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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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2.1.1 Gigabit Ethernet<br />

Such implementations will not communicate with the more recent<br />

implementations (such as <strong>IBM</strong>'s).<br />

Also note that the last method covers not only the IEEE 802.3 networks, but also<br />

the IEEE 802.4 <strong>and</strong> 802.5 networks, such as the <strong>IBM</strong> token-ring LAN.<br />

As advances in hardware continue to provide faster transmissions across<br />

networks, Ethernet implementations have improved in order to capitalize on the<br />

faster speeds. Fast Ethernet increased the speed of traditional Ethernet from 10<br />

megabits per second (Mbps) to 100 Mbps. This was further augmented to 1000<br />

Mbps in June of 1998, when the IEEE defined the st<strong>and</strong>ard for Gigabit Ethernet<br />

(IEEE 802.3z). Finally, in 2005, IEEE created the 802.3-2005 st<strong>and</strong>ard<br />

introduced 10 Gigabit Ethernet, also referred to as 10GbE. 10GbE provides<br />

transmission speeds of 10 gigabits per second (Gbps), or 10000 Mbps, 10 times<br />

the speed of Gigabit Ethernet. However, due to the novelty of 10GbE, there are<br />

still limitations on the adapters over which 10GbE can be used, <strong>and</strong> no one<br />

implementation st<strong>and</strong>ard has yet gained commercial acceptance.<br />

2.2 Fiber Distributed Data Interface (FDDI)<br />

The FDDI specifications define a family of st<strong>and</strong>ards for 100 Mbps fiber optic<br />

LANs that provides the physical layer <strong>and</strong> media access control sublayer of the<br />

data link layer, as defined by the ISO/OSI Model. Proposed initially by<br />

draft-st<strong>and</strong>ard RFC 1188, <strong>IP</strong> <strong>and</strong> ARP over FDDI networks became a st<strong>and</strong>ard in<br />

RFC 1390 (also STD 0036). It defines the encapsulating of <strong>IP</strong> datagrams <strong>and</strong><br />

ARP requests <strong>and</strong> replies in FDDI frames. RFC 2467 extended this st<strong>and</strong>ard in<br />

order to allow the transmission of <strong>IP</strong>v6 packets over FDDI networks. Operation<br />

on dual MAC stations is described in informational RFC 1329. Figure 2-4 on<br />

page 34 shows the related protocol layers.<br />

RFC 1390 states that all frames are transmitted in st<strong>and</strong>ard IEEE 802.2 LLC<br />

Type 1 Unnumbered Information format, with the DSAP <strong>and</strong> SSAP fields of the<br />

802.2 header set to the assigned global SAP® value for SNAP (decimal 170).<br />

The 24-bit Organization Code in the SNAP header is set to zero, <strong>and</strong> the<br />

remaining 16 bits are the EtherType from Assigned Numbers (see RFC 3232),<br />

that is:<br />

► 2048 for <strong>IP</strong><br />

► 2054 for ARP<br />

Chapter 2. Network interfaces 33

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