OpenVox DGW-1004 User Manual page 20

Figure 4-1-3 Endpoint Register with Gateway
Also you can choose registration by "This gateway registers with the endpoint", it's the same with "None", except name and password.
Figure 4-1-4 This Gateway Register with the Endpoint
Table 4-1-1 Definition of SIP Options
Options Definition
Name A name which is able to read by human. And it's only used for user's reference.
Username User name the end point use to authenticate with the gateway
Password Password the endpoint will use to authenticate with the gateway. Allowed characters
Registration Whether this endpoint will registers with this gateway.
Hostname IP address or hostname of the endpoint or 'dynamic' if the endpoint has a dynamic IP address. This will require registration.
or IP Notice: if the input here is hostname and your DNS has changed, you must reboot asterisk.
Address
Transport This sets the possible transport types for outgoing. Order of usage, when the respective transport protocols are enabled, is UDP,
TCP, TLS. The first enabled transport type is only used for outbound messages until a Registration takes place. During the peer
Registration the transport type may change to another supported type if the peer requests so.
NAT Addresses NAT-related issues in incoming SIP or media sessions.
Traversal