Independent Submission                                            D. Liu
Request for Comments: 9296                                    J. Halpern
Category: Informational                                         C. Zhang
ISSN: 2070-1721                                                 Ericsson
                                                            August 2022


 ifStackTable for the Point-to-Point (P2P) Interface over a LAN Type:
                       Definition and Examples

Abstract

  RFC 5309 defines the Point-to-Point (P2P) circuit type, one of the
  two circuit types used in the link-state routing protocols, and
  highlights that it is important to identify the correct circuit type
  when forming adjacencies, flooding link-state database packets, and
  monitoring the link state.

  This document provides advice about the ifStack for the P2P interface
  over a LAN Type to facilitate operational control, maintenance, and
  statistics.

Status of This Memo

  This document is not an Internet Standards Track specification; it is
  published for informational purposes.

  This is a contribution to the RFC Series, independently of any other
  RFC stream.  The RFC Editor has chosen to publish this document at
  its discretion and makes no statement about its value for
  implementation or deployment.  Documents approved for publication by
  the RFC Editor are not candidates for any level of Internet Standard;
  see Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc9296.

Copyright Notice

  Copyright (c) 2022 IETF Trust and the persons identified as the
  document authors.  All rights reserved.

  This document is subject to BCP 78 and the IETF Trust's Legal
  Provisions Relating to IETF Documents
  (https://trustee.ietf.org/license-info) in effect on the date of
  publication of this document.  Please review these documents
  carefully, as they describe your rights and restrictions with respect
  to this document.

Table of Contents

  1.  Introduction
  2.  Requirements Language
  3.  Interface Stack Table for P2P Interface Type
    3.1.  P2P Interface: higher-layer-if and lower-layer-if
    3.2.  P2P Interface Statistics
    3.3.  P2P Interface Administrative State
  4.  Security Considerations
  5.  IANA Considerations
  6.  References
    6.1.  Normative References
    6.2.  Informative References
  Appendix A.  Examples
  Acknowledgements
  Authors' Addresses

1.  Introduction

  [RFC5309] defines the Point-to-Point (P2P) circuit type and
  highlights that it is important to identify the correct circuit type
  when forming adjacencies, flooding link-state database packets, and
  monitoring the link state.

  To simplify configuration and operational control, it is helpful to
  represent the fact that an interface is to be considered a P2P
  interface over a LAN type explicitly in the interface stack.  This
  enables, for example, routing protocols to automatically inherit the
  correct operating mode from the interface stack without further
  configuration (i.e., there is no need to explicitly configure the P2P
  interface in routing protocols).

  It is helpful to map the P2P interface over a LAN type in the
  interface management stack table.  If no entry specifies the lower
  layer of the P2P interface, then management tools lose the ability to
  retrieve and measure properties specific to lower layers.

  In standard network management protocols that make use of
  ifStackTables, the P2P interface over a LAN type is intended to be
  used solely as a means to signal that the upper-layer interface of
  link-data layer is a P2P interface.  Thus, the upper and lower layers
  of P2P over a LAN type are expected to apply appropriate semantics.
  In general, the higher layer of a P2P over a LAN type SHOULD be
  "ipForward" (value 142 in [Assignment]), and the lower layer of P2P
  over a LAN type SHOULD be any appropriate link-data layer of
  "ipForward".

  The assignment of 303 as the value for the p2pOverLan ifType was made
  by Expert Review (see [Assignment] and [RFC8126]).  The purpose of
  this document is to serve as a reference for ifType 303 by suggesting
  how the ifStackTable for the P2P interface over a LAN type is to be
  used and providing examples.

  It should be noted that this document reflects the operating model
  used on some routers.  Other routers that use different models may
  not represent a P2P as a separate interface.

2.  Requirements Language

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
  "OPTIONAL" in this document are to be interpreted as described in
  BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
  capitals, as shown here.

3.  Interface Stack Table for P2P Interface Type

3.1.  P2P Interface: higher-layer-if and lower-layer-if

  If a device implements the IF-MIB [RFC2863], then each entry in the
  "/interfaces/interface" list (see "A YANG Data Model for Interface
  Management" [RFC8343]) in the operational state is typically mapped
  to one ifEntry as required in [RFC8343].  Therefore, the P2P
  interface over a LAN type should also be fully mapped to one ifEntry
  by defining the "ifStackTable" ("higher-layer-if" and "lower-layer-
  if", defined in [RFC8343]).

  In the ifStackTable, the higher layer of the P2P interface over a LAN
  type SHALL be network layer "ipForward" to enable IP routing, and the
  lower layer of the P2P interface over a LAN type SHOULD be any link-
  data layer that can be bound to "ipForward", including
  "ethernetCsmacd", "ieee8023adLag", "l2vlan", and so on (defined in
  the iana-if-type YANG module [IANA-ifTYPE]).

  The P2P interface over the LAN type ifStackTable can be defined along
  the lines of the following example, which complies with [RFC8343] and
  [RFC6991].  In the example, "lower-layer-if" takes "ethernetCsmacd",
  but, in fact, "lower-layer-if" can be any other available link-data
  layer.  See Appendix A for more examples.

  <CODE BEGINS>
              <interface>
                <name>isis_int</name>
                <type>ianaift:ipForward</type>
              </interface>

              <interface>
                <name>eth1</name>
                <type>ianaift:ethernetCsmacd</type>
              </interface>

              <interface>
                <name>p2p</name>
                <type>ianaift:p2pOverLan</type>
                <higher-layer-if>isis_int</higher-layer-if>
                <lower-layer-if>eth1</lower-layer-if>
                <enabled>false</enabled>
                <admin-status>down</admin-status>
                <oper-status>down</oper-status>
                <statistics>
                  <discontinuity-time>
                    2021-04-01T03:00:00+00:00
                  </discontinuity-time>
                  <!-- counters now shown here -->
                </statistics>
              </interface>
  <CODE ENDS>

                                 Figure 1

3.2.  P2P Interface Statistics

  Because multiple IP interfaces can be bound to one physical port, the
  statistics on the physical port SHOULD be a complete set that
  includes statistics of all upper-layer interfaces.  Therefore, each
  P2P interface collects and displays traffic that has been sent to it
  via higher layers or received from it via lower layers.

3.3.  P2P Interface Administrative State

  The P2P interface can be shut down independently of the underlying
  interface.

  If the P2P interface is administratively up, then the "oper-status"
  (defined in [RFC8343]) of that interface SHALL fully reflect the
  state of the underlying interface; if the P2P interface is
  administratively down, then the "oper-status" of that interface SHALL
  be down.  Examples can be found in Appendix A.

4.  Security Considerations

  The writable attribute "admin-status" of the p2povervlan ifType is
  inherited from [RFC8343].  Other objects associated with the
  p2povervlan ifType are read-only.  With this in mind, the
  considerations discussed in Section 7 of [RFC8343] otherwise apply to
  the p2povervlan ifType.

5.  IANA Considerations

  In the "Interface Types (ifType)" registry, value 303 is assigned to
  p2pOverLan [Assignment].  As this document explains how the
  p2pOverLan (303) ifType is to be used, IANA has amended the reference
  for p2pOverLan (303) to point to this document (instead of [RFC5309])
  and made a similar amendment in the YANG iana-if-type module
  [IANA-ifTYPE] (originally specified in [RFC7224]).

6.  References

6.1.  Normative References

  [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119,
             DOI 10.17487/RFC2119, March 1997,
             <https://www.rfc-editor.org/info/rfc2119>.

  [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
             MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
             <https://www.rfc-editor.org/info/rfc2863>.

  [RFC5309]  Shen, N., Ed. and A. Zinin, Ed., "Point-to-Point Operation
             over LAN in Link State Routing Protocols", RFC 5309,
             DOI 10.17487/RFC5309, October 2008,
             <https://www.rfc-editor.org/info/rfc5309>.

  [RFC7224]  Bjorklund, M., "IANA Interface Type YANG Module",
             RFC 7224, DOI 10.17487/RFC7224, May 2014,
             <https://www.rfc-editor.org/info/rfc7224>.

  [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
             May 2017, <https://www.rfc-editor.org/info/rfc8174>.

  [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
             Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
             <https://www.rfc-editor.org/info/rfc8343>.

6.2.  Informative References

  [Assignment]
             IANA, "Interface Types (ifType)",
             <https://www.iana.org/assignments/smi-numbers>.

  [IANA-ifTYPE]
             IANA, "YANG Module Names",
             <https://www.iana.org/assignments/yang-parameters>.

  [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
             RFC 6991, DOI 10.17487/RFC6991, July 2013,
             <https://www.rfc-editor.org/info/rfc6991>.

  [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
             Writing an IANA Considerations Section in RFCs", BCP 26,
             RFC 8126, DOI 10.17487/RFC8126, June 2017,
             <https://www.rfc-editor.org/info/rfc8126>.

Appendix A.  Examples

  If the underlying interface is a VLAN sub-interface, the
  ifStackTable should be defined as:

  <CODE BEGINS>
            <interface>
              <name>isis_int</name>
              <type>ianaift:ipForward</type>
            </interface>

            <interface>
              <name>eth1_valn1</name>
              <type>ianaift:l2vlan</type>
            </interface>

            <interface>
              <name>p2p</name>
              <type>ianaift:p2pOverLan</type>
              <higher-layer-if>isis_int</higher-layer-if>
              <lower-layer-if>eth1_valn1</lower-layer-if>
              <enabled>false</enabled>
              <admin-status>down</admin-status>
              <oper-status>down</oper-status>
              <statistics>
                <discontinuity-time>
                  2021-04-01T03:00:00+00:00
                </discontinuity-time>
                <!-- counters now shown here -->
              </statistics>
            </interface>
  <CODE ENDS>

                                 Figure 2

  If the underlying interface is Link Aggregation Group (LAG), the
  ifStackTable should be defined as:

  <CODE BEGINS>
            <interface>
              <name>isis_int</name>
              <type>ianaift:ipForward</type>
            </interface>

            <interface>
              <name>eth1_lag1</name>
              <type>ianaift:ieee8023adLag</type>
            </interface>

            <interface>
              <name>p2p</name>
              <type>ianaift:p2pOverLan</type>
              <higher-layer-if>isis_int</higher-layer-if>
              <lower-layer-if>eth1_lag1</lower-layer-if>
              <enabled>false</enabled>
              <admin-status>down</admin-status>
              <oper-status>down</oper-status>
              <statistics>
                <discontinuity-time>
                  2021-04-01T03:00:00+00:00
                </discontinuity-time>
                <!-- counters now shown here -->
              </statistics>
            </interface>
  <CODE ENDS>

                                 Figure 3

  If the P2P interface and underlying interface are both
  administratively up and the underlying interface operational status
  is up:

  <CODE BEGINS>
            <interface>
               <name>p2p</name>
               <type>ianaift:p2pOverLan</type>
               <higher-layer-if>isis_int</higher-layer-if>
               <lower-layer-if>eth1</lower-layer-if>
               <admin-status>up</admin-status>
               <oper-status>up</oper-status>
            </interface>
  <CODE ENDS>

                                 Figure 4

  If the P2P interface and underlying interface are administratively up
  but the underlying interface operational status is down:

  <CODE BEGINS>
            <interface>
               <name>p2p</name>
               <type>ianaift:p2pOverLan</type>
               <higher-layer-if>isis_int</higher-layer-if>
               <lower-layer-if>eth1</lower-layer-if>
               <admin-status>up</admin-status>
               <oper-status>down</oper-status>
            </interface>
  <CODE ENDS>

                                 Figure 5

  If the P2P interface is administratively down:

  <CODE BEGINS>
            <interface>
               <name>p2p</name>
               <type>ianaift:p2pOverLan</type>
               <higher-layer-if>isis_int</higher-layer-if>
               <lower-layer-if>eth1</lower-layer-if>
               <admin-status>down</admin-status>
               <oper-status>down</oper-status>
            </interface>
  <CODE ENDS>

                                 Figure 6

  If the P2P interface is administratively up but the underlying
  interface is administratively down:

  <CODE BEGINS>
            <interface>
               <name>p2p</name>
               <type>ianaift:p2pOverLan</type>
               <higher-layer-if>isis_int</higher-layer-if>
               <lower-layer-if>eth1</lower-layer-if>
               <admin-status>up</admin-status>
               <oper-status>down</oper-status>
            </interface>
  <CODE ENDS>

                                 Figure 7

Acknowledgements

  The authors would like to thank Rob Wilton for his reviews and
  valuable comments and suggestions.

Authors' Addresses

  Daiying Liu
  Ericsson
  No.5 Lize East Street
  Beijing
  100102
  China
  Email: [email protected]


  Joel Halpern
  Ericsson
  Email: [email protected]


  Congjie Zhang
  Ericsson
  Email: [email protected]

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