Gigabit Ethernet Development and Testing - … Ethernet Development and Testing ... Communications...

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Guide Series

Gigabit EthernetDevelopment and Testing

The Right ProtocolAnalyzer

Table of ContentsIntroduction ..........................................................................2

The State of Ethernet Architectures................................3

Ethernet Standardization .................................................6

Architecture Development ...............................................8

Ethernet Physical Media ................................................11

Testing Issues.......................................................................14

Full versus Half Duplex .................................................16

Device Capability and Performance ..............................16

Global versus Segment Testing ......................................17

Protocol Analyzers ..............................................................18

Protocol Analyzers and Gigabit Ethernet...........................22

The Benefits of Protocol Analyzers....................................25

Attributes of a Protocol Analyzer ..................................28

Summary.............................................................................29

Glossary...............................................................................31

About the Editor…Mr. Ryan is the is the Editor in Chief of the ATG series of Technology Guides on

Communications and Web issues and is the author of numerous technology papers

on various aspects of networking. Mr. Ryan has developed and taught numerous

courses in network analysis and design for carriers, government agencies and private

industry. He has provided consulting support in the area of WAN network design,

negotiation with carriers for contract pricing and services, technology acquisition,

customized software development for network administration, billing and auditing of

telecommunication expenses, project management, and RFP generation. He was the

president and founder of Connections Telecommunications, Inc., a Massachusetts

based company specializing in consulting, education and software tools which address

network design and billing issues. Mr. Ryan is a member of the Networld+Interop

Program Committee. He holds a B.S. degree in electrical engineering.

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Copyright © 1997 by The Applied Technologies Group, One Apple Hill,

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2 • Gigabit Ethernet Development and Testing

Gigabit Ethernet has quickly become an important

part of the evolution of local networking. This is

primarily due to new, bandwidth hungry applications,

their mission-critical role in business solutions, and the

significant pressure to develop and deploy very high

speed backbones. Gigabit Ethernet technology is being

rushed to completion, driven by these market forces and

by competition from other high bandwidth backbone

solutions. The Gigabit Ethernet Alliance is moving

quickly on many fronts to assure creation of a universal

set of standards that are not only compatible with

existing 10 and 100Base-T technologies, but also

compatible with a variety of Gigabit Ethernet offerings

from the Alliance community itself. Because of this

urgency, there is a need in the industry for testing and

diagnostic systems—protocol analyzers—that will allow

fast, accurate, and comprehensive product development.

This Technology Guide explores the reasons for the

success of Gigabit Ethernet, reviews the current state of

protocol analyzers and testing capabilities, and looks at

the issues within the Gigabit Ethernet development

community. It examines the attributes of testing and

diagnosis systems that are most important to Gigabit

Ethernet protocol analysis and illustrates the cost bene-

fits of choosing the right protocol analyzer systems.

Introduction

Over the past two decades, there have been tremen-

dous changes in the ways Information Technology (IT)

is being deployed in businesses and, increasingly, in our

homes. Improvements in component technologies, better

techniques, languages for software engineering, and the

emergence of open (multi-vendor) distributed systems

allow increasingly sophisticated business applications

which lead to more and more network traffic with a

wider range of Quality of Service (QoS) demands.

High-capacity, high-quality, high-efficiency ubiquitous

networks are the key ingredient in this new computing

environment. Designing, building, and maintaining these

networks has become a critical success factor for the IT

industry of the 1990s.

Ethernet-based local area networks are the

preferred solution for the premises and campus

(deployed at over 80% of the installed connections,

according to IDC). Ethernet has been a fact of corpo-

rate life for more than fifteen years and has proven to

be extremely successful in office connectivity. The total

cost of Ethernet ownership has decreased substantially

over the years. The preferred configuration has

changed from a shared bus structure to a switched star,

and overall ease of use has improved to the point where

10Mb/s Ethernet is now considered to be a commodity

product. Re-engineering Ethernet to accommodate

emerging needs for higher speeds, to permit real time

multimedia transport, and to fully exploit the high

capacity of fiber optic media has become both a chal-

lenge and an opportunity for the IT community.

Most recently, the major focus of developments has

been on extending the various standards that define

Ethernet to allow cost-effective operations at one Gigabit

per second (1000Mb/s). The race is on to complete the

standards so that interoperable products can be delivered

to waiting purchasers. Conformance testing and perfor-

mance measuring of emerging Gigabit Ethernet prod-

ucts are and will continue to be a hot topic.

The State of Ethernet ArchitecturesThe basic Ethernet architecture and protocols

were conceived in the 1970s and became mainstream

technologies in the 1980s. Originally intended simply

as a way to share coaxial cable, Ethernet has become

the primary network infrastructure for the premises

and campus environments. The evolution of Ethernet

has mirrored the development of desktop computing

and distributed systems.

Technology Guide • 3

• New types of distributed application(s) (data

warehousing, network computing, scientific

modeling and groupware, for example) require

such processing-intensive network services as

multicast transport, streaming, and virtual LANs.

• Finally, workstations and servers are being

configured in ways that increase network traffic

(e.g., server farms, network computers, and

mobile access).

In addition, we are on the verge of an explosion

in multimedia networking. Video-conferencing, for

example, requires bandwidth in the megabit ranges

combined with stringent qualities of service (low

latency, low jitter). Other important applications

include broadcast and multicast video, Internet-based

training, audio-conferencing, and multimedia playback

from servers. Producing network support for these

applications is best accomplished through the use and

deployment of scalable technologies that avoid the

need for “fork-lift” upgrades to replacement technolo-

gies. This approach minimizes conversion costs,

reduces the need for personnel re-training, and elimi-

nates the re-tooling of network management systems.

Computer processing speeds continue to increase

at a rapid rate (Moore’s law predicts a doubling in

chip power roughly every 18 months). One result of

this is the ability to gather, process, and disseminate

increasingly large volumes of data in real time.

Network adapters operating at 100Mb/s (Fast

Ethernet) are expected to be built into PCs very soon,

and multimedia computing with its combination of

voice, data, image, and video content will easily make

use of this network capacity. Server technology, on the

other hand, now enables server CPUs to fully utilize

multiple Fast Ethernet connections. Servers are

increasingly collected into “server farms” (which is the

re-centralization of critical processing functions)

requiring client/server connections to go beyond the

Technology Requirements

Most organizations depend heavily on data

networks, with many such networks now considered to

be mission critical. Data networks have grown to be as

ubiquitous and as essential as the telephone infrastruc-

ture, and have become an equally essential part of our

social and business lives. Over the past twenty years,

10Mb/s Ethernet has become the workhorse of

premises-based networking (the data communications

equivalent of the telephone PBX) with some 100

million Ethernet nodes currently in operation world-

wide. Ethernet has also proven to be a surprisingly

adaptable and durable set of standards and is the

incumbent to beat for local networking.

Network managers, recognizing their corporate

dependency on telecommunications, are electing to

adapt well-known technologies rather than face major

architectural changes. At the desktop, this means

extending the life of Ethernet and allowing a gradual,

demand-driven transition. Increased scalability for

Ethernet has been the major goal for a number of

years, leading first to 100Mb/s and now to 1Gb/s

speeds.

Is a 100-fold increase in LAN transmission speed

necessary? Is it desirable? And, is it an urgent require-

ment? While the real answer to these questions

depends on the specifics of each installation, the

following trends provide the clues.

• The total number of network users is increasing.

This is partly due to the conversion of processes

to fully automated forms, and to the result of

graphics-based Intranets and the Internet, which

lead to higher volumes of traffic.

• Users now communicate more frequently (e.g.,

use of e-mail and Internet news services) and

many access remote services more often

increasing the transaction loads on servers and

networks.

4 • Gigabit Ethernet Development and Testing Technology Guide • 5

802.3z

802.3ab

802.3x

802.1q

802.1p

Extend the 802.3

CSMA/CD protocol to

an operating speed of

1,000Mb/s including

MAC parameters, physical

layers, repeater and

management parameters

Physical layer parameters

and specifications for

1,000Mb/s operation

over 4 pair of Category 5

balanced copper cabling,

type 1000Base-T

Specification for 802.3

Full Duplex Operation -

(for all speeds)

Standard for Virtual

Bridged Local Area

Networks (VLANs) -

(for all speeds)

Supplement to Media

Access Control Bridges:

Traffic Class Expediting

and Dynamic Multicast

Filtering-(for all speeds)

Started June, 1996;

standard targeted

for mid-1998

Started March,

1997

Started June, 1995

and approved

March, 1997

Started September,

1996

Started September,

1995

Standard Title Timing

local Ethernet segment. The traditional 80/20 rule for

LANs (80% of the traffic stays on the local segment

while 20% is routed elsewhere) has thus been reversed.

All of this is leading to new and more challenging

demands on Ethernet-based networks.

Ethernet StandardizationStandardization for Ethernet is primarily

conducted as part of the Institute of Electrical and

Electronic Engineers (IEEE) standards program.

Completed standards are submitted to the ISO for

formal review and approval. The Internet-based IETF

also produces standards relating to internetworking and

network management.

These IEEE committees are actively working on

standards in support of, or at least directly related to,

the goals of Gigabit Ethernet development.

One of the objectives of the standards effort is to

provide both switching and repeating hub versions (as

with 10/100Mb/s Ethernet). The use of CSMA/CD

mode for shared-media and a full duplex mode for

dedicated segments will both be supported. Another

goal is to maximize the allowable distances for Gigabit

Ethernet. Initial products will require fiber optic media

but advances in silicon technology and digital signal

processing will eventually enable cost-effective support

for Category 5 unshielded twisted pair wiring

(projected for 1999 or later).

Gigabit Ethernet standards development is

proceeding rapidly, with extremely good consensus on

basic directions, and should be technically complete in

1997 (with formal adoption by the IEEE in early 1998).

More than 200 individuals representing over 50 compa-

nies have been involved in the standards activities thus

far. The Gigabit Ethernet Alliance is the prerequisite

industry support and market enabling consortium,

which has expanded to over 100 member companies

within the past year.


Figure 1A. Shared Bus Ethernet

Figure 1B. Intelligent Hub Ethernet

H

H

Intelligent Hub Ethernet

Server

Shared BUS Ethernet

Server

Architecture DevelopmentThe Ethernet architecture is traditionally defined

primarily by its use of the CSMA/CD (Carrier Sense

Multiple Access with Collision Detection) protocol. This

protocol, which supports physical media sharing on a

first-come, first-served basis, was most important when a

true bus wiring structure was being used. Gigabit

Ethernet networks will use the same logical link control

protocols, the same CSMA/CD protocols, the same

frame format, and the same frame size as the other

versions of Ethernet. Gigabit Ethernet also uses the same

management objects as other versions, eliminating the

need to revise or re-work element management systems.

Ethernet implementations in the early 1980s used

coaxial cable configured in a bus structure operating at

10Mb/s half duplex (as illustrated in Figure 1A). Second

generation Ethernet networks incorporated fiber optics

and twisted pair copper wiring with hub concentrators

and either shared or dedicated media. Segmentation of

workstations onto separate wires provided a means of

avoiding collisions, and copper wiring allowed much

more flexible, cost-effective designs. Next, port switching

(equivalent to multi-port bridging) was introduced as a

hub replacement, allowing multiple paths between

segments (effectively increasing throughput). Full duplex

operation became possible with dedicated segments.

Development of Fast Ethernet standards increased the

speed of the network to 100Mb/s, which was especially

valuable for inter-switch connections and server access.

Premises networks today allow various combinations of

media types, component types, and structures, all using

the same Ethernet Data Link family of protocols.


Ethernet Physical MediaAs with its predecessors, Gigabit Ethernet is being

designed to perform with certain specific performance

goals in mind and to operate over specific distance

limits. The distances that are being specified are illus-

trated below.

Gigabit Ethernet will be fully compatible with existing

networks and will preserve user investments in applica-

tions, network operating systems, protocols, and network

management. In particular, Gigabit Ethernet does this

by preserving the 802.3 frame format, CSMA/CD

protocols and managed object specifications.

Initially, Gigabit Ethernet will be deployed using

fiber optic media and the full duplex mode of opera-

tion. The Fiber Channel Physical Layer standard, oper-

ating at line speed of 1,250Mb/s, which results in

1,000Mb/s of delivered data after consideration for

8B10B coding, will be used. Half duplex modes will

only be offered when gigabit speeds to the desktop

become a requirement.

The following table lists the cabling designations to

be used with Gigabit Ethernet. Note that standards for

Cat 5 copper wire are not expected to be completed

until 1999.

Ethernet

(10Base-T)

Fast Ethernet

(100Base-T)

Gigabit

Ethernet

(1000Base-X)

--Goals--

Data Rate

Twisted Pair (Cat 5)

Shielded

TWP/Coax

Multimode Fiber

Single-mode Fiber

10Mb/s

100m (min)

500m

2Km

25Km

100Mb/s

100m

100m

412m(H),2Km (F)*

20Km

1000Mb/s

100m

25m

500m

3Km

Figure 1C. Switched Ethernet

As noted earlier, faster workstations and advanced

applications can easily generate traffic that exceeds the

capacity of a 10Mb/s Ethernet segment. New applica-

tions that incorporate graphics, audio, and video

components can be bandwidth hogs (files from 10-100

Mb/s are not unusual), and even word processing docu-

ments are now hundreds of times larger than they were

just a few years ago. Video and audio-conferencing,

video streaming, Web based training, 3D modeling,

distributed CAD/CAM designs, medical imaging, and

many other similar applications have requirements for

high speed and high quality network services. To meet

these needs, Fast Ethernet (100mb/s) is being

introduced for horizontal distribution, and even higher

speeds are needed for the backbone.

Switched Ethernet

H H

Server

Server Server

Server


Figure 2. Intelligent Hub Ethernet

Each workstation requires a bandwidth from both

its immediate access link and the backbone links

through which they communicate. The majority of

Ethernet LANs today use 10Mb/s shared or dedicated

to the workstation, with high performance workstations

beginning to use Fast Ethernet. The higher the speed

to the end system, the more capacity is required on the

backbone. Hence, while today’s 10Mb/s LANs use

100Mb/s backbones, soon the workstation will need

100Mb/s while the local backbones will be at least

1,000Mb/s.

Increasing the utilization of an Ethernet segment

(by adding more users or by having more applications

that communicate) increases congestion and the chance

of collisions. One solution is to increase the segmenta-

tion (smaller LANs, with the limit being one station per

segment) but this primarily pushes the load onto the

backbone network. This is made even more acute by

the creation of server farms (centralization of servers)

that require the majority of traffic to transfer across

multiple segments. At some point in LAN growth, it

becomes necessary to increase capacity, and this is

where Gigabit Ethernet provides relief.

SWSW

Switch

Switch

100/1000Mbps

100/1000Mbps

100Mbps

1000Mbps

FDXSwitch

Server

Server Server

Because Gigabit Ethernet follows the same Data

Link Layer standards as its predecessors, it also suffers

from the same technical limitations. In particular,

Ethernet has no native support for Quality of Service

such as real time data transfer (due to the variable

length frames and potential for collision delays).

Standards for explicit support of QoS being developed

in IEEE 802.1q and in the IETF (RSVP and RTP) will

improve performance in this area but still cannot over-

come the limitations of variable frame sizes.

Hierarchy of Speeds

Gigabit Ethernet is one part of the hierarchy of

speeds used by premises networks, which include, for

example, 10Mb/s at the workstation, 100Mb/s between

floors, and 1,000Mb/s for buildings in a campus or

within a server farm (see Figure 2).

Copper

Fiber Optic

1000Base-CX

1000Base-T

1000Base-SX

1000Base-LX

150 ohm shielded

twisted pair

(short haul)

Category 5

unshielded twisted

pair (long haul)

850nm multimode

fiber

1300nm

multimode and

Single-mode fiber

Designation Wiring Type


switch-to-workstation. Gigabit Ethernet products are

expected to be used initially for:

• backbone, server, switch, and gateway

interconnections;

• switch-to-workstation links for specialized

multimedia applications, distributed processing,

imaging, medical, CAD/CAM, and pre-press

applications; and

• upgrades to 10/100Mb/s connections for very

high performance workstations.

Figure 3.

Testing will be required at all levels of the

networking hierarchy. It is the high performance back-

bone that offers the greatest challenge for test tool

designers. The high wire speeds needed for Gigabit

Ethernet make real time data capture a difficult task,

the vast quantities of data that could be flowing

require large amounts of data storage, and the impossi-

bility of examining all the data manually makes inte-

gration of expert analysis and diagnosis a basic

requirement for developing and deploying Gigabit

Ethernet. The premises/campus backbone provides

the “glue” that holds the network together, so failures

will have a corresponding wide impact.

Switch SwitchRouter

Hub

Workstation

Server

Product Positioning

The overall market potential for Gigabit Ethernet is

huge—it will eventually include all of the existing lower

speed Ethernet nodes. In practice, however, ordinary

office PCs whose main task is e-mail and word

processing will neither need to send nor be able to

consume data at 1,000Mb/s (at least not yet). The

market for Gigabit Ethernet will develop first in the

backbone and inter-switch levels and will penetrate the

desktop over time as companies upgrade their IT infra-

structure and expand the range of applications they use.

A number of pre-standard products have already

been announced and/or delivered to the marketplace.

Most of the large producers have at least created state-

ments of direction and are active in the standards

committees. Hewlett-Packard has announced the

industry’s first portable Gigabit Ethernet protocol

analyzer, which should help to accelerate the deploy-

ment of Gigabit Ethernet technologies. Other devices

that are being promoted for use with Gigabit Ethernet

include buffered distributors (full duplex, flow

controlled hubs) and server switches (a switch targeted

at server-to-server communications).

One of the primary selling features of Gigabit

Ethernet is its price performance. The target is to

produce 10 times the speed (compared to Fast

Ethernet) for only two to three times the cost. It is also

claimed that the total cost of ownership is lower since

applications need not change, existing management

systems should function, and re-training of technical

support people will be unnecessary.

Testing Issues

Any typical LAN has four main connectivity

requirements (as illustrated in the following): switch-to-

switch, switch-to-server, router- or switch-to-WAN, and


performance of switches, in particular, becomes more

critical when the very high speeds achievable with

Gigabit Ethernet are involved.

A methodology for benchmarking network inter-

connect devices is provided in RFC1944 which is

published by the IETF. These tests are performed in a

test laboratory with the inputs and outputs of the

“device under test” connected to the tester. Tests for a

network device would include:

• Latency, which is the time needed for a switch to

process a packet;

• Throughput, which is the rate at which data transfer

occurs with no packet loss;

• Packet loss rate, which is the percentage of packets that

are not forwarded in a specific time window;

• Congestion level, which is a measure of the ability to

release packets to their outbound destinations.

Similar testing is needed for devices that are

already deployed in a production network. It can be

expected that remote monitoring, embedded diagnostic

routines, multiple “spot checks” using protocol

analyzers, and databases of historical statistics will

eventually be combined into a comprehensive testing

architecture.

Global versus Segment TestingProtocol analyzers have typically been used to

observe and analyze a single shared Ethernet segment,

to which the test system is physically attached. For

simple networks, it may be possible to observe all traffic

flows from a single point of observation. In the case of

full duplex operations, however, a connection is needed

for each direction and the requests and responses need

to be correlated. With switching, this can become even

more complicated since each station may be on a

different dedicated LAN segment.

Testing of any form of Ethernet network should

be the same, at least in principle. Some issues, however,

that are unique to Gigabit Ethernet are discussed in

the following sections.

Full versus Half DuplexGigabit Ethernet provides either full- or half-

duplex modes of operation (as do other versions of

Ethernet). Test systems will need to be capable of

supporting either mode.

Full duplex operation is supported on point-to-

point links at a total throughput of 2Gb/s without the

need for the CSMA/CD protocol (since there can be

no collisions). Full duplex configurations use two sepa-

rate data paths and can make use of the flow control

techniques defined in IEEE802.3x. Testing requires the

capturing of data from both links and correlating

traffic in each direction.

Half duplex operation is needed for shared

segments. To avoid large propagation delays (relative to

the frame transmission time) two changes were

required to the basic Ethernet standards. Carrier

extension is used to de-couple the slot time on the

media from the minimum frame length so that slot

times can be increased (from 512 bits to 512 bytes)

without changing the Ethernet frame format. Frame

bursting is a technique used to reduce the overhead for

transmitting small frames by allowing a node to

transmit more than one frame without releasing

control of the channel.

Device Capability and PerformanceTesting both the functionality of the protocols

being used (including management, security, and route

processing) and the performance of each of the

network elements (the switches, routers, and servers) is

needed to get the complete picture of a network. The


A detailed examination of all protocols being

executed and the validation of their correct operation

is most often the first step in the resolution of both

design and operational problems.

Testing Frequency

Network monitoring may be performed at one or

more test points on a continuous basis, on some peri-

odic schedule, or whenever a problem arises.

Continuous testing is the most expensive and is best

accomplished using test routines that are designed into

the network itself. Continuous testing provides data for

dynamic recovery, feedback control mechanisms, and

fault tolerance. Non-intrusive testing using a portable

protocol analyzer that is separate from the network

resources can provide for scheduled and reactive testing.

Methods of connection to the network

Any protocol analyzer must be attached physically

to the network it is to observe. Three basic methods are

used (see figures 4A–4D).

NIC-based attachment: The protocol analyzer is

connected to a test port on a switch and the switch is

programmed to copy all data from a user port onto the

test port.

Figure 4A. NIC Attachment

Hub-based attachment: A hub repeater is connected

onto a segment and all data is repeated to the tester.

NIC Attachment

Switch/Router Protocol Analyzer

One of the emerging issues in LAN testing is to

examine, test, and analyze the network globally as well as

on a segment by segment basis. For example, traffic gener-

ated by any workstations on a switch may be directed to a

server, another switch, a router, or to another workstation.

Testing the transport service provided by the network

involves capturing, checking, and correlating traffic flows

on multiple segments and on both the input and output

ports of the switch. Separating the traffic by user address,

by VLAN grouping, by protocol, and by QoS classifica-

tion would be highly desirable.

Product Maturity

Gigabit Ethernet is presently at the beginning of its

technology life cycle and, in fact, standards for it have not

even been formally adopted yet (as of mid-1997).

Support for twisted pair wiring, explicit Quality of

Service control, interworking with ATM-based services,

and even general production-level experience are all

issues to be overcome. Providing testing systems that can

meet the challenges of both full duplex inter-switch links,

CSMA/CD-based shared segments, and multi-speed

environments is an important step in the development.

Protocol Analyzers

A protocol analyzer is the fundamental tool used

by the network engineer to understand what is

happening or not happening in a network. The three

major purposes of any protocol analyzer are:

• to prevent problems by measuring changes in

performance,

• to resolve problems through observation and

expert analysis, and

• to optimize performance using baselining and

trend analysis.


Analyzer Functions

Every protocol analyzer should be able to perform

certain major functions that are essential to the testing

process. These include:

• automatic capture and storage of large amounts

of traffic (preferably all frames for a period of

time) so that data may be analyzed off-line,

• generation of test traffic both for stress testing

and for simulation of faults,

• decoding of the protocols at all seven layers of

the protocol stack and for all nodes,

• wire speed analysis and interpretation of the data

so that it can be reduced and converted into

useful information, and

• presentation of results in the form most desirable

for the user.

Typically, a protocol analyzer needs to be able to

distinguish among different users and protocols

including such things as routing protocols,

management protocols, and network signaling.

Analysis and filtering of the traffic generated by each

user or application in real time is essential when the

large volumes of data associated with Gigabit

Ethernet are involved. Large amounts of off-line

storage are also preferable.

When used in a non-production test environment,

the protocol analyzer must also be able to generate

traffic. It must be possible to purposely stress the

network by overloading it, and to test the effects of

errors by generating various types of faults. Examples of

controllable parameters include frame size and submis-

sion rate, frame check sequence errors, utilization,

numbers of frames to transmit, transmit windows, etc.

A number of benchmarking tests for internetwork

components have been specified in RFC1944,

published by the IETF. The general goal should

Figure 4B. Hub Attached

Splitter-based attachment: A splitter is placed in the

circuit (either permanently or when needed) and the

analyzer copies all the data.

Figure 4C. Splitter Attached

Segment-based attachment: The protocol analyzer is

connected onto the segment and serves as an in-line

repeater, copying data as it passes through the

analyzer ports.

Figure 4D. Segment Attached

Switch/Router

Switch/Router

Protocol Analyzer

Splitter Attached Switch/Router

Switch/Router

Protocol Analyzer

HUB Attached

Protocol Analyzer

Switch/Router

HUB


time there will be a further need to test various HDX

and shared topologies.

Needless to say, the ability to connect to 10 and

100Mb/s Ethernet segments and to provide testing for

all versions of Ethernet is highly desirable. Modular

construction of the tester will provide the best combi-

nation of cost, flexibility, and capability.

Collecting the Data

Gigabit Ethernet uses a line rate of 1.25Gb/s

transmission in order to produce an effective

throughput of 1000Mb/s to the user, the Network

Layer protocols. Segments that are not shared will be

able to operate in full duplex mode, thereby doubling

the amount of data to be captured.

Data flowing across the segment first must be

captured and then stored for subsequent analysis. This

will inevitably involve very large amounts of data. It is

conceivable that a process of simply capturing raw data

for subsequent analysis could easily overwhelm a protocol

analyzers storage capacity. An effective protocol analyzer,

therefore, must include some methodology for

intelligently capturing, synthesizing, and analyzing suffi-

cient data during selected time periods. Also, it must be

adequate for relevant system analysis. This is

accomplished in a variety of ways, including the use of

various programmable filters that allow on-line data

selection and reduction. This assures that a wide range of

information can be captured and the analyzer can focus

as quickly as possible on that subset most relevant for the

task at hand. This usually includes utilization, protocol

errors, traffic flows, congestion, media faults, etc.

Producing Test Data

Prior to deploying systems in a working

environment, systems must be tested through the genera-

tion of various sets of test data. An important function of

protocol analyzers provides the ability to control traffic

always be to use a standard set of test cases and

testing points. Automation of testing in accordance

with RFC1944 (i.e., the various test packets, intervals,

etc.) can be provided by test systems such as those

provided by Hewlett-Packard, thereby simplifying the

job of the user.

User Interface

Needless to say, the protocol analyzer’s user inter-

face must provide for graphical displays of any desired

information and should provide intuitive controls for

the testing process. Vital signs, such as utilization,

collision rates, delays, and frame errors, should be

readily available. Other information, such as trend

analysis, network topology maps, and so on, should be

available in standard and customizable formats.

Protocol Analyzers andGigabit Ethernet

Gigabit Ethernet provides new challenges for the

designers of protocol analyzers, and it is very impor-

tant to employ a tool that meets all the testing needs

for high speed networks. The four major challenges

are the physical connection, data collection, test data

generation, and data interpretation.

Connecting to the Network

As described earlier, Gigabit Ethernet will initially

be deployed using fiber optic cabling and will be used

to interconnect Fast Ethernet switches or to connect a

switch to a server. Standards for using Coax and Cat 5

UTP are now in development. As these evolve, the

protocol analyzer will be needed to assure rigorous

testing and service compliance.

Connectivity also requires the ability to initially

test FDX point-to-point segments, but within a short


For manufacturers, perhaps the greatest benefit of

a protocol analyzer is the information it provides about

the implementation’s conformance to networking stan-

dards. This can reduce the time it takes to get a

product onto the market and also improves the chances

of interoperability with related products and services.

The Benefits of ProtocolAnalyzers

An effective protocol analyzer will provide signifi-

cant benefits at every stage in the development, deploy-

ment, and exploitation of almost any networking tech-

nology. The software used in today’s internetworks is

sufficiently complex that it requires operational and

stress testing during development and is unlikely to work

correctly forever in a live environment. Protocol

analyzers can help in the detection and debugging of

faults both on a test bench and in a production situation.

Making independent protocol analysis available at

the earliest possible point in a product’s development

cycle decreases the time it takes to bring the product to

the market, which can mean the difference between

success and failure for a supplier. While this alone

would justify having testing devices, there are other

valuable benefits. These are described briefly below.

Manufacturers

Manufacturers need protocol analyzers throughout

product development. Obvious requirements include

conformance testing, debugging software implementa-

tions, and verifying actual performance. Traffic genera-

tion, protocol decoding, fault generation, and

performance measuring are typical functions that are

required. Use of third-party products for in-house

testing provides a means for detecting specification issues

(the builder of the tester may interpret a standard in a

loads, to force errors, and to perform stress testing that is

invaluable, especially during the product design phase.

After a network is deployed and is operational, it

may be useful to introduce test data into an operational

network for certain types of testing. For example, loop-

back tests can check the status of various components.

Test sequences (such as a ping) can be used to test

addressing, to check for existence of resources, etc.

Interpreting the Data

Collecting network-related data provides little

value to the network operator unless there is a way to

use it to draw conclusions or make changes. Testing of

an operational network helps to determine what the

problem is, to decide why it is happening, and to iden-

tify who is causing it.

• An initial requirement is to monitor and report on

the overall health of the network. Questions such

as whether there is a specific fault or a design

problem need to be answered. Characterizing

network use by user, by location, by protocol, and

by path all help to establish both the current status

and a historical database. These can be processed

to develop an understanding of trends; and to

create benchmarks for performance and capacity.

• A second level of testing is used to detect and

correct problems, both during the development

stage and in operational situations. The protocol

analyzer can be used to verify the operation of a

protocol, can be used to measure performance

characteristics, and can exercise parts of a system

(such as recovery procedures) that would not be

visible in normal operation. A protocol analyzer

can be used to set thresholds, limits, and/or time

windows that result in alerts if the conditions are

not met. Information concerning achieved Quality

of Service can be compared to historical trends

and design specifications.


however, there is often a need for interoperability testing.

Protocol analyzers allow a wide variety of tests to be

performed including function testing, checking of

performance limits, stress testing, and integration testing.

Re-sellers and system integrators

Re-sellers and system integrators will often need to

perform tests during the implementation and commis-

sioning processes. Testing the operation of an assem-

bled system, both at the elemental level and at the inte-

gration level, is necessary when a formal project hand-

over is involved. Distributed systems will, in most cases,

include equipment from several manufacturers, which

can complicate the testing process.

Systems integration may be performed before live

operation (in a test bed) but typically must also be

performed in a full production environment.

Carriers and service providers

Carriers and service providers typically provide

wide area networks that interconnect premises

networks such as Ethernet. Detecting and correcting

problems within their networks (both reactive

troubleshooting and operational audits) is an essential

component of service excellence. Large scale carrier

networks use continuous testing via embedded systems

and large network control centers so that problems

may be identified and services restored, hopefully

before the user even realizes there is a problem. Fault

tolerant network operations make use of functions such

as automatic re-routing, congestion control, and admis-

sion controls in order to optimize network availability.

Portable protocol analyzers can complement this level

of network management by providing a more detailed

view and by including expert analysis tools.

For a telecommunications service provider, it is often

the quality of their services that provides the competitive

edge and distinguishes one supplier from another.

different way than does the product developer). In-house

testing supports the ultimate goal of any manufacturer:

to get a standard-based product to the market as quickly

as possible with as few bugs and incompatibilities as

possible. Being able to establish product performance

statements is also a fundamental requirement.

Thorough testing during the design and develop-

ment stages helps to increase the buyer’s (and seller’s)

confidence in the product and the certainty that it can

meet its performance claims. This can also reduce

manufacturer finger-pointing by allowing publication

of verifiable performance and conformance claims.

It goes without saying that efficiency improvements

in the product development stages results in lower

overall costs, making the product more attractive to

buyers. Cost containment is an extremely important

factor, especially in markets that are as competitive as

internetworking.

Test laboratories

Test Labs use protocol analyzers for third-party

testing of individual products, for network tests, and for

interoperability testing. Typically, lab tests are in a

controlled environment, not in a production network.

The test laboratory must depend on the quality of the

test systems it has available, since the test is only as

good as the tool used to do the testing. Third-party

laboratories would be used by manufacturers who have

no in-house facilities, by users who need unbiased

product evaluations, and by regulators who require

product compliance testing performed by a recognized

third party.

Testing in a laboratory that is well respected within

the industry adds credibility to a vendor’s claims for a

product.

Test laboratories also provide formal certification of

conformance to standards, especially when there is a

legal requirement. In addition to static conformance,


be more portable, possibly allowing more than one

interface to be built into the same set.

• High performance test systems allow for full duplex

data capture at full line speeds, real time analysis of

captured data, and presentation of summary and

detailed information.

• Multi-port testing should be available allowing simulta-

neous testing of each direction in full duplex systems.

• Advanced QoS testing is necessary not only to prove

component performance, but also to test for QoS

contracts, to exercise dynamic system operation, and

to identify bottlenecks and weaknesses.

• Graphical presentation of test results can make the

engineer’s job much easier.

Summary

Gigabit Ethernet has developed into a useful technology

rapidly. Its introduction into corporate networks when the

standards are adopted is expected to be equally rapid.

Clearly, users are pushing for Ethernet scalability beyond

100Mb/s and believe that their requirements are for the

near future. The ability to aggregate premises networks

using a common, well-understood technology can simplify

the transition, reduce re-training needs, and allow more flex-

ibility in network planning. Testing Gigabit Ethernet for

functionality and Quality of Service is fundamental to

success from both the user’s and producer’s perspectives.

The Ethernet products of the future will offer:

• a wide range of speeds to the workstation and among

switches and servers,

• dedicated and shared attachment with support for full

and half duplex operations,

• support for multiple physical media types and

arrangements,

User network managers

User network managers are ultimately responsible

for the quality of the corporate network and for its

total cost of ownership. Ownership costs include both

implementation and operations costs. For example,

every network operator will need to perform

troubleshooting, planners will need to manage network

assets and their ongoing changes, planners should also

track utilization and traffic patterns, and sometimes

accounting will be necessary for chargeback purposes.

The end user needs to be confident that the

networks they are using are capable of providing their

services in a reliable and consistent manner, especially

for mission-critical networks. The process of

performing tests, carrying out routine maintenance,

and repairing faults should be effectively transparent to

the end user; their goal is a “perfect” network that is

always available, is highly scaleable, and is essentially

invisible. Identification and characterization of prob-

lems must be done quickly and efficiently.

Since Gigabit Ethernet networks route more traffic

onto a single segment, they can become a weak link in

a networking strategy.

The end user can only be satisfied if key resources

such as a server link or a backbone are as reliable as

possible. To this end, designing in fault tolerance is just as

important as being able to test after a failure has occurred.

Attributes of a Protocol AnalyzerWhat are the characteristics that distinguish a

good protocol analyzer? The following are suggestions

that may or may not be relevant to any given situation

but are generally thought to be beneficial.

• Modular construction is one means for reducing

cost and minimizing complexity. Selecting only

those physical interfaces and protocols that are

needed can reduce cost.

• High density packaging allows the test system to


Glossary • 31

Glossary

10Base-T—The IEEE 802.3 specification for ethernet

over unshielded twisted pair (UTP).

100Base-T Fast Ethernet—A 100 Mbps technology

based on the Ethernet/CD network access method.

802.3—CSMA/CD (Ethernet) standards, which apply

at the physical layer and the media access control

(MAC) sublayer.

8B/10B Encoding—An encoding scheme at the

Gigabit Ethernet physical coding sublayer adopted from

the FC-1 Fiber Channel specification. It transmits eight

bits as a 10 bit code group.

Backbone—1) The part of a network used as the

primary path for transporting traffic between network

segments. 2) A high-speed line or series of connections

that forms a major pathway within a network.

Bridge/Router—A device that can provide the func-

tions of a bridge, router, or both concurrently.

Bridge/router can route one or more protocols, such as

TCP/IP and/or XNS, and bridge all other traffic.

Buffered Distributors—A new class of Gigabit

Devices with features found on repeaters and switches;

low-cost alternatives to full-blown switches.

Bus Topology—Linear LAN architecture in which

transmissions from network stations propagate the

length of the medium and are received by all other

stations attached to the medium.

Carrier Extension—A mechanism that makes a 200-

meter network diameter possible: a Gigabit network

adapter transmits a frame less than 512 bytes long, the

gigabit MAC sends out a special signal (while continuing

to monitor for collisions).

• a mix of hubs, bridges, switches, and routers for

network connectivity,

• interoperability with a range of wide area

networks and legacy LANs, and

• fully integrated diagnostic and management func-

tionality using in-line and portable test equipment.

Gigabit Ethernet is taking its place in the network

designer’s toolkit of useful technologies. Pre-standard prod-

ucts, usually with guarantees of upgrades to the final stan-

dard, are already available for the early adopters. Fully

standardized products that are thoroughly tested and

highly interoperable will be delivered by mid-1998. Hence,

those applications requiring a low-cost, dependable, high

speed network infrastructure will soon be justifiable.

Gigabit Ethernet also provides a solid migration

path for users who already know and are comfortable

with Ethernet. An incremental upgrade approach that

mixes and matches 10M, 100M and 1G segments

should suit most traffic flows and geographical distribu-

tions. Increasing the speed does not change the funda-

mental protocols, thereby reducing the total cost of

ownership (training and operations re-tooling) and

increasing the useful life of older equipment.

Since rigorous testing of any new technology is

important both before and after installation, a protocol

analyzer is an essential part of any network manager’s

toolkit. Making Gigabit Ethernet testers available as

quickly as possible increases the efficiency of product

development, enhances the buyer’s confidence in their

decisions, and allows more rapid diagnosis and repair

during the shakedown phase of product deployment.

Monitoring and testing effectively at high speeds is,

however, non-trivial. The right test instrument, one that

captures the data, analyzes the events, and digests

masses of data all in real time, will make Gigabit

Ethernet the success it is expected to be.

30 • Gigabit Ethernet Development and Testing

32 • Gigabit Ethernet Development and Testing Glossary • 33

Carrier Sense Multiple Access/Collision

Detection (CSMA/CD)—A channel access mecha-

nism wherein devices wishing to transmit first check the

channel for a carrier. If no carrier is sensed for some

period of time, devices can transmit. If two devices

transmit simultaneously, a collision occurs and is detected

by all colliding devices, which subsequently delays their

retransmissions for some random length of time.

CSMA/CD access is used by Ethernet and IEEE 802.3.

Category 5 Unshielded Twisted Pair (CAT-5)—

Industry standard for unshielded twisted wire pair

capable of supporting high speed data traffic over short

(LAN and CAN) distances.

Client/Server—A distributed system model of

computing that brings computing power to the desktop,

where users (“clients”) access resources from servers.

Collisions—Within Ethernet, the circumstance when

two (or more) messages are transmitted within the same

time period and thus interfere with each other.

Congestion—Excessive network traffic.

Data Link Layer—Layer 2 of the OSI reference

model. This layer takes a raw transmission facility and

transforms it into a channel that appears, to the network

layer, to be free of transmission errors. Its main services

are addressing, error detection, and flow control.

Data Warehouse—A subject oriented, integrated,

time-variant, non-volatile collection of data in support

of management’s decision making process. A reposi-

tory of consistent historical data can that can be easily

accessed and manipulated for decision support. (2) An

implementation of an informational database used to

store sharable data sourced from an operational data-

base-of-record. It is typically a subject database that

allows users to tap into a company’s vast store of opera-

tional data to track and respond to business trends and

facilitate forecasting and planning efforts.

Delay—Amount of time a call spends waiting to be

processed.

Dynamic Multicast Filtering—The process of

scanning multicast addresses to restrict unnecessary

distribution; accomplished according to dynamically

variable parameters.

Element Management Systems—Network manage-

ment technology and software intended to interact with

specific objects, subsystems, and components.

Ethernet—(1) A baseband LAN specification invented

by Xerox Corporation and developed jointly by Xerox,

Intel, and Digital Equipment Corporation. Ethernet

networks operate at 10 Mbps using CSMA/CD to run

over coaxial cable. Ethernet is similar to a series of stan-

dards produced by IEEE referred to as IEEE 802.3. (2)

A very common method of networking computers in a

local area network (LAN). Ethernet will handle about

10,000,000 bits per second and can be used with almost

any kind of computer.

Fiber Channel Physical Layer—The physical

medium interface specification to interface to the higher

level fiber channel elements.

Flow Control—A technique for ensuring that a trans-

mitting entity does not overwhelm a receiving entity. In

IBM networks, this technique is called pacing.

Frame—A logical grouping of information sent as a

link-layer unit over a transmission medium. The terms

packet, datagram, segment, and message are also used

to describe logical information groupings at various

layers of the OSI reference model and in various

technology circles.

Frame Bursting—The technique of aggregating

multiple frames of traffic and sending them as a single

transmission.


Intranet—A private network that uses Internet soft-

ware and standards.

ISO Development Environment (ISODE)—A

popular implementation of the upper layers of OSI.

Pronounced “eye-so-dee-eee.”

Jitter—Analogue communication line distortion

caused by a variation of signals from its reference

timing positions. Jitter can also cause data loss, particu-

larly at high speeds.

Latency—The delay between the time a device

receives a frame and the frame is forwarded out of the

destination port.

Logical Link Control (LLC)—IEEE-defined sub

layer of the OSI link layer. LLC handles error control,

flow control, and framing. The most prevalent LLC

protocol is IEEE 802.2, which includes both connec-

tionless and connection-oriented variants.

Logical Link Control, type 2 (LLC2)—A connec-

tion-oriented OSI logical link control sub layer protocol.

Management Objects—Within network

management systems, the specific, defined targets

of interest.

Media Access Control (MAC)—A method of

controlling access to a transmission medium. For

example, token ring, Ethernet, FDDI, etc.

Mobile Access—The ability to access a computer or

server site from different remote locations.

Multi-port Bridging—A LAN interface that inter-

connects switched LAN segments with the same logical

link protocol.

Multicast—Single packets copied to a specific subset

of network addresses. These addresses are specified in

the destination-address field. In contrast, in a broadcast,

packets are sent to all devices in a network.

Framing—Method for distinguishing digital channels

that have been multiplexed together.

Full Duplex—LAN Technique for transmitting full

duplex between a LAN station and the wiring hub.

Supports 10 Mbps in each direction (20 Mbps) for

Ethernet and 16 Mbps in each direction (32 Mbps) for

Token Ring. It only supports single stations, not LAN

segments.

Gigabit—One billion bits.

Gigabit Ethernet Alliance—An association of

Gigabit Ethernet manufacturers and suppliers formed

for the purpose of promoting Gigabit Ethernet

Technology.

Groupware—A network-based application that lets

users collaborate.

Half-Duplex Transmission—Data transmitted in

either direction, one direction at a time.

Horizontal Distribution—The part of the cable

wiring system that is deployed on the same floor;

emanating from centralized risers.

Hub—Common name for a repeater. Strictly, it is a

non-retiming device.

Institute of Electrical and Electronic

Engineers (IEEE)—Professional organization that

defines network standards. IEEE LAN standards are

the predominant LAN standards today, including

protocols similar or virtually equivalent to Ethernet

and Token Ring.

Internet—A collection of networks interconnected by

a set of routers which allow them to function as a

single, large virtual network.

Internet Engineering Task Force (IETF)—An

organization that provides coordination of standards

and specifications development for TCP/IP networking.


Resource Reservation Protocol (RSVP)—A

proposed IETF standard which allows Internet applica-

tions to request reservation of resources along the path

of a data flow so that applications can obtain

predictable quality of service on end-to-end basis.

Router—(1) An OSI Layer 3 device that can decide

which of several paths network traffic will follow based

on some optimality metric. Also called a gateway

(although this definition of gateway is becoming increas-

ingly outdated), routers forward packets from one

network to another based on network-layer information.

(2) A dedicated computer hardware and/or software

package which manages the connection between two or

more networks.

Routing - 80/20 rule—In LANS, the theory that

80% of LAN traffic originates and terminates within

the same collision domain, while 20% originates or

terminates elsewhere.

Routing Information Protocol (RIP)—An IGP

supplied with Berkeley UNIX systems. It is the most

common IGP in the Internet. RIP uses hop count as a

routing metric. The largest allowable hop count for RIP

is 16.

Routing Protocol—A protocol that accomplishes

routing through the implementation of a specific

routing algorithm. Examples of routing protocols

include IGRP, RIP, and OSPF.

Server—(1) A software application that responds with

requested information or executes tasks on the behalf

of a client application. Also, a network host, such as

a web server, running a set of protocol server applica-

tions. (2) Any computer that allows other computers

to connect to it. Most of the time servers are

dedicated machines. Most machines using UNIX

are servers.

Network Computing—The architectural model of

computing based on distributed servers and peer

processors.

Network Interface Card (NIC)—The circuit board

or other hardware that provides the interface between a

communicating DTE and the network.

Packet Loss Rate—The measure loss, over time,

of data packets as a percentage of the total traffic

transmitted.

Physical Layer (PHY)—The bottom layer of the

OSI and ATM protocol stack, which defines the inter-

face between ATM traffic and the physical media. The

PHY consists of two sublayers: the transmission conver-

gence (TC) sublayer and the physical medium-depen-

dent (PMD) sublayer.

Ping (Packet Internet Grouper)—Refers to the

ICMP echo message and its reply. Often used to test the

reachability of a network device.

Protocol—(1)A formal description of a set of rules and

conventions that govern how devices on a network

exchange information. (2) Set of rules conducting interac-

tions between two or more parties. These rules consist of

syntax (header structure) semantics (actions and reactions

that are supposed to occur) and timing (relative ordering

and direction of states and events).(3) A formal set of rules.

Protocol Analyzer—An external monitoring device

used to intercept and translate the protocol commands

within the data stream.

Quality of Service (QoS)—Term for the set of

parameters and their values which determine the

performance of a given virtual circuit.

Repeater—(1) A device that regenerates and propa-

gates electrical signals between two network segments.

(2) Device that restores a degraded digital signal for

continued transmission; also called a regenerator.

38 • Gigabit Ethernet Development and Testing Notes • 39

NOTES

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Server Farms—The aggregation of file and database

servers in a single location, interconnected with each

other and with the host community via a collapsed

backbone.

Server Switches—Device that combines the capabili-

ties of both a file server and a network switch.

Streaming—(1) A condition in which a device

remains in a transmit mode for an abnormal length of

time. (2) A method of writing data onto magnetic tape

as continuous fields without record boundaries.

Throughput—The effective data transfer rate.

Traffic Class Expediting—A technique to provide

priority (expedited) to certain traffic types.

Video Conferencing—The technique of intercon-

necting simultaneous video signals and displaying them

at multiple interconnected sites.

Virtual LAN—Membership to a Virtual LAN is

defined administratively independent of the physical

network topology. A virtual LAN segment is a unique

broadcast domain.

Wide Area Network (WAN)—(1) A network which

encompasses interconnectivity between devices over a

wide geographic area. Such networks would require

public rights-of-way and operate over long distances.

(2) A network that covers an area larger than a single

building or campus.

Visit ATG’s Web Site

to read, download, and print

all the Technology Guides

in this series.

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“The significant problems we face cannot be solved

by the same level of thinking that created them.”

Albert Einstein

A quick argument for solvingnetwork problems the first time.

Connect, Capture, Comprehend

HP Internet Advisor LAN, WAN, ATM network analysis.

To find out how we can help you solve your network

problems call us at 1–800–425–4844, Ext. 5541. Outside

the US, please contact your local HP Sales Office.

Connect with us!http://www.hp.com/go/internetadvisor

Produced and Published by

One Apple Hill, Suite 216, Natick, MA 01760

Tel: (508) 651-1155 Fax: (508) 651-1171 E-mail: [email protected]

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by ATG, designed to put complex

communications and networking

technology concepts into practical

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Each guide provides objective,

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