Addis Ababa University
Addis Ababa Institute of Technology
School of Electrical and Computer
Engineering
HIGH PERFORMANCE NETWORKS
Assignment One on
Comparison of the Three High Performance LAN Protocols
Name: Henok Abebe
ID No: GSE/3802/12
Submitted To: Dr. Yihenew Wondie
May 2020
Contents
1. Introduction .........................................................................................................................1
1.1. The Emergence of High‐speed LANs ............................................................................1
1.2. Requirements for High‐Speed LANs .............................................................................1
1.3. Classifications of High Speed LANs .............................................................................1
2. The Generation of Ethernet..................................................................................................2
2.1. Ethernet Protocol ..........................................................................................................2
2.2. Fast Ethernet Protocol ...................................................................................................3
2.3. Gigabit Ethernet Protocol ..............................................................................................4
3. Fiber Channel Protocol ........................................................................................................4
4. Wireless LAN Protocol .......................................................................................................5
4.1. IEEE 802.11 Wlan Protocol ..........................................................................................6
4.2. ETSI HiperLAN Protocol..............................................................................................7
i
1. INTRODUCTION
1.1. THE EMERGENCE OF HIGH‐SPEED LANS
The speed and computing power of personal computers has continued to enjoy explosive
growth. Today’s more powerful platforms support graphics intensive applications and ever more
elaborate graphical user interfaces to the operating system. organizations have recognized the LAN
as a viable and indeed essential computing platform, resulting in the focus on network computing.
Both approaches involve the frequent transfer of potentially large volumes of data in a transaction‐
oriented environment. The effect of these trends has been to increase the volume of data to be
handled over LANs and, because applications are more interactive, to reduce the acceptable delay
on data transfers.
1.2. REQUIREMENTS FOR HIGH‐SPEED LANS
Centralized server farms: In many applications, there is a need for user or client systems to
be able to draw huge amounts of data from multiple centralized servers, called server farms. An
example is a color publishing operation, in which servers typically contain hundreds of gigabytes
of image data that must be downloaded to imaging workstations. As the performance of the servers
themselves has increased, the bottleneck has shifted to the network.
Power workgroups: These groups typically consist of a small number of cooperating users
who need to draw massive data files across the network. Examples are a software development
group that runs tests on a new software version, or a computer aided design (CAD) company that
regularly runs simulations of new designs. In such cases, large amounts of data are distributed to
several workstations, processed, and updated at very highspeed for multiple iterations.
High‐speed local backbone: As processing demand grows, LANs proliferate at a site, and
high‐speed interconnection is necessary.
1.3. CLASSIFICATIONS OF HIGH SPEED LANS
The most widely used high‐speed LANs today are based on Ethernet and were developed by the
IEEE 802.3 standards committee. To keep pace with the changing local networking needs of
business, a number of approaches to high speed LAN design have become commercial products.
The most important of these are:
1
Gigabit Ethernet: The extension of 10‐Mbps CSMA/CD(Standard Ethernet) to higher speeds
is a logical strategy because it tends to preserve the investment in existing systems.
Fiber Channel: This standard provides a low‐cost, easily scalable approach for achieving very
high data rates in local areas.
High‐speed wireless LANs: Wireless LAN technology and standards have at last come of
age, and high‐speed standards and products are being introduced.
2. THE GENERATION OF ETHERNET
The original Ethernet was created in 1976 at Xerox’s Palo Alto Research Center (PARC). Since
then, it has gone through four generations.
2.1. ETHERNET PROTOCOL
Ethernet protocols (10Base-T) refer to the family of local-area networks (LAN) covered
by a group of IEEE 802.3 standards. In the Ethernet standard, there are two modes of operation:
half-duplex and full-duplex. In the half-duplex mode, data are transmitted using the popular
Carrier-Sense Multiple Access/Collision Detection (CSMA/CD) protocol on a shared medium.
The main disadvantages of the half-duplex are the efficiency and distance limitation, in which the
link distance is limited by the minimum MAC frame size. This restriction reduces the efficiency
drastically for high-rate transmission. Therefore, the carrier extension technique is used to ensure
the minimum frame size of 512 bytes in Gigabit Ethernet to achieve a reasonable link distance.
Four data rates are currently defined for operation over optical fiber and twisted-pair cables:
✓ 10 Mbps—10Base-T Ethernet (802.3)
✓ 100 Mbps—Fast Ethernet (802.3u)
✓ 1000 Mbps—Gigabit Ethernet (802.3z)
✓ 10-Gigabit Ethernet - IEEE 802.3ae
The Ethernet system consists of three basic elements:
➢ The physical medium used to carry Ethernet signals between computers,
➢ A set of medium access control rules embedded in each Ethernet interface that allows
multiple computers to fairly arbitrate access to the shared Ethernet channel, and
➢ An Ethernet frame that consists of a standardized set of bits used tocarry data over the
system.
As with all IEEE 802 protocols, the ISO data link layer is divided into two IEEE 802 sublayers,
the Media Access Control (MAC) sub-layer and the MAC-client sublayer. The IEEE 802.3
physical layer corresponds to the ISO physical layer.
2
The MAC sublayer has two primary responsibilities:
✓ Data encapsulation, including frame assembly before transmission, and frame parsing/error
detection during and after reception
✓ Media access control, including initiation of frame transmission and recovery from
transmission failure
The MAC-client sublayer may be one of the following:
✓ Logical Link Control (LLC), which provides the interface between the Ethernet MAC and
the upper layers in the protocol stack of the end station. The LLC sublayer is defined by
IEEE 802.2 standards.
✓ Bridge entity, which provides LAN-to-LAN interfaces between LANs that use the same
protocol (for example, Ethernet to Ethernet) and also between different protocols
(for example, Ethernet to Token Ring). Bridge entities are defined by IEEE 802.1
standards.
All stations attached to an Ethernet are connected to a shared signaling system, also called the
medium. To send data a station first listens to the channel and, when the channel is idle then
transmits its data in the form of an Ethernet frame, or packet. After each frame transmission, all
stations on the network must contend equally for the next frame transmission opportunity. Access
to the shared channel is determined by the medium access control (MAC) mechanism embedded
in the Ethernet interface located in each station. The medium access control mechanism is based
on a system called Carrier Sense Multiple Access with Collision Detection (CSMA/CD).
As each Ethernet frame is sent onto the shared signal channel, all Ethernet interfaces look at the
destination address. If the destination address of the frame matches with the interface address, the
frame will be read entirely and be delivered to the networking software running on that computer.
All other network interfaces will stop reading the frame when they discover that the destination
address does not match their own address. When it comes to how signals flow over the set of media
segments that make up an Ethernet system, it helps to understand the topology of the system.
2.2. FAST ETHERNET PROTOCOL
Fast Ethernet (100BASE-T) offers a speed increase ten times that of the 10BaseT Ethernet
specification, while preserving such qualities as frame format, MAC mechanisms, and MTU. Such
similarities allow the use of existing 10BaseT applications and network management tools on Fast
Ethernet networks. Officially, the 100BASE-T standard is IEEE 802.3u. Like Ethernet, 100BASE-
T is based on the CSMA/CD LAN access method. There are several different cabling schemes that
can be used with 100BASE-T, including:
➢ 100BASE-TX: two pairs of high-quality twisted-pair wires
➢ 100BASE-T4: four pairs of normal-quality twisted-pair wires
➢ 100BASE-FX: fiber optic cables
3
2.3. GIGABIT ETHERNET PROTOCOL
Ethernet protocols refer to the family of local-area network (LAN) covered by the IEEE
802.3 standard. The Gigabit Ethernet protocol is based on the Ethernet protocol but has tenfold
speed increase over Fast Ethernet, using shorter frames with carrier Extension. Carrier Extension
is a simple solution, but it wastes bandwidth. Packet Bursting is “Carrier Extension plus a burst of
packets”. Burst mode is a feature that allows a MAC to send a short sequence (a burst) of frames
equal to approximately 5.4 maximum-length frames without having to relinquish control of the
medium.
The Gigabit Ethernet standards are fully compatible with Ethernet and Fast Ethernet installations.
They retain Carrier Sense Multiple Access/ Collision Detection (CSMA/CD) as the access method.
Full-duplex as well as half duplex modes of operation are supported, as are single-mode and multi-
mode fiber and short-haul coaxial cable, and twisted pair cables.
IEEE 802.3z defines the Gigabit Ethernet over fiber and cable and has the physical media standard
1000Base-X (1000BaseSX– short wave covering up to 500m, and 1000BaseLX– long wave covers
up to 5km). The IEEE 802.3ab defines the Gigabit Ethernet over the unshielded twisted pair wire
(1000Base-T covers up to 75m).
Many large-scale digital CCTV networks use switchers with individual ports of 100 Mb/s
per channel and then such switchers interconnect between themselves using the Gigabit
Ethernet.
3. FIBRE CHANNEL PROTOCOL
As the speed and memory capacity of personal computers, workstations, and servers have
grown, and as applications have become ever more complex with greater reliance on graphics and
video, the requirement for greater speed in delivering data to the processor has grown. This
requirement affects two methods of data communications with the processor: I/O channel and
network communications.
An I/O channel is a direct point‐to‐point or multipoint communications link, predominantly
hardware based and designed for high speed over very short distances. The I/O channel transfers
data between a buffer at the source device and a buffer at the destination device, moving only the
user contents from one device to another, without regard to the format or meaning of the data.
Fibre channel combines both Simplicity and speed of channel communications.
The Fibre Channel network is quite different from the IEEE 802 LANs. Fibre Channel is
more like a traditional circuit‐switching or packetswitching network, in contrast to the
typical shared‐medium LAN. Fibre Channel need not be concerned with medium access
control issues.
The key elements of a Fibre Channel network are the end systems, called nodes, and the network
itself, which consists of one or more switching elements. The collection of switching elements is
4
referred to as a fabric. These elements are interconnected by point-to-point links between ports on
the individual nodes and switches. Communication consists of the transmission of frames across
the point-to-point links. Each node includes one or more ports, called N_ports, for interconnection.
Similarly, each fabric-switching element includes multiple ports, called F_ports.
Interconnection is by means of bidirectional links between ports. Any node can
communicate with any other node connected to the same fabric using the services of the fabric.
All routing of frames between N_ports is done by the fabric. Frames may be buffered within the
fabric, making it possible for different nodes to connect to the fabric at different data rates. A fabric
can be implemented as a single fabric element with attached nodes (a simple star arrangement) or
as a more general network of fabric elements. In either case, the fabric is responsible for buffering
and for routing frames between source and destination nodes.
Features of Fibre Channel protocols are:
➢ Full‐duplex links with two fibers per link
➢ Performance from 100 Mbps to 800 Mbps on a single line (full‐duplex 200 Mbps to 1600
Mbps per link)
➢ Support for distances up to 10 km
➢ High‐capacity utilization with distance insensitivity
➢ Greater connectivity than existing multi drop channels
➢ Broad availability (i.e., standard components)
➢ Support for multiple cost/performance levels, from small systems to supercomputers
➢ Ability to carry multiple existing interface command sets for existing channel and network
protocols
➢ The transmission media options that are available under Fibre Channel include shielded
twisted pair, video coaxial cable, and optical fiber.
As a practical scenario the Fibre Channel standards define a high-speed data transfer
mechanism that can be used to connect workstations, mainframes, supercomputers, storage
devices and displays.
4. WIRELESS LAN PROTOCOL
wireless LAN or WLAN is a wireless local area network that uses radio waves as its
carrier. The last link with the users is wireless, to give a network connection to all users in a
building or campus, the backbone network usually uses cables. Wireless communication is one
of the fastest‐growing technologies. The demand for connecting devices without the use of
cables is increasing everywhere. Wireless LANs can be found on college campuses, in office
buildings, and in many public areas.
5
Two main standard families for Wireless Lan are:
➢ IEEE 802.11 (802.11b, 802.11a, 802.11g...)
➢ ETSI Hiperlan (Hiperlan Type 1, Type 2, HiperAccess, HiperLink...)
4.1. IEEE 802.11 WLAN PROTOCOL
IEEE 802.11 defined the specifications for a wireless LAN which covers the physical
and data link layers. There are currently four specifications in the family: 802.11, 802.11a,
802.11b, and 802.11g. All four use the Ethernet protocol and CSMA/CA (carrier sense multiple
access with collision avoidance instead of CSMA/CD) for path sharing. if the medium is sensed
to be free the node access medium for transmission; if the medium is busy, the node backs off
(defers access) for a contention time, when back off time expires the station can access the
medium.
➢ 802.11 applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz
band using either frequency hopping spread spectrum (FHSS) or direct sequence spread
spectrum (DSSS).
➢ 802.11a -- an extension to 802.11 that applies to wireless LANs and provides up to 54
Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing
(OFDM) encoding scheme rather than FHSS or DSSS. The 802.11a specification applies
to wireless ATM systems and is used in access hubs.
➢ 802.11b (also referred to as 802.11 High Rate or Wi-Fi) an extension to 802.11 that applies
to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps)
in the 2.4 GHz band. 802.11b uses only DSSS and it is a modification of the original 802.11
standard, allowing wireless functionality comparable to Ethernet.
➢ 802.11g offers wireless transmission over relatively short distances at 20 – 54 Mbps in the
2.4 GHz band. 802.11g also uses the OFDM encoding scheme.
Problems making WLAN design a complicated task:
✓ Address is not a physical location: The station is not always stationary. The address does
not give any information about location.
✓ Dynamically changed topology: The network connectivity is partial at times.
✓ Medium boundaries are soft: The communication range cannot be determined precisely in
wireless networks.
✓ Hidden and exposed terminal problems: Some nodes should (not) be allowed to
communicate at a certain time.
6
There are four application areas for wireless LANs:
✓ LAN extension,
✓ Cross- building interconnect,
✓ Nomadic access and
✓ Ad hoc networks.
4.2. ETSI HIPERLAN PROTOCOL
HIPERLAN is an European (ETSI) standardization initiative for a HIgh PERformance
wireless Local Area Network. Radio waves are used instead of a cable as a transmission
medium to connect stations. Either, the radio transceiver is mounted to the movable station as
an add-on and no base station has to be installed separately, or a base station is needed in
addition per room. The stations may be moved during operation-pauses or even become
mobile. The max. data rate for the user depends on the distance of the communicating stations.
With short distances (<50 m) and asynchronous transmission a data rate of 20 Mbit/s is
achieved, with up to 800 m distance a data rate of 1 Mbit/s are provided. For connection-
oriented services, e.g. video-telephony, at least 64 kbit/s are offered.
HiperLAN Type 1
✓ Developed by ETSI during 1991 to 1996
✓ Goal: to achieve higher data rate than IEEE 802.11 data rates: 1~2 Mbps, and to be
used in ad hoc networking of portable devices
✓ Support asynchronous data transfer, carrier-sense multiple access multiple access
with collision avoidance (CSMA/CA), no QoS guaranteed.
HiperLANType 2
✓ Next generation of HiperLANfamily: Proposed by ETSI BRAN (Broadband Radio
Access Networks) in 1999, and is still under development.
✓ Goal: Providing high-speed (raw bit rate ~54Mbps) communications access to
different broadband core networks and moving terminals
✓ Features: connection-oriented, QoS guaranteed, security mechanism, highly
flexibility
✓ Optimal throughput scheme
✓ Flexible transmission modes
HiperAccessand HiperLink: In parallel to developing the HIPERLAN Type 2 standards,
ETSI BRAN has started work on standards complementary to HIPERLAN Type 2
7
Typical application scenarios
✓ HiperLAN: A complement to present-day wireless access systems, giving high
data rates to end-users in hot-spot areas.
✓ Typical app. Environment: Offices, homes, exhibition halls, airports, train
stations, etc.
✓ Different with Bluetooth, which is mainly used for linking individual
communication devices within the personal area network
Table1: Comparison of HiperLAN2 with Peers
Pros
✓ High rate with QoS support: Suitable for data and multimedia app.
✓ Security mechanism
✓ Flexibility: different fixed network support, link adaptation, dynamic frequency
selection…
Cons
✓ High cost
✓ Tedious protocol specification
✓ Limited outdoor mobility
✓ No commercial products in market till now
