The following information may interest departments that are planning to convert from Thinnet, Thicknet or LocalTalk to 10BASE-T ethernet as they are cut over from the current UCDNet infrastructure to the new Network 21 infrastructure. If your department already has a LAN that is using 10BASE-T LAN wiring exclusively, you do not need to purchase replacement NICs and you will not need to study this document.
Ideally, each computer and network device will connect to the new Network 21 infrastructure directly via a Network 21 10BASE-T NAM ( i.e., one Network 21 10BASE-T NAM for each and every computer and network device ). However, due to funding limitations in the department as well as with the Network 21 project, this may not be feasible. For more information on port expansion options ( i.e., options that allow multiple computers and network devices to connect via a single Network 21 10BASE-T NAM ), please see the Network Expansion recommendations.
Please note that 100BASE-T cards and connectors are beyond the scope of this paper. This paper describes 10BASE-T combo cards: 10BASE-T network interface cards with multiple connectors. This paper does not describe 10/100BASE-T combo cards. For more information about 100BASE-T options, see the Fast Ethernet and Network Expansion recommendations.
A combo card is a Network Interface Card (NIC) that has a wiring connector for two or more types of LAN wiring. While only one connector is used at a time, the multiple connectors allow you to switch easily from one type of LAN wiring to a different type of LAN wiring.
For example, a combo card may have an AUI connector in addition to either a BNC or 10BASE-T connector. Some cards have all three types of connectors.
Combo cards typically cost about 20% more than a NIC with a single connector type. Traditionally, combo cards have been used when a new NIC is purchased and when the LAN wiring for an area is known to be undergoing plans for an upgrade to a new type of LAN wiring.
Since the new workstation will be added to the department LAN immediately, a combo card with both Thinnet and 10BASE-T connectors is purchased. The workstation can be added to the LAN immediately (using the BNC connector on the combo card) and the workstation can easily be switched to 10BASE-T (by switching to the RJ-45 connector on the NIC) when the LAN upgrade is completed.
This makes good fiscal sense: it costs less to purchase one combo card (in anticipation of the LAN wiring change) than it does to purchase two single-connector cards (one for use on the existing Thinnet and another for future use with 10BASE-T wiring).
Many departments currently have LANs that use Thinnet or Thicknet LAN wiring. The primary wiring method under the Network 21 infrastructure is 10BASE-T LAN wiring. Workstations that will be cut over from Thinnet or Thicknet to a Network 21 10BASE-T NAM may require the purchase of a new NIC.
When a new NIC must be purchased for a desktop computer or network device, a combo connector replacement NIC may be helpful when the desktop computer or network device
Your decision to buy combo connector NICs may be influenced by the value of lost productivity versus the dollar cost.
If it is most important to reduce network downtime as a workstation is cut over to the Network 21 infrastructure, a combo connector NIC will help reduce lost network time. If it is most important to reduce the dollar cost of replacement NICs that you purchase, a combo connector NIC will be less advantageous.
If you are purchasing a new combo connector NIC, look for one that auto detects the connector or uses software for configuration. Avoid NICs that use hardware jumpers to designate the connector that will be monitored by the card.
If your combo connector NIC uses hardware jumpers and you are not yet using 10BASE-T wiring, you'll have to open the PC to adjust the jumpers at Network 21 cutover time.
Caution: If you open the CPU chassis of your PC, protect yourself and your equipment by following all safety precautions; if you do not know the proper safety precautions, do not attempt to open the CPU chassis.
|Cost Disadvantage||Dollar cost||Combo cards typically cost about 20% more than a NIC with a single connector
If your single overriding concern is to reduce dollar cost, then combo connector NICs may not be the best solution for your department. In this case, the dollar savings are more important than the possible downtime savings.
If you have many workstations in your department, the cost differential between single connector NICs and combo connector NICs becomes more significant.
|Time Advantage||Possible software driver problems||In most cases, when you replace an internal NIC with a different brand or
model of NIC, you will also need to replace the software driver for the
NIC (e.g., Windows for Workgroups NIC driver, packet driver, Macintosh Network
control panel driver).
Most NICs come with a software diskette that contains software drivers for the card. However, it is not always a straight-forward task to find the proper software driver for your network configuration. You may need to contact the NIC vendor or download the software driver from an FTP site.
If you run into problems loading your new NIC software driver, the workstation network downtime will increase.
|Time Advantage||Possible NIC hardware fault||If you purchase your new NICs from a well-known manufacturer, you can expect
good quality NICs with few hardware defects. However, there is always a possibility
of a NIC hardware defect.
If you run into a NIC hardware defect, you'll have to get a replacement for the faulty NIC; this typically means returning the card to the vendor.
|Time Advantage||Possible workstation hardware fault||Any time you open the case of a CPU, there is a risk of damage to the contents.
It helps to be careful and to use proper grounding straps, but you simply never know
what might happen. Perhaps the CMOS battery is dead; maybe a loose wire becomes disconnected.
With proper care and precautions, these problems are rare, but can occur.
If you run into a workstation hardware fault, you may experience more than just network downtime as you resolve the problem.
|Time Advantage||Changing three things at once||If you choose to change the NIC at the same time that you cut over to the
Network 21 infrastructure, you will be changing three significant components at
once (NIC change, TCP/IP kernel change, LAN wiring change). If a problem arises,
will you be able to determine whether the problem is due to a hardware fault, software
drivers, the TCP/IP kernel configuration or the LAN wiring?
When you use a combo card, you'll be able to install and test the new NIC and NIC software drivers before you change the TCP/IP kernel configuration or LAN wiring. If a problem arises, it may be easier to isolate and correct the problem.
|Time Advantage||Scheduling conflicts||Although you will have flexibility in selecting your Network 21 cutover date,
there may be a few workstations in your area that will not allow significant
downtime on your scheduled Network 21 cutover date.
When you use a combo card, you'll be able to install and test the new NIC and NIC software drivers before the Network 21 cutover date. At Network 21 cutover time, switch the wiring that is connected to the NIC by disconnecting the existing UCDNet wiring and switching to a 10BASE-T cable. Note: You will need to make the TCP/IP kernel changes at cutover time in either case.
|Time Advantage||Sheer number of workstations||When you use a combo card, you'll be able to install and test the new NIC and NIC
software drivers before the Network 21 cutover. At Network 21 cutover time,
switch the wiring that is connected to the NIC by disconnecting the existing
UCDNet wiring and switching to a 10BASE-T cable. Note: You will need to make the
TCP/IP kernel changes at cutover time in either case.
If you have many workstations in your area, you may not physically be able to replace NICs in a timely manner on your Network 21 cutover date. The cutover will proceed much more quickly if you have replaced the NICs in advance of cutover.
Example of need for quick cutover: You have a file server in your area that is heavily used. At any point during the cutover process, some workstations will be on the UCDNet infrastructure and some workstations will be on the new Network 21 infrastructure. This means that some will be unable to access the file server until both the file server and the workstation are on the new Network 21 infrastructure.
|Cost Disadvantage||Fan-out devices||Most of the advantages/disadvantages listed above assume that you will convert all
workstations to 10BASE-T LAN wiring at the same time you cut over to the Network 21
It is allowable to use fan-out devices to connect multiple devices to a single Network 21 NAM. Depending on your current LAN wiring method, the number of workstations in your area and other factors, it may be more cost effective to use a fan-out device than to purchase new NICs (combo cards or plain 10BASE-T NICs).
For more information, please refer to the Network Expansion recommendations.
|Mitigate Time Disadvantage||Test one workstation start to finish with comparable combo card.||Some manufacturers make card models that are exactly the same except for the
combo connector feature.
You may want to purchase a limited number of combo cards for pre-cutover testing. You can install and test the combo card in a representative workstation and resolve any driver or configuration issues at that time. You can then deal with at-cutover single-connector NIC installations in a more confident, straight-forward manner.
|Mitigate Time Disadvantage||Identify low use workstations that can absorb the downtime.||In the best of worlds, NIC installations proceed with ease -- no problem!
If you are confident that you can install NICs on the day of your Network 21 cutover,
you may want to identify a few workstations that can bear the brunt of unexpected NIC
If you run into a NIC hardware fault, you may be able let a low-use workstation languish while you complete other NIC installations in other workstations and return the faulty NIC.
|Mitigate Time Disadvantage||Prepare backup workstation(s).||In the best of worlds, you can crack the case of a CPU, flip cards in and out,
blow out the dust bunnies, replace the case and everything powers up as expected --
no problem! If you are confident that you can install NICs on the day of your Network
21 cutover, you may want to line up some backup workstations to put in service if
there are unexpected workstation failures.
If you run into an unexpected workstation failure, you may be able to bring in a backup workstation to handle work load while you complete other NIC installations and repair the damaged workstation.
|Mitigate Cost Disadvantage||Buy combo cards for only the most mission-critical workstations.||You may have a few workstations that are truly mission-critical. If you want to lower
NIC costs, but you also want to anticipate and minimize network downtime for a few
critical workstations, you can purchase combo cards just for the mission-critical workstations.
This will allow you the time advantages of the combo card for the mission-critical workstations without bearing the additional cost of the combo card for all workstations.