The challenge of autoconfiguration vs. DHCPv6

Stateless Address Autoconfiguration is touted as a feature for IPv6. As the line goes, stateless address autoconfiguration makes it possible for small devices such as sensors to easily acquire their own IPv6 addresses.

Such a statement ignores the ground that DHCPv4 (which is typically only referred to as DHCP) has gained in the 12 years since IPv6 was first introduced and how pervasive and easy it has become. My $90 home wireless router can be both a DHCPv4 client and a DHCPv4 server. My home security camera has a DHCPv4 client. It is hard to think of many devices that would be too small or too simple that they couldn’t sport a DHCP client implementation.

So why is stateless address autoconfiguration so special? In my opinion, it isn’t. Even more so, there were few engineering types that I talked to at IETF in San Diego that thought stateless address autoconfiguration made more sense than DHCPv6.

One of the biggest problems with stateless autoconfiguration is that it cannot provide a client with DNS server addresses. This is a major drawback. This very limitation is one of the main contributors to the disappearance of the RARP protocol.

A possible easy fix for SAA not providing DNS server information existed with site local addressing. By default an operating system stack could look for a DNS server at specific site-local address if a DNS server address was not already defined. However, since site-local has been deprecated, this solution is no longer available.

One concern that pushes network administrators to select DHCPv6 over stateless address autoconfiguration is the perception that DHCPv6 provides more control than SAA does. There are some who think that this is primarily because administrators prefer DHCP because they are already familiar with it.

Time will tell if SAA becomes the mechanism of choice (or even a choice used anywhere) for acquiring IPv6 addresses. We will have to wait until functional DCHPv6 clients and servers exist before we can genuinely evaluate the merits of SAA and its place as a benefit of IPv6.

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