SIP Trunk in China — Beijing, Shanghai, Shenzhen Inbound + Outbound

1. What a SIP trunk in China actually is

A SIP trunk is the IP delivery pipe between a carrier and your PBX, AI voice agent, or call-control platform; it carries signaling over SIP and audio over RTP, replacing the old TDM hand-off. A China SIP trunk is the same thing but with one critical wrinkle: the numbers riding it are +86 mainland Chinese DIDs allocated under the Ministry of Industry and Information Technology (MIIT), the strictest national telecom regulator most foreign operators will ever interact with.

That regulatory layer changes everything about how the trunk is provisioned, who can hold the numbers, what use cases are allowed, and how outbound CLI is verified. The technical layer underneath is standard SIP. The compliance layer on top is where the work happens.

DIDHub delivers Chinese DIDs via two operator routes: a regulated MIIT-licensed partner inside mainland China handles the number-holder relationship, and we route the SIP leg through edge SBCs in Hong Kong (primary) and Singapore (failover). The result is a single SIP trunk you authenticate against, with Chinese numbers behaving like any other DIDs in your PBX while we handle the Beijing-side paperwork.

2. China regulation: MIIT, KYC, compliance

MIIT registration is the first thing that has to happen before any Chinese DID rings. The requirements are stricter than EU GDPR-style KYC and unique to China.

Who can hold a Chinese number

• A licensed mainland Chinese entity. That's either your own Chinese subsidiary (WFOE, Wholly Foreign-Owned Enterprise), a JV with a local partner, or a contract relationship with a licensed local operator that holds the number on your behalf.
• A foreign company with no Chinese presence cannot directly hold a Chinese DID under current MIIT rules. The number is held by a licensed local entity (DIDHub's regulated mainland partner) and routed to you over SIP.
• An ICP-style filing describes the use case, the responsible party, and the business intent. Vague intents (cold outbound, mass-marketing) are rejected.

What DIDHub handles for you

• The mainland operator relationship and number allocation.
• Document preparation and translation (English ↔ Simplified Chinese).
• Submission to MIIT and the responsible carrier (typically China Telecom, China Unicom, or China Mobile for the underlying inventory).
• Ongoing compliance monitoring and use-case verification.

Use cases MIIT routinely approves

• Customer service inbound for an established product (B2C or B2B).
• Sales callbacks to customers who have requested contact (opted-in lists, CRM-tracked).
• Two-factor authentication and transactional SMS tied to the registered service.
• AI voice agents for inbound (incoming-only) servicing existing customers.
• Microsoft Teams Direct Routing for employees of registered entities operating in China.

Use cases that get rejected

• Cold outbound calling, telemarketing, mass voice broadcasts.
• Unsolicited SMS campaigns.
• Gambling, adult-content, political-advocacy, or anything touching MIIT's restricted-content categories.
• Anonymous-relay use cases (no identifiable end-user attribution).

For the broader regulatory picture across countries, see our guide to international DID compliance & KYC bundles. For the SIP-trunk concept end-to-end, see the DID Number Provider guide.

3. Number types you can route over the trunk

China uses 2–4 digit area codes with trunk prefix 0; the international format drops the leading 0 and prefixes +86. The trunk can carry any of these number types simultaneously:

Two specifically Chinese pitfalls to know up front. 800 toll-free in China is reachable only from Chinese landlines (Chinese mobile users cannot dial 800 numbers; it's a regulatory carve-out that surprises every Western operator). Almost every modern Chinese consumer use case wants 400 instead, which is reachable from both mobile and landline and where the caller pays the normal long-distance rate.

Chinese mobile DIDs (147/152/170/171/178 ranges and others) are extremely restricted; allocation to non-carriers is severely limited and most foreign operators cannot get them at all. If your use case requires sending or receiving SMS, plan around 400 or geographic numbers, or coordinate with us upfront.

For a deeper look at how number types differ globally, see DID number types explained.

4. How DIDHub's SIP trunk works in China

The technical surface of the trunk is standardised; the China-specific choices are the POP, the codec list, and the failover topology.

Ingress POPs

• Hong Kong (primary), lowest latency to Chinese mainland endpoints, sub-50ms to Shanghai and Shenzhen, sub-80ms to Beijing.
• Singapore (failover), secondary route used if the Hong Kong path is degraded; adds ~30–60ms latency.
• Shanghai (mainland, select customers), a directly-attached SBC inside mainland China is available for enterprise customers with their own ICP-licensed entity. Contact sales for qualification.

Transport & security

• TLS:5061 is the recommended SIP transport for any China trunk. Plain UDP signaling is permitted but discouraged.
• SRTP for media via DTLS-SRTP or SDES, depending on your endpoint capability.
• SIP authentication: digest registration (PBX behind NAT) or IP-ACL (static peering). See SIP authentication.

Codecs

• G.711 a-law (PCMA), the default in China, preferred over μ-law. Always negotiated first.
• G.722, wideband HD voice where the far-side endpoint supports it; same bitrate as G.711 with much better quality.
• Opus, for AI voice agents and any IP-native softphone; encoder-side rate control adapts to mainland China network jitter.
• G.729, available on request for bandwidth-constrained branches; royalty-free since 2017.

For the codec deep-dive, see voice codecs explained.

DTMF

• RFC 4733 (telephone-events over RTP) is the default. SIP INFO and in-band DTMF available for legacy interop on request.

Channel concurrency

• Trunks start at 5 concurrent channels and scale to 200 per trunk off the shelf. Larger requires a custom arrangement.
• Channels are independent of DID count; you can carry 200 numbers on a 10-channel trunk if your concurrent-call peak is 10. See multiple concurrent calls on one DID.

STIR/SHAKEN

• Not applicable in China. The North-American STIR/SHAKEN attestation framework is a US/Canada construct that doesn't exist in mainland China. Trust signals come instead through MIIT registration, ICP licensing of the responsible entity, and operator-side caller-ID validation.

5. Outbound calling from your China trunk

Outbound from a China-allocated DID to Chinese landline and mobile destinations is allowed within approved use cases. The per-minute economics:

Outbound caller-ID rules

• Your outbound CLI must match a DID you've allocated through the trunk. Setting an arbitrary +86 caller ID is rejected at the SBC.
• Origin-based rating (OBR) applies on cross-border outbound: pairing a Chinese DID as caller-ID with a call to an EU destination may attract the regulated EEA tier under the source carrier's framework.
• For multi-region operators, see origin-based rating savings.

6. Setup in 6 steps

Asterisk pjsip example

; /etc/asterisk/pjsip.conf
[transport-tls]
type=transport
protocol=tls
bind=0.0.0.0:5061
cert_file=/etc/asterisk/keys/asterisk.crt
priv_key_file=/etc/asterisk/keys/asterisk.key
method=tlsv1_2

[didhub-china]
type=auth
auth_type=userpass
username=YOUR_DIDHUB_USERNAME
password=YOUR_DIDHUB_PASSWORD

[didhub-china]
type=aor
contact=sip:sip.didhub.io:5061;transport=tls
qualify_frequency=30

[didhub-china]
type=endpoint
transport=transport-tls
context=from-didhub
disallow=all
allow=alaw,g722,opus
outbound_auth=didhub-china
aors=didhub-china
dtmf_mode=rfc4733
media_encryption=sdes
direct_media=no

3CX SIP trunk template snapshot

# 3CX -> SIP Trunks -> Add SIP Trunk -> Generic SIP Trunk
Trunk name:        DIDHub China
Registrar:         sip.didhub.io
Transport:         TLS
Port:              5061
Authentication:    Register/Account based
Auth ID:           YOUR_DIDHUB_USERNAME
Auth password:     YOUR_DIDHUB_PASSWORD
Outbound caller ID: +86 10 XXXX XXXX  (one of your allocated DIDs)
Codecs (priority):  G.711 a-law, G.722, Opus

7. Integration patterns

Every modern PBX, UC platform, and AI voice stack can authenticate against the trunk:

8. Pricing

Four line items: per-DID monthly rental, per-minute inbound usage on every China DID (even landline geographic numbers carry an inbound MOU charge in China), channel capacity, and per-minute outbound. Setup is $0 once MIIT paperwork is approved.

Per-DID monthly

Channel capacity

Per-minute outbound

See section 5 above and the full global rate sheet.

9. Porting an existing China number

Porting in mainland China is rare, possible, and slow. Realistic expectations:

• Geographic numbers (010, 021, 0755 …): 6–12 weeks, carrier-dependent.
• 400 numbers: 4–8 weeks.
• 800 numbers: generally not portable in practice.
• Required documents: Chinese business license + Letter of Authority + ICP filing + carrier-specific port forms.
• Cost: $80 port-in fee per number, plus any carrier-side fees passed through.

For the full porting playbook (US/UK/EU + the global gotchas), see number porting explained.

10. FAQ

Can a foreign company directly hold a Chinese SIP trunk DID?

Not directly under current MIIT rules. The number is held by a licensed mainland Chinese entity (DIDHub's regulated partner, or your own WFOE / Chinese subsidiary if you have one) and routed to you over SIP. The trunk authentication and SIP delivery to your platform looks identical to any other DIDHub trunk.

How long does activation take?

5 to 15 business days after KYC documents are received and the use case is approved. The variability is on MIIT and the underlying mainland carrier; the SIP-side provisioning is hours, not days.

Which POP should I connect to for a China SIP trunk?

Hong Kong is the recommended primary for almost everyone. Singapore is the standard failover. Mainland Shanghai ingress is available for enterprise customers with their own ICP-licensed Chinese entity.

What is the difference between 400 and 800 in China?

400 is a national service number reachable from both mobile and landline; caller pays the normal long-distance rate. 800 is true toll-free for the caller, but reachable only from Chinese landlines. Chinese mobile users cannot dial 800 numbers. Almost every modern B2C use case wants 400.

Can I use my China SIP trunk with Microsoft Teams?

Yes, via Microsoft Teams Direct Routing through DIDHub's managed SBC. Microsoft Calling Plans don't cover mainland China, so Direct Routing through DIDHub is the standard path for Teams users operating in China.

What codecs should I configure for a China SIP trunk?

G.711 a-law (PCMA) as the default, G.722 for HD voice on capable endpoints, Opus for AI voice agents and IP-native softphones. G.729 available on request. Always offer G.711 a-law before mu-law on China-bound trunks.

Does STIR/SHAKEN apply in China?

No. STIR/SHAKEN is a US/Canada framework that doesn't exist in China. Trust signals in China come through MIIT registration and operator-side caller-ID validation against the registered number holder.

Can I send SMS over the SIP trunk to Chinese numbers?

SMS is a separate provisioning track from voice. In China, commercial SMS is heavily regulated. Inbound works on most numbers; outbound requires content pre-approval and is restricted to MIIT-licensed templates. DIDHub manages SMS compliance for legitimate use cases.

How many concurrent calls can one Chinese DID handle?

The DID itself is just an address; concurrent-call capacity is set by the channel count on the trunk. A 50-channel trunk with 1 Chinese DID can carry 50 concurrent calls to that one number; the same trunk with 200 DIDs can carry 50 concurrent calls across any combination of those numbers.

What use cases get rejected by MIIT?

Cold outbound calling, unsolicited SMS campaigns, anonymous-relay setups, and anything touching MIIT's restricted-content categories (gambling, adult content, political advocacy). Customer service, opted-in callbacks, transactional 2FA, inbound AI voice agents, and Teams Direct Routing for registered entities are routinely approved.

11. Related country pages