py Eyeballs-strategies are unnecessary. Deploying IPv6 in 3GPP Networks 3.10 Implications of IPv6 for Other Protocols In this section we will describe implications of IPv6 for some of the key protocols used in the Internet, as well as describing generally what kinds of implications IPv6 brings to higher level protocols. This section will by no means give an exhaustive list of affected protocols. 3.10.1 Transport Layer Protocols All protocols directly above IP face changes due to the introduction of IPv6. The three most widely used transport layer protocol are UDP [135], TCP [136], and ICMPv6 (dis- cussed in depth in Section 3.3). There are also other transport layer protocols, such as Stream Control Transmission Protocol (SCTP) [137]. A major implication for all upper layer protocols is caused by the design decision of not having a checksum field as part of the IPv6 header, as illustrated in Figure 3.8. The upper layer protocols, if they wish to verify the correctness of the IPv6 header, have to include a so-called IPv6 pseudo header, illustrated in Figure 3.23, in their checksum calculation. Inclusion of the pseudo header is important, for example, in the case of ICMPv6 which has no other means to verify that the packet was received at the intended address and that the sender address was received without error. In the pseudo header of Figure 3.23, the destination's IPv6 address is the final destination (not any intermediary address, e.g. if routing headers are used), the next header value points to an upper layer protocol such as TCP (but not to IPv6 extension headers), and the packet length field content depends on the upper layer. In the case of UDP, a protocol that carries its own length information, the length used in pseudo header is directly the UDP's length. In the case of TCP, as TCP headers do not have a length field, the payload length from the IPv6 header minus any extension headers is used. RFC 2460 states that UDP must include the checksum field that covers both the UDP itself and the pseudo header.