Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

The elements in the IEEE 802.21 architecture are:

■■ The various L2 media types: 802.3 (Ethernet), 802.11 (Wi-Fi), 802.16

(WiMAX), and the 3G mobile service layers 3GPP and 3GPP2.

■■ The service layers: SIP, MIPv4 (for IPv4), MIPv6 (for IPv6), the Host

Identity Protocol (HIP), and others.

■■ Between the two (L2 and L3-L5, respectively), three services have been

defined:

1. Media Independent Event Service to report L2 events to the upper
   layers. Local L2 events happen inside the device, while remote L2
   events happen in the network. Common events are Link UP, Link
   Down, Link Parameters Change, Link Going Down, L2 Handover
   Imminent, and so on.


2. Media Independent Command Service to control the lower layers
   with commands to poll, scan, configure, and switch at L2 and below.


3. The Media Independent Information Service provides rich data to
   both upper and lower layers for channel information, MAC address,
   security information, and everything else required to make correct
   handover decisions. The data formats can be XML or ASN1.

Joint work on a test bed reported by Telcordia, Toshiba, and Columbia Uni-

versity for 802.21 MIH-assisted SIP mobility has been reported in [19]. Figure

15.10 shows some of the results for the audio output at the mobile node using

802.11 networks.

Figure 15.10 Audio output at the mobile node with and without 802.21-assisted SIP

mobility

Non-802.21 assisted SIP-based mobility

802.21 assisted SIP-based mobility – Optimized hand-off

268 Chapter 15