Internet DRAFT - draft-ietf-isis-auto-conf
draft-ietf-isis-auto-conf
isis B. Liu, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track L. Ginsberg
Expires: November 10, 2017 Cisco Systems
B. Decraene
Orange
I. Farrer
Deutsche Telekom AG
M. Abrahamsson
T-Systems
May 9, 2017
ISIS Auto-Configuration
draft-ietf-isis-auto-conf-05
Abstract
This document specifies IS-IS auto-configuration mechanisms. The key
components are IS-IS System ID self-generation, duplication detection
and duplication resolution. These mechanisms provide limited IS-IS
functions, and so are suitable for networks where plug-and-play
configuration is expected.
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
[RFC2119] when they appear in ALL CAPS. When these words are not in
ALL CAPS (such as "should" or "Should"), they have their usual
English meanings, and are not to be interpreted as [RFC2119] key
words.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on November 10, 2017.
Copyright Notice
Copyright (c) 2017 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
(http://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. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Specification . . . . . . . . . . . . . . . . . . . 3
3.1. IS-IS Default Configuration . . . . . . . . . . . . . . . 3
3.2. IS-IS NET Generation . . . . . . . . . . . . . . . . . . 4
3.3. Router-Fingerprint TLV . . . . . . . . . . . . . . . . . 5
3.4. Protocol Operation . . . . . . . . . . . . . . . . . . . 6
3.4.1. Start-Up mode . . . . . . . . . . . . . . . . . . . . 6
3.4.2. Adjacency Formation . . . . . . . . . . . . . . . . . 7
3.4.3. IS-IS System ID Duplication Detection . . . . . . . . 7
3.4.4. Duplicate System ID Resolution Procedures . . . . . . 7
3.4.5. System ID and Router-Fingerprint Generation
Considerations . . . . . . . . . . . . . . . . . . . 8
3.4.6. Duplication of both System ID and Router-Fingerprint 9
3.5. Additional IS-IS TLVs Usage Guidelines . . . . . . . . . 10
3.5.1. Authentication TLV . . . . . . . . . . . . . . . . . 11
3.5.2. Metric Used in Reachability TLVs . . . . . . . . . . 11
3.5.3. Dynamic Host Name TLV . . . . . . . . . . . . . . . . 11
4. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
This document specifies mechanisms for IS-IS [RFC1195]
[ISO_IEC10589][RFC5308] to be auto-configuring. Such mechanisms
could reduce the management burden for configuring a network,
especially where plug-and-play device configuration is required.
IS-IS auto-configuration is comprised of the following functions:
1. IS-IS default configuration.
2. IS-IS System ID self-generation.
3. System ID duplication detection and resolution.
4. ISIS TLV utilization (Authentication TLV, metrics in reachability
advertisements, and Dynamic Host Name TLV).
This document also defines mechanisms to prevent the unintentional
interoperation of auto-configured routers with non-autoconfigured
routers. See Section 3.3.
2. Scope
The auto-configuration mechanisms support both IPv4 and IPv6
deployments.
These auto-configuration mechanisms aim to cover simple deployment
cases. The following important features are not supported:
o Multiple IS-IS instances.
o Multi-area and level-2 routing.
o Interworking with other routing protocols.
IS-IS auto-configuration is primarily intended for use in small (i.e.
10s of devices) and unmanaged deployments. It allows IS-IS to be
used without the need for any configuration by the user. It is not
recommended for larger deployments.
3. Protocol Specification
3.1. IS-IS Default Configuration
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
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Point-to-Point Protocol (PPP) interfaces will be auto-configured
as Point-to-Point interfaces.
o IS-IS auto-configuration instances MUST be configured as level-1,
so that the interfaces operate as level-1 only.
o originatingLSPBufferSize is set to 512.
o MaxAreaAddresses is set to 3
o Extended IS Reachability and IP Reachability TLVs [RFC5305] MUST
be used i.e. a router operating in auto configuration mode MUST
NOT use any of the following TLVs:
* IS Neighbors (2)
* IP Internal Reachability (128)
* IP External Reachability (130)
TLVs listed above MUST be ignored on receipt.
3.2. IS-IS NET Generation
In IS-IS, a router (known as an Intermediate System) is identified by
a Network Entity Title (NET) which is a type of Network Service
Access Point (NSAP). The NET is the address of an instance of the
IS-IS protocol running on an Intermediate System (IS).
The auto-configuration mechanism generates the IS-IS NET as the
following:
o Area address
In IS-IS auto-configuration, this field MUST be 13 octets long
and set to all 0.
o System ID
This field follows the area address field, and is 6 octets in
length. There are two basic requirements for the System ID
generation:
- As specified by the IS-IS protocol, this field must be
unique among all routers in the same area.
- After its initial generation, the System ID SHOULD remain
stable. Changes such as interface enable/disable, interface
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connect/disconnect, device reboot, firmware update, or
configuration changes SHOULD NOT cause the system ID to
change. System ID change as part of the System ID collision
resolution process MUST be supported. Implementations
SHOULD allow the System ID to be cleared by a user initiated
system reset.
More specific considerations for System ID generation are
described in Section 3.4.5.
3.3. Router-Fingerprint TLV
The Router-Fingerprint TLV is similar to the Router-Hardware-
Fingerprint TLV defined in [RFC7503]. However, the TLV defined here
includes a flags field to support indicating that the router is in
Start-up mode and is operating in auto-configuration mode.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags Field | |
+-+-+-+-+-+-+-+-+ Router Fingerprint (Variable) .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: to be assigned by IANA.
Length: the length of the value field. Must be >= 33.
Flags field (1 octet)
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|S|A| Reserved |
+-+-+-+-+-+-+-+-+
S flag: when set, indicates the router is in "start-up" mode.
A flag: when set, indicates that the router is operating in
auto-configuration mode. The purpose of the flag is so that
two routers can identify if they are both using auto-configuration.
If the A flag setting does not match in hellos then no adjacency
should be formed.
Reserved: these bits MUST be set to zero and MUST be ignored by
the receiver.
Router Fingerprint: 32 or more octets.
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More specific considerations for Router-Fingerprint are described in
Section 3.4.5.
Router Fingerprint TLV MUST be included in Intermediate System to
Intermediate System Hellos (IIHs) originated by a router operating in
auto-configuration mode. An auto-configuration mode router MUST
ignore IIHs that don't contain the Router Fingerprint TLV.
Router Fingerprint TLV MUST be included in Link State PDU (LSP) #0
originated by a router operating in auto-configuration mode. If an
LSP #0 which does NOT contain a Router Fingerprint TLV is received by
a Router operating in auto-configuration mode the LSP is flooded as
normal, but the entire LSP set originated by the sending router MUST
be ignored when running the Decision process.
The router fingerprint TLV MUST NOT be included in an LSP with a non-
zero number and when received MUST be ignored.
3.4. Protocol Operation
This section describes the operation of a router supporting auto-
configuration mode.
3.4.1. Start-Up mode
When a router starts operation in auto-configuration mode, both the S
and A bits MUST be set in the Router Fingerprint TLV included in both
hellos and LSP #0. During this mode only LSP #0 is generated and IS
or IP/IPv6 reachability TLVs MUST NOT be included in LSP #0. A
router remains in Start-up mode for a minimum period of time
(recommended to be 1 minute). This time should be sufficient to
bring up adjacencies to all expected neighbors. A router leaves
Start-up mode once the minimum time has elapsed and full LSP database
synchronization is achieved with all neighbors in the UP state.
When a router exits startup-mode it clears the S bit in Router
Fingerprint TLVs it sends in hellos and LSP#0. The router MAY now
advertise IS neighbor and IP/IPv6 prefix reachability in its LSPs and
MAY generate LSPs with a non-zero number.
The purpose of Start-up Mode is to minimize the occurrence of System
ID changes for a router once it has become fully operational. Any
System ID change during Start-up mode will have minimal impact on a
running network because while in Start-up mode the router is not yet
being used for forwarding traffic.
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3.4.2. Adjacency Formation
Routers operating in auto-configuration mode MUST NOT form
adjacencies with routers which are NOT operating in auto-
configuration mode. The presence of the Router Fingerprint TLV with
the A bit set indicates the router is operating in auto-configuration
mode.
NOTE: The use of the special area address of all 0's makes it
unlikely that a router which is not operating in auto-configuration
mode will be in the same area as a router operating in auto-
configuration mode. However, the check for the Router Fingerprint
TLV with A bit set provides additional protection.
3.4.3. IS-IS System ID Duplication Detection
The System ID of each node MUST be unique. As described in
Section 3.4.5, the System ID is generated based on entropies (e.g.
MAC address) which are generally expected to be unique. However,
since there may be limitations to the available entropies, there is
still the possibility of System ID duplication. This section defines
how IS-IS detects and resolves System ID duplication. Duplicate
System ID may occur between neighbors or between routers in the same
area which are not neighbors.
Duplicate System ID with a neighbor is detected when the System ID
received in an IIH is identical to the local System ID and the
Router-Fingerprint in the received Router-Fingerprint TLV does NOT
match the locally generated Router-Fingerprint.
Duplicate System ID with a non-neighbor is detected when an LSP #0 is
received, the System ID of the originator is identical to the local
System ID, and the Router-Fingerprint in the Router-Fingerprint TLV
does NOT match the locally generated Router-Fingerprint.
3.4.4. Duplicate System ID Resolution Procedures
When duplicate System ID is detected one of the systems MUST assign
itself a different System ID and perform a protocol restart. The
resolution procedure attempts to minimize disruption to a running
network by choosing a router which is in Start-up mode to be
restarted whenever possible.
The contents of the Router-Fingerprint TLVs for the two routers with
duplicate System IDs are compared.
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If one TLV has the S bit set (router is in Start-up mode) and one TLV
has the S bit clear (router is NOT in Start-up mode) the router in
Start-up mode MUST generate a new System ID and restart the protocol.
If both TLVs have the S bit set (both routers are in Start-up mode)
or both TLVs have the S bit clear (neither router is in Start-up
mode) then the router with numerically smaller Router-Fingerprint
MUST generate a new System ID and restart the protocol.
Fingerprint comparison is performed octet by octet starting from the
first received octet until a difference is detected. If the
fingerprints have different lengths and all octets up to the shortest
length are identical then the fingerprint with smaller length is
considered smaller.
If the fingerprints are identical in both content and length (and
state of the S bit is identical) and the duplication is detected in
hellos then the both routers MUST generate a new System ID and
restart the protocol.
If fingerprints are identical in both content and length and the
duplication is detected in LSP #0 then the procedures defined in
Section 3.4.6 MUST be followed.
3.4.5. System ID and Router-Fingerprint Generation Considerations
As specified in this document, there are two distinguishing items
that need to be self-generated: the System ID and Router-Fingerprint.
In a network device, normally there are some resources which can
provide an extremely high probability of uniqueness (some examples
listed below). These resources can be used as seeds to derive
identifiers.
o MAC address(es)
o Configured IP address(es)
o Hardware IDs (e.g. CPU ID)
o Device serial number(s)
o System clock at a certain specific time
o Arbitrary received packet(s) on an interface(s)
This document recommends the use of an IEEE 802 48-bit MAC address
associated with the router as the initial System ID. This document
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does not specify a specific method to re-generate the System ID when
duplication happens.
This document also does not specify a specific method to generate the
Router-Fingerprint.
There is an important concern that the seeds listed above (except MAC
address) might not be available in some small devices such as home
routers. This is because of hardware/software limitations and the
lack of sufficient communication packets at the initial stage in home
routers when doing ISIS auto-configuration. In this case, this
document suggests using the MAC address as System ID and generating a
pseudo-random number based on another seed (such as the memory
address of a certain variable in the program) as the Router-
Fingerprint. The pseudo-random number might not have a very high
probability of uniqueness in this solution, but should be sufficient
in home networks scenarios.
The considerations surrounding System ID stability described in
section Section 3.2 also need to be applied.
3.4.6. Duplication of both System ID and Router-Fingerprint
As described above, the resources for generating System ID/
Fingerprint might be very constrained during the initial stages.
Hence, the duplication of both System ID and Router-Fingerprint needs
to be considered. In such a case it is possible that a router will
receive an LSP with System ID and Router-Fingerprint identical to the
local values but the LSP is NOT identical to the locally generated
copy i.e. sequence number is newer or sequence number is the same but
the LSP has a valid checksum which does not match. The term DD-LSP
is used to describe such an LSP.
In a benign case, this will occur if a router restarts and it
receives copies of its own LSPs from its previous incarnation. This
benign case needs to be distinguished from the pathological case
where there are two different routers with the same System ID and the
same Router-Fingerprint.
In the benign case, the restarting router will generate a new version
of its own LSP with higher sequence number and flood the new LSP
version. This will cause other routers in the network to update
their LSPDB and synchronization will be achieved.
In the pathological case the generation of a new version of an LSP by
one of the "twins" will cause the other twin to generate the same LSP
with a higher sequence number - and oscillation will continue without
achieving LSPDB synchronization.
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Note that comparison of S bit in the Router-Fingerprint TLV cannot be
performed as in the benign case it is expected that the S bit will be
clear. Also note that the conditions for detecting duplicate System
ID will NOT be satisfied because both the System ID and the Router-
Fingerprint will be identical.
The following procedure is defined:
DD-state is a boolean which indicates if a
DD-LSP #0 has been received
DD-count is the count of the number of occurences
of reception of a DD-LSP
DD-timer is a timer associated with reception of
DD-LSPs. Recommended value is 60 seconds.
DD-max is the maximum number of DD-LSPs allowed
to be received in DD-timer interval.
Recommended value is 3.
When a DD-LSP is received:
If DD-state is FALSE:
DD-state is set to TRUE
DD-timer is started
DD-count is initialized to 1.
If DD-state is TRUE:
DD-count is incremented
If DD-count is >= DD-max:
Local system MUST generate a new System ID
and Router-Fingerprint and restart the protocol
DD-state is (re)initialized to FALSE and
DD-timer cancelled.
If DD-timer expires:
DD-state is set to FALSE.
Note that to minimze the likelihood of duplication of both System ID
and Router-fingerprint reoccuring, routers SHOULD have more entropies
available. One simple way to achieve this is to add the LSP sequence
number of the next LSP it will send to the Router-Fingerprint.
3.5. Additional IS-IS TLVs Usage Guidelines
This section describes the behavior of selected TLVs when used by a
router supporting IS-IS auto-configuration.
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3.5.1. Authentication TLV
It is RECOMMENDED that IS-IS routers supporting this specification
offer an option to explicitly configure a single password for HMAC-
MD5 authentication as specified in[RFC5304].
3.5.2. Metric Used in Reachability TLVs
It is RECOMMENDED that IS-IS auto-configuration routers use a high
metric value (e.g. 100000) as default in order to allow manually
configured adjacencies to be preferred over auto-configured.
3.5.3. Dynamic Host Name TLV
IS-IS auto-configuration routers MAY advertise their Dynamic Host
Name TLV (TLV 137, [RFC5301]). The host name could be provisioned by
an IT system, or just use the name of vendor, device type or serial
number, etc.
To guarantee the uniqueness of the host name, the System ID SHOULD be
appended as a suffix in the names.
4. Security Considerations
In the absence of cryptographic authentication it is possible for an
attacker to inject a PDU falsely indicating there is a duplicate
system-id. This may trigger automatic restart of the protocol using
the duplicate-id resolution procedures defined in this document.
Note that the use of authentication is incompatible with auto-
configuration as it requires some manual configuration.
For wired deployment, the wired connection itself could be considered
as an implicit authentication in that unwanted routers are usually
not able to connect (i.e. there is some kind of physical security in
place preventing the connection of rogue devices); for wireless
deployment, the authentication could be achieved at the lower
wireless link layer.
5. IANA Considerations
This document requires the definition of a new IS-IS TLV to be
reflected in the "IS-IS TLV Codepoints" registry:
Type Description IIH LSP SNP Purge
---- ------------ --- --- --- -----
TBA Router-Fingerprint Y Y N Y
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6. Acknowledgements
This document was heavily inspired by [RFC7503].
Martin Winter, Christian Franke and David Lamparter gave essential
feedback to improve the technical design based on their
implementation experience.
Many useful comments were made by Acee Lindem, Karsten Thomann,
Hannes Gredler, Peter Lothberg, Uma Chundury, Qin Wu, Sheng Jiang and
Nan Wu, etc.
This document was produced using the xml2rfc tool [RFC7991].
(initially prepared using 2-Word-v2.0.template.dot. )
7. References
7.1. Normative References
[ISO_IEC10589]
"Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473), ISO/IEC
10589:2002, Second Edition.", Nov 2002.
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <http://www.rfc-editor.org/info/rfc1195>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5301] McPherson, D. and N. Shen, "Dynamic Hostname Exchange
Mechanism for IS-IS", RFC 5301, DOI 10.17487/RFC5301,
October 2008, <http://www.rfc-editor.org/info/rfc5301>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <http://www.rfc-editor.org/info/rfc5304>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>.
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[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008,
<http://www.rfc-editor.org/info/rfc5308>.
7.2. Informative References
[RFC7503] Lindem, A. and J. Arkko, "OSPFv3 Autoconfiguration",
RFC 7503, DOI 10.17487/RFC7503, April 2015,
<http://www.rfc-editor.org/info/rfc7503>.
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, DOI 10.17487/RFC7991, December 2016,
<http://www.rfc-editor.org/info/rfc7991>.
Authors' Addresses
Bing Liu (editor)
Huawei Technologies
Q10, Huawei Campus, No.156 Beiqing Road
Hai-Dian District, Beijing, 100095
P.R. China
Email: leo.liubing@huawei.com
Les Ginsberg
Cisco Systems
821 Alder Drive
Milpitas CA 95035
USA
Email: ginsberg@cisco.com
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Ian Farrer
Deutsche Telekom AG
Bonn
Germany
Email: ian.farrer@telekom.de
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Mikael Abrahamsson
T-Systems
Stockholm
Sweden
Email: mikael.abrahamsson@t-systems.se
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