IS-IS Database FingerprintingNetDEFrenato@netdef.orgHPE Juniper Networkingantoni.przygienda@hpe.com
In large IS-IS networks it is useful to quickly verify whether the link-state
databases on all routers have synchronized properly and to derive a rough metric
of flooding diffusion behavior. This document proposes a lightweight database
fingerprinting mechanism for IS-IS along with YANG model extensions providing
easy access to such information.
In large IS-IS networks in stable state it is useful to observe
whether all databases have synchronized properly and derive the delays involved
in the propagation of information across the network.
This document defines a database fingerprinting mechanism that allows for quick
validation of database synchronization across all nodes. A node implementing this
specification computes a fingerprint over all fragments per level. The fingerprint
includes the time difference from the last fingerprint change which facilitates
measurement of flooding behavior across the network.
Aged out LSPs are excluded from the fingerprint calculation.
A reference checksum algorithm for a fragment is given in . The overall fingerprint
is the XOR of all fragment checksums.
This document uses the graphical representation of data models per .The following shows the tree diagram of the module:The following is the YANG module:
module ietf-isis-database-checksumming {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-isis-database-checksumming";
prefix isis-db-csum;
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing
Management (NMDA Version)";
}
import ietf-isis {
prefix isis;
reference
"RFC 9130: YANG Data Model for the IS-IS Protocol";
}
organization
"IETF LSR - LSR Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/lsr>
WG List: <mailto:mpls@ietf.org>
Author: Renato Westphal
<renato@netdef.org>
Author: Tony Przygienda
<mailto:antoni.przygienda@hpe.com>
Author: Colby Barth
<mailto:colby.barth@hpe.com>
";
description
"The YANG module augments the base IS-IS YANG data model with
operational state related to IS-IS LSDB fingerprinting.
Copyright (c) 2026 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";
reference
"RFC XXXX: IS-IS Database Fingerprinting";
revision 2026-06-26 {
description
"Initial Version";
reference
"RFC XXXX: IS-IS Database Fingerprinting";
}
/* LSDB fingerprint */
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/isis:isis/isis:database/"
+ "isis:levels" {
when "derived-from-or-self(../../../rt:type, 'isis:isis')" {
description
"This augment ISIS routing protocol when used";
}
container fingerprint {
description
"Information about the LSDB fingerprint for this level.";
leaf value {
type uint64;
description
"A 64-bit fingerprint derived from the set of LSPs at this
level.
The fingerprint is computed by XOR-combining a per-LSP
component value for each LSP whose remaining lifetime is
non-zero. The per-LSP component value is derived from the
LSP identifier, the LSP checksum, and the LSP length, as
specified in Appendix A of RFC XXXX.
The fingerprint is intended for detecting potential LSDB
synchronization differences. Different values indicate
different LSDB contents; identical values do not guarantee
equivalence due to possible collisions.";
}
leaf last-update {
type uint32;
units "seconds";
description
"Time elapsed since the fingerprint for this level's LSDB
was last updated.";
}
}
}
}
The fingerprint mechanism defined in this document is purely informational and
does not influence protocol behavior. It does not introduce new attack vectors
beyond those inherent in IS-IS itself. The fingerprint value is derived from
information already present in the LSDB and does not leak additional data.
TBDYANG Tree DiagramsThis document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language.
pub(crate) fn lsdb_fingerprint_component(&self) -> u64 {
let mut result: u64 = 0;
let system_id: &[u8] = self.lsp_id.system_id.as_ref();
for i in system_id.iter().chain(&[self.lsp_id.pseudonode]) {
result <<= 8;
result ^= *i as u64;
}
// fragment checksum
result ^= (self.cksum as u64) << 48;
// This is equal to the PDU length advertised by the fragment
result ^= (self.raw.len() as u64) << 32;
result
}
]]>