IPv6 Essentials

Further Issues in IP QoS

Besides the issue of having to harmonize the competing IntServ and DiffServ architectures, a number of other open issues drive the further development of QoS on the Internet:

• Some QoS services will be based on complex multicast mechanisms; thus, full interoperability with the Internet-wide multicasting will have to be maintained, while not disturbing the operation of the non-QoS Internet.

• QoS mechanisms need to operate properly in tunneling and IPSEC environments, which may require a mapping function of QoS requirements between “inner” and “outer” IP packets. In some topologies, QoS determination may not be possible at all—in particular, when the “inner” IP packet is protected by encryption.

• QoS for mobile IP networks is still a topic of research. As a mobile system uses different access points in the Internet, the path to the mobile system also changes, which in turn leads to varying QoS behavior. A recent IETF working draft proposes a new IPv6 option (QoS object) carried by a destination, of Hop-by-Hop Extension header and signaling QoS requirements.

• Finally, the main issue with Internet QoS is the inherent complexity of the problem and of possible solutions. This complexity affects designers, vendors, managers, and users of QoS services alike, and it can only be compensated for by careful design, standardization, implementation, and deployment.

Despite all the open issues, QoS provisioning on the Internet will eventually become a reality. It will most ...