Gigabit Ethernet; The Cisco Ios - Cisco RJ-45-to-AUX Brochure

backward compatible to most of the equipment in use at the time. Although the standards bodies debated the
merits of each of the camps, the marketplace decided for them. Fast Ethernet is the overwhelming winner, so
much so that even HP sells Fast Ethernet on almost all its products.
Note In 1995, Cisco purchased both Kalpana and Grand Junction and incorporated their innovations into its
hardware. These devices became the Catalyst line of Cisco products.

Gigabit Ethernet

In order to implement Gigabit Ethernet (GE), the CSMA/CD method was changed slightly to maintain a
200−meter collision diameter at gigabit−per−second data rates. This slight modification prevented Ethernet
packets from completing transmission before the transmitting station sensed a collision, which would violate
the CSMA/CD rule.
GE maintains a packet length of 64 bytes, but provides additional modifications to the Ethernet specification.
The minimum CSMA/CD carrier time and the Ethernet slot time have been extended from 64 bytes to 512
bytes. Also, packets smaller than 512 bytes have an extra carrier extension added to them. These changes,
which can impact the performance of small packets, have been offset by implementing a feature called packet
bursting, which allows servers, switches, and other devices to deliver bursts of small packets in order to utilize
the available bandwidth.
Because it follows the same form, fit, and function as its 10− and 100Mbps predecessors, GE can be
integrated seamlessly into existing Ethernet and Fast Ethernet networks using LAN switches or routers to
adapt between the different physical line speeds. Because GE is Ethernet, only faster, network managers will
find the migration from Fast Ethernet to Gigabit Ethernet to be as smooth as the migration from Ethernet to
Fast Ethernet.
Avoiding Fork−Lift Upgrades
Although dedicated switch connections provide the maximum benefits for network users, you don't want to
get stuck with fork−lift upgrades. In a fork−lift upgrade, you pay more to upgrade your computer or
networking equipment than it would cost to buy the equipment already installed. The vendor knows that you
are not going to buy all new equipment, so the vendor sells you the upgrade at an enormous price. In order to
exchange it for the bigger, better, faster equipment It may sometimes be necessary to support legacy
equipment.
Fortunately for Ethernet switches you can provide connectivity in a number of ways. You can attach shared
hubs to any port on the switch in the same manner that you connect end stations. Doing so makes for a larger
collision domain, but you avoid paying the high costs of upgrades.
Typically, your goal would be to migrate toward single−station segments as bandwidth demands increase.
This migration will provide you with the increased bandwidth you need without wholesale replacement of
existing equipment or cabling.
In this lower cost setup, a backbone switch is created in which each port is attached to the now−larger
collision domain or segment. This switch replaces existing connections to routers or bridges and provides
communication between each of the shared segments.

The Cisco IOS

The Cisco Internetwork Operating System (IOS) is the kernel of Cisco routers and switches. Not all Cisco
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