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Audio Networking 8-3

References

8-45

Reference Documents for this Section

ATSC, “Guide to the Use of the Digital Television Standard,” Advanced Television Systems

Committee, Washington, D.C., Doc. A/54, Oct. 4, 1995.

Craig, Donald: “Network Architectures: What does Isochronous Mean?,” IBC Daily News, IBC,

Amsterdam, September 1999.

Dahlgren, Michael W.: “Servicing Local Area Networks,” Broadcast Engineering, Intertec Pub-

lishing, Overland Park, Kan., November 1989.

Fibush, David: A Guide to Digital Television Systems and Measurement, Tektronix, Beaverton,

OR, 1994.

Gaggioni, H., M. Ueda, F. Saga, K. Tomita, and N. Kobayashi, “The Development of a High-

Definition Serial Digital Interface,” Sony Technical Paper, Sony Broadcast Group, San
Jose, Calif., 1998.

Gallo and Hancock: Networking Explained, Digital Press, pp. 191–235, 1999.

Goldman, J: Applied Data Communications: A Business Oriented Approach, 2md ed., Wiley,

New York, N.Y., 1998.

Goldman, J: Local Area Networks: A Business Oriented Approach, 2nd ed., Wiley, New York,

N.Y., 2000.

Goldman, James E.: “Network Communication,” in The Electronics Handbook, Jerry C. Whi-

taker (ed.), CRC Press, Boca Raton, Fla., 1996.

Held, G.: Ethernet Networks: Design Implementation, Operation and Management, Wiley, New

York, N.Y., 1994.

Held, G.: Internetworking LANs and WANs, Wiley, New York, N.Y., 1993.

Held, G.: Local Area Network Performance Issues and Answers, Wiley, New York, N.Y., 1994.

Held, G.: The Complete Modem Reference, Wiley, New York, N.Y., 1994.

International Organization for Standardization: “Information Processing Systems—Open Sys-

tems Interconnection—Basic Reference Model,” ISO 7498, 1984.

Legault, Alain, and Janet Matey: “Interconnectivity in the DTV Era—The Emergence of SDTI,”

Proceedings of Digital Television '98, Intertec Publishing, Overland Park, Kan., 1998.

Miller, Mark A.: “Servicing Local Area Networks,” Microservice Management, Intertec Publish-

ing, Overland Park, Kan., February 1990.

Miller, Mark A.: LAN Troubleshooting Handbook, M&T Books, Redwood City, Calif., 1990.

“Networking and Internet Broadcasting,” Omneon Video Networks, Campbell, Calif, 1999.

“Networking and Production,” Omneon Video Networks, Campbell, Calif., 1999.

Owen, Peter: “Gigabit Ethernet for Broadcast and Beyond,” Proceedings of DTV99, Intertec

Publishing, Overland Park, Kan., November 1999.

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Audio Networking

8-4 Section Eight

Piercy, John: “ATM Networked Video: Moving From Leased-Lines to Packetized Transmission,”

Proceedings of the Transition to Digital Conference, Intertec Publishing, Overland Park,
Kan., 1996.

“SMPTE Recommended Practice—Error Detection Checkwords and Status Flags for Use in Bit-

Serial Digital Interfaces for Television,” RP 165-1994, SMPTE, White Plains, N.Y., 1994.

“SMPTE Recommended Practice—SDTI-CP MPEG Decoder Templates,” RP 204 (Proposed),

SMPTE, White Plains, N.Y., 1999.

“SMPTE Standard for Television—24-Bit Digital Audio Format for HDTV Bit-Serial Interface,”

SMPTE 299M-1997, SMPTE, White Plains, N.Y., 1997.

“SMPTE Standard for Television—Ancillary Data Packet and Space Formatting,” SMPTE

291M-1998, SMPTE, White Plains, N.Y., 1998.

“SMPTE Standard for Television—Bit-Serial Digital Interface for High-Definition Television

Systems,” SMPTE 292M-1998, SMPTE, White Plains, N.Y., 1998.

“SMPTE Standard for Television—Element and Metadata Definitions for the SDTI-CP,”

SMPTE 331M-2000, SMPTE, White Plains, N.Y., 2000.

“SMPTE Standard for Television—Encapsulation of Data Packet Streams over SDTI (SDTI-

PF),” SMPTE 332M-2000, SMPTE, White Plains, N.Y., 2000.

“SMPTE Standard for Television—Mapping of AES3 Data into MPEG-2 Transport Stream,”

SMPTE 302M-1998, SMPTE, White Plains, N.Y., 1998.

“SMPTE Standard for Television—SDTI Content Package Format (SDTI-CP),” SMPTE 326M-

2000, SMPTE, White Plains, N.Y., 2000.

“SMPTE Standard for Television—Serial Data Transport Interface,” SMPTE 305M-1998,

SMPTE, White Plains, N.Y., 1998.

SMPTE 344M (Proposed), “540 Mb/s Serial Digital Interface,” SMPTE, White Plains, N.Y.,

2000.

“SMPTE Standard for Television (Proposed)—High Data-Rate Serial Data Transport Interface

(HD-SDTI),” SMPTE 348M, SMPTE, White Plains, N.Y., 2000.

“SMPTE Standard for Television (Proposed)—Signals and Generic Data over High-Definition

Interfaces,” SMPTE 346M, SMPTE, White Plains, N.Y., 2000.

“SMPTE Standard for Television (Proposed)—Vertical Ancillary Data Mapping for Bit-Serial

Interface, SMPTE 334M, SMPTE, White Plains, N.Y., 2000.

“Technology Brief—Networking and Storage Strategies,” Omneon Video Networks, Campbell,

Calif., 1999.

Turow, Dan: “SDTI and the Evolution of Studio Interconnect,” International Broadcasting Con-

vention Proceedings, IBC, Amsterdam, September 1998.

Wilkinson, J. H., H. Sakamoto, and P. Horne: “SDDI as a Video Data Network Solution,” Inter-

national Broadcasting Convention Proceedings, IBC, Amsterdam, September 1997.

Wu, Tsong-Ho: “Network Switching Concepts,” The Electronics Handbook, Jerry C. Whitaker

(ed.), CRC Press, Boca Raton, Fla., p. 1513, 1996.

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Audio Networking

8-5

Chapter

8.1

Network Concepts

James E. Goldman, Michael W. Dahlgren

Jerry C. Whitaker, Editor-in-Chief

8.1.1

Introduction

The open system interconnections (OSI) model is the most broadly accepted explanation of LAN
transmissions in an open system. The reference model was developed by the International Orga-
nization for Standardization (ISO) to define a framework for computer communication. The OSI
model divides the process of data transmission into the following steps:

•

Physical layer

•

Data link layer

•

Network  layer

•

Transport  layer

•

Session layer

•

Presentation layer

•

Application layer

8.1.2

OSI Model

The OSI model allows data communications technology developers as well as standards develop-
ers to talk about the interconnection of two networks or computers in common terms without
dealing in proprietary vendor jargon [1]. These common terms are the result of the layered archi-
tecture of the seven-layer OSI model. The architecture breaks the task of two computers commu-
nicating with each other into separate but interrelated tasks, each represented by its own layer.
The top layer (layer 7) represents network services provided to the application program running
on each computer and is therefore aptly named the application layer. The bottom layer (layer 1)
is concerned with the actual physical connection of the two computers or networks and is there-

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Source: Standard Handbook of Audio and Radio Engineering

8-6 Audio Networking

fore named the physical layer. The remaining layers (2–6) may not be as obvious but, nonethe-
less, represent a sufficiently distinct logical group of functions required to connect two
computers as to justify a separate layer.

To use the OSI model, a network analyst lists the known protocols for each computing device

or network node in the proper layer of its own seven-layer OSI model. The collection of these
known protocols in their proper layers in known as the protocol stack of the network node. For
example, the physical media employed, such as unshielded twisted pair, coaxial cable, or fiber
optic cable, would be entered as a layer 1 protocol, whereas Ethernet or token ring network archi-
tectures might be entered as a layer 2 protocol.

The OSI model allows network analysts to produce an accurate inventory of the protocols

present on any given network node. This protocol profile represents a unique personality of each
network node and gives the network analyst some insight into what protocol conversion, if any,
may be necessary in order to allow any two network nodes to communicate successfully. Ulti-
mately, the OSI model provides a structured methodology for determining what hardware and
software technologies will be required in the physical network design in order to meet the
requirements of the logical network design.

The basic elements and parameters of each layer are detailed in the following sections.

8.1.2a

Physical Layer

Layer 1 of the OSI model is responsible for carrying an electrical current through the computer
hardware to perform an exchange of information [2]. The physical layer is defined by the follow-
ing parameters:

•

Bit transmission rate

•

Type of transmission medium (twisted pair, coaxial cable, or fiber optic cable), sometimes
referred to as Layer 0

•

Electrical specifications, including voltage- or current-based, and balanced or unbalanced

•

Type of connectors used (for example, RJ-45 or DB-9)

Many different implementations exist at the physical layer

Layer 1 can exhibit error messages as a result of over usage. For example, if a file server is

being burdened with requests from workstations, the results may show up in error statistic that
reflect the server's inability to handle all incoming requests. An overabundance of response time-
outs may also be noted in this situation. A response timeout (in this context) is a message sent
back to the workstation stating that the waiting period allotted for a response from the file server
has passed without action from the server.

Error messages of this sort, which can be gathered by any number of commercially available

software diagnostic utilities, can indicate an overburdened file server or a hardware flaw within
the system. Intermittent response timeout errors can also be caused by a corrupted network inter-
face card (NIC) in the server. A steady flow of timeout errors throughout all nodes on the net-
work may indicate the need for another server or bridge.

Hardware problems are among the easiest to locate in a networked system. In a simple con-

figuration where something has suddenly gone wrong, the physical layer and the data-link layer
are usually the first suspects.

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Network Concepts

Network Concepts 8-7

8.1.2b

Data Link Layer

Layer 2 of the OSI model, the data-link layer, describes hardware that enables data transmission
(NICs and cabling systems) [2]. This layer integrates data packets into messages for transmission
and checks them for integrity. Sometimes layer 2 will also send an “arrived safely” or “did not
arrive correctly” message back to the transport layer (layer 4), which monitors this communica-
tions layer. The data link layer must define the frame (or package) of bits that is transmitted
down the network cable. Incorporated within the frame are several important fields:

•

Addresses of source and destination workstations

•

Data to be transmitted between workstations

•

Error control information, such as a cyclic redundancy check (CRC), which assures the integ-
rity of the data

The data link layer must also define the method by which the network cable is accessed,

because only one workstation can transmit at a time on a baseband LAN. The two predominant
schemes are:

•

Token passing, used with token ring and related networks

•

Carrier sense multiple access with collision detection (CSMA/CD), used with Ethernet and
and related networks

At the data link layer, the true identity of the LAN begins to emerge.

Because most functions of the data-link layer (in a PC-based system

1

) take place in integrated

circuits on NICs, software analysis is generally not required in the event of a failure. As men-
tioned previously, when something happens on the network, the data-link layer is among the first
to suspect. Because of the complexities of linking multiple topologies, cabling systems, and
operating systems, the following failure modes may be experienced:

•

RF disturbance. Transmitters, ac power controllers, and other computers can all generate
energy that may interfere with data transmitted on the cable. RF interference (RFI) is usually
the single biggest problem in a broadband network. This problem can manifest itself through
excessive checksum errors and/or garbled data.

•

Excessive cable runs. Problems related to the data-link layer can result from long cable runs.
Ethernet runs can stretch 1,000 ft. or more, depending on the cable and the Ethernet imple-
mentation. A basic token ring system can stretch 600 ft. or so with the same qualification.
The need for additional distance can be accommodated by placing a bridge, gateway, active
hub, equalizer, or amplifier on the line.

The data-link layer usually includes some type of routing hardware, including one or more of

the following:

•

Active hub

•

Passive hub

•

Multiple access units (for token ring-type networks

1. In this context, the term “PC” is used to describe any computer, workstation, or laptop device.

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Network Concepts