| AVP | No. | Incoming | Outgoing |
| Message Type | 0 | Value 2 | Value 2 |
| Protocol Version | 2 | Value 1 expected | Value 1 |
| Framing Capabilities | 3 | Ignored | Value 3 |
| Bearer Capabilities | 4 | Ignored | Not sent |
| Firmware Revision | 6 | Ignored | FireBrick s/w ID number |
| Host Name | 7 | Logged as hostname for tunnel | Configured hostname, if defined |
| Vendor Name | 8 | Ignored | FireBrick Ltd |
| Assigned Tunnel ID | 9 | Expected as far end ID | Mandatory, our tunnel ID |
| Receive Window Size | 10 | Accepted, assumed 4 if not present or less than 4 | Not sent, assume 4 |
| Challenge | 11 | Accepted if a configured secret is defined, a response is sent in the SCCCN | Not sent at present |
| Challenge Response | 13 | Not expected at present | Sent if SCCRQ contained a challenge and we have a secret defined |
