IPv6 brokenness and DNS whitelisting
Encyclopedia
In the field of IPv6 deployment
, IPv6 brokenness is bad behavior seen in tunneled or dual stack IPv6
deployments where unreliable or bogus IPv6 connectivity is chosen in preference to working IPv4 connectivity. This often results in long delays in web page
loading, where the user has to wait for each attempted IPv6 connection to time out before the IPv4 connection will be tried.
These timeouts may range from being near-instantaneous in the best cases, to taking anywhere between four seconds to three minutes.
Google
, a major provider of services on the Internet, is currently using DNS whitelisting on a per-ISP basis to prevent this. In the DNS whitelisting approach, ISPs are determined from DNS lookup source IP addresses by correlating them with network prefixes derived from routing table
s. There is an IETF draft entitled "IPv6 AAAA DNS Whitelisting Implications" that describes the issues around whitelisting. AAAA records are only sent to ISPs that can demonstrate that they are providing reliable IPv6 to their customers. Other ISPs are sent only A records, thus preventing users from attempting to connect over IPv6.
Numerous concerns have been raised about the practicality of DNS whitelisting as a long-term large-scale solution, such as scalability and maintenance issues relating to the maintenance of large numbers of bilateral agreements. Several of the major web service providers have met to discuss pooling their DNS whitelisting information in an attempt to avoid these scaling problems.
As of May 2011, IPv6 brokenness as measured by instrumenting a set of mainstream Norwegian websites is now down to ~0.015%, most of which is caused by older versions of Mac OS X
which would often prefer non-working IPv6 connectivity when it was not justified.
This behavior was fixed in Mac OS X 10.6.5, and is likely to decline further as Mac OS X 10.6.5 and subsequent versions roll out to a wider audience. However, there is no upgrade path for PowerPC
-based Macs.
The main problem for Mac OS X is the presence of rogue routers, such as wrongly configured Windows Internet Connection Sharing
devices pretending to have IPv6 connectivity, while 6to4 tunneled IPv6 traffic is blocked at a firewall. Another problem was pre-10.50 versions of Opera.
IPv6 deployment
Internet Protocol Version 6 is the next generation of the Internet Protocol that is currently in various stages of deployment on the Internet...
, IPv6 brokenness is bad behavior seen in tunneled or dual stack IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
deployments where unreliable or bogus IPv6 connectivity is chosen in preference to working IPv4 connectivity. This often results in long delays in web page
Web page
A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...
loading, where the user has to wait for each attempted IPv6 connection to time out before the IPv4 connection will be tried.
These timeouts may range from being near-instantaneous in the best cases, to taking anywhere between four seconds to three minutes.
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
, a major provider of services on the Internet, is currently using DNS whitelisting on a per-ISP basis to prevent this. In the DNS whitelisting approach, ISPs are determined from DNS lookup source IP addresses by correlating them with network prefixes derived from routing table
Routing table
In computer networking a routing table, or Routing Information Base , is a data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics associated with those routes. The routing table contains information about the...
s. There is an IETF draft entitled "IPv6 AAAA DNS Whitelisting Implications" that describes the issues around whitelisting. AAAA records are only sent to ISPs that can demonstrate that they are providing reliable IPv6 to their customers. Other ISPs are sent only A records, thus preventing users from attempting to connect over IPv6.
Numerous concerns have been raised about the practicality of DNS whitelisting as a long-term large-scale solution, such as scalability and maintenance issues relating to the maintenance of large numbers of bilateral agreements. Several of the major web service providers have met to discuss pooling their DNS whitelisting information in an attempt to avoid these scaling problems.
As of May 2011, IPv6 brokenness as measured by instrumenting a set of mainstream Norwegian websites is now down to ~0.015%, most of which is caused by older versions of Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
which would often prefer non-working IPv6 connectivity when it was not justified.
This behavior was fixed in Mac OS X 10.6.5, and is likely to decline further as Mac OS X 10.6.5 and subsequent versions roll out to a wider audience. However, there is no upgrade path for PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
-based Macs.
The main problem for Mac OS X is the presence of rogue routers, such as wrongly configured Windows Internet Connection Sharing
Internet Connection Sharing
Internet Connection Sharing is the use of a device with Internet access such as 3G cellular service, broadband via Ethernet, or other Internet gateway as an access point for other devices...
devices pretending to have IPv6 connectivity, while 6to4 tunneled IPv6 traffic is blocked at a firewall. Another problem was pre-10.50 versions of Opera.