問題文
A SIP phone registers with the router that stands in for its call control, and the REGISTER carries a Contact that names a host rather than an address. How does the router treat that name?
選択肢
- It resolves the name again for each call that it routes, since an answer held in a store would go stale over an outage that runs on for hours.
- It keeps the name whole and resolves it once a call arrives, since a name held whole carries on working after the phone has moved to another address of its own.
- It turns the registration away and asks for an address instead, since the database it builds is able to hold addresses and nothing else at all.
- It resolves the name before the contact enters the database, since the servers that resolve names can be out of reach exactly when the standby is doing the work.