An editorial change in the beginning of
  the document that distinguishes path-keys from cryptographic keys is
  necessary to avoid confusion.
 
  Adrian Farrel has proposed the following text to resolve this concern:
  >
  > Please note that the terms "path key" and "key" used in this document
  > refer to an identifier allocated by a PCE to represent a segment of a
  > computed path. The terms have no relation to the term "cryptographic
  > key" used in some documents that describe security issues.
  >
  It resolve my concers, except: s/issues/mechanisms/

[Ballot discuss]
Section 3.2.3:

The usage of formal language to define protocol does require an reference to a definition of that formal language. This to make sure that a reader know which formal language has been used. This requirement is documented in an IESG statement:
http://www.ietf.org/IESG/STATEMENTS/pseudo-code-in-specs.txt

I guess that this document is using the RBNF that is currently being collected for publication (http://www.ietf.org/internet-drafts/draft-farrel-rtg-common-bnf-07.txt). Is that correct?

If it is can you please add a reference to this.

IANA Last Call comments:

[ Note: Actions in this document are dependent upon successful
completion of the actions in draft-ietf-pce-pcep ]

Action 1 (Section 7.1):

Upon approval of this document, the IANA will make the following assignments
in the "Path Computation Element Protocol (PCEP)" registry located at
http://www.iana.org/assignments/TBD-PCEP
sub-registry "PCEP Objects / 7: ERO"

7 | ERO | [RFC-pce-pcep-12]



|| TBD(64): Path Key with 32-bit PCE ID | [RFC-pce-path-key-03]
|| TBD(65): Path Key with 128-bit PCE ID | [RFC-pce-path-key-03]




Action 2 (Section 7.2):

Upon approval of this document, the IANA will make the following assignments
in the "Path Computation Element Protocol (PCEP)" registry located at
http://www.iana.org/assignments/TBD-PCEP
sub-registry "PCEP Objects"

[TBD(16)] | PATH-KEY | [RFC-pce-path-key-03]


| Object Type
| 1: Path Key | [RFC-pce-path-key-03]



|| SubObjects:
|| 64: Path Key with 32-bit PCE ID | [RFC-pce-path-key-03]
|| 65: Path Key with 128-bit PCE ID | [RFC-pce-path-key-03]




Action 3 (Section 7.3):

Upon approval of this document, the IANA will make the following assignments
in the "Path Computation Element Protocol (PCEP)" registry located at
http://www.iana.org/assignments/TBD-PCEP
sub-registry "RP Object"

Bit Description Reference
---- ---------- -----------
TBD(15) Path Key (P-bit) [RFC-pce-path-key-03]


Action 4 (Section 7.4):

NOTE: Bit #1 is already assigned to "PCE currently Unavailable"

Upon approval of this document, the IANA will make the following assignments
in the "Path Computation Element Protocol (PCEP)" registry located at
http://www.iana.org/assignments/TBD-PCEP
sub-registry "NO-PATH-VECTOR TLV"

Bit Number Name Reference
---- ---------- -----------
[TBD] PKS expansion failure [RFC-pce-path-key-03]


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

Intended status : Standards Track

> (1.a)  Who is the Document Shepherd for this document?  Has the
>        Document Shepherd personally reviewed this version of the
>        document and, in particular, does he or she believe this
>        version is ready for forwarding to the IESG for publication?

Adrian Farrel is the document shepherd.
He has personally reviewed the I-D and believes it is ready for
forwarding to the IESG for publication.

Please note that the document shepherd is also an author of this I-D.
Both PCE working group chairs are authors of this document although
the editor is a third party.

> (1.b)  Has the document had adequate review both from key WG members
>        and from key non-WG members?  Does the Document Shepherd have
>        any concerns about the depth or breadth of the reviews that
>        have been performed?

I-D has had a good level of discussions and review in the PCE working
group. The most debate took place with early revisions when there were
some choices to be made.

No concerns about the level of review.

> (1.c)  Does the Document Shepherd have concerns that the document
>        needs more review from a particular or broader perspective,
>        e.g., security, operational complexity, someone familiar with
>        AAA, internationalization or XML?

No concerns.

> (1.d)  Does the Document Shepherd have any specific concerns or
>        issues 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.  Has an IPR disclosure related to this document
>        been filed?  If so, please include a reference to the
>        disclosure and summarize the WG discussion and conclusion on
>        this issue.

The document is sound.

An IPR disclosure can be found at https://datatracker.ietf.org/ipr/871/
This disclosure was made as soon as the I-D became a working group
draft, and was brought to the attention of the working group at once.
There was no objection made on the mailing list to continuing with the
draft.

> (1.e)  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?

Consensus is good.
WG last call issues were limited to editorial and minor functional nits.

> (1.f)  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
>        entered into the ID Tracker.)

No threats. No discontent.

> (1.g)  Has the Document Shepherd personally verified that the
>        document satisfies all ID nits?  (See
>        http://www.ietf.org/ID-Checklist.html and
>        http://tools.ietf.org/tools/idnits/).  Boilerplate checks are
>        not enough; this check needs to be thorough.  Has the document
>        met all formal review criteria it needs to, such as the MIB
>        Doctor, media type and URI type reviews?

All checks made.

> (1.h)  Has the document split its references into normative and
>        informative?  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
>        strategy for their completion?  Are there normative references
>        that are downward references, as described in [RFC3967]?  If
>        so, list these downward references to support the Area
>        Director in the Last Call procedure for them [RFC3967].

References split.
No downrefs.

> (1.i)  Has the Document Shepherd verified that the document IANA
>        consideration section exists and is consistent with the body
>        of the document?  If the document specifies protocol
>        extensions, are reservations requested in appropriate IANA
>        registries?  Are the IANA registries clearly identified?  If
>        the document creates a new registry, does it define the
>        proposed initial contents of the registry and an allocation
>        procedure for future registrations?  Does it suggest a
>        reasonable name for the new registry?  See [RFC2434].  If the
>        document describes an Expert Review process has Shepherd
>        conferred with the Responsible Area Director so that the IESG
>        can appoint the needed Expert during the IESG Evaluation?

The document defines small protocol enhancements to PCEP. The PCEP
specification is progressing through the IESG approval process and no
IANA registry has yet been created. Nevertheless, this I-D requests
further allocations from the PCEP registry that IANA will create and
manage.

The IANA section of this I-D uses the same language as the PCEP
specification and, in particular, uses the same sub-registry names.

Further, to help ensure consistent allocation of protocol codepoints, a
temporary (non-definitive) registry is maintained at
www.olddog.co.uk/pcep-codepoints.txt

> (1.j)  Has the Document Shepherd verified that sections of the
>        document that are written in a formal language, such as XML
>        code, BNF rules, MIB definitions, etc., validate correctly in
>        an automated checker?

No such formal language is used.

The message formats are described in relatively simple BNF. No automated
checker has been used.

Note that the symbol "|" is used to denote an alternative whereas RFC
5234 specifies the use of "/". This choice was made deliberately as the
"|" symbol is found in related RFCs (e.g. RFCs 2205, 3209, 3473) and the
base PCEP specification.

> (1.k)  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
>          Relevant content can frequently be found in the abstract
>          and/or introduction of the document.  If not, this may be
>          an indication that there are deficiencies in the abstract
>          or introduction.

Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
Traffic Engineering (TE) Label Switched Paths (LSPs) may be computed by
Path Computation Elements (PCEs). Where the TE LSP crosses multiple
domains, such as Autonomous Systems (ASes), the path may be computed by
multiple PCEs that cooperate, with each responsible for computing a
segment of the path. However, in some cases (e.g., when ASes are
administered by separate Service Providers), it would break
confidentiality rules for one PCE to supply a path segment to a PCE in
another domain, thus disclosing AS-internal topology information. This
issue may be circumvented by returning a loose hop and by invoking a new
path computation from the domain boundary Label Switching Router (LSR)
during TE LSP setup as the signaling message enters the second domain,
but this technique has several issues including the problem of
maintaining path diversity.

This document defines a mechanism to hide the contents of a segment of a
path, called the Confidential Path Segment (CPS). The CPS may be
replaced by a path-key that can be conveyed in the PCE Communication
Protocol (PCEP) and signaled within in a Resource Reservation Protocol
TE (RSVP-TE) explicit route object.

Note that a separate draft in the CCAMP working group (draft-ietf-ccamp-
path-key-ero) describes the use of this feature in RSVP-TE.

>        Working Group Summary
>          Was there anything in WG process that is worth noting?  For
>          example, was there controversy about particular points or
>          were there decisions where the consensus was particularly
>          rough?

WG has good consensus with no disputes or disagreements.
An IPR disclosure has been filed, but the WG has decided to proceed with
this I-D.

>        Document Quality
>          Are there existing implementations of the protocol?  Have a
>          significant number of vendors indicated their plan to
>          implement the specification?  Are there any reviewers that
>          merit special mention as having done a thorough review,
>          e.g., one that resulted in important changes or a
>          conclusion that the document had no substantive issues?  If
>          there was a MIB Doctor, Media Type or other expert review,
>          what was its course (briefly)?  In the case of a Media Type
>          review, on what date was the request posted?

An informal, private survey has revealed one implementation of the PCEP
extensions defined in this document with two implementations in the
pipe-line. Given how small the protocol extensions defined in this
document are, it is considered that proceeding on the basis of one
implementation is OK.