The IPv6 addressing architecture [1] allows multiple unicast addresses to be assigned to interfaces. These addresses may have different reachability scopes (link-local, site-local, or global). These addresses may also be "preferred" or "deprecated" [2]. Privacy considerations have introduced the concepts of "public addresses" and "temporary addresses" [3]. The mobility architecture introduces "home addresses" and "care-of addresses" [8]. In addition, multi- homing situations will result in more addresses per node. For example, a node may have multiple interfaces, some of them tunnels or virtual interfaces, or a site may have multiple ISP attachments with a global prefix per ISP.
The end result is that IPv6 implementations will very often be faced with multiple possible source and destination addresses when initiating communication. It is desirable to have default
3.5. Mobility Addresses
Some nodes may support mobility using the concepts of a home address and a care-of address (for example see [8]). Conceptually, a home address is an IP address assigned to a mobile node and used as the permanent address of the mobile node. A care-of address is an IP address associated with a mobile node while visiting a foreign link. When a mobile node is on its home link, it may have an address that is simultaneously a home address and a care-of address.
For the purposes of this document, it is sufficient to know whether or not one's own addresses are designated as home addresses or care- of addresses. Whether or not an address should be designated a home address or care-of address is outside the scope of this document.
还给了例子 Destination: 2001::1 Candidate Source Addresses: 2001::2 (care-of address) or 3ffe::2 (home address) Result: 3ffe::2 (prefer home address)