Understand the benefits and risks to make informed decisions to allow changes to enter production.

inform

nsure that you are aware of guidelines or obligations defined by yourorganizational governance and external factors, such as regulatory compliance requirements andindustry standards, that may mandate or emphasize specific focus

Enabling IPv6 routers to convey information about networkconstraints such as maximum number of addressees per node.

Such guidance would elaborate, among other things, on the usage ofIPv6 addresses for incoming communications and for outgoingcommunications. For example, for incoming communications, hostsmight want to employ only the smallest-scope applicable addresses(if available) and, if stable addresses were available, onlyaccept incoming connections on such addresses. For outgoingcommunications, hosts might prefer temporary addresses, unless thecorresponding communication instances are expected to be long-lived (e.g., SSH sessions).

Inthe most simple analysis, one might expect nodes in a typicalenterprise network to employ only stable addresses.

SLAAC hastraditionally employed long lifetimes for network configurationinformation, meaning that stale information could be employed for anunacceptably long period of time. DCHPv6 operates on the samepremise, and lacks widespread support for RECONFIGURE messages

A host may end up employing predictable addresses resulting fromDHCPv6, thus thwarting the security and privacy improvements ofSLAAC-configured addresses (i.e., [RFC7217] and [RFC8981]).

difficulting

Most of the challenges associated with the use of multiple addressescan be addressed by allocating one /64 per host via mechanisms suchas DHCPv6-PD [RFC8415].

Secondly, as discussed inSection 5.2.1, it would require application programmers to understandall the subtleties associated with IPv6 addressing, and would alsolead to duplicate code on all applications.

Secondly, performing address/selection filtering at theapplication level may not mitigate some possible attacks.

In order to better mitigate network activity correlation and/orpossibly reduce host exposure, an implementation might want to eitherreduce the preferred lifetime of temporary addresses or, even better,generate one new IPv6 address for each application or new transportprotocol instance (sometimes referred to as "ephemeral addresses").However, reduced address lifetimes and the use of multiple IPv6addresses may have a negative impact on the network (please seeSection 6.3).

Ability of an attacker to correlate network activity* Exposure to attack

Address reachability represents the area of the network (and theassociated conditions), where an address can be used for receivingand transmitting packets.

Some organizations have opted to employ NPT [RFC6296] such that:* The local network is isolated of renumbering events caused by theupstream provider.* The local network employs the same address space regardless of theupstream provider employed to communicate with the external realm.

As a result, addresses that do not uniquely identifyinterfaces Internet-wide are considered to have "non-global" or"limited" scope. Grouping addresses in such a way is simply usefulfor the purpose of discussing address properties.