Biomedical Engineering Reference
In-Depth Information
networks. Unlike the OSI protocols, these standards define specific low-level functionality, such as
operating frequency, bandwidth, message format, signal voltage, and connector style for computer
networks. For example, the IEEE-802.3 10BaseT standard defines Ethernet over ordinary twisted pair
cable. The standard defines the cable, the connector type, pin connections, voltage levels, and noise
immunity requirements. The most important IEEE standards in bioinformatics are listed in
Table 3-2
.
Table 3-2. Key Network Protocols.
Standard
Description
IEEE 488
Computer to electronic instrument communications; also known as GPIB and
HPIB
IEEE-802
LAN and MAN standards
IEEE-802.3
Ethernet; the most common LAN specification
IEEE-802.3 10Base-T Ethernet over twisted pair cable
IEEE-802.11
Wireless LANs
IEEE-802.11a
5 GHz, 54 Mbps wireless LAN; shorter range than 2.4 GHz systems, higher
bandwidth, and more channels than WiFi
IEEE-802.11b
2.4 GHz, 11 Mbps wireless LAN; the most common, most mature; limited
channels, also known as WiFi
IEEE-802.11e
2.4 GHz, 11 Mbps wireless LAN; enhanced quality of service
IEEE-802.11g
2.4 GHz, 22 Mbps wireless LAN; higher-bandwidth version of 802.11b,
limited channels
IEEE-802.11i
2.4 GHz, 11 Mbps wireless LAN; enhanced security
CCITT/ITU-T ISDN
Digital communications over standard phone lines
CCITT/ITU-T X.25
Switched packet communications
ANSI FDDI
High-speed (200 Mbps) fiber backbone LAN
ECSA SONET
Very high-speed (10 Gbps) optical network standard
DARPA TCP/IP
The protocol of the Internet
The relatively short list of standards in
Table 3-2
may give the false impression that there are only a
few basic standards that network manufacturers abide by. In reality, there are dozens of extensions
to these and other protocols. For example, the extensions shown for IEEE 802.11 illustrate how the
standard for wireless LANs has several extensions, each of which provides for significant differences
in the frequency, bandwidth, and feature of the communications. The relative contribution of each
factor to the overall bioinformatics project depends on the nature of the project. For example, when
working with 3D images, bandwidth becomes an issue.
The CCITT/ITU-T develops international network standards that generally involve the telephone
network. For example, a prominent standard developed by CCITT/ITU-T is Integrated Services Digital
Network (ISDN). The ISDN standard defines digital communications at a rate of up to 128 Kbps over
ordinary twisted pair cable. The X.25 protocol, also known as packet switched network, forms the
basis for packet communications that is similar to that used by the Internet. ANSI is a U.S.
equivalent of the CCITT/ITU-T, in that it publishes voluntary protocols for use by the U.S. computer
industry. The most significant ANSI standard that applies to computer networks is the Fiber
Distributed Data Interface (FDDI). This networking standard defines a fiber-optic network that
operates between 100 and 200 Mbps. A FDDI LAN is often called a Backbone LAN because it's used to
