Enum Kind 

pub enum Kind {
    Public,
    Temporary,
}

Which of the two GRUUs a UA puts in a Contact (§4.4).

Why the default is Kind::Public

The two differ in exactly one property each way, and the trade is not sipx’s to make.

A public GRUU is a stable identifier for the instance. It survives re-registration, and §5.2 has a registrar keep treating it as valid even after the binding lapses — answering 480 until the device comes back — so an address handed out under one still names this device tomorrow. What it does not offer is privacy: two public GRUUs for one instance are the same URI, so anyone holding two of them can see they are the same device.

A temporary GRUU buys precisely that privacy. §5.4: “Given a pair of GRUUs, it MUST be computationally infeasible to determine whether they were issued for the same AOR or instance ID or for different AORs and instance IDs.” It pays for it in lifetime — §4.2 requires a UA to discard every temporary GRUU it learned whenever its Call-ID changes, so an address handed out under one stops resolving as soon as the UA registers afresh.

So the default is the public one, because it is the choice that keeps working, and because only the application knows whether the address it is about to put in a Contact has to outlive this registration. Unlinkability is a property that must be asked for — and, having been asked for, is never quietly downgraded: see Gruus::preferred.

Variants

Public

One stable URI for this instance, usable for as long as the instance exists.

Temporary

An address that cannot be correlated with any other GRUU, and that lapses with the registration that produced it.

Trait Implementations

impl Clone for Kind

fn clone(&self) -> Kind

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Kind

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Kind

fn default() -> Kind

Returns the “default value” for a type.

impl PartialEq for Kind

fn eq(&self, other: &Kind) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Kind

impl Eq for Kind

impl StructuralPartialEq for Kind