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ISIS Auto-Configuration

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Bing Liu , Bruno Decraene , Ian Farrer , Mikael Abrahamsson
Last updated 2014-09-02
Replaced by draft-ietf-isis-auto-conf, RFC 8196
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Network Working Group                                            B. Liu
Internet Draft                                      Huawei Technologies
Intended status: Standards Track                         Bruno Decraene
Expires: March 6, 2015                                           Orange
                                                              I. Farrer
                                                    Deutsche Telekom AG
                                                         M. Abrahamsson
                                                      September 3, 2014

                          ISIS Auto-Configuration

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on March 6, 2015.

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   This document describes mechanisms for IS-IS to be self-configuring.
   Such mechanisms could reduce the management burden to configure a
   network. One obvious environment that could benefit from these
   mechanisms is IPv6 home network where plug-and-play would be expected.
   Besides home network, some simple enterprise/ISP networks might also
   benefit from the self-configuring mechanisms.

Table of Contents

   1. Introduction ................................................. 3
   2. Design Scope ................................................. 3
   3. Protocol Specification ....................................... 4
      3.1. IS-IS Default Configuration ............................. 4
      3.2. IS-IS NET Generation .................................... 4
      3.3. IS-IS NET Duplication Detection and Resolution........... 5
         3.3.1. Router-Hardware-Fingerprint TLV .................... 5
         3.3.2. NET Duplication Detection and Resolution Procedures. 5
      3.4. Authentication TLV ...................................... 6
      3.5. Wide Metric ............................................. 7
      3.6. Adjacency Formation Consideration ....................... 7
   4. Co-existence with Other IGP Auto-configuration ............... 7
   5. Security Considerations ...................................... 7
   6. IANA Considerations .......................................... 8
   7. Acknowledgments .............................................. 8
   8. References ................................................... 8
      8.1. Normative References .................................... 8
      8.2. Informative References .................................. 8

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1. Introduction

   This memo describes mechanisms for IS-IS [RFC1195][RFC5308] to be
   auto-configuring. Such mechanisms could reduce the management burden
   to configure a network. One example is home network where plug-and-
   play would be expected. Besides home network, some simple
   enterprise/ISP networks might also potentially benefit from the auto-
   configuring mechanisms.

   In addition, this memo defines how such un-configured routers should
   behave, also limits the risk on existing network using IS-IS (Setcion
   3.4 & 3.5).

   IS-IS auto-configuration mainly contains the following aspects:

   1. IS-IS Default Configuration

   2. IS-IS NET self-generation

   3. NET duplication detection and resolution

   4. Authentication and Wide Metric TLV

2. Design Scope

   The auto-configuring mechanisms are not specifically designed based
   on IPv4 or IPv6.

   The auto-configuring mechanisms enabled interfaces are assumed to
   have a 48-bit MAC address.

   The main targeted application scenarios are supposed to be home
   networks or small enterprise networks .etc. where plug-n-play is
   expected and complex topology/hierarchy is not needed. Sophisticate
   requirements from service provider networks are out of scope.

   So this document does not provide a complete configuration-free
   alternative to the IS-IS protocol. The following features of IS-IS
   are NOT supported by this document:

   o Auto-configuring multiple IS-IS processes. The auto-configuration
   mechanisms only support configuring a single process.

   o Route between multiple IS-IS areas. The auto-configuration
   mechanisms only support routers that are within a single area.

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   o Auto-configuring multiple operation levels. The auto-configuration
   mechanisms only support level-1 operation mode.

   o This document does not consider interoperability with other routing

3. Protocol Specification

3.1. IS-IS Default Configuration

   o IS-IS SHOULD be enabled on all interfaces in a router that requires
   the IS-IS auto-configuration as default. For some specific situations,
   interface MAY be excluded if it is a clear that running IS-IS on the
   interface is not required.

   o IS-IS interfaces MUST be auto-configured to an interface type
   corresponding to their layer-2 capability. For example, Ethernet
   interfaces will be auto-configured as broadcast networks and Point-
   to-Point Protocol (PPP) interfaces will be auto-configured as Point-
   to-Point interfaces.

   o IS-IS auto-configuration interfaces MUST be configured with level-1.

3.2. IS-IS NET Generation

   In IS-IS, a router (known as an IS) is identified by an Network
   Entity Title (NET) which is the address of a Network Service Access
   Point (NSAP) and represented with an IS-IS specific address format.
   The NSAP is a logical entity which represents an instance of the IS-
   IS protocol running on an IS.

   The NET consists of three parts. The auto-generation mechanisms of
   each part are described as the following:

   Area address: This field is 1 to 13 octets in length. In IS-IS auto-
   configuring, this field MUST be 0 in 13 octets length.

   System ID: This field follows the area address field, and is 6 octets
   in length. As specified in IS-IS protocol, this field must be unique
   among all level-1 routers in the same area when the IS operates at
   Level 1. In IS-IS auto-configuring, this field SHOULD be the MAC
   address of one IS-IS enabled interface.

   NSEL: This field is the N-selector, and is 1 octet in length. In IS-
   IS auto-configuring, it must be set to "00".

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3.3. IS-IS NET Duplication Detection and Resolution

   As described in Section 3, in IS-IS auto-configuring the NETs are
   distinguished by the System ID field in which it is a MAC address. So
   for IS-IS neighbors' NET duplication, it is equal to MAC address
   duplication in a LAN, which means a serious problem that devices need
   to be changed. So the NET duplication detection and resolution
   mechanism is actually used between non-neighbors which are within
   the same IS-IS area.

   The rational of IS-IS NET duplication detection and resolution is
   described as the following.

3.3.1. Router-Hardware-Fingerprint TLV

   The Router-Hardware-Fingerprint TLV is defined in [OSPFv3AC]. This
   document re-uses it to achieve NET duplication detection.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |     Type      |    Length     |
   |           Router Hardware Fingerprint (Variable)              |
   .                                                               .
   .                                                               .
   .                                                               .
              Figure 1 Router-Hardware-Fingerprint TLV Format

   As defined in [OSPFv3AC], the contents of the hardware fingerprint
   should be some combination of CPU ID, or serial number(s) that
   provides an extremely high probability of uniqueness. It MUST be
   based on hardware attributes that will not change across hard and
   soft restarts. The length of the Router-Hardware-Fingerprint is
   variable but must be 32 octets or greater.

   Note that, since the TLV is to detect MAC address based NET
   duplication, the TLV content MUST NOT only use MAC address. MAC
   address plus other information are also not recommended to use.

3.3.2. NET Duplication Detection and Resolution Procedures

   1) Flood the Router-Hardware-Fingerprint TLVs

   When an IS-IS auto-configuration router gets online, it MUST include
   the Router-Hardware-Fingerprint TLV in the first originated level-1

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   LSP. Then all the routers in the area could receive the information
   in the TLV.

   2) Compare the received Router-Hardware-Fingerprint TLVs

   An IS-IS auto-configuring router MUST compare a received self-
   originated LSP's Router-Hardware-Fingerprint TLV against its own one.
   If they are equal, it means the LSP was indeed originated by the
   router itself; if they are not equal, it means some other router has
   the same NET originated the LSP, thus there is a NET duplication.

   3) Duplication resolution

   When NET duplication occurs, the router with the numerically smaller
   router hardware fingerprint MUST generate a new NET.

   4) Purge the LSPs containing duplicated NET

   Before flooding the new NET, the LSP with the prior duplicate NET
   MUST be purged. And any IS-IS neighbor adjacencies MUST be

   5) Re-join the network with the new NET

   After purging the LSPs with the duplicated NET, the router re-join
   the IS-IS auto-configuration network with the newly generated NET.

3.4. Authentication TLV

   Every IS-IS auto-configuration message MUST include an authentication
   TLV (TLV 10, [RFC5304]) with the Type 1 authentication mode
   ("Cleartext Password") in order to avoid the auto-conf router to
   accidentally join an existing IS-IS network which is not intended to
   be auto-configured.

   This feature is necessary because a low end CPE joining an existing
   IS-IS network might seriously break it or cause unnecessary
   management confusion.

   The cleartext password is specified as "isis-autoconf". Routers that
   implement IS-IS auto-configuration MUST use this password as default,
   so that different routers could authenticate each other with no human
   intervene as default. And routers MUST be able to set manual password
   by the users.

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3.5. Wide Metric

   IS-IS auto-configuration routers SHOULD support wide metric (TLV 22,
   [RFC5305]). It is recommended that IS-IS auto-configuration routers
   use a high metric value (e.g. 1000000) as default in order to
   typically prefer the manually configured adjacencies rather than the
   auto-conf ones.

3.6. Adjacency Formation Consideration

   ISIS does not require strict hold timers matching to form adjacency.
   But a reasonable range might be needed. Whether we need to specify a
   best practice timers in ISIS-AC is an open question.[TBD].

4. Co-existence with Other IGP Auto-configuration

   If a router supports multiple IGP auto-configuration mechanisms (e.g.
   both IS-IS auto-configuration and OSPF auto-configuration), then in
   practice it is a problem that there should be a mechanism to decide
   which IGP to be used, or even both.

   However, it is not proper to specify choice/interaction of multiple
   IGPs in any standalone IGP auto-configuration protocols. It should be
   done in the CPE level. Currently, there is some relevant work
   emerging, for example, the suggestion from [HOMENET-HNCP] is to have
   the proposed HNCP (Home Network Control Protocol) choose what IGP
   should be used.

5. Security Considerations

   Unwanted routers could easily join in an existing IS-IS auto-
   configuration network by setting the authentication password as
   "isis-autoconf" default value or sniff the cleartext password online.
   However, this is a common security risk shared by other IS-IS
   networks that don't set proper authentication mechanisms. For wired
   deployment, the wired line itself could be considered as an implicit
   authentication that normally unwanted routers are not able to connect
   to the wire line; for wireless deployment, the authentication could
   be achieve at the lower wireless link layer.

   Malicious router could modify the SystemID field to cause NET
   duplication detection and resolution vibrate thus cause the routing
   system vibrate.

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6. IANA Considerations

   The Router Hardware Fingerprint TLV type code needs an assignment by

7. Acknowledgments

   Many useful comments and contributions were made by Sheng Jiang.

   This document was inspired by [OSPFv3AC].

8. References

8.1. Normative References

   [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
             dual environments", RFC 1195, December 1990.

   [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
             Authentication", RFC 5304, October 2008.

   [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
             Engineering", RFC 5305, October 2008.

   [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October

8.2. Informative References

   [OSPFv3AC]Lindem, A., and J. Arkko, "OSPFv3 Auto-Configuration", Work
             in Progress, October 2013

             Stenberg, M., and S. Barth, "Home Networking Control
             Protocol", Work in Progress, February 05

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Authors' Addresses

   Bing Liu
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus
   No.156 Beiqing Rd.
   Hai-Dian District, Beijing  100095
   P.R. China


   Bruno Decraene


   Ian Farrer
   Deutsche Telekom AG


   Mikael Abrahamsson


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