STUN_SERVER - Session Traversal Utilities for NAT

What is STUN_SERVER?

STUN server helps devices behind a NAT (Network Address Translation) discover their public IP address and the type of NAT they are behind. This is essential for peer-to-peer communication over the internet.

Why is STUN important in WebRTC?

STUN is crucial in WebRTC to: * Discover the public-facing IP and port of a device * Enable direct peer-to-peer connections * Facilitate NAT traversal without requiring a relay server (like TURN)

How does a STUN server work?

The client sends a binding request to the STUN server, which replies with the public IP and port it sees. This helps the client understand how it appears to the outside world.

What is the difference between STUN and TURN?

  • STUN: Used to discover public IP and port; works for most NATs

  • TURN: Used when STUN fails; relays media through a server, which is more resource-intensive

Are STUN servers free to use?

Yes, many public STUN servers are available for free. For example: * stun.l.google.com:19302 * stun1.l.google.com:19302

Can I host my own STUN server?

Yes. You can use open-source software like: * Coturn (supports both STUN and TURN) * reTurnServer

What ports do STUN servers use?

Typically, STUN uses: * UDP port 3478 (default) * Can also use TCP or TLS for secure communication

Is STUN secure?

STUN itself is not encrypted. For secure communication, use STUN over TLS or combine it with DTLS-SRTP in WebRTC.

What are common issues with STUN?

  • Some NAT types (e.g., Symmetric NAT) may not work well with STUN

  • Firewalls may block STUN traffic

  • STUN alone doesn’t guarantee connectivity — TURN may be needed

How do I test if a STUN server is working?

You can use tools like: * stunclient (CLI tool) * trickle ICE (WebRTC testing tool) * Browser-based WebRTC test pages

Which OSI layer does STUN belong to?

  • STUN is a control protocol that assists applications in NAT traversal

  • It operates between the Transport Layer (Layer 4) and Application Layer (Layer 7)

  • Most commonly considered to function at Layer 7 due to its use in signaling and real-time communication protocols

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

sno

Stun version

RFC - Version

Core / Contribution

Year

1

STUN (Original)

RFC 3489

Introduced STUN protocol for NAT traversal; defined Binding

2003

request/response.

2

STUN (Updated)

RFC 5389

Redefined STUN as a standalone protocol; added Magic cookie

2008

improved security.

RFC 5769

For validating implementations

2010

RFC 5780

Extends STUN functionality

RFC 7350

Adds secure transport option

2014

RFC 7443

Enables STUN/TURN over TLS

2015

RFC 8489

Current STUN standard

2020

  • Setup

  • Setup

Binding Request

sno.

Protocol Packets

Decription

Sizeof Bytes

1

Binding Request

Client asks the STUN server for its public IP and port.

56

Message Type

Identifies the type of STUN message (Binding Request = 0x0001)

2

Message Length

Length of the message body (excluding the 20-byte header)

2

Magic Cookie

Fixed value (0x2112A442) to aid in distinguishing STUN packets

4

Transaction ID

Random identifier used to correlate requests and responses

12

Attributes (optional)

Additional information like username, priority, etc. (can vary)

~36

Binding Success Response

2

Binding Success Response

Server responds with the public IP and port.

64

Message Type

Identifies the type of STUN message (Binding Success Response = 0x0101)

2

Message Length

Length of the message body (excluding the 20-byte header)

2

Magic Cookie

Fixed value (0x2112A442) to aid in distinguishing STUN packets

4

Transaction ID

Random identifier used to correlate requests and responses

12

XOR-MAPPED-ADDRESS

Contains the public IP and port of the client, XORed with the magic cookie

12

MAPPED-ADDRESS

(Optional) Contains the public IP and port in plain format

8

Other Attributes

May include attributes like SOFTWARE, MESSAGE-INTEGRITY, FINGERPRINT, etc.

~24

Binding Error Response

3

Binding Error Response

Server indicates an error in processing the request.

60

Message Type

Identifies the type of STUN message (Binding Error Response = 0x0111)

2

Message Length

Length of the message body (excluding the 20-byte header)

2

Magic Cookie

Fixed value (0x2112A442) to aid in distinguishing STUN packets

4

Transaction ID

Random identifier used to correlate requests and responses

12

ERROR-CODE Attribute

Contains the error class and number (e.g., 400 Bad Request, 401 Unauthorized)

8

Reason Phrase

Human-readable explanation of the error

~20

Other Attributes

May include SOFTWARE, FINGERPRINT, etc.

~12

Shared Secret Request

4

Shared Secret Request

(Deprecated) Used to request a shared secret.

60

Message Type

Identifies the type of STUN message (Shared Secret Request = 0x0002)

2

Message Length

Length of the message body (excluding the 20-byte header)

2

Magic Cookie

Fixed value (0x2112A442) to aid in distinguishing STUN packets

4

Transaction ID

Random identifier used to correlate requests and responses

12

Username Attribute

(Optional) Username for authentication

~20

Realm Attribute

(Optional) Realm used in message integrity checks

~10

Nonce Attribute

(Optional) Used to prevent replay attacks

~10

Shared Secret Response

5

Shared Secret Response

(Deprecated) Server responds with the shared

80

secret.

Message Type

Identifies the type of STUN message (Shared Secret Response = 0x0102)

2

Message Length

Length of the message body (excluding the 20-byte header)

2

Magic Cookie

Fixed value (0x2112A442) to aid in distinguishing STUN packets

4

Transaction ID

Random identifier used to correlate requests and responses

12

Username Attribute

Contains the username to be used in future requests

~20

Password Attribute

Contains the password (shared secret)

~20

Realm Attribute

Defines the protection domain

~10

Other Attributes

May include SOFTWARE, FINGERPRINT, etc.

~12

Shared Secret Error

6

Shared Secret Error

(Deprecated) Error in shared secret request.

60

Message Type

Identifies the type of STUN message (Shared Secret Error = 0x0112)

2

Message Length

Length of the message body (excluding the 20-byte header)

2

Magic Cookie

Fixed value (0x2112A442) to aid in distinguishing STUN packets

4

Transaction ID

Random identifier used to correlate requests and responses

12

ERROR-CODE Attribute

Contains the error class and number (e.g., 401 Unauthorized, 420 Unknown Attr)

8

Reason Phrase

Human-readable explanation of the error

~20

Other Attributes

May include SOFTWARE, FINGERPRINT, etc.

~12

STUN Server cases

sno

Use cases

Description

1

NAT Traversal for VoIP and WebRTC

STUN helps devices behind NAT (Network Address Translation)

discover their public IP address and port. This is essential for

peer-to-peer communication in VoIP (e.g., SIP) and WebRTC

applications.

2

Peer-to-Peer (P2P) Connectivity

STUN enables direct P2P connections by revealing the external

IP/port of each peer, allowing them to bypass centralized

servers for data transfer.

3

WebRTC Signaling Support

In WebRTC, STUN is used during the ICE (Interactive Connectivity

Establishment) process to gather candidate IP addresses for

media streams.

4

Firewall and NAT Type Detection

STUN can help determine the type of NAT or firewall a client

is behind (e.g., full cone, symmetric NAT), which influences

connection strategies.

5

Fallback Mechanism for TURN

If STUN fails to establish a direct connection, the system can

fall back to TURN (Traversal Using Relays around NAT), which

relays traffic through a server.

6

Gaming and Real-Time Applications

Online games and real-time apps use STUN to reduce latency

by enabling direct communication between players.

Basic Features

Sno

Features

Description

1

Public IP Discovery

Allows a client behind NAT to discover its public IP address

and port as seen by external servers.

2

NAT Type Detection

Helps determine the type of NAT (e.g., full cone, symmetric)

the client is behind, which affects connectivity.

3

Port Mapping Discovery

It reveals the public port number that the NAT has assigned to

the clients private port. This is important for routing incoming

trafic correctly.

4

Lightweight Protocol

STUN is designed to be simple and efficient. It uses UDP (User

Datagram Protocol) and requires minimal overhead, making it

suitable for real-time applications.

5

Client-Server Architecture

STUN operates on a client-server model where the client send

a request to the STUN server, and the server responds with

the public IP and port information.

6

Support for IPv4 and IPv6

Modern STUN servers support both IPv4 and IPv6, ensuring

compatibility with a wide range of network environments.

7

Used in WebRTC and VoIP

STUN is a foundational protocol in WebRTC and VoIP systems,

enabling peer-to-peer media streaming by helping clients

traverse NATs.

Public IP Discovery - Testcases

Public IP Discovery

S.No

Test Case

Description

Expected Result

1

Basic STUN Request

Send STUN binding request

Public IP and port returned

2

STUN Server Reachable

STUN server is online

Response received

3

STUN Server Unreachable

STUN server is offline

Request times out

4

STUN Server Port Blocked

Block port 3478

Request fails

5

STUN over UDP

Use UDP transport

Public IP returned

6

STUN over TCP

Use TCP transport

Public IP returned

7

STUN over IPv4

Use IPv4 network

IPv4 public IP returned

8

STUN over IPv6

Use IPv6 network

IPv6 public IP returned

9

NAT Type Full Cone

Behind full cone NAT

Public IP returned correctly

10

NAT Type Restricted Cone

Behind restricted cone NAT

Public IP returned

11

NAT Type Port Restricted

Behind port-restricted NAT

Public IP returned

12

NAT Type Symmetric

Behind symmetric NAT

Public IP returned, port may vary

13

NAT Type Detection

Use STUN to detect NAT type

Correct NAT type identified

14

Multiple STUN Servers

Query multiple servers

Consistent public IP returned

15

STUN Server Failover

Primary server fails

Secondary server used

16

STUN Response Delay

Simulate network delay

Response received after delay

17

STUN Response Timeout

No response within timeout

Request fails

18

STUN Response Parsing

Parse STUN response

Public IP extracted correctly

19

STUN Response Integrity

Validate message integrity

Message passes integrity check

20

STUN Response with XOR-MAPPED-ADDRESS

Use XOR-mapped address

Public IP decoded correctly

21

STUN Response with MAPPED-ADDRESS

Use mapped address

Public IP decoded correctly

22

STUN Binding Request Format

Validate request format

Server accepts request

23

STUN Binding Response Format

Validate response format

Client parses successfully

24

STUN with Authentication

Use long-term credentials

Authenticated response received

25

STUN with Invalid Credentials

Use wrong credentials

Request rejected

26

STUN with No Credentials

Send unauthenticated request

Response received (if allowed)

27

STUN with TLS

Use STUN over TLS

Secure response received

28

STUN with DTLS

Use STUN over DTLS

Secure response received

29

STUN with IPv6 NAT

Behind IPv6 NAT

Public IPv6 returned

30

STUN with Dual Stack

Use dual-stack client

Both IPv4 and IPv6 discovered

31

STUN with Mobile Network

Use mobile data

Public IP returned

32

STUN with Wi-Fi

Use Wi-Fi network

Public IP returned

33

STUN with Ethernet

Use wired connection

Public IP returned

34

STUN with VPN

Use VPN connection

VPN-assigned public IP returned

35

STUN with Proxy

Use HTTP/SOCKS proxy

STUN may fail or return proxy IP

36

STUN with Firewall

Behind firewall

Public IP returned if allowed

37

STUN with NAT64

Use NAT64 environment

IPv6 to IPv4 mapping handled

38

STUN with Carrier-Grade NAT

Behind CGNAT

Public IP returned (shared)

39

STUN with Multiple Interfaces

Use multiple NICs

Correct IP per interface

40

STUN with Interface Binding

Bind to specific interface

IP of that interface returned

41

STUN with Port Mapping

NAT port mapping enabled

Mapped port returned

42

STUN with Port Preservation

NAT preserves port

Same port returned

43

STUN with Port Translation

NAT changes port

New port returned

44

STUN with Packet Loss

Simulate packet loss

Retransmission occurs

45

STUN with Retransmission

No response initially

Retry succeeds

46

STUN with Invalid Response

Corrupt response

Client discards response

47

STUN with Malformed Request

Send invalid request

Server returns error

48

STUN with Rate Limiting

Exceed request rate

Server throttles or blocks

49

STUN with Logging Enabled

Enable client logs

Request/response logged

50

STUN with Debug Mode

Enable debug mode

Detailed diagnostics shown

NAT Type Detection - Testcases

NAT Type Detection

S.No

Test Case

Description

Expected Result

1

Full Cone NAT

Client behind full cone NAT

STUN detects Full Cone NAT

2

Restricted Cone NAT

Client behind restricted cone NAT

STUN detects Restricted Cone NAT

3

Port Restricted Cone NAT

Client behind port-restricted NAT

STUN detects Port Restricted Cone NAT

4

Symmetric NAT

Client behind symmetric NAT

STUN detects Symmetric NAT

5

No NAT (Open Internet)

Client directly on public IP

STUN detects Open Internet

6

Symmetric UDP Firewall

Firewall blocks unsolicited UDP

STUN detects UDP blocked

7

NAT with Hairpinning

NAT supports hairpinning

STUN detects NAT with hairpinning

8

NAT without Hairpinning

NAT does not support hairpinning

STUN detects lack of hairpinning

9

NAT with Endpoint-Independent Mapping

Mapping is consistent

STUN detects endpoint-independent mapping

10

NAT with Address-Dependent Mapping

Mapping changes with destination IP

STUN detects address-dependent mapping

11

NAT with Address and Port-Dependent Mapping

Mapping changes with IP and port

STUN detects address+port-dependent mapping

12

NAT with Endpoint-Independent Filtering

Filtering allows any external IP

STUN detects endpoint-independent filtering

13

NAT with Address-Dependent Filtering

Filtering allows only known IPs

STUN detects address-dependent filtering

14

NAT with Address and Port-Dependent Filtering

Filtering allows only known IP+port

STUN detects address+port-dependent filtering

15

NAT with Static Port Mapping

Port remains unchanged

STUN detects static port mapping

16

NAT with Dynamic Port Mapping

Port changes per request

STUN detects dynamic port mapping

17

NAT with Port Preservation

NAT preserves source port

STUN detects port preservation

18

NAT with Port Translation

NAT changes source port

STUN detects port translation

19

NAT with Consistent Mapping

Mapping remains stable

STUN detects consistent mapping

20

NAT with Inconsistent Mapping

Mapping changes frequently

STUN detects inconsistent mapping

21

NAT with Multiple Public IPs

NAT uses multiple external IPs

STUN detects multiple mappings

22

NAT with Single Public IP

NAT uses one external IP

STUN detects single mapping

23

NAT with Symmetric Response

Different IP/port for each request

STUN detects symmetric NAT

24

NAT with Cone Behavior

Same IP/port for all requests

STUN detects cone NAT

25

NAT with UDP Timeout

NAT closes port quickly

STUN detects timeout behavior

26

NAT with Long UDP Timeout

NAT keeps port open

STUN detects long timeout

27

NAT with Firewall Blocking STUN

Firewall blocks STUN packets

STUN fails to detect NAT type

28

NAT with STUN Server Unreachable

STUN server down

NAT type detection fails

29

NAT with STUN Server Timeout

No response from server

NAT type detection fails

30

NAT with STUN Server Error

Server returns error

NAT type detection fails

31

NAT with STUN Server Delay

Delayed response

NAT type detection delayed

32

NAT with STUN Server Retry

Retry after failure

NAT type detected on retry

33

NAT with Multiple STUN Servers

Use multiple servers

Consistent NAT type detected

34

NAT with IPv6

Use IPv6-only network

NAT type detection not applicable

35

NAT with Dual Stack

Use IPv4 and IPv6

NAT type detected for IPv4 only

36

NAT with VPN

Use VPN connection

NAT type reflects VPN NAT

37

NAT with Mobile Network

Use mobile data

NAT type detected (usually symmetric)

38

NAT with Wi-Fi

Use Wi-Fi network

NAT type detected

39

NAT with Ethernet

Use wired connection

NAT type detected

40

NAT with Carrier-Grade NAT

Behind CGNAT

STUN detects symmetric NAT

41

NAT with Home Router

Use typical home NAT

STUN detects cone or restricted NAT

42

NAT with Enterprise Firewall

Use corporate network

STUN detects restricted or symmetric NAT

43

NAT with Port Forwarding

Port forwarding enabled

STUN may detect open internet

44

NAT with DMZ Host

Device in DMZ

STUN detects open internet

45

NAT with Static IP

Public IP assigned

STUN detects open internet

46

NAT with Dynamic IP

IP changes periodically

STUN detects NAT type per session

47

NAT with NAT64

IPv6 to IPv4 translation

STUN may fail or detect NAT

48

NAT with Proxy

Use HTTP/SOCKS proxy

STUN fails or gives incorrect result

49

NAT with STUN over TLS

Use secure STUN

NAT type detected securely

50

NAT with STUN over DTLS

Use STUN over DTLS

NAT type detected securely

Port Mapping Discovery - Testcases

Port Mapping Discovery

S.No

Test Case

Description

Expected Result

1

Basic Port Mapping

Send STUN request

Public IP and port returned

2

NAT with Port Preservation

NAT preserves source port

Same port returned by STUN

3

NAT with Port Translation

NAT changes source port

Different port returned

4

Symmetric NAT Mapping

Different port for each destination

STUN detects port change

5

Full Cone NAT Mapping

Same port for all destinations

STUN detects consistent port

6

Port Restricted NAT Mapping

Port changes with destination port

STUN detects port dependency

7

Multiple STUN Requests

Send multiple requests

Port mapping behavior observed

8

Mapping Consistency

Send requests to same STUN server

Port remains same if NAT preserves

9

Mapping Inconsistency

Send requests to different STUN servers

Port changes if symmetric NAT

10

Mapping Lifetime

Wait between requests

Port mapping may expire

11

Mapping Refresh

Send periodic requests

Port mapping remains active

12

Mapping Expiry

Wait beyond timeout

Port mapping expires, new port assigned

13

Mapping with UDP

Use UDP transport

Port mapping discovered

14

Mapping with TCP

Use TCP transport

Port mapping discovered

15

Mapping with TLS

Use STUN over TLS

Port mapping discovered securely

16

Mapping with DTLS

Use STUN over DTLS

Port mapping discovered securely

17

Mapping with NAT64

Use IPv6 to IPv4 NAT

Port mapping discovered if supported

18

Mapping with Dual Stack

Use IPv4 and IPv6

Mapping discovered for IPv4 only

19

Mapping with VPN

Use VPN connection

VPN-assigned port returned

20

Mapping with Mobile Network

Use mobile data

Port mapping discovered

21

Mapping with Wi-Fi

Use Wi-Fi network

Port mapping discovered

22

Mapping with Ethernet

Use wired connection

Port mapping discovered

23

Mapping with Carrier-Grade NAT

Behind CGNAT

Port mapping discovered (shared IP)

24

Mapping with Home Router

Use home NAT

Port mapping discovered

25

Mapping with Enterprise Firewall

Use corporate network

Port mapping discovered or blocked

26

Mapping with Port Forwarding

Port forwarding enabled

Public port matches internal port

27

Mapping with DMZ Host

Device in DMZ

Public port matches internal port

28

Mapping with Static IP

Public IP assigned

No mapping needed

29

Mapping with Dynamic IP

IP changes periodically

Mapping changes accordingly

30

Mapping with NAT Timeout

NAT closes port quickly

Mapping expires

31

Mapping with Long NAT Timeout

NAT keeps port open

Mapping remains stable

32

Mapping with Firewall Blocking

Block STUN port

Mapping discovery fails

33

Mapping with STUN Server Timeout

No response

Mapping discovery fails

34

Mapping with STUN Server Retry

Retry after failure

Mapping discovered on retry

35

Mapping with Multiple Interfaces

Use multiple NICs

Mapping per interface discovered

36

Mapping with Interface Binding

Bind to specific NIC

Mapping for that NIC discovered

37

Mapping with NAT Hairpinning

NAT supports hairpinning

Mapping remains consistent

38

Mapping with NAT Loopback

NAT supports loopback

Mapping remains consistent

39

Mapping with NAT Filtering

NAT filters by port

Mapping changes with destination

40

Mapping with NAT Mapping Behavior

NAT maps based on destination

Mapping varies accordingly

41

Mapping with STUN Server Change

Use different STUN server

Mapping may change

42

Mapping with STUN Server Load Balancer

Behind load balancer

Mapping may vary

43

Mapping with STUN Server Cluster

Use clustered STUN servers

Mapping consistency tested

44

Mapping with Packet Loss

Simulate packet loss

Mapping discovered after retry

45

Mapping with Delayed Response

Simulate delay

Mapping discovered after wait

46

Mapping with Invalid Response

Corrupt STUN response

Mapping discovery fails

47

Mapping with Malformed Request

Send invalid request

Server returns error

48

Mapping with Logging Enabled

Enable logs

Mapping details logged

49

Mapping with Debug Mode

Enable debug mode

Detailed mapping info shown

50

Mapping with NAT Type Detection

Combine with NAT detection

Mapping behavior explained by NAT type

Lightweight Protocol - Testcases

Lightweight Protocol

S.No

Test Case

Description

Expected Result

1

Minimal Packet Size

Send STUN binding request

Packet size < 100 bytes

2

Low Bandwidth Usage

Measure bandwidth during STUN exchange

Bandwidth usage is minimal

3

UDP Transport

Use UDP for STUN

Request and response succeed

4

TCP Transport

Use TCP for STUN

Request and response succeed

5

Stateless Server

STUN server does not maintain session state

Server responds without session tracking

6

Stateless Client

Client does not store session info

Client handles response independently

7

No Authentication Required

Send unauthenticated request

Server responds successfully

8

Simple Request Format

Validate STUN request structure

Request is compact and efficient

9

Simple Response Format

Validate STUN response structure

Response is compact and efficient

10

Low CPU Usage

Monitor CPU during STUN exchange

CPU usage remains low

11

Low Memory Usage

Monitor memory during STUN exchange

Memory usage remains low

12

Fast Request Handling

Measure response time

Response received in < 100ms

13

No Encryption Overhead

Use plain STUN

No TLS/DTLS overhead present

14

Minimal Dependencies

Use STUN client library

Few external dependencies required

15

Lightweight NAT Detection

Detect NAT type with minimal traffic

NAT type detected efficiently

16

Lightweight Port Mapping

Discover port mapping

Mapping discovered with minimal data

17

No Persistent Connection

STUN does not require persistent connection

Connection closes after response

18

No Session Management

STUN does not manage sessions

Stateless behavior confirmed

19

No Keep-Alive Required

STUN does not require keep-alive

Connection closes after use

20

Small Binary Footprint

STUN client binary size

Binary is < 1MB

21

Embedded Device Support

Run STUN on IoT device

Protocol functions correctly

22

Mobile Device Support

Run STUN on mobile

Protocol functions efficiently

23

Browser Support

Use STUN in WebRTC

Protocol works in browser

24

No Configuration Needed

Use default STUN settings

Protocol works out of the box

25

Minimal Logging

Enable logging

Logs are concise and minimal

26

Minimal Error Handling

Handle invalid request

Error response is lightweight

27

Minimal Retry Logic

Retry on timeout

Retry logic is simple and efficient

28

Minimal Header Overhead

Inspect STUN headers

Header size is small

29

Minimal Payload Overhead

Inspect STUN payload

Payload is compact

30

Efficient NAT Traversal

Use STUN for NAT traversal

Traversal succeeds with minimal traffic

31

Efficient Public IP Discovery

Discover public IP

IP returned with minimal data

32

Efficient Port Discovery

Discover public port

Port returned with minimal data

33

Efficient Firewall Detection

Detect UDP blocking

Detection succeeds with minimal traffic

34

Efficient Packet Parsing

Parse STUN packet

Parsing is fast and simple

35

Efficient Packet Construction

Construct STUN packet

Construction is fast and simple

36

Minimal RTT

Measure round-trip time

RTT is low

37

Minimal Packet Loss Impact

Simulate packet loss

Protocol retries efficiently

38

Minimal Impact on Network

Monitor network load

STUN traffic is negligible

39

Minimal Impact on Application

Run STUN alongside app

No performance degradation

40

Lightweight Library Integration

Integrate STUN library

Integration is simple

41

Lightweight Protocol Stack

Use STUN in protocol stack

Stack remains small

42

Lightweight Debugging

Enable debug mode

Output is minimal and useful

43

Lightweight Testing

Run unit tests

Tests execute quickly

44

Lightweight Deployment

Deploy STUN server

Setup is fast and simple

45

Lightweight Client Deployment

Deploy STUN client

Setup is fast and simple

46

Lightweight Protocol Compliance

Validate against RFC 5389

Protocol conforms with minimal overhead

47

Lightweight Error Codes

Inspect error codes

Codes are concise and standardized

48

Lightweight NAT Type Detection

Detect NAT type

Detection uses minimal packets

49

Lightweight Logging Format

Inspect logs

Logs are readable and compact

50

Lightweight Protocol Upgrade

Upgrade STUN version

Upgrade process is simple

Client-Server Architecture - Testcases

Client-Server Architecture

S.No

Test Case

Description

Expected Result

1

Client Sends Binding Request

Client sends STUN request to server

Server receives and processes request

2

Server Sends Binding Response

Server replies to client

Client receives public IP and port

3

Server Listens on Port 3478

Server listens on default port

Client connects successfully

4

Client Uses UDP

Client uses UDP transport

Server responds correctly

5

Client Uses TCP

Client uses TCP transport

Server responds correctly

6

Server Handles Multiple Clients

Multiple clients send requests

Server handles all requests concurrently

7

Stateless Server Behavior

Server does not store session state

Each request handled independently

8

Client Retries on Timeout

No response received

Client retries request

9

Server Handles Retransmissions

Client resends request

Server responds without error

10

Client Parses Response

Client receives response

Public IP and port extracted correctly

11

Server Handles Malformed Request

Client sends invalid request

Server returns error or ignores

12

Server Handles Authenticated Request

Client sends credentials

Server validates and responds

13

Server Rejects Invalid Credentials

Client sends wrong credentials

Server denies request

14

Server Handles Concurrent Requests

Multiple clients send requests simultaneously

Server responds to all

15

Client Handles Delayed Response

Server delays response

Client waits and processes correctly

16

Server Handles Packet Loss

Simulate packet loss

Server handles retransmission

17

Client Handles Server Downtime

Server is offline

Client times out gracefully

18

Server Restarts

Server restarts during session

Client reconnects successfully

19

Client Handles Server IP Change

Server IP changes

Client reconnects to new IP

20

Server Handles High Load

Simulate high traffic

Server remains responsive

21

Client Handles Server Overload

Server drops requests

Client retries or fails gracefully

22

Server Logs Requests

Enable logging

Requests logged correctly

23

Client Logs Responses

Enable client logging

Responses logged correctly

24

Server Handles IPv4

Client uses IPv4

Server responds with IPv4 mapping

25

Server Handles IPv6

Client uses IPv6

Server responds with IPv6 mapping

26

Client Handles NAT Mapping

Client behind NAT

Server returns mapped address

27

Server Handles NAT Detection

Server detects NAT type

Client receives NAT type info

28

Client Handles Port Mapping

Client behind NAT

Server returns mapped port

29

Server Handles Binding Request Format

Validate request format

Server accepts valid format

30

Server Handles Binding Response Format

Validate response format

Client parses successfully

31

Client Handles Server Certificate

Use TLS

Client validates certificate

32

Server Handles TLS Handshake

Use secure connection

Handshake completes successfully

33

Client Handles DTLS

Use DTLS transport

Client receives response securely

34

Server Handles DTLS

Accept DTLS request

Server responds securely

35

Client Handles Server Timeout

Server does not respond

Client retries or fails

36

Server Handles Client Timeout

Client disconnects

Server cleans up resources

37

Client Handles Server Error Code

Server returns error

Client interprets correctly

38

Server Handles Unknown Attributes

Client sends unknown attributes

Server ignores or returns error

39

Client Handles Alternate Server

Server redirects to another

Client connects to alternate server

40

Server Handles Alternate Server Attribute

Include alternate server info

Client switches server

41

Client Handles Multiple Interfaces

Client has multiple NICs

Server returns correct mapping per interface

42

Server Handles Multiple IPs

Server has multiple IPs

Client connects to correct one

43

Client Handles NAT Rebinding

NAT changes port

Client re-initiates request

44

Server Handles NAT Rebinding

Client port changes

Server responds to new port

45

Client Handles Server Load Balancer

Behind load balancer

Client receives valid response

46

Server Handles Load Balancing

Distribute requests

All clients served correctly

47

Client Handles Server Clustering

Server is part of cluster

Client receives consistent response

48

Server Handles Cluster Sync

Sync state across nodes

Responses remain consistent

49

Client Handles Server Failover

Primary server fails

Client switches to backup

50

Server Handles Client Failover

Client reconnects

Server accepts new session

Support for IPv4 and IPv6 - Testcases

Support for IPv4 and IPv6

S.No

Test Case

Description

Expected Result

1

IPv4 Client Request

Client sends STUN request over IPv4

Server responds with IPv4-mapped address

2

IPv6 Client Request

Client sends STUN request over IPv6

Server responds with IPv6-mapped address

3

Dual Stack Client

Client supports both IPv4 and IPv6

Server responds based on selected protocol

4

IPv4 Server Binding

Server listens on IPv4 address

IPv4 clients connect successfully

5

IPv6 Server Binding

Server listens on IPv6 address

IPv6 clients connect successfully

6

Dual Stack Server

Server supports both IP versions

Handles both IPv4 and IPv6 requests

7

IPv4 NAT Mapping

Client behind IPv4 NAT

Server returns public IPv4 and port

8

IPv6 NAT Mapping

Client behind IPv6 NAT

Server returns public IPv6 and port

9

IPv4-only Client

Client supports only IPv4

Server responds with IPv4 address

10

IPv6-only Client

Client supports only IPv6

Server responds with IPv6 address

11

IPv4 Packet Format

Validate IPv4 STUN packet

Packet conforms to RFC 5389

12

IPv6 Packet Format

Validate IPv6 STUN packet

Packet conforms to RFC 5389

13

IPv4 DNS Resolution

Resolve STUN server via A record

IPv4 address returned

14

IPv6 DNS Resolution

Resolve STUN server via AAAA record

IPv6 address returned

15

IPv4 Firewall Traversal

Client behind IPv4 firewall

STUN request succeeds

16

IPv6 Firewall Traversal

Client behind IPv6 firewall

STUN request succeeds

17

IPv4 NAT Detection

Detect NAT type over IPv4

NAT type correctly identified

18

IPv6 NAT Detection

Detect NAT type over IPv6

NAT type correctly identified

19

IPv4 Port Mapping

Discover port mapping over IPv4

Mapping returned

20

IPv6 Port Mapping

Discover port mapping over IPv6

Mapping returned

21

IPv4 Packet Loss

Simulate IPv4 packet loss

Retransmission succeeds

22

IPv6 Packet Loss

Simulate IPv6 packet loss

Retransmission succeeds

23

IPv4 Latency

Measure latency over IPv4

Response time recorded

24

IPv6 Latency

Measure latency over IPv6

Response time recorded

25

IPv4 MTU Handling

Send large IPv4 packet

Fragmentation handled

26

IPv6 MTU Handling

Send large IPv6 packet

Fragmentation handled

27

IPv4 NAT Hairpinning

Test hairpinning over IPv4

Behavior observed

28

IPv6 NAT Hairpinning

Test hairpinning over IPv6

Behavior observed

29

IPv4 STUN over UDP

Use UDP transport

IPv4 response received

30

IPv6 STUN over UDP

Use UDP transport

IPv6 response received

31

IPv4 STUN over TCP

Use TCP transport

IPv4 response received

32

IPv6 STUN over TCP

Use TCP transport

IPv6 response received

33

IPv4 STUN over TLS

Use TLS over IPv4

Secure response received

34

IPv6 STUN over TLS

Use TLS over IPv6

Secure response received

35

IPv4 STUN over DTLS

Use DTLS over IPv4

Secure response received

36

IPv6 STUN over DTLS

Use DTLS over IPv6

Secure response received

37

IPv4 NAT Timeout

Simulate timeout

Mapping expires

38

IPv6 NAT Timeout

Simulate timeout

Mapping expires

39

IPv4 Address Conflict

Duplicate IPv4 mapping

Conflict detected

40

IPv6 Address Conflict

Duplicate IPv6 mapping

Conflict detected

41

IPv4 Server Load

High load on IPv4 interface

Server remains responsive

42

IPv6 Server Load

High load on IPv6 interface

Server remains responsive

43

IPv4 Server Restart

Restart IPv4 listener

Clients reconnect successfully

44

IPv6 Server Restart

Restart IPv6 listener

Clients reconnect successfully

45

IPv4 Client Logging

Log IPv4 request/response

Logs contain correct info

46

IPv6 Client Logging

Log IPv6 request/response

Logs contain correct info

47

IPv4 Server Logging

Log IPv4 traffic

Logs contain correct info

48

IPv6 Server Logging

Log IPv6 traffic

Logs contain correct info

49

IPv4/IPv6 Failover

Fail IPv4, fallback to IPv6

Client switches to IPv6

50

IPv6/IPv4 Failover

Fail IPv6, fallback to IPv4

Client switches to IPv4

Used in WebRTC and VoIP - Testcases

Used in WebRTC and VoIP

S.No

Test Case

Description

Expected Result

1

WebRTC Peer Connection

Establish WebRTC call

STUN used to discover public IP

2

VoIP Call Setup

Initiate VoIP call

STUN resolves NAT mapping

3

STUN in SDP Exchange

Include STUN in SDP

ICE candidates include STUN info

4

STUN with TURN Fallback

STUN fails, TURN used

Call still connects

5

STUN with ICE Framework

Use ICE with STUN

ICE gathers candidates via STUN

6

STUN with NAT Traversal

WebRTC behind NAT

STUN discovers public IP and port

7

STUN with Symmetric NAT

WebRTC behind symmetric NAT

STUN detects NAT type

8

STUN with Full Cone NAT

WebRTC behind full cone NAT

STUN returns consistent mapping

9

STUN with Port Restricted NAT

WebRTC behind port-restricted NAT

STUN returns mapped address

10

STUN with Mobile VoIP

Use VoIP on mobile network

STUN returns public IP

11

STUN with Wi-Fi VoIP

Use VoIP on Wi-Fi

STUN returns public IP

12

STUN with Ethernet VoIP

Use VoIP on LAN

STUN returns public IP

13

STUN with Browser WebRTC

Use WebRTC in browser

STUN request sent automatically

14

STUN with Native App

Use STUN in native VoIP app

Public IP discovered

15

STUN with IPv4

Use IPv4 network

STUN returns IPv4 address

16

STUN with IPv6

Use IPv6 network

STUN returns IPv6 address

17

STUN with Dual Stack

Use dual-stack client

Both IPv4 and IPv6 candidates gathered

18

STUN with UDP

Use UDP transport

STUN request succeeds

19

STUN with TCP

Use TCP transport

STUN request succeeds

20

STUN with TLS

Use STUN over TLS

Secure connection established

21

STUN with DTLS

Use STUN over DTLS

Secure connection established

22

STUN Server Unreachable

STUN server down

ICE candidate gathering fails

23

STUN Server Timeout

STUN server slow

ICE retries or fails gracefully

24

STUN Server Failover

Primary STUN fails

Secondary STUN used

25

STUN with ICE Restart

ICE restarts mid-call

STUN re-discovers candidates

26

STUN with Call Reconnection

Reconnect dropped call

STUN re-used for new mapping

27

STUN with Call Transfer

Transfer VoIP call

STUN resolves new path

28

STUN with Call Hold/Resume

Hold and resume call

STUN mapping remains valid

29

STUN with Call Recording

Record VoIP call

STUN ensures media path is stable

30

STUN with Group Call

Multi-party WebRTC call

STUN used for each peer

31

STUN with Video Call

WebRTC video call

STUN resolves media path

32

STUN with Audio Call

WebRTC audio call

STUN resolves media path

33

STUN with Screen Sharing

Share screen via WebRTC

STUN resolves media path

34

STUN with NAT Timeout

NAT closes port

STUN re-discovers mapping

35

STUN with ICE Candidate Gathering

Gather ICE candidates

STUN provides server reflexive candidates

36

STUN with STUN Binding Request

Send binding request

Server returns mapped address

37

STUN with STUN Binding Response

Receive response

Client parses public IP and port

38

STUN with Call Quality Monitoring

Monitor call stats

STUN ensures stable connection

39

STUN with Call Encryption

Encrypt media

STUN used only for signaling

40

STUN with SIP Integration

Use STUN in SIP call

NAT traversal succeeds

41

STUN with Jitsi Meet

Use STUN in Jitsi

ICE candidates gathered

42

STUN with Zoom

Use STUN in Zoom (if applicable)

NAT traversal handled

43

STUN with Google Meet

Use STUN in Meet

ICE candidates include STUN

44

STUN with Microsoft Teams

Use STUN in Teams

Public IP discovered

45

STUN with Discord

Use STUN in Discord voice

NAT traversal succeeds

46

STUN with WhatsApp Web

Use STUN in browser call

ICE candidates gathered

47

STUN with Signal

Use STUN in Signal call

Public IP discovered

48

STUN with Telegram

Use STUN in Telegram call

NAT traversal handled

49

STUN with SIP Trunk

Use STUN in SIP trunking

Public IP resolved

50

STUN with VoIP Gateway

Use STUN in VoIP gateway

NAT traversal succeeds

  • Reference links