Implementation-Level PIXIT Extension¶

SIG-GW / IBCF — Execution Parameters & Environment Control

Author: Daniel
Purpose: Define implementation-specific execution parameters (PIXIT) for all test matrices
Scope: Applies to IBCF, STIR/SHAKEN, LI, Emergency

PIXIT = Protocol Implementation eXtra Information for Testing

This document defines: - Timer settings - Codec policies - TLS profiles - Peer profiles - STIR enforcement modes - LI activation states - Emergency override rules - Scaling thresholds - Chaos injection controls

1. Global Timer Profile (Baseline)¶

Parameter	Default	Test Override Range	Notes
T1	500 ms	100–1000 ms	SIP base retransmission
T2	4 s	2–8 s	Non-INVITE retrans max
Timer B	32 s	16–64 s	INVITE client timeout
Timer F	32 s	16–64 s	Non-INVITE timeout
Session Timer	1800 s	90–3600 s	re-INVITE refresh
Max Dialogs	50,000	1k–100k	Capacity test
Max CPS	2,000	100–20k	Load envelope

2. Codec Policy PIXIT¶

Parameter	Default	Allowed Values
Audio Codecs	AMR-WB, G.711	Configurable allowlist
Video Codecs	H.264	Add/remove
Transcoding	Disabled	Enabled/Disabled
SRTP Required	Yes (NNI)	Yes/No
DTMF Mode	RFC2833	RFC2833 / SIP INFO

3. TLS / Security Profile¶

Parameter	Default	Options
TLS Version	1.2/1.3	Configurable
Cipher Suites	ECDHE-ECDSA-AES256-GCM	Custom set
mTLS Required	Yes (NNI)	Yes/No
Cert Reload Mode	Hot	Restart
OCSP Mode	Soft-fail	Hard/Soft
STIR Enforcement	Soft	Soft/Hard

4. Peer Profile Definition Template¶

Each test must reference a peer profile.

Field	Example Value
Peer ID	PEER-A
Transport	SIP-TLS
IP Version	IPv4
Auth Mode	mTLS
STIR Trust Level	Trusted / External
Emergency Routing Flag	Enabled
LI Cooperation Flag	Enabled
Max CPS	1000
Topology Hiding Mode	Full

5. STIR PIXIT Controls¶

Parameter	Default	Test Override
Attestation Policy	A/B/C auto	Force A/B/C
iat Skew Tolerance	±60 sec	±0–300 sec
Cert Cache TTL	24h	1h–72h
Signing Key Source	HSM	File / Vault
Re-sign Transit Calls	No	Yes/No
Identity Header Max Size	8 KB	2–16 KB

6. Lawful Intercept PIXIT Controls¶

Parameter	Default	Options
LI Mode	Disabled	Signaling / Full
Mediation IP	10.1.1.10	Configurable
Intercept Target List	Dynamic DB	Static
LI Overload Policy	Preserve LI	Drop LI
Audit Log Retention	180 days	Custom
TLS Decrypt for LI	Enabled	Disabled

7. Emergency PIXIT Controls¶

Parameter	Default	Options
Emergency Numbers	911,112	Custom list
Emergency Priority Queue	Enabled	Disabled
STIR Override	Enabled	Disabled
Fraud Override	Enabled	Disabled
Emergency Route	PSAP-A	Fallback list
Location Header Mandatory	Yes	Optional

8. Chaos Injection Controls¶

Parameter	Default	Range
Packet Loss	0%	0–20%
Jitter	0 ms	0–200 ms
DNS Failure	Off	On
TLS Cert Expiry Simulation	Off	On
Signing Service Crash	Off	On
State Store Partition	Off	On
Media Relay Kill	Off	On

9. Example: PIXIT Overlay for Specific Test¶

Example: STR-012 (OCSP outage test)

PIXIT Parameter	Value
OCSP Mode	Hard-fail
Cert TTL	24h
iat Skew	±60 sec
TLS Version	1.3
CPS	2000
Chaos	OCSP responder disabled

Expected Result: - Calls fail verification - Hard-fail blocks call - No CPU spike - Metrics increment verification_fail counter

10. Example: Emergency During Failover (LIE-107)¶

PIXIT Parameter	Value
Emergency Priority	Enabled
STIR Override	Enabled
Active/Active Nodes	2
Chaos	Kill primary instance
CPS Background	5000
Emergency CPS	200

Expected Result: - Emergency call continues - No PDD violation - No STIR enforcement block - No LI drop

11. Example: IBCF Flood Protection (SEC-002)¶

PIXIT Parameter	Value
Max CPS	2000
Rate Limit	2500 CPS
Peer Max CPS	1000
Chaos	20k CPS burst
TLS Required	Yes

Expected Result: - Legit calls pass - Excess rejected with 503 - No crash - CPU stable <85%

12. Execution Discipline¶

Every test must log:

SIP ladder trace
Timer values in effect
Codec negotiation result
STIR verification state
LI state
Emergency policy state
Peer profile used
Chaos injection status

13. Traceability Matrix (Linking Documents)¶

Test Matrix	Requires PIXIT Section
IBCF Functional	Sections 1–4, 8
STIR/SHAKEN	Sections 3, 5, 8
LI Tests	Sections 6, 8
Emergency	Sections 7, 8
Resilience	Sections 1, 8

14. PIXIT Configuration File Format¶

Tests can load PIXIT parameters from YAML/JSON:

pixit:
  timers:
    t1: 500ms
    t2: 4s
    timer_b: 32s
    timer_f: 32s
    session_timer: 1800s

  codec:
    audio: ["AMR-WB", "G.711"]
    video: ["H.264"]
    srtp_required: true

  tls:
    version: ["1.2", "1.3"]
    mtls_required: true
    ocsp_mode: "soft-fail"

  stir:
    enforcement: "soft"
    iat_skew: 60s
    cert_cache_ttl: 24h

  li:
    mode: "disabled"
    mediation_ip: "10.1.1.10"
    overload_policy: "preserve"

  emergency:
    numbers: ["911", "112"]
    priority_queue: true
    stir_override: true

  chaos:
    packet_loss: 0%
    jitter: 0ms
    dns_failure: false

15. Test Execution with PIXIT¶

Command Line¶

# Run test with PIXIT override
./testrig -test STR-012 \
  -pixit ocsp_mode=hard-fail \
  -pixit chaos=ocsp_disabled

# Load PIXIT from file
./testrig -test LIE-107 \
  -pixit-file pixit/emergency-failover.yaml

Programmatic¶

pixit := LoadPIXIT("pixit/str-012.yaml")
test := NewTest("STR-012", pixit)
result := test.Run()