isis B. Liu
Internet-Draft Huawei Technologies
Intended status: Standards Track B. Decraene
Expires: December 1, 2015 Orange
I. Farrer
Deutsche Telekom AG
M. Abrahamsson
T-Systems
May 30, 2015
ISIS Auto-Configuration
draft-liu-isis-auto-conf-04
Abstract
This document specifies an IS-IS auto-configuration technology. The
key mechanisms of this technology are IS-IS NET (Network Entity
Title) self-generation, duplication detection and duplication
resolution. This technology fits the environment where plug-and-play
is expected, e.g., home networks and small or medium size enterprise
networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 1, 2015.
Copyright Notice
Copyright (c) 2015 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
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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 NET Duplication Detection and Resolution . . . . . 4
3.3.1. Router-Fingerprint TLV . . . . . . . . . . . . . . . 5
3.3.2. NET Duplication Detection and Resolution Procedures . 5
3.3.3. SysID and Router-Fingerprint Generation
Considerations . . . . . . . . . . . . . . . . . . . 6
3.3.4. Double-Duplication of both NET and Router-Fingerprint 7
3.4. IS-IS TLVs Usage . . . . . . . . . . . . . . . . . . . . 7
3.4.1. Authentication TLV . . . . . . . . . . . . . . . . . 7
3.4.2. Wide Metric TLV . . . . . . . . . . . . . . . . . . . 8
3.4.3. Dynamic Host Name TLV . . . . . . . . . . . . . . . . 8
3.4.4. Purge Originator Identification TLV . . . . . . . . . 8
3.5. Routing Behavior Considerations . . . . . . . . . . . . . 8
3.5.1. Adjacency Formation . . . . . . . . . . . . . . . . . 8
3.5.2. Co-existing with Other IGP Auto-configuration . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
This document describes mechanisms for IS-IS [RFC1195] [RFC5308] to
be auto-configuring. Such mechanisms could reduce the management
burden to configure a network. Home networks and small or medium
size enterprise networks where plug-n-play is expected can benefit
from these mechanisms.
In addition, this document defines how such un-configured routers
should behave, in order to limit the risk on existing network using
IS-IS (please refer to Section 3.4.1 andSection 3.5).
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IS-IS auto-configuration contains the following aspects:
1. IS-IS default configurations
2. IS-IS NET (Network Entity Title) self-generation
3. NET duplication detection and resolution
4. ISIS TLVs utilization such as Authentication TLV, Wide Metric TLV
etc.
2. Scope
The auto-configuring mechanisms does not specifically distinguish
IPv4 or IPv6.
This auto-configuration mechanism aims at simple case. The following
advanced features are out of scope:
o Multiple IS-IS instances
o Multi-area and level-2 routers
o Interworking with other routing protocols
3. Protocol Specification
3.1. IS-IS Default Configuration
o IS-IS SHOULD be enabled as default on all interfaces in a router
that requires the IS-IS auto-configuration. For some specific
situations, interface MAY be excluded if it is a clear that
running IS-IS auto-configuration 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 Intermediate System) is identified by
an 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
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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:
o Area address
This field is 1 to 13 octets in length. In IS-IS auto-
configuration, this field MUST be 0 in 13 octets length.
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 in IS-IS protocol, this field must be unique
among all routers in the same area.
- In order to make the routing system stable, the System ID
SHOULD remain the same after it is firstly generated. It
SHOULD not be changed due to device status change (such as
interface enable/disable, interface plug in/off, device
reboot, firmware update .etc) or configuration change (such
as changing system configurations or IS-IS configurations
.etc); but it MUST allow be changed by collision resolution
and SHOULD allow be cleared by user enforced system reset.
More specific considerations for SysID generation are described
in Section 3.3.3 .
o NSEL
This field is the N-selector, and is 1 octet in length. In IS-
IS auto-configuration, it SHOULD be set to "00".
3.3. IS-IS NET Duplication Detection and Resolution
NET addresses need to be distinct within one IS-IS area. As
described in Section 3.3.3, the NET address is generated based on
entropies such as MAC address which are supposed to be unique, but in
theory there is still possibility of duplication. This section
defines how IS-IS detects and corrects NET duplication.
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3.3.1. Router-Fingerprint TLV
The Router-Fingerprint TLV re-uses the design of Router-Hardware-
Fingerprint TLV defined in [RFC7503].
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 Fingerprint (Variable) |
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The length of the Router-Fingerprint is variable but must be 32
octets or greater; and the content is also supposed to be unique
among all the routers.
More specific considerations for Router-Fingerprint is described in
Section 3.3.3 .
3.3.2. NET Duplication Detection and Resolution Procedures
1) Flood the Router-Distinguisher TLVs
When an IS-IS auto-configuration router gets online, it MUST
include the Router-Fingerprint TLV in the first originated level-1
LSP. Then all the routers in the area could receive the
information in the TLV.
2) Compare the received Router-Fingerprint TLVs
When receiving a LSP having its own NET address, an IS-IS router
MUST check the Router-Fingerprint TLV. If the Router-Fingerprint
TLV is different from its own, there is a NET duplication and the
following procedure SHOULD be performed.
3) Duplication resolution
When NET duplication occurs, the router with the numerically
smaller Router-Fingerprint MUST generate a new NET. Note that,
the router MUST compare the two Router-Fingerprint in terms of two
numeric numbers (e.g. Unsigned integer).
4) Re-join the network with the new NET
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The router with the smaller Router-Fingerprint advertise new LSPs
based on the newly generated NET to re-join the IS-IS auto-
configuration network.
Note that, since the other router still uses the old NET, the
smaller Router-Distinguisher router MUST NOT purge it's LSPs; the
router with the highest Router-Distinguisher MUST re-advertise its
own LSP (after increasing the sequence number).
The newly generated NET SHOULD take a NET duplication detection as
well.
3.3.3. SysID and Router-Fingerprint Generation Considerations
As specified in this document, there are two distinguisher need to be
self-generated, which is SysID and Router-Fingerprint. In a network
device, normally there are resources which 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
This document does not specify a certain method to generate the SysID
and Router-Fingerprint. However, the generation of SysID 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 the hardware/software limitation and the
lack of sufficient communication packets at the initial stage in the
home routers when doing ISIS-autoconfiguration. In this case, this
document suggests to use MAC address as SysID and generate a pseudo-
random number based on another seed (such as the memory address of a
certain variable in the program) as Router-Fingerprint. The pseudo-
random number might not have a very high quality in this solution,
but should be sufficient in home networks scenarios.
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Note that, the Router-Fingerprint SHOULD also remain the same after
it is firstly generated. It SHOULD not be changed due to device
status change (such as interface enable/disable, interface plug in/
off, device reboot, firmware update .etc) or configuration change
(such as changing system configurations or IS-IS configurations
.etc); but it MUST allow be changed by double-duplication resolution
Section 3.3.4 and SHOULD allow be cleared by user enforced system
reset.
3.3.4. Double-Duplication of both NET and Router-Fingerprint
As described above, the resources for generating the distinguisher
might be very constrained at the initial stage. Hence, the double-
duplication of both NET and Router-Fingerprint needs to be
considered.
ISIS-autoconfiguring routers SHOULD support detecting NET duplication
by LSP war. LSP war is a phenomenon that if a router receives a LSP
originated with it's NET, 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 doesn't own, or IS neighbors that the router
doesn't see), then Per 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 have the above behavior. After multiples iterations,
the program should be able to deduce that double-duplication happens.
At the point when double-duplication happens, routers should have
much more entropies available. Thus, the router is 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
3.4.1. 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 since it might seriously break an existing
IS-IS network or cause unnecessary management confusion if a low end
CPE (which might be the normal form of ISIS-autoconf routers)
occasionally joins the network.
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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.
3.4.2. Wide Metric TLV
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.
3.4.3. Dynamic Host Name TLV
IS-IS auto-configuration routers SHOULD advertise their Dynamic Host
Names TVL (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.
3.4.4. Purge Originator Identification TLV
For troubleshooting purpose, the Purge Originator Identification TLV
(TLV 13, [RFC6232]) MAY be used to determine the origin of the purge.
Please refer to [RFC6232] for details.
3.5. Routing Behavior Considerations
3.5.1. Adjacency Formation
Since ISIS does not require strict hold timers 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, 30 seconds for
holdtime and 20 minutes for LSP lifetime.)
3.5.2. Co-existing 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, the behavior of multiple IGP protocols interaction should be
done in the router level rather than in any IGP protocols. For
example, with the Home Network Control Protocol
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([I-D.ietf-homenet-hncp]), the routers could achieve a consensus on
what IGP to use.
4. Security Considerations
In general, auto-configuration is mutually incompatible with
authentication. So we can't have both. This is not really specific
to IS-IS.
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 SysID field to cause NET
duplication detection and resolution vibrate thus cause the routing
system vibrate.
5. IANA Considerations
The Router Hardware Fingerprint TLV type code needs an assignment by
IANA.
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 and contributions
were made by Sheng Jiang, Qin Wu, Hannes Gredler, Peter Lothberg, Uma
Chundury, Nan Wu, Acee Lindem, Les Ginsberg and some other people in
ISIS working group.
This document was produced using the xml2rfc tool [RFC2629].
(initially prepared using 2-Word-v2.0.template.dot. )
7. References
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7.1. Normative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC5301] McPherson, D. and N. Shen, "Dynamic Hostname Exchange
Mechanism for IS-IS", RFC 5301, October 2008.
[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
2008.
[RFC6232] Wei, F., Qin, Y., Li, Z., Li, T., and J. Dong, "Purge
Originator Identification TLV for IS-IS", RFC 6232, May
2011.
7.2. Informative References
[I-D.ietf-homenet-hncp]
Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", draft-ietf-homenet-hncp-04 (work in
progress), March 2015.
[RFC7503] Lindem, A. and J. Arkko, "OSPFv3 Autoconfiguration", RFC
7503, April 2015.
Authors' Addresses
Bing Liu
Huawei Technologies
Q14, Huawei Campus, No.156 Beiqing Road
Hai-Dian District, Beijing, 100095
P.R. China
Email: leo.liubing@huawei.com
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Bruno Decraene
Orange
Issy-les-Moulineaux FR
FR
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
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