Experimental

RFC 5286 - Basic Specification for IP Fast Reroute: Loop-Free Alternates

Every requirement this repository extracted from RFC 5286, the tests bound to it, and what a reader has verified about them. This summary is enrolled and gated by ./le rfc check.

Overview

Positive

what Ze has

Tested both ways60.0%3 of 5 binding obligations

a positive test proves Ze does what the requirement demands and a negative one proves it refuses what the requirement forbids

One polarity plus reason0.0%0 of 5 binding obligations

the requirement admits no counter-case, so one polarity plus a recorded reason is the whole proof available for it

One polarity, unexcused0.0%0 of 5 binding obligations

one direction is tested, the other is neither tested nor excused, and nothing states which

Proven by a recorded break0.0%0 of 6 tagged units

a red was observed once under a recorded procedure, and the unit, the claim and the producer it rested on still hash to what was recorded. The break is not re-run. A test pair is not a proof until one has been observed

Neutral

measures that are neither good news nor bad

Gated MUSTs6of 30 this summary declares

MUST-level requirements the gate HOLDS. A population, not a result: the shares beside it are what says how Ze stands

Out of scope1of 6 gated MUSTs

a {not-applicable} annotation says the obligation does not bind Ze. Scope, not coverage: it is in no share below

Negative

what Ze owes

No test at all40.0%2 of 5 binding obligations

no test carries the requirement id, whether or not a gap states why

The 4 shares marked as a part above are the whole of the 5 obligations that bind Ze: they add to 100%. Proven by a recorded break is a share of TAGGED UNITS, a different population, so it is not one of them.

How to read the colors

A color names what the measure MEANS, not how well Ze scores on it. Green is a good outcome at any value, red is a bad one, and neither a population nor a scope count is an outcome, so both take no color. The number under the label is what says how far Ze has got.

Card	Tone here	Why that color
Gated MUSTs	neutral	no color: a population is a scale, and a larger one is neither good news nor bad. It is the accounting total
Out of scope	neutral	no color: an obligation that never bound Ze is neither an achievement nor a failure, and counting it either way would be a claim
Tested both ways	ok	green at every value: a test pair is the outcome this gate exists to produce, and the share under the label is what says how far Ze has got
One polarity plus reason	ok	green at every value: where no counter-case exists, one polarity IS the complete answer, and a recorded reason is what the gate demands beside it
One polarity, unexcused	ok	green at zero, RED above it: half a proof with no reason for the other half
No test at all	bad	green at zero, RED above it: a binding obligation nothing exercises is a claim with nothing behind it, whether or not a reason is stated
Proven by a recorded break	ok	green at every value: an observed break is the outcome the discrimination gate exists to produce. The denominator is TAGGED UNITS, not obligations, so this share is not one of the parts above
Audit verdicts	warn	RED on the first weak, wrong or unimplemented verdict, amber while a verdict is no longer current or a gated MUST is unjudged, green when every one is judged sound and current

At a glance

Field	Value
Public status	Experimental
Enrolment	Enrolled
Requirements	30
Gated MUST-level	6
Obligations that bind Ze	5
Not applicable, so out of scope	1
Declared gaps	2
Gated with no test	0
Nightly-only evidence	0
Test tags	7
Tagged units	6
Recorded audit verdicts	0
Discrimination records	0
Summary	`rfc/short/rfc5286.md`
Requirement shard	`rfc/requirements/rfc5286.md`
RFC text	`rfc/full/rfc5286.txt`

Enrolment

Enrolled: IP Fast Reroute: Loop-Free Alternates (LFA): six MUST-level requirements, computed in OSPF only (internal/plugins/ospf/spf/lfa.go). x-1 (Inequality 1 strict loop-free criterion), x-2 (no alternate over a link with forward/reverse cost LSInfinity), and x-3 (OSPF: exclude a neighbor whose every reverse link is LSInfinity) each carry positive+negative tags. x-4 (IS-IS overload-bit exclusion) is {not-applicable}: ze has no IS-IS LFA code path. x-5 (alternate only for shortest-path traffic) and x-6 (bound the alternate's lifetime) are {gap}: the backup is attached to every SPF route with no address-family guard so an OSPFv3 multicast AF route inherits it, and ze has no explicit RFC 5286 Section 4.1 hold-down/termination timer (only SPF reconvergence). Disclosed in the docs/features/rfc-status.md RFC 5286 row.

What the public ledger says

Status: Experimental

What the ledger says is covered:

LFA and TI-LFA fast reroute: per-neighbor SPFs, loop-free / node-protecting / downstream backup selection, SR repair lists, multi-area suppression.

What the ledger says remains

Two MUST gaps gated in rfc/short/rfc5286.md: the LFA backup is attached to every SPF route regardless of address family, so an OSPFv3 multicast AF (RFC 5838) route inherits it (RFC5286-x-5); and no explicit Section 4.1 hold-down timer bounds how long an alternate stays active, only SPF reconvergence (RFC5286-x-6). IS-IS has no LFA.

Coverage

Bucket	Count	What it counts
Positive and negative tests	3	one part of the gated population
Annotated instead of tested	3	one part of the gated population
One polarity only	0	one part of the gated population
No test and no annotation	0	one part of the gated population
Evidence that runs nightly only	0	an overlay: each of these is also counted by the part it falls in
Gated MUST-level requirements	6	every gated MUST falls in exactly one bucket above

Positive and negative tests (3): RFC5286-x-1, RFC5286-x-2, RFC5286-x-3

Annotated instead of tested (3): RFC5286-x-4, RFC5286-x-5, RFC5286-x-6

Requirements

Requirement	Level	Section	Tests
`RFC5286-x-1`	Alternate next-hops MUST conform to at least the loop-freeness
	MUST	x	positive`unit/verifyTestRFC5286LoopFreeInequality1` negative`unit/verifyTestRFC5286LoopFreeInequality1`
`RFC5286-x-2`	For computing an alternate, a router MUST NOT use an alternate
	MUST NOT	x	positive`unit/verifyTestRFC5286CostReverseCostGate` negative`unit/verifyTestRFC5286CostReverseCostGate`
`RFC5286-x-3`	In OSPF, if all links from S to a neighbor N_i have reverse
	MUST NOT	x	positive`unit/verifyTestRFC5286ReverseCostAllInfinite` negative`unit/verifyTestRFC5286ReverseCostAllInfinite`
`RFC5286-x-4`	In IS-IS, if N_i has the overload bit set, S MUST NOT consider using N_i as an alternate
	MUST NOT	x	positive`no test`no positive test negative`no test`no negative test {not-applicable}: ze computes Loop-Free Alternates only in OSPF (internal/plugins/ospf/spf/lfa.go); IS-IS has no LFA/backup-next-hop computation code path, so the IS-IS overload-bit exclusion has nothing to apply to
`RFC5286-x-5`	The alternate next-hop MUST be used only for traffic types routed according to the shortest path
	MUST	x	positive`no test`no positive test negative`no test`no negative test {gap}: ze attaches the RFC 5286 alternate to a route's Loc-RIB Path unconditionally in Installer.insert (internal/plugins/ospf/spf/install.go:213-229) with no guard confining it to unicast shortest-path forwarding; an OSPFv3 multicast address-family engine (family.IPv4Multicast / family.IPv6Multicast, internal/plugins/ospf/multiaf.go:102-115) installs through the same NewInstallerFamily path (internal/plugins/ospf/spf_wiring.go:34) and inherits fast-reroute config (internal/plugins/ospf/config.go:709-711), so a multicast-AF route receives the same backup next-hop, which Section 4 confines to shortest-path traffic and Section 6.5 excludes from multicast RPF. Disclosed in the docs/features/rfc-status.md RFC 5286 row
`RFC5286-x-6`	A router MUST limit the amount of time an alternate next-hop is used after the primary becomes unavailable
	MUST	x	positive`no test`no positive test negative`no test`no negative test {gap}: ze relies on SPF reconvergence to replace a route with a stale alternate (internal/plugins/ospf/spf/install.go:171-195) and the kernel RTNH_F_LINKDOWN flag (internal/plugins/fib/kernel/nexthop_linux.go:113), but implements no explicit RFC 5286 Section 4.1 hold-down timer or termination-condition bounding how long an alternate stays active. Disclosed in the docs/features/rfc-status.md RFC 5286 row
`RFC5286-x-7`	A router SHOULD select a link-and-node-protecting LFA over a
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-8`	It SHOULD be assumed that an alternate offers no node protection
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-9`	If the primary next-hop uses a broadcast link, an alternate
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-10`	A router SHOULD NOT specify the "local protection available"
	SHOULD NOT	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-11`	A router SHOULD NOT use an alternate next-hop along a link
	SHOULD NOT	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-12`	A router supporting this specification SHOULD attempt to select
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-13`	S SHOULD select a loop-free node-protecting alternate if one is
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-14`	Given a choice between a link-and-node-protecting alternate and a
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-15`	With multiple primary next-hops, S SHOULD select as alternate
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-16`	If no node-protecting alternate and no other primary can provide
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-17`	Implementations SHOULD support a mode preferring other primary
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-18`	On primary next-hop failure the router SHOULD remove the failed
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-19`	A router implementing [MICROLOOP] SHOULD follow that document's
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-20`	A router implementing [ORDERED-FIB] SHOULD follow that document's
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-21`	An implementation SHOULD continue to use the alternate next-hops
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-22`	Use of the alternate next-hops SHOULD terminate when (a) the new
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-23`	A router SHOULD compute the alternate next-hop for an IGP
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-24`	For OSPF external routes with a forwarding address set, alternate
	SHOULD	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-25`	Alternate next-hops SHOULD NOT be used for multicast Reverse
	SHOULD NOT	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-26`	A router MAY decide not to use an available loop-free alternate
	MAY	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-27`	If no node-protecting alternate is available, S MAY select a
	MAY	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-28`	Implementations considering SRLGs MAY use SRLG protection to
	MAY	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-29`	The router MAY remove other next-hops it believes (via SRLG
	MAY	x	positive`no test`no positive test negative`no test`no negative test
`RFC5286-x-30`	A router MAY safely simplify the multi-homed-prefix calculation by
	MAY	x	positive`no test`no positive test negative`no test`no negative test

Gaps and untested MUSTs

Requirement	State	Reason
`RFC5286-x-4` In IS-IS, if N_i has the overload bit set, S MUST NOT consider using N_i as an alternate	no test	no test carries this requirement id; annotated {not-applicable}: ze computes Loop-Free Alternates only in OSPF (internal/plugins/ospf/spf/lfa.go); IS-IS has no LFA/backup-next-hop computation code path, so the IS-IS overload-bit exclusion has nothing to apply to
`RFC5286-x-5` The alternate next-hop MUST be used only for traffic types routed according to the shortest path	{gap}, no test	ze attaches the RFC 5286 alternate to a route's Loc-RIB Path unconditionally in Installer.insert (internal/plugins/ospf/spf/install.go:213-229) with no guard confining it to unicast shortest-path forwarding; an OSPFv3 multicast address-family engine (family.IPv4Multicast / family.IPv6Multicast, internal/plugins/ospf/multiaf.go:102-115) installs through the same NewInstallerFamily path (internal/plugins/ospf/spf_wiring.go:34) and inherits fast-reroute config (internal/plugins/ospf/config.go:709-711), so a multicast-AF route receives the same backup next-hop, which Section 4 confines to shortest-path traffic and Section 6.5 excludes from multicast RPF. Disclosed in the docs/features/rfc-status.md RFC 5286 row
`RFC5286-x-6` A router MUST limit the amount of time an alternate next-hop is used after the primary becomes unavailable	{gap}, no test	ze relies on SPF reconvergence to replace a route with a stale alternate (internal/plugins/ospf/spf/install.go:171-195) and the kernel RTNH_F_LINKDOWN flag (internal/plugins/fib/kernel/nexthop_linux.go:113), but implements no explicit RFC 5286 Section 4.1 hold-down timer or termination-condition bounding how long an alternate stays active. Disclosed in the docs/features/rfc-status.md RFC 5286 row

Proof state

A tagged unit reads unproven where no discrimination record exists for it: nothing in this tree has been observed to break it, so the claim its tag makes is unproven.