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CPaaS WebSocket Media Relay — Architecture & Integration Plan

Version: 1.0
Status: Design
Scope: Inbound + outbound voice media relay for Bonvoice (and future providers)
Primary goal: Act as a transparent WebSocket tunnel between the telecom provider and the customer AI backend, with authentication and routing control at the relay layer and no added media processing latency.

1. Executive Summary

Your CPaaS sits between:

Leg	Party	Protocol
Provider leg	Bonvoice (or other CPaaS)	WebSocket + JSON media frames
Customer leg	Tenant AI / voicebot backend	WebSocket + same JSON frame format

The relay must not decode, transcode, re-chunk, or buffer audio in the hot path. It forwards WebSocket text frames as-is after authentication and tenant routing.

You own:

Provider credentials (Bonvoice token, DID inventory)
Customer API keys / JWT issuance
Session routing (call_id, stream_id, DID → tenant)
Audit logs, rate limits, billing metadata
Outbound call orchestration API

Customers own:

AI logic, STT/TTS, conversation state
Their backend WebSocket endpoint (or pre-connect to your upstream socket)

2. Design Principles

2.1 Zero-processing media path

Bonvoice WS  ──►  Relay (auth + route)  ──►  Customer WS
     ▲                    │                      │
     └────────────────────┴──────────────────────┘
              raw JSON text frames, both directions

Do	Don't
Forward raw WebSocket text frames	`json.loads()` on every `media` event
Parse only control events (`start`, `connected`, `end`)	Base64 decode / PCM transcoding
Use async bidirectional copy (`asyncio.gather`)	Artificial `sleep()` or batching
Colocate relay in same region as provider	Cross-region relay for real-time audio
Pre-resolve tenant route before bridging	DB lookups inside media loop

Target added latency: < 5 ms p99 per hop (relay processing only, excluding network RTT to customer).

2.2 Fail closed on auth

If authentication or routing fails, reject before bridging. Never forward media to an unauthenticated or unmapped session.

2.3 Provider URL is always yours

Bonvoice (inbound template + outbound API) is configured with your wss:// endpoint. Customers never expose their URL to the provider directly. This gives you full control over access, metering, and multi-tenancy.

3. System Context

flowchart LR
    subgraph Provider["Telecom Provider (Bonvoice)"]
        DID[Virtual DID]
        PBX[PBX / Voicebot Platform]
    end

    subgraph Relay["Your CPaaS Relay"]
        GW[WebSocket Gateway]
        AUTH[Auth & Routing]
        API[REST Control API]
        SESS[Session Store]
    end

    subgraph Customer["Customer Tenant"]
        BOT[AI Voicebot Backend]
    end

    Caller((Caller)) --> DID
    DID --> PBX
    PBX <-->|wss JSON media| GW
    GW <--> AUTH
    AUTH <--> SESS
    API --> SESS
    Customer -->|API key| API
    GW <-->|wss JSON media| BOT

4. Bonvoice Provider Protocol Reference

Based on validated integration behaviour.

4.1 Connection

Transport: WebSocket (wss://), not HTTP POST
Bonvoice server IP observed: 103.131.25.5 (maintain allowlist)
Endpoint must use wss://, not https://

4.2 Message types

Call start

{
  "event": "start",
  "data": {
    "stream_id": "<id>",
    "call_id": "<id>",
    "from": "<caller>",
    "to": "<did>"
  }
}

Media (bidirectional)

{
  "event": "media",
  "stream_id": "<id>",
  "media": {
    "packet_id": 1,
    "timestamp": 0,
    "payload": "<base64 PCM>"
  }
}

Audio: PCM 16-bit, 8000 Hz, mono
Chunk size: 320 bytes (20 ms), multiples of 320 only

Interruption (customer → provider)

{
  "event": "clear",
  "stream_id": "<id>"
}

Additional events observed

Event	Direction	Relay action
`connected`	Provider → relay	Forward as-is; optional metadata log
`end`	Provider → relay	Forward, then close both legs gracefully

4.3 Outbound API (control plane)

POST https://backend.pbx.bonvoice.com/autoDialManagement/autoCallBridging/
Authorization: Token <provider_token>

{
  "autocallType": "5",
  "destination": "<callee>",
  "legACallerID": "<did>",
  "eventID": "<unique_id>",
  "voicebotProvider": "BONVOICE",
  "voicebotURL": "wss://<your-relay-host>/v1/media/<session_token>"
}

Response:

{
  "responseCode": 200,
  "responseDescription": "Success",
  "responseType": "Success",
  "eventID": "..."
}

5. Relay Component Architecture

flowchart TB
    subgraph ControlPlane["Control Plane"]
        REST[REST API]
        PROV[Provider Adapter - Bonvoice]
        TENANT[Tenant Registry]
        KEYS[API Key / JWT Service]
    end

    subgraph DataPlane["Data Plane - hot path"]
        PWS[Provider WebSocket Handler]
        TUNNEL[Frame Tunnel]
        CWS[Customer WebSocket Client/Handler]
    end

    REST --> PROV
    REST --> KEYS
    REST --> TENANT
    PWS --> TUNNEL
    TUNNEL --> CWS
    TENANT --> PWS
    KEYS --> PWS
    KEYS --> CWS

Component	Responsibility
Provider WebSocket Handler	Accept Bonvoice WS; provider-side auth
Customer WebSocket Client	Dial customer upstream WS (outbound leg)
Frame Tunnel	Bidirectional raw frame copy
Session Store	Redis: session_token → tenant, upstream URL, metadata
Tenant Registry	DID → tenant; tenant → upstream WS URL + credentials
Provider Adapter	Bonvoice outbound API, token rotation
REST API	Customer-facing call control + config

6. WebSocket Tunnel — Core Mechanism

6.1 Session lifecycle

1. Provider connects → wss://relay/v1/media/{session_token}
2. Relay validates session_token (or resolves inbound by DID on `start`)
3. Relay opens upstream → wss://customer/configured-endpoint
4. Relay starts two async copy loops
5. On `end` or disconnect → cancel both loops, purge session

6.2 Tunnel pseudocode (hot path)

async def tunnel(provider_ws, customer_ws):
    async def p2c():
        async for raw in provider_ws:
            await customer_ws.send(raw)  # no parse, no modify

    async def c2p():
        async def c2p():
        async for raw in customer_ws:
            await provider_ws.send(raw)

    await asyncio.gather(p2c(), c2p())

6.3 Optional control-plane hook (non-blocking)

Parse only the first start frame (and end) in a side task for logging/billing. Never block the copy loop.

async def observe_control_events(raw: str, session: Session):
    if '"event":"start"' in raw:   # or parse once with orjson
        session.mark_started()
    elif '"event":"end"' in raw:
        session.mark_ended()

Use string prefix check or single parse on non-media events only.

6.4 Upstream connection modes

Mode	Latency	Use case
A. Relay dials customer on `start`	+1 WS handshake (~30–150 ms)	Simplest; acceptable for most bots
B. Customer pre-connects to relay	Lowest	Customer opens `wss://relay/v1/upstream/{session_token}` before answering
C. Persistent tenant socket	Low	Customer keeps one WS open; relay multiplexes by `stream_id` (complex)

Recommendation: Start with Mode A; offer Mode B for latency-sensitive tenants.

7. Authentication Model

Authentication is enforced at three layers.

7.1 Layer 1 — Provider leg (Bonvoice → Relay)

Method	Implementation
IP allowlist	Only accept WS from known Bonvoice egress IPs
Session token in URL	Outbound: `wss://relay/v1/media/{session_token}` — token is single-use, TTL 5 min
Inbound DID routing	On `start`, map `to` (DID) → tenant; reject unknown DID
mTLS (optional)	Mutual TLS if Bonvoice supports client certs

Provider token (Authorization: Token ...) is used only on outbound REST API calls from relay to Bonvoice, never exposed to customers.

7.2 Layer 2 — Relay control plane (Customer → Relay REST)

Method	Implementation
API key	`Authorization: Bearer sk_live_...` on all REST endpoints
Scoped permissions	`calls:write`, `numbers:read`, etc.
Rate limiting	Per-tenant token bucket

7.3 Layer 3 — Customer leg (Relay → Customer backend)

Choose one per tenant (configured in dashboard):

Method	Header / mechanism
Static secret	`Authorization: Bearer <tenant_upstream_secret>`
Signed JWT	Short-lived JWT signed by relay, claims: `tenant_id`, `session_id`, `call_id`
HMAC query param	`wss://customer/bot?sig=HMAC(session_token, secret)`
mTLS	Client cert per tenant

Customer validates the relay; relay validates the customer using pre-shared secret or JWT.

7.4 Session token design

session_token = base64url(tenant_id || call_uuid || HMAC-SHA256(...))

Properties:

Single-use or idempotent per eventID
TTL: 300 seconds
Bound to: tenant, direction, destination/caller, DID
Stored in Redis before outbound API call

8. Inbound Call Flow

sequenceDiagram
    participant Caller
    participant Bonvoice
    participant Relay
    participant Redis
    participant Customer

    Caller->>Bonvoice: Inbound call to DID
    Bonvoice->>Relay: wss connect /v1/media/inbound
    Bonvoice->>Relay: event=start {to: DID, from, call_id, stream_id}
    Relay->>Redis: Lookup DID → tenant + upstream URL
    alt Unknown DID or tenant suspended
        Relay-->>Bonvoice: Close WS (4403)
    else OK
        Relay->>Customer: wss connect + auth headers
        Relay->>Relay: Start bidirectional tunnel
        loop Every 20ms
            Bonvoice->>Relay: event=media
            Relay->>Customer: forward raw frame
            Customer->>Relay: event=media
            Relay->>Bonvoice: forward raw frame
        end
        Bonvoice->>Relay: event=end
        Relay->>Customer: forward end
        Relay->>Relay: Close both sockets
    end

8.1 Bonvoice configuration (per DID)

Field	Value
Provider	BONVOICE
Endpoint	`wss://media.yourcpaas.com/v1/media/inbound`

All tenants share one inbound WS URL; routing happens on start.data.to (DID).

8.2 Inbound routing table

DID 7946350706 → tenant_abc → wss://bot.customer.com/voice
DID 7946350707 → tenant_xyz → wss://api.other.com/ws/bonvoice

9. Outbound Call Flow

sequenceDiagram
    participant Customer
    participant Relay
    participant Redis
    participant Bonvoice
    participant Callee

    Customer->>Relay: POST /v1/calls {to, from_did} + API key
    Relay->>Relay: Validate API key, quota
    Relay->>Redis: Store session_token → tenant, upstream, metadata
    Relay->>Bonvoice: POST autoCallBridging {voicebotURL: wss://relay/.../session_token}
    Bonvoice-->>Relay: 200 Success
    Relay-->>Customer: {call_id, session_id, status: initiated}

    opt Mode B - pre-connect
        Customer->>Relay: wss /v1/upstream/{session_token}
    end

    Bonvoice->>Callee: Ring
    Callee->>Bonvoice: Answer
    Bonvoice->>Relay: wss /v1/media/{session_token}
    Relay->>Redis: Validate session_token
    Relay->>Customer: wss connect upstream (Mode A) or attach pre-connect (Mode B)
    Relay->>Relay: Tunnel media both ways

9.1 Customer REST API (your CPaaS)

POST /v1/calls
Authorization: Bearer sk_live_...
Content-Type: application/json

{
  "to": "9149154337",
  "from": "7946350706",
  "upstream": "wss://bot.customer.com/voice",
  "metadata": { "campaign_id": "xyz" }
}

Response:

{
  "id": "call_01J...",
  "session_token": "...",
  "status": "initiated",
  "provider_event_id": "11A31A12FF1C4455"
}

Relay internally calls Bonvoice with voicebotURL = wss://media.yourcpaas.com/v1/media/{session_token}.

10. URL & Routing Scheme

Endpoint	Purpose	Auth
`wss://media.../v1/media/inbound`	All inbound Bonvoice streams	IP allowlist + DID routing on `start`
`wss://media.../v1/media/{session_token}`	Outbound + optional direct sessions	Session token validation
`wss://media.../v1/upstream/{session_token}`	Customer pre-connect (Mode B)	API key or session_token
`POST /v1/calls`	Initiate outbound	Customer API key
`GET /v1/calls/{id}`	Call status	Customer API key
`POST /v1/numbers`	Assign DID to tenant	Customer API key

11. Multi-Tenancy & Data Model

11.1 Core entities

Tenant
  - id, name, status
  - api_key_hash
  - upstream_ws_url
  - upstream_auth_type, upstream_secret
  - quota_limits

PhoneNumber (DID)
  - e164, tenant_id, provider, provider_account_id

CallSession
  - session_token, tenant_id, direction
  - call_id, stream_id, from, to
  - status: pending | bridging | active | ended | failed
  - created_at, answered_at, ended_at

ProviderAccount
  - provider: bonvoice
  - token_encrypted, default_caller_id

11.2 Redis session record (ephemeral)

{
  "session_token": "abc123",
  "tenant_id": "ten_01",
  "direction": "outbound",
  "upstream_ws": "wss://bot.customer.com/voice",
  "upstream_auth": "Bearer xxx",
  "to": "9149154337",
  "from": "7946350706",
  "status": "pending",
  "expires_at": 1699999999
}

TTL matches Bonvoice ring timeout + margin (e.g. 10 minutes).

12. Latency Budget

Stage	Target
Relay frame forward (provider → customer)	< 2 ms p99
Relay frame forward (customer → provider)	< 2 ms p99
Session lookup (Redis)	< 1 ms
Upstream WS connect (Mode A, one-time)	30–150 ms (not per frame)
JSON parse on hot path	0 (avoided)
Audio transcoding	0 (avoided)

20 ms audio frames: relay must sustain > 50 frames/sec per call with headroom for 500+ concurrent calls per node.

13. Failure Handling

Scenario	Behaviour
Invalid session token	Close provider WS immediately with code `4401`
Unknown inbound DID	Close after `start` with `4403`; log alert
Customer upstream unreachable	Retry connect 2× with 100 ms backoff; then close provider leg
Customer WS drops mid-call	Close provider leg; emit webhook `call.upstream_disconnected`
Provider WS drops	Close customer leg
Bonvoice sends POST not WS	Return `426` + log; misconfigured URL
Provider API failure on outbound	Return error to customer; do not create session

13.1 Webhook events (control plane, async)

Deliver to customer via HTTP POST (not in media path):

call.initiated
call.answered
call.media_started
call.ended
call.failed

14. Security Checklist

Provider token stored encrypted (KMS / vault); never in logs
Customer API keys stored as hashes
Session tokens: cryptographically random, single-use, short TTL
TLS 1.2+ on all WS and REST
IP allowlist for Bonvoice egress
Per-tenant rate limits on /v1/calls
No customer can specify arbitrary voicebotURL to Bonvoice — relay always injects its own URL
Audit log: who initiated call, DID used, duration, bytes relayed

15. Observability

15.1 Metrics (per call)

relay_session_active{tenant, direction}
relay_frame_forward_total{direction=provider_to_customer|customer_to_provider}
relay_frame_forward_latency_ms (histogram)
relay_upstream_connect_duration_ms
relay_auth_failure_total{reason}

15.2 Tracing

Trace ID = call_id or session_token
Span: provider.accept → session.resolve → upstream.connect → tunnel.active

15.3 Logging

Log control events only (start, end, connected). Do not log media payloads.

16. Implementation Roadmap

Phase 1 — MVP tunnel (2–3 weeks)

WebSocket gateway with raw frame tunnel
Redis session store
Outbound: POST /v1/calls → Bonvoice API → session routing
Inbound: DID → tenant lookup on start
API key auth on REST
Provider IP allowlist
Basic metrics + structured logs

Phase 2 — Production hardening (2 weeks)

Customer upstream auth (JWT / HMAC)
Mode B pre-connect upstream endpoint
Webhooks for call lifecycle
Graceful shutdown / connection draining
Horizontal scaling behind L4 LB with sticky sessions OR shared Redis session state

Phase 3 — Platform (ongoing)

Multi-provider adapter interface (abstract Bonvoice)
Dashboard: DID management, API keys, call logs
Billing meter: call duration + minute rounding
HA Redis cluster, multi-region consideration

17. Deployment Topology

flowchart TB
    subgraph Internet
        BV[Bonvoice]
        CUST[Customer Backends]
    end

    subgraph YourCloud["Your CPaaS Region (e.g. ap-south-1)"]
        LB[L4/L7 Load Balancer]
        R1[Relay Node 1]
        R2[Relay Node 2]
        REDIS[(Redis Cluster)]
        API[Control API]
        DB[(PostgreSQL)]
    end

    BV -->|wss| LB
    LB --> R1
    LB --> R2
    R1 --> REDIS
    R2 --> REDIS
    API --> DB
    API --> REDIS
    R1 -->|wss| CUST
    R2 -->|wss| CUST
    CUST -->|REST| API

Notes:

WebSocket LB must support connection upgrade and long-lived connections
Sticky sessions optional if session state is fully in Redis
Run relay nodes close to Bonvoice infrastructure (India) to minimize RTT

18. Provider Abstraction (future-proof)

Define a provider interface so Bonvoice is one adapter:

class VoiceProvider(Protocol):
    async def initiate_outbound(self, req: OutboundCallRequest) -> ProviderCallRef: ...
    def media_websocket_path(self) -> str: ...
    def validate_inbound(self, start_event: dict) -> bool: ...

Bonvoice adapter implements autoCallBridging and protocol quirks (connected, end events).

19. Customer Integration Guide (summary for docs)

19.1 Inbound

Customer claims a DID via your dashboard/API
Customer registers upstream WebSocket URL
You configure Bonvoice template → wss://media.yourcpaas.com/v1/media/inbound
Customer implements Bonvoice JSON protocol on their WS server
Customer receives start, then media frames; responds with media and optional clear

19.2 Outbound

Customer calls POST /v1/calls with API key
Optional: pre-connect to wss://media.yourcpaas.com/v1/upstream/{session_token}
Relay bridges Bonvoice ↔ customer when callee answers
Customer handles protocol identically to direct Bonvoice integration

19.3 What customers do NOT need

Bonvoice account or token
Direct exposure of their WS URL to Bonvoice
Provider-specific outbound API knowledge

20. Risks & Mitigations

Risk	Mitigation
Added latency from relay hop	Raw tunnel, no parsing, regional colocation
Upstream connect delay (Mode A)	Offer pre-connect Mode B
Single relay node failure	Multiple nodes + LB + Redis
Token leakage in URL	Short TTL, single-use, HTTPS/WSS only
Tenant sends malformed media	Provider enforces 320-byte rule; relay forwards as-is
Bonvoice protocol changes	Provider adapter layer + contract tests

21. Success Criteria

Metric	Target
Relay processing latency	< 5 ms p99 per frame
Call setup (outbound, excl. ring time)	< 200 ms from answer to first media frame forwarded
Auth failure rate (invalid sessions)	100% blocked, 0% bridged
Concurrent calls per node	≥ 500 with < 60% CPU
Uptime	99.9% for media gateway

22. Appendix — Mapping from Current PoC

Your existing PoC maps to the relay as follows:

PoC file	Relay equivalent
`main.py` (`handle_media_stream`)	Replace playback logic with `tunnel(provider_ws, customer_ws)`
`outbound_call.py`	Becomes internal `BonvoiceProvider.initiate_outbound()`
`audio_utils.py`	Not used in relay — only in test/demo tooling
Bonvoice template endpoint	`wss://<relay>/v1/media/inbound`
`voicebotURL` in outbound API	`wss://<relay>/v1/media/{session_token}`

23. Appendix — Bonvoice Credentials & API Reference (PoC / Test)

Security warning: This section contains live credentials used during PoC testing.
Do not commit this file to a public repository. Rotate the provider token before production.
Store secrets in a vault (e.g. AWS Secrets Manager, HashiCorp Vault) in the relay implementation.

23.1 Provider account credentials

Item	Value	Usage
Auth Token	`8de97c5932280c84c4bbf36140a1ec7ab7ae0b23`	`Authorization: Token <token>` on Bonvoice REST APIs
Virtual DID	`7946350706`	Inbound number; use as `legACallerID` on outbound
Provider name	`BONVOICE`	Voicebot template + `voicebotProvider` field

23.2 Bonvoice API endpoints

API	Method	URL
Auto Call Bridging (outbound voicebot)	`POST`	`https://backend.pbx.bonvoice.com/autoDialManagement/autoCallBridging/`
Media stream (WebSocket)	`GET` (Upgrade)	Configured per template / `voicebotURL` — must be `wss://`, not `https://`

Outbound request headers:

Authorization: Token 8de97c5932280c84c4bbf36140a1ec7ab7ae0b23
Content-Type: application/json

Outbound request body (validated PoC example):

{
  "autocallType": "5",
  "destination": "9149154337",
  "legACallerID": "7946350706",
  "eventID": "11A31A12FF1C4455",
  "voicebotProvider": "BONVOICE",
  "voicebotURL": "wss://<your-relay-or-ngrok-host>/ws/media"
}

Successful outbound response (observed):

{
  "responseCode": 200,
  "responseDescription": "Success",
  "responseType": "Success",
  "eventID": "11A31A12FF1C4455"
}

Field	Description
`autocallType`	`"5"` — voicebot auto-call type per Bonvoice API
`destination`	Callee E.164 (no `+` in PoC tests)
`legACallerID`	Caller ID shown to callee; use assigned DID
`eventID`	Unique tracking ID (UUID / random hex recommended)
`voicebotProvider`	Must be `BONVOICE` for Bonvoice voicebot templates
`voicebotURL`	Your relay WebSocket URL — Bonvoice connects here when call is answered

23.3 Inbound voicebot template (Bonvoice portal)

Configure under Voicebot Templates → Create new template:

Field	PoC value
Template Name	`test` (or any label)
Provider	`BONVOICE`
Endpoint	`wss://<your-relay-or-ngrok-host>/ws/media`

Important: Use wss:// (WebSocket Secure). Using https:// causes Bonvoice to send HTTP POST instead of a WebSocket upgrade, resulting in 404 Not Found.

23.4 Network & infrastructure (observed during PoC)

Item	Value	Notes
Bonvoice media server IP	`103.131.25.5`	Source IP for inbound WebSocket connections — add to provider allowlist
Local dev server	`http://0.0.0.0:8000`	Uvicorn PoC
PoC WebSocket path	`/ws/media`	Also accepts `/` in PoC
ngrok URL (ephemeral)	`https://1af5-2401-4900-88ce-916c-2c02-6571-5bcd-b1eb.ngrok-free.app`	Changes every ngrok restart; WSS = same host with `wss://`

PoC WebSocket endpoint used in tests:

wss://1af5-2401-4900-88ce-916c-2c02-6571-5bcd-b1eb.ngrok-free.app/ws/media

23.5 Test phone numbers

Number	Role
`7946350706`	Assigned virtual DID (inbound destination / outbound caller ID)
`9149154337`	Test mobile used for outbound dial + inbound caller during PoC
`9846098460`	Example destination from Bonvoice API documentation

23.6 Observed call / stream identifiers (PoC logs)

Successful inbound WebSocket session (for correlation testing):

Field	Value
`stream_id`	`6379`
`call_id`	`12775`
`from`	`9149154337`
`to`	`7946350706`

Additional WebSocket events observed from Bonvoice (forward in relay; do not drop):

Event	When
`connected`	Immediately after WS handshake, before `start`
`start`	Call metadata — use for DID routing / session binding
`media`	Audio frames (320-byte PCM chunks, Base64)
`clear`	Barge-in / flush playback buffer
`end`	Call teardown

23.7 Ready-to-run curl (outbound)

Replace voicebotURL with your current relay or ngrok WSS URL:

curl -X POST "https://backend.pbx.bonvoice.com/autoDialManagement/autoCallBridging/" \
  -H "Authorization: Token 8de97c5932280c84c4bbf36140a1ec7ab7ae0b23" \
  -H "Content-Type: application/json" \
  -d '{
    "autocallType": "5",
    "destination": "9149154337",
    "legACallerID": "7946350706",
    "eventID": "TEST'"$(date +%s)"'",
    "voicebotProvider": "BONVOICE",
    "voicebotURL": "wss://YOUR-RELAY-HOST/ws/media"
  }'

PoC script equivalent (auto-detects ngrok URL):

cd test_bonvoice
source .venv/bin/activate
python3 outbound_call.py 9149154337

23.8 Environment variables (recommended for relay implementation)

Variable	PoC / example value
`BONVOICE_TOKEN`	`8de97c5932280c84c4bbf36140a1ec7ab7ae0b23`
`BONVOICE_DID`	`7946350706`
`BONVOICE_VOICEBOT_URL`	`wss://media.yourcpaas.com/v1/media/inbound`
`BONVOICE_API_URL`	`https://backend.pbx.bonvoice.com/autoDialManagement/autoCallBridging/`
`BONVOICE_MEDIA_ALLOWLIST`	`103.131.25.5`

23.9 Audio format requirements (provider-enforced)

Parameter	Value
Encoding	PCM
Bit depth	16-bit
Sample rate	8000 Hz
Channels	Mono
Chunk size	320 bytes (multiples of 320 only)
Wire format	Base64 in JSON `media.payload`

24. Urmi CPaaS — Implemented Customer API Routes

Urmi exposes production voice relay endpoints under /api/v1/voice (REST + WebSocket). All outbound calls validate that from is a purchased DID assigned to the authenticated account.

24.1 REST control plane

Method	Path	Auth	Description
`POST`	`/api/v1/voice/calls`	API key or session cookie	Initiate outbound call
`GET`	`/api/v1/voice/calls/{id}`	API key or session cookie	Poll call status
`GET`	`/api/v1/voice/docs`	API key or session cookie	API reference for integrators

Create outbound call

POST /api/v1/voice/calls
Authorization: Bearer urmi_live_...
Content-Type: application/json

{
  "to": "9149154337",
  "from": "7946350706",
  "bridge_mode": "upstream",
  "upstream": "wss://bot.customer.com/voice"
}

Console testing (Urmi dashboard at /console/voice):

{
  "to": "9149154337",
  "from": "7946350706",
  "bridge_mode": "console"
}

Validation rules:

from must match a phone_numbers row with status=assigned and user_id = caller
upstream is required when bridge_mode=upstream
Relay always injects Bonvoice voicebotURL — customers never pass provider URLs

24.2 Media relay (provider leg)

WebSocket	Purpose	Auth
`wss://<host>/api/v1/voice/ws/media`	Bonvoice outbound voicebotURL	IP allowlist + pending call match on `start`
`wss://<host>/api/v1/voice/media/{session_token}`	Legacy alias	Same handler

Configure Bonvoice outbound API voicebotURL:

wss://<public-host>/api/v1/voice/ws/media

Set VOICE_RELAY_PUBLIC_URL=wss://<public-host>/api/v1/voice in production.

24.3 Console audio bridge (outbound testing)

WebSocket	Purpose
`wss://<host>/api/v1/voice/console`	Browser mic/speaker bridge for `bridge_mode: console`

When placing a console-bridged outbound call from /console/voice, the account must have an active console WebSocket. Provider media is forwarded to the browser; browser mic frames are relayed back to Bonvoice.

24.4 Environment variables (Urmi)

Variable	Example
`REDIS_URL`	`redis://redis:6379/0`
`BONVOICE_TOKEN`	`8de97c5932280c84c4bbf36140a1ec7ab7ae0b23`
`BONVOICE_API_URL`	`https://backend.pbx.bonvoice.com/autoDialManagement/autoCallBridging/`
`BONVOICE_MEDIA_ALLOWLIST`	`103.131.25.5`
`VOICE_RELAY_PUBLIC_URL`	`wss://media.yourcpaas.com/api/v1/voice`

25. Next Steps

Approve URL scheme and auth model (Section 7, 10)
Implement Phase 1 tunnel with Redis session store (Urmi MVP shipped)
Migrate Bonvoice template + outbound API to relay URLs
Load test at 320-byte / 20 ms frame rate per call
Document customer-facing API and WebSocket protocol (derived from this plan)

Document maintained by CPaaS platform team. Update when adding providers or changing auth model.

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