Build Your Skills: Use Gigabit Ethernet to eliminate LAN bottlenecks
After three decades, Ethernet has become the most widely deployed internetworking topology in the world. During those 30 years, there has been constant change in the technology and speed of Ethernet. First, we had 10 Mbps (million bits per second), and then the need and technology progressed to 100 Mbps, also known as Fast Ethernet. Now, networks operating at 10/100 Mbps are finding a need for increased transfer rates, as even more high-bandwidth applications and converged networks evolve. What is one of the most cost-effective ways to drastically increase bandwidth within local area networks while utilizing investments in current network cabling? The answer is simple: Gigabit Ethernet over copper, also known as 1000BaseT.
Fiber vs. copper
When most people think of Gigabit connectivity, they usually think of fiber-optic lines. Since 1998, Gigabit Ethernet has been standardized for use on fiber-optic cabling. However, many organizations, although realizing the need for increased bandwidth, could not justify the cost of implementing a fiber-optic infrastructure. Thus, the deployment of Gigabit Ethernet has traditionally been limited to areas where fiber cabling was required or desired. But more than 85 percent of cabling inside buildings today is Category 5 copper. Not surprisingly, organizations have been reluctant to replace their existing Cat5 cabling in order to deploy high-speed networking.
However, the approval of the 1000BaseT standards two years ago has enabled the widespread deployment of Gigabit over the existing copper infrastructure. Now, virtually every organization, regardless of size, can utilize the copper cabling they already have in place to easily and dramatically upgrade their LAN performance at a small cost.
I say virtually every organization because existing Cat5 cabling must meet certain transmission characteristics before it can be used for Gigabit Ethernet. In 1995, ANSI/TIA/EIA provided transmission performance specifications for twisted pair copper cabling that addressed the two issues of “crosstalk” and “return loss.”
Many Cat5 systems installed prior to 1995 may not meet these standards and will encounter problems if their cabling is used with a Gigabit solution. The only way to determine whether your existing cabling is sufficient is to check that it is indeed compliant with the Cat5 specifications and to run a cable test for crosstalk and return loss. New Category 5e (enhanced) cabling standard and the emerging Category 6 specification are supersets of the Category 5 specification. Because Category 5e specification includes the testing parameters for far-end crosstalk and return loss, Category 5e cabling is recommended for all new installations to ensure compatibility with 1000BaseT use.
Time for Gigabit
Many organizations already have migrated to Fast Ethernet (100 Mbps) for their entire network infrastructure. This migration included the increase in bandwidth to the desktop in order to boost LAN performance. However, that solution has created other problems. While 100 Mbps implementation has increased LAN performance to the desktop, it has also created a bottleneck at server connections, switch stacks, and other points of aggregation. Network professionals are turning to Gigabit Ethernet over copper solutions to relieve these bottlenecks. There are several solutions in which 1000BaseT solutions can be implemented for an organization. We’re going to look at three solutions: server connectivity, switch uplinks, and desktop connectivity.
Today’s servers can process larger files and move more data faster than ever before. Traditional 10/100 Mbps network interface cards (NICs) can quickly become a bottleneck when hundreds of clients are passing what can potentially be terabytes of data to and from the server. This is even more evident when the network involves a lot of server-to-server communication. Outfitting these powerful back-end servers with Gigabit NICs can dramatically improve traffic flow. With the price of Gigabit NICs hovering in the $200 range, going with a 1000BaseT solution here provides the most performance enhancement for the money.
Deployment steps might include replacing 10/100 Mbps adapters with auto-negotiating 10/100/1000 adapters. Of course, these servers would need to be connected to a Gigabit-enabled switch. With the 1000BaseT standard, Gigabit NICs and switches can support both 100/1000 and 10/100/1000 auto-negotiation between Fast Ethernet and Gigabit Ethernet. This allows network professionals to deploy 1000BaseT incrementally into the network. For instance, a 100/1000 server NIC may be installed into a new server while the server switch remains 100BaseTX, or vice versa.
If your network consists of two or more segments that traverse large amounts of data, a Gigabit switch uplink solution may provide a much-needed performance boost. The 1000BaseT standard provides high-bandwidth connectivity from desktop switches to the next point of aggregation. A Gigabit solution here can help ensure responsiveness by moving traffic quickly from the back end to the front end. Deployment steps might include adding a Gigabit uplink switch at endpoint of each of your network segments. Various vendors, such as Cisco and 3-Com, offer these uplink switches at an economical price.
Last but certainly not least will be the adoption of Gigabit at the desktop. At the workstation level, organizations may find that more bandwidth is needed for high-performance workstations to run bandwidth-intensive applications. As Gigabit adapters become more affordable, users will begin implementing Gigabit at the desktop. However, this solution does require that all connected switches be able to operate at 1000-Mbps speeds as well. There are a wide variety of 10/100/1000 connectivity devices that will allow network professionals to negotiate network speed throughout the organization and even down to the desktop, based on their requirements.
Figure A illustrates the three spots where Gigabit Ethernet can make an impact.
The future of Gigabit
The Gigabit Ethernet we have been referring to is also known as One Gigabit Ethernet. Even though the ability to transfer 1 billion bits per second is sometimes difficult to imagine, an even faster 10 Gigabit Ethernet standard is nearing completion. This new standard, referred to as 802.3ae, is being led by the 10 Gigabit Ethernet Alliance. This group was established to promote standards-based 10 Gigabit Ethernet technologies and to encourage the use and implementation of 10 Gigabit Ethernet as a key networking technology. Founding members of the 10 Gigabit Ethernet Alliance include such prominent names as 3Com, Cisco Systems, Intel, Nortel Networks, and Sun Microsystems.
This new 10 Gigabit technology will not be able to run over copper cabling, so an upgrade to fiber optics will be required to take advantage of this technology. However, don’t use this as a reason not to move to Gigabit solutions now. Hardware solutions created around 10 Gigabit technology won’t be available until the latter part of 2002 or the beginning of 2003.
Like it or not, the need for bandwidth is increasing at an explosive rate. Just as we once thought that “64 kilobytes of memory will be more than we’ll ever need,” we’re now finding that we’re quickly exceeding the 100 Mbps capacity for our local area networks. Fortunately, with 1000BaseT, organizations can have the benefits of Gigabit performance without the expense of upgrading to fiber cabling.
How have you implemented Gigabit Ethernet?
We look forward to getting your input and hearing about your experiences regarding this topic. Join the discussion below or send the editor an e-mail.
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Absolutely. In fact, Ethernet (esp half duplex) DEPENDS on the statistical likelyhood that the wire is only really really busy a small fraction of the time. Your conclusion that gigabit to the desktop won't help as much follows logically. Better to link the switches over gigabit, and the most used servers as well.
>If you have power users (like large DBA's), put them on thier own dedicated 100 Mbps switch port (and make sure it's FORCED to 100, not 10/100 autoselect
Ya. Niether Autonegotiate nor autosense are STANDARDS BASED processes and both processes fail as often as they suceed, at least in my experience.
Now consider the modern data center- several or dozens of servers, hundreds or more users. Odds are good that users A thru M are using server 1, while dozens of others are using servers 2, 8, 10, and 43.
In this situation, where use of bandwidth is concentrated on a small number (but more than one) of servers, it make sense to use a gig switch with gig links to all medium and highly used servers, gig links to the wiring closets, and from there, 100mb FD links to the workstations.
Total gig solution unrealistic!
Here's a more realistic scenario: Get the biggest baddest gigabit switch you can afford for your MDF (main NOC). Make sure the switch has a fast enough backplane and fast enough thruput to service all those gig ports. Give your busiest servers gig links to the BUS (big ugly switch) and gradually upgrade all servers to gigbit links. Make sure all your IDF (closet or worksgroup) switches can 1. support the thruput it takes to handle a bunch of 100mb and a smaller number of gig links and 2. has slots or module port to add gigabit interfaces to. Run your IDF switches at 10/100mb, but change over the uplinks to them to gigabit over the next year.
Your high demand workstations can have 100mb full duplex connections, but save bandwidth for lower demand (e-mail and word processing) machines and run them at 10mb full duplex if possible. Don't tell people what speed their workstation is- I defy the average user to determine for sure if their workstation is 10 or 100mb. Unless they are a heavy CAD or engineering user or similar. You could even start upgrading some workstations to gigabit, but that's hideously expensive.
Make sure you look down the road a little when picking your switches.
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