SIP Registration Process

For the purpose of this document, we will NOT discuss what ports and protocols are used in the registration process as we are looking at the actual process, not the ports and transport methods. In this discussion, we used an Algo 8180 and were NOT using SIP over TLS, This was done on purpose to simply the review of the SIP packets.

Overview

The registration process is basically a 4 step process which is outlined here 

1. Register request from the device to 8x8 
2. Unauthorized response from 8x8 (407 Proxy Registration Required packet) to the device
3. 2nd Registration attempt (with credentials) from the device to 8x8
4. OK from 8x8 to the device

Deeper Dive

When reading packet information you need to pay attention not only to the Source and Destination IPs but also the Header IP as well.  When using NAT connections the source/destination IPs will be on the public side, but in the packet header, the private IP will be displayed.  These communications must originate and return from the same port. 

Register without authentication 

The first step is to attempt to register without authentication. Note the header contains no authentication details.

 

If the phone continues to re-send a register packet over and over again it is an indication that it is not receiving the 401 unauthorized responses from 8x8, check firewall restrictions. 

8x8 Responds with Proxy Registration Required (407) 

This is a security measure of 8x8, it is a requirement to register with authentication. In this response, 8x8 provides the Realm information. Note the CSEQ number is the same as the registration attempt.

Phone attempts to register with authentication 

The phone sends a 2nd registration attempt this time with SIP credentials. This time the Sceq is incremented by 1, and the header contains authentication information.

8x8 responds with OK (200) 

This indicates the registration was accepted by 8x8 and the phone is now ready to be used.

 
 

Forbidden response (403) 

If a forbidden response is received (403) it usually indicates the user name/password is incorrect. 

 

Options request 

Verify that the options request is being received by the device (and is responded to with SIP 200 ok). These packets are used to maintain the binding/registration in a NAT environment. These packets are sent every 30 seconds. 

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Paul Chase
8x8 Network Engineer (Pre-Sales and Deployment)
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As always Paul, great tip. Good to know how SIP devices register on this platform and what to look for from a troubleshooting perspective.

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Jahmal Abbott
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Original Message:
Sent: 11-30-2021 07:14
From: Paul Chase
Subject: Pro Tip Tuesday: SIP Registration Explained

SIP Registration Process

For the purpose of this document, we will NOT discuss what ports and protocols are used in the registration process as we are looking at the actual process, not the ports and transport methods. In this discussion, we used an Algo 8180 and were NOT using SIP over TLS, This was done on purpose to simply the review of the SIP packets.

Overview

The registration process is basically a 4 step process which is outlined here 

1. Register request from the device to 8x8 
2. Unauthorized response from 8x8 (407 Proxy Registration Required packet) to the device
3. 2nd Registration attempt (with credentials) from the device to 8x8
4. OK from 8x8 to the device

Deeper Dive

When reading packet information you need to pay attention not only to the Source and Destination IPs but also the Header IP as well.  When using NAT connections the source/destination IPs will be on the public side, but in the packet header, the private IP will be displayed.  These communications must originate and return from the same port. 

Register without authentication 

The first step is to attempt to register without authentication. Note the header contains no authentication details.

 

If the phone continues to re-send a register packet over and over again it is an indication that it is not receiving the 401 unauthorized responses from 8x8, check firewall restrictions. 

8x8 Responds with Proxy Registration Required (407) 

This is a security measure of 8x8, it is a requirement to register with authentication. In this response, 8x8 provides the Realm information. Note the CSEQ number is the same as the registration attempt.

Phone attempts to register with authentication 

The phone sends a 2nd registration attempt this time with SIP credentials. This time the Sceq is incremented by 1, and the header contains authentication information.

8x8 responds with OK (200) 

This indicates the registration was accepted by 8x8 and the phone is now ready to be used.

 
 

Forbidden response (403) 

If a forbidden response is received (403) it usually indicates the user name/password is incorrect. 

 

Options request 

Verify that the options request is being received by the device (and is responded to with SIP 200 ok). These packets are used to maintain the binding/registration in a NAT environment. These packets are sent every 30 seconds. 

------------------------------
Paul Chase
8x8 Network Engineer (Pre-Sales and Deployment)
------------------------------