24.1 Understanding Local Area Networks

A local area network (LAN) provides a communications channel designed to connect information processing equipment in a limited area such as a room, a building, or a complex of buildings (for example, a campus). Nodes in a LAN can be linked by the following types of data transmission media:

Ethernet---One of the earliest and the most common LANs. Ethernet can refer to either a general LAN application (for example, Ethernet address) or to the specific CSMA/CD (carrier sense multiple access with collision detection) technology that implements the Intel, Xerox, and Compaq intercompany Ethernet specifications.
There are three types of Ethernet LANs as follows:
Ethernet (802.3) with transmission speeds of 10Mbps
Fast Ethernet (802.3u) with transmission speeds of 100Mbps
Gigabit Ethernet (802.3z) with transmission speeds of 1000Mbps

All three types of Ethernet employ CSMA/CD protocol, and the same frame format and same frame size.
FDDI (Fiber Distributed Data Interface) --- Implemented as dual-ring, token ring LANs.
Token Ring---The IEEE 802.5 standard token passing ring.
ATM (Asynchronous Transfer Mode) --- The following standard is supported:
LAN emulation over ATM supports the ATM Forum's LAN Emulation V1.0 (LANE) standard.
Classical IP over ATM supports the RFC 1577 standard. (DGLTA, DGLPA, DGLPB only)

http://de.wikipedia.org/wiki/Token_Ring

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Note added at 7 hrs (2010-12-16 17:23:51 GMT)
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http://virtualizationreview.com/articles/2009/01/01/hardware...
Hardware-Assist Architecture
One of the core elements of first-generation hardware-assisted virtualization was the creation of a new layer in the x86 CPU ring architecture, known as Ring -1. With hardware-assisted virtualization, hypervisors that support the technology could load at Ring -1 and guest OSes could access the CPU at Ring 0, just as they normally would when running on a physical host. So VM guest OSes could be virtualized without any required modifications to the guest OS. Previously, paravirtualization of the guest OS kernel-adopted by the major Linux vendors-was used to overcome performance latency associated with privileged CPU instruction trapping and emulation