 However, certain classes of applications can benefit of receiving packets that contain some errors: audio and video codecs can manage with some errors. For tunneling protocols it is usually enough to have checksum calculation only Source address Destination address Upper-layer packet length Zeros Next header Figure 3.23 IPv6 pseudo header [21]. Introduction to IPv6 for the tunneled (inner) packets and there are benefits for not calculating a checksum for outer packets. For those applications, UDP-Lite has been defined, which allows checksum protection to cover only sensitive parts of a packet [139]. As UDP-Lite is a separate transport layer protocol, even if very similar to UDP, it faces deployment challenges as not all devices such as firewalls support it. As a consequence, IETF is standardizing ways to allow UDP packets without checksum calculation [140]. Besides the checksum calculation, the ability to work with longer IPv6 addresses, and the capability required to parse error codes provided by ICMPv6, the transport layer protocols do not have to change. That said, transport layer protocols may want to take the existence of IPv6 addresses into account for other reasons. For example, SCTP allows communication of nodes' IPv4 and IPv6 addresses to the peer within an 'Initiation'- message. Hence, the SCTP protocol by design can utilize both IPv4 and IPv6 addresses at the same time. The transport layer protocols may also assist in finding the Path MTU, as described in Section 3.2.3, and by providing peer reachability information for the Neighbor Cache as mentioned in Section 3.4.5. 3.10.2 Domain Name System IPv6 has significant implications for the DNS [141], which must be known by everyone working with IPv6. The main point of reference is the 'DNS Extensions to Support IP Version 6' RFC 3596 [142]. The most important implication of IPv6 for DNS is the introduction of the new AAAA DNS resource record type. The quadruple 'A' indi- cates that the 128-bit IPv6 address contained in this resource record type is four ti