Ethernet Overview

    This chapter is designed to illustrate basic Ethernet deployment for
    various cabling types. The...
Goals
Beginning about 1972, Xerox Corporation’s Palo Alto research Center (PARC) began
developing a LAN system known as Ex...
Addressing flexibility
The addressing mechanism should provide the capability to direct data frames to a single
station, a...
Maintainability
 The Ethernet design should allow for network maintenance, operation and planning.

 Layered architecture
...
Since a transmission is heard by all stations connected to the channel, Ethernet is classified
as a broadcast-type network...
Ethernet vs. IEEE 802.3


Overview
The original Ethernet standard developed by Digital, Intel and Xerox was first known as...
Frame formats
The most significant difference between the original Ethernet and the IEEE 802.3 standard is
the difference ...
One of the differences between the two frame formats is in the preamble. The purpose of the
preamble is to announce the fr...
Designing basic 10Base-5 Ethernet networks


Introduction
10Base-5 Ethernet is also known as Thick Ethernet and is more co...
Transceivers
A transceiver is a small box that provides for the electrical isolation of the cable from the
attached device...
Transceiver cable
Transceiver cables are shielded twisted-pair cables and far more flexible than the trunk
cable. They are...
N-series connectors
Three types of N-series connectors are used in a 10Base-5 installation. These are as
follows:
     •  ...
10Base-5 design

Basic 10Base-5 design - Trunk cable deployment
The first step in 10Base-5 design is determining where the...
FIGURE 6.2: DEPLOYING THE 10BASE -5 TRUNK CABLE



     Thicknet trunk cable




                                       Te...
Basic 10Base-5 design - Transceiver deployment
 Thicknet transceivers—sometimes referred to as Media Attachment Units (MAU...
Basic 10Base-5 design - Station deployment
Network devices attach to the transceivers using transceiver cable. This cable ...
FIGURE 6.4: 10B ASE-5 STATION DEPLOYMENT



                    Single-port
                    transceiver          Trunk...
Designing basic 10Base-2 Ethernet networks


Introduction
10Base-2 Ethernet is also known as Thin Ethernet, and is often r...
Components

RG-58 coaxial cable
RG-58 coaxial cable is used as the 10Base-2 main trunk cable. It is a 50 Ω , 20 AWG
cable ...
BNC connectors
BNC connectors must be attached to all cable segment ends. Cable connector kits include
a center pin, a hou...
10Base-2 design

Basic 10Base-2 design
The design of 10Base-2 Ethernet networks requires running the correct type of coaxi...
FIGURE 6.5: 10B ASE-2 DEPLOYMENT



       Thinnet trunk cable




                                                       ...
Designing basic 10Base-T Ethernet networks


Introduction
10Base-T Ethernet is also known as twisted-pair Ethernet. It was...
Components

Unshielded twisted-pair cable
UTP cable is used to connect stations to the 10Base-T hub. The UTP cable must ha...
10Base-T design

Basic 10Base-T design
While the physical appearance of a 10Base-T Ethernet network is that of a star, it
...
FIGURE 6.6: BASIC 10BASE -T CONFIGURATION




                              10Base-T NIC
                               wi...
FIGURE 6.7: STRUCTURED 10BASE-T DESIGN




                                                                               ...
Other Ethernet networks


Combined 10Base-5 and 10Base-2
Thick and thin Ethernet trunk cable can be combined into one netw...
10Base-FL
10Base-FL Ethernet is also known as Fiber Link Ethernet. It was formally introduced in 1993.
In 10Base-FL, a two...
Troubleshooting Ethernet networks


Introduction
The most important criteria for the success of any network is its reliabi...
General troubleshooting guidelines
Network problems are often blamed on one of the hardware components. That is, the cabli...
•   It should be verified that all power supplies are connected and functioning properly.
     •   Diagnostic software sho...
Troubleshooting Ethernet
In the case of Ethernet networks, a distinction needs to be made between coaxial cable
based-Ethe...
•   The cable may need to be checked for opens, shorts and missing terminators. An
         intact, properly terminated ca...
Transceivers
     •   Verify that power and transceiver cables are properly connected.
     •   It should be verified that...
Software considerations
     •   All addresses must be of the same format. While addresses in the IEEE 802.3
         stan...
Ethernet performance


Overview
Ethernet is a contention-based technology, meaning that all attached devices have equal
ac...
Frame transmission rate
The amount of information carried in an Ethernet frame can vary—it is not a predefined
amount. The...
The Frame Transmission Rate is calculated as follows:

                                          1
  Transmission Rate =
 ...
1000 ms / second
 Transmission Rate =
                           1.2304 ms / frame


 Transmission Rate = 812.74 frames/ s...
EXAMPLE 6.2: FRAME TRANSMISSION RATE FOR A 72 BYTE FRAME SIZE
 For a minimum frame size of 72 bytes, the amount of time re...
The equivalent transmission rate in bytes is:

                                                  frames      bytes        ...
The maximum theoretical throughput of a traditional Ethernet network is 10 Mbps.
However, when a maximum frame size is use...
Estimating network traffic
While it is not possible to determine exactly what the amount of network traffic will be, it is...
EXAMPLE 6.3: ESTIMATING NETWORK TRAFFIC
In order to illustrate how network traffic load can be estimated in an Ethernet en...
Clerical                              Transmission         Number of       Total bytes
                                   ...
Totals           Total per person       Number of people         Total per group
Managerial          2,792,000            ...
E XAMPLE 6.4:
ESTIMATING NETWORK TRAFFIC WHEN LARGE FILES NEED TO BE ACCESSED
In this extension of the above example, the ...
Design                                Transmission              Number of       Total bytes
                              ...
Ethernet growth


Overview
An Ethernet network can connect more than a single group of users on a common floor.
Ethernet c...
CONTENTS •
                     Ethernet Overview .................................................................. 1
   ...
CONTENTS •
                       Designing basic 10Base-5 Ethernet networks .................... 9
                      ...
CONTENTS •
                        Designing basic 10Base-T Ethernet networks ................. 23
                       ...
CONTENTS •
                       Troubleshooting Ethernet networks .................................. 30
                ...
• EXAMPLES • EXAMPLES • EXAMPLES •

                                        Example 6.1: Frame transmission rate
         ...
• FIGURES • FIGURES • FIGURES • FIGURES •

                                                 Figure 6.1:        IEEE 802.3 ...
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Ethernet Overview

  1. 1. Ethernet Overview This chapter is designed to illustrate basic Ethernet deployment for various cabling types. The assumption is that all users are on a common floor and that a structured cabling system approach has been adopted. The design of more complex Ethernet networks will be discussed in later chapters and will cover Ethernet backbones and Ethernet internetworking. Introduction Developed in the 1970’s and popularized in the 1980’s, Ethernet is the most popular network technology today. Ethernet connections are available for personal computers, high- performance design and scientific workstations, minicomputers and mainframe systems. Ethernet is an architecture that provides best-effort datagram service. It has error detection but not error correction. It is a multi-access, packet-switched network using a passive broadcast medium. Ethernet has no central control unit with data packets being transmitted over the network, reaching every station. Each station is responsible for recognizing the address in a data unit and for accepting data units addressed to it. Access to the transmission medium is controlled by the individual station using a probabilistic access method known as contention. Chapter 6 - Ethernet Design 1 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  2. 2. Goals Beginning about 1972, Xerox Corporation’s Palo Alto research Center (PARC) began developing a LAN system known as Experimental Ethernet. Early Ethernet specifications contributed substantially to work done later by the IEEE 802.3 committee defining the CSMA/ CD access control standard. The original Ethernet goals are consistent with what have become the telecommunications requirements driving the development and increased use of LANs. These original Ethernet specifications are as follows: Simplicity Features that could complicate the network design without making substantial contribution to meeting other goals have been excluded. Low cost The cost of connection to an Ethernet network should be minimized. Technological improvements will continue to reduce the overall cost of connecting stations to Ethernet. Compatibility All implementations of Ethernet should be capable of exchanging data at the Data Link layer. To eliminate the possibility of incompatible variations of Ethernet, the specification avoids optional features. … Goals, continued Chapter 6 - Ethernet Design 2 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  3. 3. Addressing flexibility The addressing mechanism should provide the capability to direct data frames to a single station, a group of stations or broadcast the message to all stations attached to the network. Fairness All attached stations should have equal access to the network—averaged over time. Progress No one station attached to the network, operating in accordance with the Ethernet protocol, should be able to prevent the operation of other stations. High speed The network should operate efficiently at a data rate of 10 Mbps. Low delay At any given level of network traffic, as little delay as possible should be introduced in the transfer of a data frame. Stability The network should be stable under all load conditions. Delivered messages should make up a constant percentage of the total network traffic. … Goals, continued Chapter 6 - Ethernet Design 3 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  4. 4. Maintainability The Ethernet design should allow for network maintenance, operation and planning. Layered architecture The Ethernet design should be specified in layered terms so as to separate the logical aspects of the Data Link layer protocols from the physical details of the communications channel. Functionality On an Ethernet network, all stations have equal opportunity at all times to initiate communications over a common transmission channel. Because of this, some mechanism must exist to resolve the conflict when more than one station attempts to transmit at the same instant in time. The mechanism used in Ethernet for this function is referred to as CSMA/CD —Carrier Sense Multiple Access with Collision Detection. In CSMA/CD, any station wishing to transmit must first establish that the communications channel is clear. The station then begins its transmission, while at the same time continuing to monitor the channel for an indication of a collision. If a collision is detected, the stations involved will stop transmitting, send a jamming signal indication a collision, wait a random amount of time (different for each station) and attempt to transmit again. Since a station can perform this operation several times in the space of one second, collisions are seldom noticed by users on a well-designed Ethernet system. … Functionality, continued Chapter 6 - Ethernet Design 4 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  5. 5. Since a transmission is heard by all stations connected to the channel, Ethernet is classified as a broadcast-type network. The stations on an Ethernet network listen for, detect and recover after any collision caused during normal operations. Critical to proper operations is the ability for a transmitting station to detect a collision between its transmission and that of another station. Without this ability, the station cannot recover and rebroadcast its message. Instead, it will assume that the transmission was successful. If this occurs, error-recovery will have to be initiated by higher-level software, rather than the Data Link layer. This in turn adds greater delays to network operation. In order for a station to detect a collision during its transmission, the time delay in the propagation of the collision signal must be limited. The collision signal must travel over the cabling system back to the station in less time than the maximum time period the station has for the detection of a collision. The Ethernet specifications allow for the use of two types of coaxial cabling, unshielded twisted-pair cabling or optical fiber cabling. In all cases, distance limitations have been imposed to allow for proper operation without excessive propagation delay. The focus of this chapter is to describe the design recommendations and limitations for each of these cable types. It should be noted that vendor-specific enhancements to Ethernet have produced products which can successfully operate beyond the limits described here. By respecting these recommendations, however, the designs will allow for reliable Ethernet operation regardless of the equipment used. Chapter 6 - Ethernet Design 5 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  6. 6. Ethernet vs. IEEE 802.3 Overview The original Ethernet standard developed by Digital, Intel and Xerox was first known as Experimental Ethernet and later as DIX Ethernet, in reference to the developers. This Ethernet was the first technology to gain wide acceptance as a local area connectivity solution. In the early 1980’s, DIX turned the Ethernet standard over to the IEEE, where it became the model for what is today known as IEEE 802.3. The IEEE made improvements to the original Ethernet and published the IEEE 802.3 standard for the first time in 1983. While IEEE 802.3 and Ethernet are similar, they are not identical. The differences between them are significant enough to make the two incompatible. All versions of Ethernet are similar in that they share the same CSMA/CD bus architecture. However, the IEEE 802.3 standard has evolved over time so that it now supports multiple Physical Layer options—including both 50 Ω and 75 Ω coaxial cable, unshielded twisted-pair cable and optical fiber. Other differences between the two include transmission speed, signaling method and maximum cable length. Chapter 6 - Ethernet Design 6 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  7. 7. Frame formats The most significant difference between the original Ethernet and the IEEE 802.3 standard is the difference in their frame formats. This difference is significant enough to make the two versions incompatible. FIGURE 6.1: 7 bytes Preamble IEEE 802.3 FRAME FORMAT VERSUS Start Frame Preamble 1 byte 8 bytes Delimiter E THERNET FRAME FORMAT 2 or 6 bytes Destination Address 6 bytes Destination Address 2 or 6 bytes Source Address 6 bytes Source Address 2 bytes Length Count 2 bytes Type 0 - n bytes Information 0 - n bytes Information 0 - n bytes Pad 0 - n bytes Pad Frame Check Frame Check 4 bytes Sequence 4 bytes Sequence IEEE 802.3 frame format Ethernet frame format … Frame formats, continued Chapter 6 - Ethernet Design 7 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  8. 8. One of the differences between the two frame formats is in the preamble. The purpose of the preamble is to announce the frame and to enable all receivers on the network to synchronize themselves to the incoming frame. It also ensures that there is sufficient time between frames for error detection and recovery operations—9.6 microseconds for 10 Mbps Ethernet. The preamble is 8 bytes in length for Ethernet but 7 bytes for IEEE 802.3, where the eighth byte becomes the start frame delimiter. The second difference in frame format is the Type field found in an Ethernet frame. A Type field was used to specify the protocol being carried in the frame. This enabled several protocols to be carried independently of one another. The Type field was replaced in the IEEE 802.3 standard by a Length Count field, which is used to indicate the number of bytes found in the following field—the Information field. The third difference between the two frame formats is found in the Address fields— Destination and Source. While the IEEE 802.3 format permits the use of either 2- or 6-byte addresses, the Ethernet standard permits only 6-byte address fields. This is less of an issue, since most vendor IEEE 802.3 implementations use the 6-byte length. The 2-byte address field was included to accommodate early LANs using 16-bit address fields. Summary Over time, the trend has been towards the adoption of IEEE 802.3. Vendors helped the migration to the IEEE 802.3 standard from the original Ethernet by providing dual-function hardware, capable of using either format. Today, vendors are providing migration paths from 10 Mbps Ethernet to 100 Mbps Ethernet. The predominant frame format in today’s Ethernet environments is IEEE 802.3, but the network technology continues to be referred to as Ethernet. Chapter 6 - Ethernet Design 8 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  9. 9. Designing basic 10Base-5 Ethernet networks Introduction 10Base-5 Ethernet is also known as Thick Ethernet and is more commonly referred to as Thicknet. It was formally introduced in 1980 and represents the original Ethernet specification. Thicknet features a thick coaxial trunk cable with attachments called transceivers. Network devices are connected to the transceivers using a shielded twisted-pair cable known as a transceiver cable. 10Base-5 is falling into disuse as a network technology. However, there are a large number of existing installations that may require expansion. As well, existing installations may migrate towards newer technologies. Components RG-8-type coaxial cable RG-8-type coaxial cable is used as the main cable, known as a trunk cable in a 10Base-5 Ethernet network. It is a stiff, 50 Ω , 12 AWG coaxial cable with a 10 mm (0.4 in) outside diameter. A special stripping and crimping tool is needed to be able to mount connectors on this cable. Many vendors supply this cable, either in bulk or in precut sections. Versions of the cable are available as plenum cable, indoors nonplenum cable, underground-rated cable and aerial-rated cable. … Components, continued Chapter 6 - Ethernet Design 9 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  10. 10. Transceivers A transceiver is a small box that provides for the electrical isolation of the cable from the attached device. It acts as a junction box on the trunk cable that permits the attachment of stations. A transceiver has three connectors on it. They function as follows: • Two of the connectors attach to the Ethernet trunk cable—one for the incoming cable and one for the outgoing cable. • The third connector is used to attach the station to the trunk cable using a transceiver cable. Transceivers can be attached to the trunk cable in two ways. This is referred to as tapping the cable and can be done as follows: • One method of attachment is known as a vampire tap. This is a clamping method where the transceiver actually pierces the cable. This eliminates the need to cut the cable and mount connectors. • The second method of attachment uses a transceiver with a T-type connector. Both the trunk and transceiver cables attach to this T-connector. In this method, the trunk cable must be cut and connectors attached. The transceiver is also responsible for performing a test known as the SQE (Signal Quality Error) or Heartbeat Test. This is used to confirm that the transceiver is properly connected to the trunk cable. … Components, continued Chapter 6 - Ethernet Design 10 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  11. 11. Transceiver cable Transceiver cables are shielded twisted-pair cables and far more flexible than the trunk cable. They are usually supplied with the transceiver unit. A DIX-type connector is mounted on either end of the transceiver cable. One connector is female and the other male. The female connector is used to attach to the external transceiver unit and the male connector is used to attach to the station. Slide locks on the connectors are used to lock the cable into place onto the Network Interface Card. Network Interface Card (NIC) Most NICs are capable of supporting both 10Base-5 and 10Base-2 Ethernet. For the attachment of the transceiver cable, the NIC should have a female DIX-type connector. DIX refers to Digital-Intel-Xerox. … Components, continued Chapter 6 - Ethernet Design 11 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  12. 12. N-series connectors Three types of N-series connectors are used in a 10Base-5 installation. These are as follows: • N-series male connectors. When T-type transceivers are used, N-series connectors are used on the two ends of the trunk cable to be attached to the transceiver. Preassembled cables come with the N-series connectors already installed. • N-series barrel connectors. These connectors are used to join two cable segments. • N-series terminators. These are 50 Ω terminators used at both ends of a cable segment. For each cable segment, one of these terminators must have a ground wire attached. Chapter 6 - Ethernet Design 12 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  13. 13. 10Base-5 design Basic 10Base-5 design - Trunk cable deployment The first step in 10Base-5 design is determining where the main trunk cable will run. The cable must be placed where it is accessible to stations needing to attach to the network. Some considerations when determining the placement of the trunk cable include the following: • The trunk cable can be a maximum of 500 m (1640 ft) in length. • The cable must be terminated on both ends with 50 Ω, N-series terminators. • One of the N-series terminators must be grounded—not both. • The maximum length of a transceiver cable is 50 m (164 ft), therefore a station needing to attach to the trunk cable must be within 50 m (164 ft) of it. … 10Base-5 design, continued Chapter 6 - Ethernet Design 13 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  14. 14. FIGURE 6.2: DEPLOYING THE 10BASE -5 TRUNK CABLE Thicknet trunk cable Telecommunications Closet (TC) Terminator (grounded) Terminator (not grounded) Common floor, divided into zones … 10Base-5 design, continued Chapter 6 - Ethernet Design 14 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  15. 15. Basic 10Base-5 design - Transceiver deployment Thicknet transceivers—sometimes referred to as Media Attachment Units (MAUs)—are used to attach network devices to the coaxial trunk cable. Some considerations when placing the transceivers include the following: • There can be a maximum of 100 Transceiver (MAU) transceivers attached to the trunk cable. At least 2.5 m (8.2 ft) b etween two • Transceivers transceivers must be at least 2.5 m (8.2 ft) Telecommunications apart. Closet (TC) FIGURE 6.3: 10B ASE -5 TRANSCEIVER DEPLOYMENT Common floor, divided into zones … 10Base-5 design, continued Chapter 6 - Ethernet Design 15 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  16. 16. Basic 10Base-5 design - Station deployment Network devices attach to the transceivers using transceiver cable. This cable is sometimes referred to as an Attached Unit Interface (AUI) cable. Transceiver cable is a twisted-pair cable consisting of four 20 AWG stranded twisted-pairs covered by a common shield. The cable can be a maximum of 50 m (164 ft) in length. Of the four pairs, one is used for transmission (called Data Out by IEEE 802.3), one for reception (called Data In by IEEE 802.3), one to detect collisions (called Control by IEEE 802.3) and one for powering the transceiver from the station (called Voltage by IEEE 802.3). A single transceiver can connect one station to the trunk cable or it may connect several devices to the trunk cable. Each station is equipped with an Ethernet Network Interface Card (NIC). The NIC is connected to the transceiver cable. This NIC connection point is sometimes referred to as a DIX (Digital-Intel-Xerox) connector. … 10Base-5 design, continued Chapter 6 - Ethernet Design 16 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  17. 17. FIGURE 6.4: 10B ASE-5 STATION DEPLOYMENT Single-port transceiver Trunk cable Transceiver Maximum of cable 50 m (164 ft) Station NIC Ethernet station Ethernet station with NIC with NIC Maximum of Transceiver 50 m (164 ft) cable TC Trunk cable Multi-port transceiver Chapter 6 - Ethernet Design 17 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  18. 18. Designing basic 10Base-2 Ethernet networks Introduction 10Base-2 Ethernet is also known as Thin Ethernet, and is often referred to as Thinnet. Thinnet was formally introduced in 1985 and is based on a coaxial cable transmission medium. The coaxial cable is thinner, more flexible and lower in cost than the traditional thick coaxial cable used in 10Base-5. For this reason 10Base-2 is sometimes referred to as Cheapernet. In Thinnet, the transceiver is integrated into the station NIC. This permits the Thinnet trunk cable to be attached directly to each station. This Thinnet trunk cable is a smaller diameter coaxial cable, which makes it physically easier to work with. However, this relative thinness of the conductor imposes a more restrictive design on the network. As is the case with 10Base-5, 10Base-2 is falling into disuse as a network technology for new installations. However, a large number of installations do exist and they may require expansion and potentially, migration to a new technology. Chapter 6 - Ethernet Design 18 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  19. 19. Components RG-58 coaxial cable RG-58 coaxial cable is used as the 10Base-2 main trunk cable. It is a 50 Ω , 20 AWG cable with a 5 mm (0.2 in) diameter. It is commonly referred to as RG-58 A/U or RG-58 C/U cable. Many vendors supply this cable either in bulk or in precut sections. Bulk cable needs to be cut to the proper length and have connectors attached. Precut cable typically comes with connectors attached. Versions of the cable are available as plenum cable, indoors nonplenum cable, underground-rated cable and aerial-rated cable. Network Interface Card (NIC) The 10Base-2 NIC will have a BNC-type connector on the board. It may also have a Thicknet connector or a 10Base-T connector. The trunk cable will attach to a BNC T-connector which is in turn connected to a male BNC connector on the back of the NIC. … Components, continued Chapter 6 - Ethernet Design 19 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  20. 20. BNC connectors BNC connectors must be attached to all cable segment ends. Cable connector kits include a center pin, a housing and a clamp-down sleeve. A stripping and crimping tool will be required to mount the connectors. Three types of BNC connectors are used in a 10Base-2 installation. These are as follows: • BNC T-connectors. T-connectors are attached to the BNC connector on the back of the NIC. These T- connectors provide two connection points for the trunk cable—one for the incoming signal and one for the outgoing signal. These T-connectors are required for each station on the network. • BNC barrel connectors. These connectors are used to join two cable segments together. • BNC terminators. These are 50 Ω terminators used at both ends of a cable segment. For each cable segment, one of these terminators must have a ground wire attached. The last station on a trunk cable requires a BNC terminator attached to the open end of its T-connector. Chapter 6 - Ethernet Design 20 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  21. 21. 10Base-2 design Basic 10Base-2 design The design of 10Base-2 Ethernet networks requires running the correct type of coaxial trunk cable from one network device to the next, in a bus configuration. RG-58 A/U or RG-58 C/U is used to connect one station to the next—no transceiver cables are needed. Stations are connected to the trunk cable using a BNC T-connector on the NIC. The cable must be terminated at both ends with 50 Ω, BNC-type terminators. One of these terminators must be grounded. Some considerations when designing 10Base-2 Ethernet networks are as follows: • The maximum length of a trunk segment is 185 m (607 ft). • There can be a maximum of 30 devices attached to a trunk cable segment. • The T-connectors must be at least 0.5 m (1.6 ft) apart. … 10Base-2 design, continued Chapter 6 - Ethernet Design 21 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  22. 22. FIGURE 6.5: 10B ASE-2 DEPLOYMENT Thinnet trunk cable Minimum of 0.5 m (1.6 ft) Telecommunications Closet (TC) Terminator (grounded) Terminator (not grounded) Common floor, divided into zones Chapter 6 - Ethernet Design 22 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  23. 23. Designing basic 10Base-T Ethernet networks Introduction 10Base-T Ethernet is also known as twisted-pair Ethernet. It was formally introduced in 1990 and has become popular for both new and existing installations. Part of the 10Base-T specification is to ensure compatibility with other versions of the IEEE 802.3 standard—making the transition easier. Some of these compatibility features include the following: • Existing Ethernet NICs can be used with 10Base-T installations through the use of adapters. • Twisted-pair trunk cables can be added to existing trunks by using repeaters supporting both twisted-pair and coaxial cable. In 10Base-T, as in 10Base-2, the transceiver is built into the station NIC. As well, the coax trunk cable is replaced with an electronic concentrator—often referred to as a 10Base-T hub. Each station is connected directly to a port in the hub. The 10Base-T specification includes a cable testing feature known as Link Integrity Testing. This monitoring is done from a central point and tests the twisted-pair wires on an ongoing basis for open (cut) wires and shorts (unintended electrical contact between wires). Chapter 6 - Ethernet Design 23 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  24. 24. Components Unshielded twisted-pair cable UTP cable is used to connect stations to the 10Base-T hub. The UTP cable must have Category 3 or better transmission characteristics—as specified in the ANSI/TIA/EIA-568-A cabling standard. The UTP can be 24 or 22 AWG. Network Interface Card (NIC) The connection point on a 10Base-T NIC is in the form of an 8-position modular jack-type connection. Some Ethernet NICs are available with a Thicknet DIX, Thinnet BNC, or both, in addition to the 8-position modular jack connector for 10Base-T. If a 10Base-5 or 10Base-2 NIC is to be connected to a 10Base-T Ethernet network, an adapter known as a 10Base-T transceiver must be used. This device converts a signal intended for transmission on a 50 W coaxial cable to a signal that can be transmitted over a 100 Ω UTP cable. 10Base-T hub 10Base-T hubs are also referred to as concentrators. Each port on the hub provides a connection point for a UTP cable to a network station. Some models also provide coaxial cable or optical fiber connections for links to other Ethernet segments. In essence, the 10Base-T hub represents the trunk cable of a traditional Ethernet. It shrinks the thick coax trunk cable to a very short length and stations attach to this short coaxial trunk cable through the hub port via a length of UTP cable, which replaces the traditional AUI transceiver cable. Chapter 6 - Ethernet Design 24 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  25. 25. 10Base-T design Basic 10Base-T design While the physical appearance of a 10Base-T Ethernet network is that of a star, it continues to operate logically in linear bus topology. This linear bus is miniaturized and fully contained in the 10Base-T hub. 10Base-T Ethernet uses 24 or 22 AWG unshielded twisted-pair cabling with Category 3 or better classification as specified in the ANSI/TIA/EIA-568-A cabling standard. Two pairs are used, one for transmission (pins 1 and 2) and the other for reception (pins 3 and 6). Collisions are detected and relayed to stations by the hub, which is an active (powered) device. Some considerations when designing a UTP-based 10Base-T Ethernet network are as follows: • The total distance from a hub to a station cannot exceed 100 m (328 ft). • Two hubs can be separated by a maximum of 100 m (328 ft). • A theoretical maximum of 1024 stations can be connected to one 10Base-T LAN. … 10Base-T design, continued Chapter 6 - Ethernet Design 25 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  26. 26. FIGURE 6.6: BASIC 10BASE -T CONFIGURATION 10Base-T NIC with built-in transceiver 10Base-T hub 10Base-T hub Maximum of Maximum of 100 m (328 ft) 100 m (328 ft) Common floor, divided into zones … 10Base-T design, continued Chapter 6 - Ethernet Design 26 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  27. 27. FIGURE 6.7: STRUCTURED 10BASE-T DESIGN Work Area TC UTP Horizontal Cable Cross-connect Hardware 10Base-T hub Patch Cord Cross-connect Hardware Equipment Cable Telecommunications Closet Chapter 6 - Ethernet Design 27 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  28. 28. Other Ethernet networks Combined 10Base-5 and 10Base-2 Thick and thin Ethernet trunk cable can be combined into one network. The combination of thick and thin trunk cable requires using BNC to N-series connector adapters. Combination thick and thin coaxial cable segments used in one combination trunk segment can range from 185 to 500 meters (607 to 1640 feet) in length. To determine the maximum amount of thin coaxial cable that can be used in such an installation, the following equation is used: (Thin coax length x 3.28) + Thick coax length = 500 meters (1640 ft) maximum The constant 3.28 is used to compensate for the lower performance of thin coax cable. Chapter 6 - Ethernet Design 28 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  29. 29. 10Base-FL 10Base-FL Ethernet is also known as Fiber Link Ethernet. It was formally introduced in 1993. In 10Base-FL, a two-fiber optical fiber cable is used in a manner similar to UTP in 10Base-T. One fiber is used for transmission and the other for reception. In place of the 10Base-T hub, a 10Base-FL hub is used. The network also follows a physical star topology with all devices directly connected to the hub. Some considerations for designing a 10Base-FL Ethernet network are as follows: • Multimode, 62.5/125 µm optical 10Base-FL NIC fiber is recommended to connect stations and hubs. • The maximum distance between a 10Base-FL hub station’s NIC and a port on a 10Base-FL hub is Maximum of 2000 m (6560 ft). 2000 m (6560 ft) Two-fiber cable, 62.5/125 µm optical FIGURE 6.8: fiber recommended BASIC 10B ASE -FL CONFIGURATION Common floor, divided into zones Chapter 6 - Ethernet Design 29 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  30. 30. Troubleshooting Ethernet networks Introduction The most important criteria for the success of any network is its reliability. If the LAN is not operating consistently or worse, not operating at all, it is not meeting its primary objective— the ability for users to share devices, software programs and user-created files. Therefore, if the LAN experiences problems, it is important to solve those problems as quickly as possible. The increasing use of structured cabling systems has made network troubleshooting easier. Problems will continue to occur from time to time, but structured cabling systems have helped to eliminate some types of difficulties. Some examples of the benefits of structured cabling systems include the following: • A single station failure should not cause the whole network to fail. • A failure in a single cable will not bring the whole network down. • Fewer connection points represent fewer points of failure. • Much of the diagnostic testing can be done from a central location. Chapter 6 - Ethernet Design 30 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  31. 31. General troubleshooting guidelines Network problems are often blamed on one of the hardware components. That is, the cabling system, the Network Interface Cards, the station or one of the other connected components—which may vary with the technology employed. However, software problems should not be overlooked. Sometimes a new software application that has been installed may conflict with existing applications. Also, problems can happen that are not specifically related to the network technology at all. Problems can occur because of inadequate grounding systems, for example. While some problems are specific to a certain technology, there are also network problems that may occur independent of the networking technology being used. Therefore, some troubleshooting is also independent of the networking technologies. Some general items to consider if a network problem should occur include the following: Station/NIC problems • The Network Interface Card may not be properly seated. That is, it is not making contact and is unable to communicate with the network. It may be necessary to remove the NIC, clean it and reinstall it. • There may be conflicts between the NIC and other boards in the station. In the PC environment, conflicts can occur due to shared IRQs (Interrupt Request Lines), DMAs (Direct Memory Address) lines, and/or I/O (Input/Output) base addresses. • The NIC should be checked to ensure that all jumpers and dip switches are set properly. It is important to have the appropriate documentation at hand to check what the correct settings are. … General troubleshooting Chapter 6 - Ethernet Design 31 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 guidelines, continued
  32. 32. • It should be verified that all power supplies are connected and functioning properly. • Diagnostic software should be used to check for duplicate network addresses. Cabling • The cable should be checked for continuity, kinks, crimps, sharp bends, opens and shorts. • It should be verified that the cabling has been configured properly. Distance limitations should be adhered to. • The cable connecting the station to the network should be visually inspected to check for loose connections. Tripping over a cable connecting the station can loosen a connection point, causing disruptions. • It should be verified that the correct connecting cables are being used and that they are terminated properly. Miscellaneous • Ensure that the products being used adhere to the networking technology being used. • Some vendors offer products with options that will extend the allowable transmission distance. These products may not work in conjunction with other products. They may be proprietary and work only with other specified products. Chapter 6 - Ethernet Design 32 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  33. 33. Troubleshooting Ethernet In the case of Ethernet networks, a distinction needs to be made between coaxial cable based-Ethernet and twisted-pair Ethernet. The type of transmission media used significantly impacts the approach that needs to be taken when troubleshooting the network. Coaxial cable Ethernet For troubleshooting purposes, coax-based Ethernet is at a disadvantage because of its bus topology. Having all devices connected to a single length of cable makes it more difficult to isolate a fault. A single device failure may affect the whole network, a segment of the network or only the device itself. Isolating the cause and location of a failure is a large part of coax Ethernet troubleshooting. The following represent some items to be considered: Cable • Any damage to the trunk cable may cause the network to fail. Damage can be caused by kinks or sharp bends in the cable or be caused by a mechanical device entering the transmission path—new connectors or transceivers. … Troubleshooting Ethernet, Chapter 6 - Ethernet Design 33 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  34. 34. • The cable may need to be checked for opens, shorts and missing terminators. An intact, properly terminated cable should produce a reading of approximately 50 Ω when a DC resistance test is done. If the cable has shorted, the reading will be much lower, in the range of 0 to 10 Ω . If the terminator at the far end is missing or the cable is open, the reading will exceed 50 Ω by a large margin. Time Domain Reflectometry (TDR) testing will provide more details regarding the problem. • Impedance mismatches may have occurred, either due to the use of the wrong type of cable or because the cable is kinked, has sharp bends or is improperly terminated. • If a cable tests open, a portion of the trunk cable may have been disconnected from the network device. Moving a station may cause the cable to come loose. • Ensure that the correct cable type has been used. For example, RG-58 A/U (50 Ω) versus RG-59 A/U (75 Ω) in 10Base-2 environments. Terminators • A terminator can be tested using a DC resistance test to see if it is defective. The DC resistance between the center conductor and the outside shield should be in the 50 Ω range. If it is not, the terminator should be replaced. • Check that cable ends are properly terminated and one terminator is grounded. … Troubleshooting Ethernet, Chapter 6 - Ethernet Design 34 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  35. 35. Transceivers • Verify that power and transceiver cables are properly connected. • It should be verified that the transceiver, the AUI cable and any options are all set to operate with the correct Ethernet version—standard Ethernet or IEEE 802.3 (important in 10Base-5). • Ensure that the minimum distance required between transceivers has not been violated. • If a transceiver appears to be faulty, removing the NIC may confirm this. Disconnecting the NIC will power down the transceiver and the network may recover. • In 10Base-2 networks, the transceiver is built into the NIC and it may have to be replaced to determine if it is causing the problem. Connectors • In the 10Base-2 environment it is important to check for disconnected or poorly assembled T-connectors, used at each station. Network Interface Card (NIC) • NICs equipped with dual connectors for both 10Base-5 and 10Base-2 require that a jumper switch be set to indicate which environment is being used. If the switch is set incorrectly, the NIC cannot communicate with the network. … Troubleshooting Ethernet, Chapter 6 - Ethernet Design 35 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  36. 36. Software considerations • All addresses must be of the same format. While addresses in the IEEE 802.3 standard may be 2 or 6 bytes in length, they must be the same for both source and destination addresses across the entire network. Miscellaneous • Ensure that products being used adhere to the version of the standard being used. This is especially important in 10Base-5 Ethernet which is closely related to the original Ethernet. However, the two technologies are not compatible. Twisted-pair Ethernet The star topology of 10Base-T Ethernet is an advantage for troubleshooting. It makes it easier to isolate failures—first to a single hub and from there to a single port on the hub. Some cabling-related problems that may be encountered on a 10Base-T network include the following: • Cables do not have pin-to-pin continuity. • Terminations do not all follow the same pin configuration—both T568A and T568B are used. • Incorrect components are installed. Chapter 6 - Ethernet Design 36 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  37. 37. Ethernet performance Overview Ethernet is a contention-based technology, meaning that all attached devices have equal access to the transmission channel at all times. This makes the prediction of actual network utilization somewhat more difficult. There are two factors to consider when estimating network performance. The first is the transmission rate—the number of Ethernet frames that can be transmitted in a given time period. The second is an estimate of network traffic produced by users. Below are some sample calculations regarding frame transmission rates and estimations of network traffic. Chapter 6 - Ethernet Design 37 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  38. 38. Frame transmission rate The amount of information carried in an Ethernet frame can vary—it is not a predefined amount. Therefore, an Ethernet frame can vary in size from a minimum of 72 bytes to a maximum of 1526 bytes. This in turn affects the frame transmission rate—the larger the frame, the fewer the number of frames that can be transmitted in a given time period. Additional factors to consider are as follows: • 10 Mbps Ethernet allows for 9.6 microseconds (µs) between frames for error detection and recovery purposes. • There is a bit time of 100 nanoseconds (ns)—this is the time required to transmit one bit of information. Before performing any calculations, please be aware of the following conversions: • 1 millisecond (ms) = 0.001 seconds (10-3) or 1,000 ms per second. • 1 microsecond (µs) = 0.000001 seconds (10-6) or 1,000,000 µs per second. • 1 nanosecond (ns) = 0.000000001 seconds (10-9) or 1,000,000,000 ns per second. Also, • 1 ms = 1,000 µs = 1,000,000 ns. • 1 µs = 1,000 ns. … Frame transmission rate, Chapter 6 - Ethernet Design 38 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  39. 39. The Frame Transmission Rate is calculated as follows: 1 Transmission Rate = Transmission Time The calculation for Transmission Time is as follows: Transmission Time = Time to transmit one frame + Time between frames EXAMPLE 6.1: F RAME TRANSMISSION RATE FOR A 1526 BYTE FRAME SIZE For a maximum frame size of 1526 bytes, the amount of time required to transmit one frame is equal to the following: bytes bits ns Transmission Time = 1526 x8 x 100 + 9.6 microseconds frame byte bit Transmission Time = 1,220,800 ns + 9,600 ns Transmission Time = 1,230,400 ns = 1.2304 ms It would take 1.2304 milliseconds to transmit one frame. … Frame transmission rate, Chapter 6 - Ethernet Design 39 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  40. 40. 1000 ms / second Transmission Rate = 1.2304 ms / frame Transmission Rate = 812.74 frames/ second Therefore, a maximum of 812 complete frames of 1526 bytes can be transmitted in one second. The equivalent transmission rate in bytes is: frames bytes bytes Transmission Rate in bytes = 812 x 1526 = 1,239,112 second frame second The equivalent transmission rate in bits is: bytes bits bits Transmission Rate in bits = 1,239,112 x8 = 9,912,896 second byte second Transmission Rate in bits = 9.912 Mbps … Frame transmission rate, Chapter 6 - Ethernet Design 40 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  41. 41. EXAMPLE 6.2: FRAME TRANSMISSION RATE FOR A 72 BYTE FRAME SIZE For a minimum frame size of 72 bytes, the amount of time required to transmit one frame is equal to the following: bytes bits ns Transmission Time = 72 x8 x 100 + 9.6 microseconds frame byte bit Transmission Time = 57,600 ns + 9,600 ns Transmission Time = 67,200 ns = 0.0672 ms It would take 0.0672 milliseconds to transmit one frame. 1000 ms / second Transmission Rate = 0.0672 ms / frame Transmission Rate = 14,880.95 frames / second Therefore, a maximum of 14,880 complete frames of 72 bytes can be transmitted in one second. … Frame transmission rate, Chapter 6 - Ethernet Design 41 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  42. 42. The equivalent transmission rate in bytes is: frames bytes bytes Transmission Rate in bytes = 14,880 x 72 = 1,071,360 second frame second The equivalent transmission rate in bits is: bytes bits bits Transmission Rate in bits = 1,071,360 x8 = 8,570,880 second byte second Transmission Rate in bits = 8.571 Mbps … Frame transmission rate, Chapter 6 - Ethernet Design 42 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  43. 43. The maximum theoretical throughput of a traditional Ethernet network is 10 Mbps. However, when a maximum frame size is used for all transmissions, the maximum possible throughput on an Ethernet network is 9.912 Mbps. When the minimum frame size is used for all transmissions, the throughput drops to 8.571 Mbps. Since it is unlikely that all frames will be the maximum or minimum size, the actual throughput in most cases will most likely be somewhere between 9.912 and 8.571 Mbps. Please note that this number is not taking into consideration such factors as collisions and retransmissions nor the number of PCs on the network and the performance levels. Taking all of these factors into account, a utilization rate of 50 percent is considered to be a heavy load. When the transmission load reaches 60 to 70 percent, network performance begins to deteriorate significantly. The problem is compounded by the fact that as the transmission load increases, the number of collision and the number of retransmissions increase proportionally. Chapter 6 - Ethernet Design 43 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  44. 44. Estimating network traffic While it is not possible to determine exactly what the amount of network traffic will be, it is possible to make a reasonable estimate. To estimate network traffic, the following steps can be taken in order: 1. Group network stations according to the general activities they perform—managerial, clerical, engineering, design, etc. 2. Estimate the amount of network activity for one station in each group. 3. Multiply the number of stations in a group by the estimated activity for a single station in that group. 4. Add together the total network activity over all the groups connected to the Ethernet segment. 5. The value calculated in step 4 is compared to network throughput to determine percent utilization. … Estimating network traffic, Chapter 6 - Ethernet Design 44 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  45. 45. EXAMPLE 6.3: ESTIMATING NETWORK TRAFFIC In order to illustrate how network traffic load can be estimated in an Ethernet environment, the following scenario is presented. An Ethernet network has a total of 63 users connected. Of these, 20 are in managerial positions, 25 are in clerical positions and 18 are involved in design work. The average amount of network activity for one station in each group is estimated as follows: Managerial Transmission Number of Total bytes size in bytes transmissions per hour File requests 2,500 4 10,000 Loading application programs 400,000 2 800,000 Loading data files 250,000 3 750,000 Saving files 300,000 4 1,200,000 Sending/receiving E-mail 4,000 8 32,000 Total 2,792,000 … Estimating network traffic, Chapter 6 - Ethernet Design 45 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  46. 46. Clerical Transmission Number of Total bytes size in bytes transmissions per hour File requests 2,000 3 6,000 Loading application programs 350,000 2 700,000 Loading data files 150,000 2 300,000 Saving files 100,000 3 300,000 Sending/receiving E-mail 3,500 12 42,000 Total 1,348,000 Design Transmission Number of Total bytes size in bytes transmissions per hour File requests 3,000 5 15,000 Loading application programs 550,000 2 1,100,000 Loading data files 800,000 5 4,000,000 Saving files 850,000 4 3,400,000 Sending/receiving E-mail 2,000 2 4,000 Total 8,519,000 … Estimating network traffic, Chapter 6 - Ethernet Design 46 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  47. 47. Totals Total per person Number of people Total per group Managerial 2,792,000 20 55,840,000 Clerical 1,348,000 25 33,700,000 Design 8,519,000 18 153,342,000 Total 242,882,000 Therefore, network traffic is estimated to be 242,882,000 bytes per hour. Dividing this number by 3600 gives the traffic in bytes per second: 242,882,000 bytes / hour = 67,467.222 bytes / second 3,600 seconds / hour To determine the value in bits per second, the above value is multiplied by 8. 67,467.222 x 8 = 539,737.8 bits / second Dividing this value by 1,000,000 gives a value in Megabits per second (Mbps). 539,737.8 bits/ second = 0.54 Mbps Therefore, the estimated network traffic in Mbps is quite low—network utilization is only at a little more than 5 percent of capacity. … Estimating network traffic, Chapter 6 - Ethernet Design 47 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  48. 48. E XAMPLE 6.4: ESTIMATING NETWORK TRAFFIC WHEN LARGE FILES NEED TO BE ACCESSED In this extension of the above example, the only change is in the work done by the designers. They produce multimedia output resulting in much larger files to transport across the network. It is not unusual to have a multimedia file that is 10 MB (10,000,000 bytes) in size. Recalculating, the values in the above example become: Managerial Transmission Number of Total bytes size in bytes transmissions per hour File requests 2,500 4 10,000 Loading application programs 400,000 2 800,000 Loading data files 250,000 3 750,000 Saving files 300,000 4 1,200,000 Sending/receiving E-mail 4,000 8 32,000 Total 2,792,000 Clerical Transmission Number of Total bytes size in bytes transmissions per hour File requests 2,000 3 6,000 Loading application programs 350,000 2 700,000 Loading data files 150,000 2 300,000 Saving files 100,000 3 300,000 Sending/receiving E-mail 3,500 12 42,000 Total 1,348,000 … Estimating network traffic, Chapter 6 - Ethernet Design 48 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1 continued
  49. 49. Design Transmission Number of Total bytes size in bytes transmissions per hour File requests 3,000 5 15,000 Loading application programs 550,000 2 1,100,000 Loading data files 10,000,000 5 50,000,000 Saving files 10,000,000 4 40,000,000 Sending/receiving E-mail 2,000 2 4,000 Total 91,119,000 Totals Total per person Number of people Total per group Managerial 2,792,000 20 55,840,000 Clerical 1,348,000 25 33,700,000 Design 91,119,000 18 1,640,142,000 Total 1,729,682,000 This translates to 480,467.22 bytes per second or 3,843,737.8 bits per second— 3.84 Mbps. At a network traffic level of 3.84 Mbps, the utilization figure is close to 40 percent of maximum possible capacity. At this point, users will begin to notice a deterioration in network speed. The purpose of this example is to show how applications being introduced today will quickly overload network bandwidth that was considered sufficient for applications used historically. Chapter 6 - Ethernet Design 49 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  50. 50. Ethernet growth Overview An Ethernet network can connect more than a single group of users on a common floor. Ethernet can be used to link hundreds of users throughout a building—or multiple buildings on a campus—using one of the following designs: • Multiple Ethernet trunks or hubs (called segments) can be linked to each other using devices called repeaters to form a single Ethernet network, on which all stations on all segments share one transmission channel. This is the least elaborate method of network growth. • Multiple Ethernet networks can be linked together using devices called bridges to form an Ethernet internetwork. Each network continues to have its own distinct transmission channel available only to attached stations. A bridge device connects to two networks simultaneously, allowing messages to travel between networks. • Finally, multiple Ethernet networks can be linked to a common backbone network, which acts as a transmission channel for all communications between bridges on an internetwork. Each bridge connects both to a network and to the backbone. These methods of expanding Ethernet are discussed in a later chapter. Chapter 6 - Ethernet Design 50 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  51. 51. CONTENTS • Ethernet Overview .................................................................. 1 Introduction ....................................................................................... 1 Goals .................................................................................................. 2 CHAPTER 6 - ETHERNET DESIGN Simplicity ............................................................................................................ 2 Low cost .............................................................................................................. 2 Compatibility ....................................................................................................... 2 OF Addressing flexibility ........................................................................................... 3 Fairness .............................................................................................................. 3 CONTENTS • TABLE Progress ............................................................................................................. 3 High speed .......................................................................................................... 3 Low delay ............................................................................................................ 3 Stability ............................................................................................................... 3 Maintainability ..................................................................................................... 4 Layered architecture ........................................................................................... 4 Functionality ..................................................................................... 4 Ethernet vs. IEEE 802.3 ......................................................... 6 Overview ............................................................................................ 6 Frame formats .................................................................................. 7 Summary ........................................................................................... 8 OF • TABLE Chapter 6 - Ethernet Design 51 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  52. 52. CONTENTS • Designing basic 10Base-5 Ethernet networks .................... 9 Introduction....................................................................................... 9 Components ..................................................................................... 9 RG-8-type coaxial cable .................................................................... 9 CHAPTER 6 - ETHERNET DESIGN Transceivers .................................................................................... 10 Transceiver cable ............................................................................. 11 OF Network Interface Card (NIC) .......................................................... 11 N-series connectors ........................................................................ 12 CONTENTS • TABLE 10Base-5 design ............................................................................ 13 Basic 10Base-5 design - Trunk cable deployment .......................... 13 Basic 10Base-5 design - Transceiver deployment .......................... 15 Basic 10Base-5 design - Station deployment ................................. 16 Designing basic 10Base-2 Ethernet networks .................. 18 Introduction..................................................................................... 18 Components ................................................................................... 19 RG-58 coaxial cable ........................................................................ 19 Network Interface Card (NIC) ......................................................... 19 OF BNC connectors .............................................................................. 20 10Base-2 design ............................................................................ 21 • TABLE Basic 10Base-2 design .................................................................... 21 Chapter 6 - Ethernet Design 52 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  53. 53. CONTENTS • Designing basic 10Base-T Ethernet networks ................. 23 Introduction ..................................................................................... 23 Components ................................................................................... 24 Unshielded twisted-pair cable ......................................................... 24 CHAPTER 6 - ETHERNET DESIGN Network Interface Card (NIC) ......................................................... 24 10Base-T hub .................................................................................. 24 OF 10Base-T design ............................................................................ 25 Basic 10Base-T design ................................................................... 25 CONTENTS • TABLE Other Ethernet networks ..................................................... 28 Combined 10Base-5 and 10Base-2 ............................................ 28 10Base-FL ....................................................................................... 29 OF • TABLE Chapter 6 - Ethernet Design 53 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  54. 54. CONTENTS • Troubleshooting Ethernet networks .................................. 30 Introduction ..................................................................................... 30 General troubleshooting guidelines .......................................... 31 Station/NIC problems .................................................................... 31 CHAPTER 6 - ETHERNET DESIGN Cabling .......................................................................................... 32 Miscellaneous ................................................................................ 32 OF Troubleshooting Ethernet ............................................................ 33 Coaxial cable Ethernet .................................................................... 33 CONTENTS • TABLE Cable ............................................................................................. 33 Terminators ................................................................................... 34 Transceivers .................................................................................. 35 Connectors .................................................................................... 35 Network Interface Card (NIC) ....................................................... 35 Software considerations ................................................................ 36 Miscellaneous ................................................................................ 36 Twisted-pair Ethernet ...................................................................... 36 Ethernet performance .......................................................... 37 Overview .......................................................................................... 37 OF Frame transmission rate .............................................................. 38 • TABLE Estimating network traffic ............................................................ 44 Ethernet growth .................................................................... 50 Overview .......................................................................................... 50 Chapter 6 - Ethernet Design 54 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  55. 55. • EXAMPLES • EXAMPLES • EXAMPLES • Example 6.1: Frame transmission rate for a 1526 byte frame size ................................ 39 CHAPTER 6 - ETHERNET DESIGN Example 6.2: Frame transmission rate for a 72 byte frame size .................................... 41 Example 6.3: Estimating network traffic ................................. 45 Example 6.4: Estimating network traffic when large files need to be accessed ....................... 48 Chapter 6 - Ethernet Design 55 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1
  56. 56. • FIGURES • FIGURES • FIGURES • FIGURES • Figure 6.1: IEEE 802.3 frame format versus Ethernet frame format ............................................. 7 CHAPTER 6 - ETHERNET DESIGN Figure 6.2: Deploying the 10Base-5 trunk cable .................. 14 Figure 6.3: 10Base-5 transceiver deployment ...................... 15 Figure 6.4: 10Base-5 station deployment .............................. 17 Figure 6.5: 10Base-2 deployment .......................................... 22 Figure 6.6: Basic 10Base-T configuration ............................. 26 Figure 6.7: Structured 10Base-T design ................................ 27 Figure 6.8: Basic 10Base-FL configuration ........................... 29 Chapter 6 - Ethernet Design 56 © 1996, BICSI LAN Design Manual - CD-ROM, Issue 1

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