Black Box Explains...High-speed networking.
What are my choices for high-speed
... more/see it nownetworking?
| 100BASE-T | ATM
| Gibabit Ethernet
Switched Ethernet relies on centralized multiport switches
to provide a physical link between multiple LAN segments.
Inside each intelligent switch, high-speed circuitry supports
wire-speed virtual connections between all the segments
for maximum bandwidth allocation on demand. Adding new segments
to a switch increases the aggregate network speed while
reducing overall congestion, so Switched Ethernet provides
superior configuration flexibility. It also gives you an
excellent migration path from 10- to 100-Mbps Ethernet,
since both segments can often operate via the same switch.
Benefits of Switched Ethernet—It’s
a cost-effective technique for increasing the overall network
throughput and reducing congestion on a 10-Mbps network.
Other than the addition of the switching hub, the Ethernet
network remains the same—the same network interface
cards, the same client software, the same LAN cabling.
100BASE-T retains the familiar CSMA/CD media access technique
used in 10-Mbps Ethernet networks. It also supports a broad
range of cabling options: two standards for twisted pair
and one for fiber. 100BASE-TX supports 2-pair Category 5
UTP or Type 1 STP cable. 100BASE-FX enables fiber optic
links via duplex multimode fiber cable.
Benefits of 100BASE-T—It
retains CSMA/CD, so existing network management systems
don’t need to be rewritten. It can easily be integrated
into existing 10-Mbps Ethernet LANs, so your previous investment
is saved (see Figures 1 and 2).
It’s also backed by hundreds of manufacturers in the
high-speed networking industry, including Black Box!
||100BASE-T (IEEE 802.3u)
of this Standard
||Category 5 (2-Pair)
||Duplex Multimode or Single-Mode
|| Category 5—100
||Backbone using Ethernet
switches to provide increased throughput. Small to medium
workgroups using applications (i.e. CAD, CAM) that output
huge data files.
Asynchronous Transfer Mode (ATM) is a cell-based fast-packet
communication technique that supports data-transfer rates
ranging from sub-T1 speeds (less than 1.544 Mbps) up to
Like other packet-switching services (Frame Relay, SMDS),
ATM achieves its high speeds in part by transmitting data
in fixed-size cells and dispensing with error-correction
protocols. Instead, it relies on the inherent integrity
of digital lines to ensure data integrity.
Benefits of ATM—Networks
are extremely versatile. An ATM network can be treated as
a single network, whether it connects points in a building
or across the country. Its fixed-length cell-relay operation,
the signaling technology of the future, offers more predictable
performance than variable-length frames. And it can be integrated
into an existing network as needed without having to upgrade
the entire LAN.
Like Ethernet and Fast Ethernet before it, Gigabit Ethernet
works with earlier versions of the IEEE 802.3 standard—both
10 and 100 Mbps— although some equipment will need
to be upgraded. The Gigabit Ethernet standard (IEEE 802.3z)
was approved in June 1998, and its speed of 1 Gbps is a
tenfold increase over Fast Ethernet.
There are two basic types of Gigabit Ethernet: shared
and switched. Shared Gigabit Ethernet
is a higher-speed version of 10/100BASE-T using CSMA/CD
Medium Access Control. Switched Gigabit Ethernet uses Logical
Link Control (LLC). Gigabit Ethernet increases frame sizes
from 64 bytes to 512 bytes minimum, and from 1514 bytes
to 9000 bytes maximum.
Benefits of Gigabit Ethernet—It
solves bandwidth problems. Its primary use is for backbones.
The medium is fiber or Category 5e 100-ohm cable. collapse
Black Box Explains...Ethernet.
If you have an existing network, there’s a 90% chance it’s Ethernet. If you’re installing a new network, there’s a 98% chance it’s Ethernet—the Ethernet standard is... more/see it nowthe overwhelming favorite network standard today.
Ethernet was developed by Xerox®, DEC®, and Intel® in the mid-1970s as a 10-Mbps (Megabits per second) networking protocol—very fast for its day—operating over a heavy coax cable (Standard Ethernet).
Today, although many networks have migrated to Fast Ethernet (100 Mbps) or even Gigabit Ethernet (1000 Mbps), 10-Mbps Ethernet is still in widespread use and forms the basis of most networks.
Ethernet is defined by international standards, specifically IEEE 802.3. It enables the connection of up to 1024 nodes over coax, twisted-pair, or fiber optic cable. Most new installations today use economical, lightweight cables such as Category 5 unshielded twisted-pair cable and fiber optic cable.
How Ethernet Works
Ethernet signals are transmitted from a station serially, one bit at a time, to every other station on the network.
Ethernet uses a broadcast access method called Carrier Sense Multiple Access/Collision Detection (CSMA/CD) in which every computer on the network hears every transmission, but each computer listens only to transmissions intended for it.
Each computer can send a message anytime it likes without having to wait for network permission. The signal it sends travels to every computer on the network. Every computer hears the message, but only the computer for which the message is intended recognizes it. This computer recognizes the message because the message contains its address. The message also contains the address of the sending computer so the message can be acknowledged.
If two computers send messages at the same moment, a collision occurs, interfering with the signals. A computer can tell if a collision has occurred when it doesn’t hear its own message within a given amount of time. When a collision occurs, each of the colliding computers waits a random amount of time before resending the message.
The process of collision detection and retransmission is handled by the Ethernet adapter itself and doesn’t involve the computer. The process of collision resolution takes only a fraction of a second under most circumstances. Collisions are normal and expected events on an Ethernet network. As more computers are added to the network and the traffic level increases, more collisions occur as part of normal operation. However, if the network gets too crowded, collisions increase to the point where they slow down the network considerably.
Standard (Thick) Ethernet (10BASE5)
Thin Ethernet (ThinNet) (10BASE2)
- Uses thick coax cable with N-type connectors for a backbone and a transceiver cable with 9-pin connectors from the transceiver to the NIC.
- Both ends of each segment should be terminated with a 50-ohm resistor.
- Maximum segment length is 500 meters.
- Maximum total length is 2500 meters.
- Maximum length of transceiver cable is 50 meters.
- Minimum distance between transceivers is 2.5 meters.
- No more than 100 transceiver connections per segment are allowed.
Twisted-Pair Ethernet (10BASE-T)
- Uses "Thin" coax cable.
- The maximum length of one segment is 185 meters.
- The maximum number of segments is five.
- The maximum total length of all segments is 925 meters.
- The minimum distance between T-connectors is 0.5 meters.
- No more than 30 connections per segment are allowed.
- T-connectors must be plugged directly into each device.
Fiber Optic Ethernet (10BASE-FL, FOIRL)
- Uses 22 to 26 AWG unshielded twisted-pair cable (for best results, use Category 4 or 5 unshielded twisted pair).
- The maximum length of one segment is 100 meters.
- Devices are connected to a 10BASE-T hub in a star configuration.
- Devices with standard AUI connectors may be attached via a 10BASE-T transceiver.
- Uses 50-, 62.5-, or 100-micron duplex multimode fiber optic cable (62.5 micron is recommended).
- The maximum length of one 10BASE-FL (the new standard for fiber optic connections) segment is 2 kilometers.
- The maximum length of one FOIRL (the standard that preceded the new 10BASE-FL) segment is 1 kilometer.
Product Data Sheets (pdf)...Gigabit Unmanaged Switches with SFP Uplinks
Gigabit Smart Switch (Eco Fanless) User Manual
User Manual for the LGB2118A & LGB2124A (Version 1)
Web Smart Gigabit Ethernet Switch User Manual
User Manual for the LGB624A (Version 1)
20 + 4 Port Gigabit Smart Switch (Eco Fanless) Firmware
Firmware for the LGB2124A (Version v1.08)
10/100 PSE Web Smart Switch User Manual
User Manual for 10/100 PSE Web Smart Switch (2)
Gigabit L3 Managed Switch with 10G Uplinks Accessories Manual
Accessories Manual for the LGB6026A, LGB6050A, LGB6001C, LGB6000SC-001, & LGB6000SC-004 (Version 1)
Black Box Explains...Ethernet hubs vs. Ethernet switches.
Although hubs and switches look very similar and are connected to the network in much the same way, there is a significant difference in the way they function.
What is a... more/see it nowhub?
An Ethernet hub is the basic building block of a twisted-pair (10BASE-T or 100BASE-TX) Ethernet network. Hubs do little more than act as a physical connection. They link PCs and peripherals and enable them to communicate over a network. All data coming into the hub travels to all stations connected to the hub. Because a hub doesnt use management or addressing, it simply divides the 10- or 100-Mbps bandwidth among users. If two stations are transferring high volumes of data between them, the network performance of all stations on that hub will suffer. Hubs are good choices for small- or home-office networks, particularly if bandwidth concerns are minimal.
What is a switch?
An Ethernet switch, on the other hand, provides a central connection in an Ethernet network in which each connected device has its own dedicated link with full bandwidth. Switches divide LAN data into smaller, easier-to-manage segments and send data only to the PCs it needs to reach. They allot a full 10 or 100 Mbps to each user with addressing and management features. As a result, every port on the switch represents a dedicated 10- or 100-Mbps pathway. Because users connected to a switch do not have to share bandwidth, a switch offers relief from the network congestion a shared hub can cause.
What to consider when selecting an Ethernet hub:
• Stackability. Select a stackable hub connected with a special cable so you can start with one hub and add others as you need more ports. The entire stack functions as one device.
• Manageability. Choose an SNMP-manageable hub if you have a large, managed network.
What to consider when selecting an Ethernet switch:
• Manageability. Ethernet switches intended for large managed networks feature built-in management, usually SNMP.
• OSI Layer operation. Most Ethernet switches operate at “Layer 2,” which is for the physical network addresses (MAC addresses). Layer 3 switches use network addresses, and incorporate routing functions to actively calculate the best way to send a packet to its destination. Very advanced Ethernet switches, often known as routing switches, operate on OSI Layer 4 and route network traffic according to the application.
• Modular construction. A modular switch enables you to populate a chassis with modules of different speeds and media types. Because you can easily change modules, the modular switch is an adaptable solution for large, growing networks.
• Stackability. Some Ethernet switches can be connected to form a stack of two or more switches that functions as a single network device. This enables you to start with fewer ports and add them as your network grows. collapse