isis B. Liu, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track B. Decraene
Expires: May 4, 2017 Orange
I. Farrer
Deutsche Telekom AG
M. Abrahamsson
T-Systems
L. Ginsberg
Cisco Systems
October 31, 2016
ISIS Auto-Configuration
draft-ietf-isis-auto-conf-03
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.
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."
This Internet-Draft will expire on May 4, 2017.
Copyright Notice
Copyright (c) 2016 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
Liu, Ed., et al. Expires May 4, 2017 [Page 1]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
(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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Specification . . . . . . . . . . . . . . . . . . . 3
3.1. IS-IS Default Configuration . . . . . . . . . . . . . . . 3
3.2. IS-IS NET Generation . . . . . . . . . . . . . . . . . . 3
3.3. IS-IS System ID Duplication Detection and Resolution . . 4
3.3.1. Router-Fingerprint TLV . . . . . . . . . . . . . . . 4
3.3.2. Duplicate System ID Detection and Resolution
Procedures . . . . . . . . . . . . . . . . . . . . . 5
3.3.3. System ID and Router-Fingerprint Generation
Considerations . . . . . . . . . . . . . . . . . . . 10
3.3.4. Double-Duplication of both System ID and Router-
Fingerprint . . . . . . . . . . . . . . . . . . . . . 11
3.4. IS-IS TLVs Usage . . . . . . . . . . . . . . . . . . . . 11
3.4.1. Authentication TLV . . . . . . . . . . . . . . . . . 11
3.4.2. Wide Metric TLV . . . . . . . . . . . . . . . . . . . 11
3.4.3. Dynamic Host Name TLV . . . . . . . . . . . . . . . . 12
3.5. Routing Behavior Considerations . . . . . . . . . . . . . 12
3.5.1. Adjacency Formation . . . . . . . . . . . . . . . . . 12
4. Security Considerations . . . . . . . . . . . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
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 configurations.
Liu, Ed., et al. Expires May 4, 2017 [Page 2]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
2. IS-IS System ID self-generation.
3. System ID duplication detection and resolution.
4. ISIS TLV utilization (Authentication TLV, Wide Metric TLV, 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 3.3.1.
2. Scope
The auto-configuration mechanism supports 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. Its allows IS-IS to be
used as the IGP 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
Point-to-Point Protocol (PPP) interfaces will be auto-configured
as Point-to-Point interfaces.
o IS-IS auto-configuration instance MUST be configured as level-1,
so that the interfaces operate as level-1 only.
3.2. IS-IS NET Generation
In IS-IS, a router (known as an Intermediate System) is identified by
a 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
Liu, Ed., et al. Expires May 4, 2017 [Page 3]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
logical entity which represents an instance of the IS-IS protocol
running on an Intermediate System.
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 to improve the stability of the routing system. It
SHOULD not be changed due to device status change (such as
interface enable/disable, interface connect/disconnect,
device reboot, firmware update etc.) or configuration change
(such as changing system configuration or IS-IS
configuration); but MUST support change as part of the
System ID collision resolution process and SHOULD allow
being cleared by a user initiated system reset.
More specific considerations for System ID generation are
described in Section 3.3.3 .
3.3. IS-IS System ID Duplication Detection and Resolution
The System ID of each node MUST be unique. As described in
Section 3.3.3, 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.
3.3.1. Router-Fingerprint TLV
The Router-Fingerprint TLV essentially re-uses the design of Router-
Hardware-Fingerprint TLV defined in [RFC7503]. However, there is one
difference in that a flag is added to indicate that the node is in
"start-up mode", which is defined in Section 3.3.2.
Liu, Ed., et al. Expires May 4, 2017 [Page 4]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|A| Reserved | |
+-+-+-+-+-+-+-+-+ Router Fingerprint (Variable) .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Router Fingerprint TLV Format
The length of the Router-Fingerprint is variable but MUST be 32
octets or greater. For correct operation, the Router-Fingerprint
MUST be unique among all the routers participating in the IS-IS area.
o Type: to be assigned by IANA.
o Length: the length of the value field. As the Router Fingerprint
length is variable, the field length is also variable.
o S flag: when set, indicates the router is in "start-up" mode.
o 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.
o Reserved: these bits MUST be set to zero and MUST be ignored by
the receiver.
o Router Fingerprint: uniquely identifies a router, variable length.
More specific considerations for Router-Fingerprint are described in
Section 3.3.3 .
3.3.2. Duplicate System ID Detection and Resolution Procedures
This section describes the duplicate System ID detection and
resolution process between two neighbors and two non-neighbors
respectively. This is due to difference in the the routing messages
between neighbors and non-neighbors.
Liu, Ed., et al. Expires May 4, 2017 [Page 5]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
3.3.2.1. Start-up Mode
While in Start-up Mode, an auto-configuration router forms
adjacencies but generates only LSP #0 which contains only the Router-
Fingerprint TLV. A router remains in startup-mode until it has
successfully completed LSPDB synchronization with all neighbors or
until 1 minute has elapsed - whichever is longer. If a duplicate
System ID is detected while in Start-up Mode stage, the Start-up Mode
router MUST clear all adjacencies, select a new System ID (subject to
rules defined in Section 3.3.2.2 ), and re-enter Start-up Mode.
The purpose of the Start-up Mode is to minimize the occurrence of
System ID changes for a router once it has become fully operational.
It has minimal impact on a running network because the Start-up Mode
node is not yet being used for forwarding traffic. Once duplicate
System IDs have been resolved the router begins normal operation. If
two routers are both in Start-up Mode and duplicate System ID is
detected, they follow the duplication resolution as specified in
Section 3.3.2.2 and Section 3.3.2.3.
When an IS-IS auto-configuration router boots up, it MUST operate in
Startup-Mode until duplicate System ID detection has successfully
completed.
3.3.2.2. Duplication Between Neighbors
In the case of duplicate System IDs being detected between neighbors,
an IS-IS auto-configuration router MUST include the Router-
Fingerprint TLV in the Hello messages, so that the duplication can be
detected before an adjacency is formed.
Start-up Mode procedures:
1. Boot up and advertisement of the Router-Fingerprint TLV in Hello
messages
The router sends Hello messages which include the Router-
Fingerprint TLV. Adjacencies are formed as normal but MUST
NOT be advertised in LSPs until the router exits Start-up
Mode.
2. Receiving Hello message(s), and System ID duplication detection
Received Hello messages are inspected for a possible duplicate
System ID. If a duplicate is detected, the router MUST check
the S flag of the Router-Fingerprint TLV.
Liu, Ed., et al. Expires May 4, 2017 [Page 6]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
+ If the S flag is NOT set (which means the Hello message was
NOT generated by a Start-up Mode neighbor), then the router
MUST re-generate the System ID and re-enter Start-up Mode.
+ If the S flag is set (meaning the neighbor is also in
Start-up Mode),
- The router which has a numerically smaller Router-
Fingerprint MUST re-generate its System ID and re-enter
Start-up Mode. Fingerprint comparison MUST be performed
octet by octet starts from the left until a difference
is found. Then, the numeric smaller fingerprint is the
one with the lowest value. If the fingerprints have
different lengths, then the shorter length fingerprint
MUST be padding with zero at the left side for
comparison.
- If the Router Fingerprints are identical, both routers
MUST re-generate the System ID and the Router
Fingerprint, and re-enter Start-up Mode.
3. Normal operation
After the System ID duplication procedure is successfully
completed, the router begins normal operation. The router
MUST re-advertise the Router-Fingerprint TLV with the S flag
disabled.
Non Start-up Mode procedures:
1. Compare the System ID in received Hello messages
When receiving a Hello message, the router MUST check the
System ID of the Hello. If the System ID is the same as its
own, it indicates that System ID duplication has occurred.
If there is no Router-Fingerprint TLV in the received Hello
message, this is interpreted as the attached router either
does not support auto-configuration, or does not have it
enabled. In this case, the auto-configuration router MUST NOT
form adjacency with the non-autoconfiguration router.
2. Duplication resolution
When duplicate System IDs are detected, the non-startup mode
router MUST check the S flag of the duplicated Router-
Fingerprint TLV:
Liu, Ed., et al. Expires May 4, 2017 [Page 7]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
+ If the S flag is NOT set, then the router with the
numerically smaller or equal Router-Fingerprint MUST
generate a new System ID. Note that, the router MUST
compare the two Router-Fingerprint octet by octet until
difference is found.
+ If the S flag is set, no further action is necessary in the
Duplication resolution process.
3. Re-joining the network with a new System ID (if required)
The router that has changed its System ID advertises new
Hellos containing the newly generated System ID to re-join the
IS-IS auto-configuration network. The conflicting SysID-
duplicated router also MUST increase the sequence number and
re-advertise its own Hellos.
The Duplication Detection process SHOULD be repeated with the
newly generated System.
3.3.2.3. Duplication Between Non-neighbors
System ID duplication may also occur between non-neighbors, therefore
an IS-IS auto-configuration router MUST also include the Router-
Fingerprint TLV in its LSP messages. The specific procedures are as
follows:
Start-up Mode procedures:
1. Boot up, adjacency formation
2. Acquiring LSPDB and checking System ID duplication
The router generates only an LSP #0 which contains only the
Fingerprint TLV; and that Fingerprint is only sent in LSP #0.
A router remains in Start-up Mode until it has successfully
completed LSPDB synchronization with all neighbors or until 1
minute has elapsed - whichever is longer. If duplicate
system-ID is detected, the router MUST check the S flag of the
Router-Fingerprint TLV of the LSP that contains the duplicated
System ID.
+ If the S flag is not set, it means the LSP was generated by
a Non Start-up Mode node, then the router itself MUST clear
all adjacencies, re-generate a new system-id and reenter
Start-up Mode.
Liu, Ed., et al. Expires May 4, 2017 [Page 8]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
+ If the S flag is set, then the router which has a
numerically smaller Router-Fingerprint MUST generate a new
System ID and reenter Start-up Mode.
3. Running in normal operation
After the System ID duplication procedure is done, the router
begins to run in normal operation. The router MUST re-
advertise the Router-Fingerprint TLV with the S flag off.
Non Start-up Mode procedures:
1. Checking the received Router-Fingerprint TLVs
When receiving a LSP containing its own System ID, the router
MUST check the Router-Fingerprint TLV. If the Router-
Fingerprint TLV is different from its own, it indicates a
System ID duplication occurs.
2. Duplication resolution
When System ID duplication occurs, the non-startup mode router
MUST check the S flag of the duplicated Router-Fingerprint
TLV:
+ If the S flag is NOT set, then the router with the
numerically smaller Router-Fingerprint MUST generate a new
System ID. Note that, the router MUST compare the two
Router-Fingerprint octet by octet until difference is
found.
+ If the S flag is set, then router does nothing.
3. Re-joining the network with the new System ID
The router changing its System ID advertises new LSPs based on
the newly generated System ID to re-join the IS-IS auto-
configuration network. The other SysID-duplicated router also
MUST re-advertise its own LSP (after increasing the sequence
number).
The newly generated System ID SHOULD perform duplication
detection as well.
Liu, Ed., et al. Expires May 4, 2017 [Page 9]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
3.3.3. 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 thus could be
used as seeds to derive distinguisher (e.g. hashing or generating
pseudo-random numbers), such as:
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
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. However, the generation of System ID and Router-
Fingerprint MUST be based on different seeds so that the two
distinguisher would not collide.
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.
Liu, Ed., et al. Expires May 4, 2017 [Page 10]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
3.3.4. Double-Duplication of both System ID and Router-Fingerprint
As described above, the resources for generating the distinguisher
might be very constrained during the initial stages. Hence, the
double-duplication of both System ID and Router-Fingerprint needs to
be considered.
ISIS-autoconfiguring routers SHOULD support detecting System ID
duplication by LSP war. LSP war is a phenomenon whereby a router
receives a LSP originated with its System ID, but it doesn't find it
in the database, or it does not match the one the router has (e.g.
it advertises IP prefixes that the router does not own, or IS
neighbors that the router does not see), then per the ISIS
specification, the router must re-originate its LSP with an increased
sequence number. If double-duplication happens, the duplicated two
routers will both continuously repeat the above behavior. After
multiples iterations, the program should be able to deduce that
double-duplication is occurring.
When this condition is detected, routers should have much more
entropies available. Thus, the router is able to extend or re-
generate its Router-Fingerprint (one simple way is just adding the
LSP sequence number of the next LSP it will send to the Router-
Fingerprint).
3.4. IS-IS TLVs Usage
This section describes the TLVs that are necessary for IS-IS auto-
configuration.
3.4.1. Authentication TLV
It is RECOMMENDED that IS-IS routers supporting this specification
minimally offer an option to explicitly configure a single password
for HMAC-MD5 authentication, which is Type 54 authentication mode of
[RFC5304]. In this case, the Authentication TLV (TLV 10) is needed.
3.4.2. Wide Metric TLV
IS-IS auto-configuration routers MUST support TLVs using wide metrics
as defined in [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
manually configured adjacencies over auto-configuringed.
Liu, Ed., et al. Expires May 4, 2017 [Page 11]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
3.4.3. Dynamic Host Name TLV
IS-IS auto-configuration routers MAY advertise their Dynamic Host
Names TLV (TLV 137, [RFC5301]). The host names 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 names, the System ID SHOULD
be appended as a suffix in the names.
3.5. Routing Behavior Considerations
3.5.1. Adjacency Formation
Since IS-IS does not require strict hold timer matching to form
adjacency, this document does not specify specific hold timers.
However, the timers should be within a reasonable range based on
current practise in the industry. (For example, the defaults defined
in [ISO_IEC10589] .)
4. Security Considerations
In general, auto-configuration is mutually incompatible with
authentication. This is a common problem that IS-IS auto-
configuration can not avoid.
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.
A malicious router could modify the System ID field to keep causing
System ID duplication detection and resolution thus cause the routing
system to oscillate. However, this is not a new attack vector as
without this document the consequences would be higher as other
routers would not have a mechanism to try and resolve this case.
5. IANA Considerations
IANA is kindly requested to assign a new TLV for the Router-
Fingerprint from the IS-IS TLV Codepoint registry.
Liu, Ed., et al. Expires May 4, 2017 [Page 12]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
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 [RFC2629].
(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", November 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>.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
DOI 10.17487/RFC2629, June 1999,
<http://www.rfc-editor.org/info/rfc2629>.
[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>.
Liu, Ed., et al. Expires May 4, 2017 [Page 13]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008,
<http://www.rfc-editor.org/info/rfc5308>.
[RFC6232] Wei, F., Qin, Y., Li, Z., Li, T., and J. Dong, "Purge
Originator Identification TLV for IS-IS", RFC 6232,
DOI 10.17487/RFC6232, May 2011,
<http://www.rfc-editor.org/info/rfc6232>.
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>.
Authors' Addresses
Bing Liu
Huawei Technologies
Q10, Huawei Campus, No.156 Beiqing Road
Hai-Dian District, Beijing, 100095
P.R. China
Email: leo.liubing@huawei.com
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Ian Farrer
Deutsche Telekom AG
Bonn
Germany
Email: ian.farrer@telekom.de
Mikael Abrahamsson
T-Systems
Stockholm
Sweden
Email: mikael.abrahamsson@t-systems.se
Liu, Ed., et al. Expires May 4, 2017 [Page 14]
Internet-Draft draft-ietf-isis-auto-conf-03 October 2016
Les Ginsberg
Cisco Systems
510 McCarthy Blvd.
Milpitas CA 95035
USA
Email: ginsberg@cisco.com
Liu, Ed., et al. Expires May 4, 2017 [Page 15]
