Internet DRAFT - draft-li-lsr-liveness
draft-li-lsr-liveness
LSR Working Group Tony. Li
Internet-Draft Juniper Networks
Intended status: Standards Track 3 February 2022
Expires: 7 August 2022
Node Liveness Protocol
draft-li-lsr-liveness-02
Abstract
Prompt notification of the loss of node liveness or reachability is
useful for restoring services in tunneled topologies. IGP
summarization precludes remote nodes from directly observing the
status of remote nodes. This document proposes a service that, in
conjunction with the IGP, provides prompt notifications without
impacting IGP summarization.
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
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This Internet-Draft will expire on 7 August 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Node Liveness Capability Advertisement . . . . . . . . . . . 3
3.1. Node Liveness Advertisement in IS-IS . . . . . . . . . . 3
3.2. Node Liveness Advertisement in OSPF . . . . . . . . . . . 5
4. Node Liveness Protocol . . . . . . . . . . . . . . . . . . . 6
4.1. Messages . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Client actions . . . . . . . . . . . . . . . . . . . . . 6
4.3. ABR actions . . . . . . . . . . . . . . . . . . . . . . . 6
4.3.1. Autonomous Notification Mode . . . . . . . . . . . . 8
4.3.2. Proxy ABRs . . . . . . . . . . . . . . . . . . . . . 8
4.4. Registration Messages . . . . . . . . . . . . . . . . . . 8
4.4.1. Liveness Registration sub-TLV . . . . . . . . . . . . 9
4.5. Notification Messages . . . . . . . . . . . . . . . . . . 9
4.5.1. Liveness Notification sub-TLV . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. Normative References . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Overlay services are increasingly common and are implemented by
creating tunnels over a physical infrastructure. The failure of one
of the tunnel endpoints implies that the traffic towards that
endpoint will be lost until the other endpoint recognizes the
situation and takes remedial action. Prompt notification of the
failure of the other endpoint is useful in minimizing the duration of
the outage.
Some network designs have come to rely on examining the IGP's Link
State Database (LSDB) to determine node liveness and, through the IGP
SPF computation, the node's reachability. However, if the network is
to scale, some form of summarization must be employed, resulting in
this information no longer being directly available. This document
proposes a protocol that will provide prompt notificaion of changes
in node liveness, even in networks that employ IGP summarization.
The service itself runs on OSPF [RFC2328] [RFC5340] Area Border
Routers (ABRs) or IS-IS [ISO10589] L1-L2 routers. For brevity, we
will use the term 'ABRs' for both cases.
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This service uses a simple, hierarchical publish-subscribe
architecture. Clients are nodes within non-backbone OSPF areas or L1
IS-IS area. They register with their local ABRs. The ABRs are fully
meshed, with the exception that ABRs of the same area need not
interact. Notifications initiated by an ABR flow to other ABRs and
from there to client nodes.
The availability of this service is advertised as part of the IGP, so
that discovery of the service is automatic. Clients can
automatically detect their local ABRs and ABRs can detect each other
and automatically form the necessary hierarchy.
The protocol runs on top of TCP [RFC0793] and/or QUIC [RFC9000] for
reliability. Security is provided by conventional transport protocol
mechanisms, such as TLS [RFC5246].
Node liveness should not be confused with service liveness. If a
node is alive, then a service may or may not be up. This protocol
only tries to convey node liveness.
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. Node Liveness Capability Advertisement
The Node Liveness Protocol is run by ABRs and is advertised in the
IGP for connections by clients and other ABRs. Advertisements are
done both into the backbone (L2) and into non-backbone (L1) areas.
The advertisements into the backbone allow ABRs to automatically
mesh. The advertisements into the non-backbone areas allow clients
to automatically determine where the service is available.
3.1. Node Liveness Advertisement in IS-IS
An ABR advertises the IS-IS Node Liveness sub-TLV as part of the IS-
IS Router Capability TLV [RFC7981]. This is injected into the ABRs
L1 and L2 LSP. The format of the IS-IS Node Liveness sub-TLV is:
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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 |O|N| Reserved | TPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Number | IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address | IPv6 Address... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD1
Length: n * (4 octets + 4 octets if O is set + 16 octets if N is
set)
O: 1 if an IPv4 Address is included
N: 1 if an IPv6 Address is included
Reserved: must be zero and ignored on receipt, 6 bits
TPI: Transport Protocol Identifier, 1 octet
0: TCP
1: QUIC
Port Number: Transport protocol port number, 2 octets
IPv4 Address: Service contact address, 4 octets if the O bit is
set, 0 otherwise.
IPv6 Address: Service contact address, 16 octets if the N bit is
set, 0 otherwise.
The advertisement of this capability indicates that the node is
providing the Node Liveness service on the designated port using the
designated protocol. The TPI indicates the transport protocol to be
used and the Port Number indicates the associated port to be used.
The TPI and Port Number pair may be included multiple times to
indicate that multiple protocols and port numbers are available. The
length of the sub-TLV can be used to determine the number of TPI and
Port Number pairs.
An IP address for the ABR MUST be included so that correspondents
will know how to access the service. An ABR MUST provide an IPv4
address, an IPv6 address, or both.
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3.2. Node Liveness Advertisement in OSPF
The availabilty of the Node Liveness service is provided by the OSPF
Node Liveness Sub-TLV. The OSPF Node Liveness Sub-TLV is used by
both OSPFv2 and OSPFv3. The semantics are the same as the IS-IS Node
Liveness Sub-TLV. The format of the OSPF Node Liveness Sub-TLV is:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|O|N| Reserved | TPI | Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD2
Length: n * 3 octets
O: 1 if an IPv4 Address is included
N: 1 if an IPv6 Address is included
Reserved: must be zero and ignored on receipt, 6 bits
TPI: Transport Protocol Identifier, 1 octet
0: TCP
1: QUIC
Port Number: Transport protocol port number, 2 octets
IPv4 Address: Service contact address, 4 octets if the O bit is
set, 0 otherwise.
IPv6 Address: Service contact address, 16 octets if the N bit is
set, 0 otherwise.
The TPI and Port Number fields are used in the same way as for IS-IS.
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4. Node Liveness Protocol
4.1. Messages
The Node Liveness Protocol sends messages in a stream inside of the
selected transport protocol. The protocol uses two message types:
Registration Messages and Notification Messages. Each has a sub-TLV
to carry specifics about the relevant prefix.
4.2. Client actions
The client may determine the set of ABRs that it wishes to
communicate with by examination of its LSDB. The client SHOULD open
connections to at least two ABRs for redundancy. If the client
cannot open two connections, then the management system should be
informed.
The client MAY send Registration Messages (with a Liveness
Registration sub-TLV) on each of its ABR connections. A client MAY
register for any number of prefixes, but it is expected that a client
will send a registration for each of the tunnel endpoints that it
will correspond with. A client may register for a host (a /32 or
/128 prefix) or a shorter prefix. A client MUST NOT send overlapping
registrations.
Clients never send Notification Messages and never recive
Registration Messages.
The actions of the client on receiving a Notification Message are out
of scope for this document.
4.3. ABR actions
Each ABR MUST advertise the availability of the Node Liveness service
into the backbone (L2) area and into any non-backbone (L1) areas.
Each ABR MUST have a single connection to each other ABR that is part
of a different non-backbone (L1) area. To prevent duplicate
connections, only one ABR should initiate the connection. For IS-IS,
the node with the lowest system ID should initiate the connection.
For OSPFv4, the node with the lowest IPv4 router ID should initiate
the connection. For OSPFv3, the node with the lowest IPv6 router ID
should initiate the connection.
Each ABR may receive Registration Messages, each containing a prefix.
These are retained in a Registration Database (RDB) along with its
associated connection information. If a transport connection closes,
then all registrations associated with the connection should be
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removed from the RDB. If an ABR receives a Registration Message
requesting a prefix be unregistered, then the prefix should be
removed from the RDB for that connection.
If an ABR receives a Registration Message for a prefix that is being
injected by a non-attached area, then it SHOULD determine the set of
ABRs that are advertising that prefix or less specifics and register
with only those ABRs. The ABR MAY register for the prefix or any of
the less specifics. It is RECOMMENDED that the ABR register for the
most specific prefix that is less specific than the original prefix.
If the ABR cannot find a matching prefix or less specific prefix,
then the ABR MAY register for all of prefixes that are more specific.
Extreme caution should be used before registering for 0/0.
If the ABR has registered for a prefix and that prefix is no longer
advertised by another ABR then an ABR MAY unregister, re-evaluate its
registration and register for a different prefix. In this way, if a
summary prefix changes, the ABR can shift to the new summary prefix.
An ABR or client SHOULD NOT send duplicate registrations. If an ABR
or client is already registered for a prefix, a duplicate
registration SHALL be ignored by the receiving ABR.
Each ABR should monitor its IGP LSDB for changes in node liveness.
If an ABR sees an addition to the LSDB, then it is considered an Up
Event for that node. If an ABR sees a LSP/LSA time out or become
unreachable, then it is considered a Down Event for that node. Up
Events and Down Events for non-host prefixes are out of scope for
this document.
If an ABR receives a Notification Message with an Up Event for a
prefix, then it is considered an Up Event for the prefix. If an ABR
receives a Notification Message with a Down Event for a prefix, then
it is considered a Down Event for the prefix.
If an ABR observes an Up Event for a host, it examines its RDB for
registrations for that node or for any less specific prefixes. If
there are any, then the ABR sends a Notification Message (with a
Liveness Notification sub-TLV) with an Up Event for that host to each
node that registered. If there are no registrations, then the event
MUST be ignored.
Similarly, if an ABR observes a Down Event for a host, it examines
its RDB for registrations for that node or for any less specific
prefixes. If there are any, then the ABR sends a Notification
Message (with a Liveness Notification sub-TLV) with a Down Event for
that host to each node that registered. If there are no
registrations, then the event MUST be ignored.
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A client may be co-located with an ABR. In other words, an ABR may
create registrations for its own purposes.
4.3.1. Autonomous Notification Mode
This section describes OPTIONAL ABR behavior.
An ABR MAY learn a set of prefixes from its management plane and
enter those prefixes into its RDB. Upon an Up or Down Event for such
a prefix, the ABR MAY send corresponding notification messages to all
other ABRs.
This may cause ABRs to receive unexpected Notification Messages.
Since these do not match client registration messages in its own RDB,
such messages SHALL be ignored.
4.3.2. Proxy ABRs
Another node may perform ABR functions instead of the ABR itself.
The alternate node is a 'proxy ABR' and performs all of the functions
of the ABR with respect to this protocol, except for injecting
capability advertisements into the LSDB. The proxy ABR should listen
to the IGP within the area so that it can correctly generate
notifications. One or more ABRs SHOULD advertise the availability of
the proxy ABR in its capability advertisements. How the real ABRs
learn about the proxy ABR is out of scope for this document.
4.4. Registration Messages
A Registration Message has the following format:
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 |R| Reserved | Sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 1 (Registration Message), 1 octet
Length: 1 + length of the sub-TLVs, 1 octet
R: 1 bit
0: Register
1: Unregister
Reserved: must be zero and ignored on receipt, 7 bits
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Sub-TLVs: One or more sub-TLVs, specifying the registration/
unregistration. Variable length.
4.4.1. Liveness Registration sub-TLV
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 | AFI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix len | Prefix ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 1 (Registration Message), 1 octet
Length: 3 + the number of octets for the prefix, 1 octet
AFI: Address Family Identifier [afireg], 2 octets
Prefix len: number of significant bits in the prefix, 1 octet
Prefix: The prefix to register/unregister, n octets
4.5. Notification Messages
A Notification Message has the following format:
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 | Sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 1 (Registration Message), 1 octet
Length: length of the sub-TLVs, 1 octet
Sub-TLVs: One or more sub-TLVs, specifying the registration/
unregistration. Variable length.
4.5.1. Liveness Notification sub-TLV
The Liveness Notification sub-TLV has the format:
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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 | AFI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Reserved | Prefix len | Prefix ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 2 (Notification Message), 1 octet
Length: 3 + number of octets of prefix, 1 octet
AFI: Address Family Identifier [afireg], 2 octets
U: 1 bit
0: Up Event
1: Down Event
Reserved: must be zero and ignored on receipt, 7 bits
Prefix len: number of significant bits in the prefix, 1 octet
Prefix: The prefix generating the notification, n octets
5. IANA Considerations
5.1. IS-IS
This document requests the following code points from the "IS-IS Sub-
TLVs for IS-IS Router CAPABILITY TLV" registry.
Type: TBD 1
Description: IS-IS Node Liveness sub-TLV
Reference: This document
5.2. OSPF
This document requests the following code points from the "OSPF
Router Information (RI) TLVs" registry:
Type: TBD 2
Description: OSPF Node Liveness Sub-TLV
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Reference: This document
6. Security Considerations
This document creates no new security issues. Security of transport
protocol connections are addressed by the use of conventional
transport protocol security techniques, such as TLS. IGP
advertisements are not expected to have privacy, so the advertisement
of the service is not a security issue.
7. Normative References
[afireg] IANA, "Address Family Numbers", November 1988,
<https://www.iana.org/assignments/address-family-numbers/
address-family-numbers.xhtml#address-family-numbers-2>.
[ISO10589] ISO, "Intermediate system to Intermediate system routing
information exchange protocol for use in conjunction with
the Protocol for providing the Connectionless-mode Network
Service (ISO 8473)", August 1987, <ISO/IEC 10589:2002>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>.
[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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/info/rfc7981>.
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[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>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
Author's Address
Tony Li,
Juniper Networks
1133 Innovation Way
Sunnyvale, California 94089
United States of America
Email: tony.li@tony.li
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