Overview

This chapter examines some of the issues that are faced by VoIP systems, particularly systems that would be used by carriers for true end-to-end anytime-anyplace connectivity, comparable to what one enjoys today with traditional PSTN voice telephony. We only focus on issues and opportunities that can be addressed by IPv6, namely scalability and end-to-end robustness. The flow mechanism of IPv6 can be employed to manage QoS-specific paths which is critical to VoIP support the value of flows is already highlighted in MPLS and the deployment/applications it is already experiencing at this time. (To be fair, it should be noted that not all issues faced by VoIP are addressed by IPv6 it is not a complete panacea. Examples here include: general security concerns; equipment interworking; carrier interworking; VoWi-Fi to cellular and/or 3G interworking; and, straightforward and reliable Unified Messaging deployments).

In the sections that follow we first briefly introduce the issue of security (Section 5.1); then we look at the NAT issue (Section 5.2). As a potential solution to some of the NAT problems, we then look in Section 5.3 at Simple Traversal of User Datagram Protocol Through Network Address Translators (STUN). STUN is a lightweight protocol that allows applications to discover the presence and types of NATs and firewalls between them and the public Internet. It also provides the ability for applications to determine the public IPv4 addresses allocated to them by the NAT. STUN works with many existing NATs and does not require any special behavior from them. As a...