Networking Terminology Tutorial for Business Continuity Planners
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Networking Terminology Tutorial for Business Continuity Planners

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Redbooks PaperCathy WarrickSuhail KafityJohn SingNetworking Terminology Tutorial for Business Continuity PlannersNetworking is one of the most important technology components of any IT infrastructure. This IBM® Redpaper includes a brief tutorial on the terminology and discusses the concepts of networking. It is intended to: Define and position the large number of networking technologies relative to each other, using the Open Systems Interconnect architecture to unify the technologies. Promote a better understanding of many commonly used networking concepts so that you can better evaluate and select the appropriate networking components for your Business Continuity solution.© Copyright IBM Corp. 2007. All rights reserved. ibm.com/redbooks 1Channel ExtendersMS Exchange DWDMSONETother...PtP, DSn, OCnFrame RelayTivoli PVCs, SVCsLANE-CIPVideoVoice VoIPVoice PSTNDB2, OracleSAPE-MAILWWWHTMLOpen Systems Interconnect network modelTo understand modern IT networking, we need to understand the architecture upon which all of today's networking technology is founded and built. That model is known as the Open Systems Interconnect network model, or OSI model for short. Understanding the OSI model architecture gives us the proper framework to understand the myriad of networking acronyms. Figure 1 illustrates an all-in-one overview of the OSI model. We discuss this chart, level-by-level. When we finish, you will be able to define many common ...

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Redbooks Paper
Cathy Warrick
Suhail Kafity
John Sing
Networking Terminology Tutorial for
Business Continuity Planners
Networking is one of the most important technology components of any IT infrastructure. This
IBM® Redpaper includes a brief tutorial on the terminology and discusses the concepts of
networking.
It is intended to:
Define and position the large number of networking technologies relative to each other,
using the Open Systems Interconnect architecture to unify the technologies.
Promote a better understanding of many commonly used networking concepts so that you
can better evaluate and select the appropriate networking components for your Business
Continuity solution.
© Copyright IBM Corp. 2007. All rights reserved. ibm.com/redbooks 1Channel
Extenders
MS Exchange DWDM
SONET
other...
PtP, DSn, OCn
Frame Relay
Tivoli PVCs, SVCs
LANE-CIP
Video
Voice VoIP
Voice PSTN
DB2, Oracle
SAP
E-MAIL
WWW
HTML
Open Systems Interconnect network model
To understand modern IT networking, we need to understand the architecture upon which all
of today's networking technology is founded and built. That model is known as the Open
Systems Interconnect network model, or OSI model for short. Understanding the OSI model
architecture gives us the proper framework to understand the myriad of networking
acronyms.
Figure 1 illustrates an all-in-one overview of the OSI model. We discuss this chart,
level-by-level. When we finish, you will be able to define many common networking
technologies, to position them in relation to each other, and to understand the basic role that
each can play in your final networking design.
Workstation Workstation
……...
……...
……...
……...7- Application 7- ApplicationA ADATA Data……...H H
……...
6- Presentation 6- PresentationP P
H H
5- Session 5- SessionS S
H H
T T
H H4- Transport 4- Transport
N N3- Network 3- NetworkH H
Internet Protocol (IP)
TR shared & switched; 4 & 16 Mbps ATM
LLC LLCL L L LEthernet shared & switched;
H T T H2-Data Link 2-Data Link10-Base2, 10-Base5, 10-BaseT,
MAC 10-BaseF, 100-BaseT, 100-BaseF, MAC
1000-BaseT, 1000-BaseF . . . . . . .
1- Physical 1- Physical
LAN - Campus
MAN - WAN
Network
Figure 1 OSI model overview
There are seven layers in the OSI model. Each layer represents a specific functionality that
allows layer 7 applications (such as e-mail, Lotus® Notes®, Web servers, and Web
browsers) to connect to each other. Figure 1 represents the details of what is required to
make this connection happen.
There are headers shown on the left-hand and right-hand side of the OSI model chart. The
application's data is encapsulated progressively with headers as the data is passed from
2 Networking Terminology Tutorial for Business Continuity Planners
Wireless
IBM SNA
Network
IBM
Coax thick thin
NetBUI
UTP 3,4,5,6
IBM
Video
APPN
Coax cable
MicroSoft
TV
NetBios
Multi Mode
Novell
Fiber - Light
IPX
Single Mode
Fiber - Laser Apple
local talk
Free Space
Optics FSO DEC
DecNet
Microwave
Banyon
Vines
Satelites otherslayer to layer in preparation for transmission to the other site. At the other end, headers are
removed progressively as the data is passed up towards the receiving application.
The header abbreviations are:
AH - application header
PH - presentation header
SH - session header
TH - transport header
NH - network header
DH - data link header
Now, let us zoom into this chart and examine the OSI model layers one-by-one.
OSI layer 1 - physical layer
Figure 2 shows the OSI layer 1 (the physical layer), and the types of physical connections that
can reside within this layer.
MAC MAC
1- Physical 1- Physical
LAN - Campus
MAN - WAN
Network
Figure 2 OSI layer 1 - physical layer
Layer 1 is the physical connection layer. Physical connections between two ends of the
network can consist of (but are not limited to):
Wireless, including variants of today’s wireless LAN technology and cell phone
technology.
Network thick or thin coax.
Unshielded Twisted Pair (UTP), which comes in various levels (3, 4, 5, 6), each of which
describes a certain level of drive distance, bandwidth capability, and resistance to
electromagnetic interference.
Video and cable, television coax.
Fiber optic cable, including the current strategic physical connection networking
technology. Fiber optic cable can be either multi-mode or single mode cable. These
modes are defined in Figure 8 on page 12.
Networking Terminology Tutorial for Business Continuity Planners 3
Wireless
Network
Coax thick thin
UTP 3,4,5,6
Video
Coax cable
TV
Multi Mode
Fiber - Light
Single Mode
Fiber - Laser
Free Space
Optics FSO
Microwave
SatelitesChannel
Extenders
DWDM
SONET
PtP, DSn, OCn
Frame Relay
PVCs, SVCs
LANE-CIP
Free Space Optics, including wireless or microwave technologies to handle one of the
biggest problems in using the strategic fiber optic capability, which can be “how do I get
fibre run the last mile from the network provider's closest connection point, to my particular
data center?”
Microwave and Satellites, including wireless technologies that are used for networking
communication especially at very long distances requiring no physical interconnect.
As shown in Figure 2, the LAN-Campus arrow shows that in the LAN-Campus environment,
the networking layer 1 physical interconnection technologies are usually one or more of the
following:
Wireless
Network coax
Unshielded Twisted Pair
Video coax
Multi-mode fiber optic
Conversely, in the Metropolitan Area Network or the Wide Area Network (that is, longer
distance than LAN-Campus), the layer 1 physical interconnection technologies are typically:
UTP
Video coax
Multi-mode and single-mode fiber optic
Free space optics
Microwave
Satellites
To begin any networking connection, the first requirement is that a physical layer 1
connection must be established, using one or more of these technologies.
OSI layer 2 - data link layer
Having established the layer 1 physical connection (which at this point is basically waiting for
something to travel upon it (whether that be electrical signals, light, or radio), the next step is
to establish the proper layer 2 data link connection. Figure 3 shows the OSI data link layer 2
and the physical protocols that reside within it:
TR shared & switched; 4 & 16 Mbps ATMLLC LLC
L L L LEthernet shared & switched;
H T T H2-Data Link 2-Data Link10-Base2, 10-Base5, 10-BaseT,
MACF, 100-BaseT, 100-BaseF, MAC
1000-BaseT, 1000-BaseF . . . . . . .
1- Physical 1- Physical
LAN - Campus
MAN - WAN
Network
Figure 3 OSI layer 2 - data link layer
4 Networking Terminology Tutorial for Business Continuity Planners
Wireless
Network
Coax thick thin
UTP 3,4,5,6
Video
Coax cable
TV
Multi Mode
Fiber - Light
Single Mode
Fiber - Laser
Free Space
Optics FSO
Microwave
SatelitesYou might think of the data link connection as the physical protocol that allows a ring or a
network of many physical connections to be managed, load-balanced, configured, and
reconfigured (dynamically in many cases). This layer specifically refers to managing,
load-balancing, and configuring at the physical connection level, not at the logical software
connection level.
Tip: The standard networking speed nomenclature is a lowercase b stands for bits and an
uppercase B stands for Bytes. Thus, a line that runs at:
1.544 Mbps is a 1.544 Mbps line or approximately 200 Kbps
100 BaseT, a 100 Mbps LAN, is approximately 10 MBps
Always make sure that you keep in mind the difference between bits and Bytes. Otherwise,
your conversation could be off by a factor of 8 or 10 in terms of the that speeds that you are
discussing.
The various technologies in the OSI link layer include (but are not limited to):
Ethernet: shared and switched, with various speeds including 10-BaseT (10 Mbps or
approximately 1 MBps raw), 100 BaseT (100 Mbps or approximately 10 MBps raw), 1000
BaseT (100 Mbps or approximately 10 MBps raw), commonly known as Gbit Ethernet.
Layer 2 note: In the LAN/campus environment, Ethernet has clearly become the
standard data link protocol that is used.
Asynchronous Transfer Mode (ATM): A method of transmitting data over this data line with
asynchronous characteristics (and reassembling the data in proper sequence at the
receiving end).
Private Virtual Circuits and Sxxx Virtual Circuits: (PVC and SVC): A method of
negotiating and establishing a private, secure connection over this data link even though
we are physically sharing Layer 1 physical links.
Frame relay: Another method of transmitting data over this data line with asynchronous
characteristics (and reassembling the data in proper sequence at the receiving end).
PtP DSn OCn: Point-to-point connections, DSn, and OCn (Optical Cable) data link
connections. This technology is used typically by telcos to describe some aspect of the
type of connection and the raw speed potential in the case of DSn, Ocn, such as:
– OC-3 denotes a raw speed capability of approximately 19 MBps
– OC-12 denotes a raw speed that is 4 times the capability of OC-3 (in other words,
approximately 78 MBps)
SONET: A a telco architecture that manages large (usually fiber optic) networks, and
allows powerful problem determination, performance monitoring, and reconfiguration
capabilities. In and of itself, SONET does not imply any particular speed.
These are raw speeds, and the effective transfer rate due to overhead from a Layer 3 and
above functions must be deducted from this raw speed.
Dense Wave Division Multiplexing (DWDM): A method of multiplexing multiple channels
of fiber optic based protocols (such as ESCON®, Fibre Channel, FICON®, Gbit Ethernet)
onto physical cable, by assigning different wavelengths of light (that is colors) to each
channel; then fanning it back out at the receiving end. Major players in the enterprise class
DWDM marketplace are: Nortel Networks, Cisco (ONS 15540), and Lucent.
Dense Wave Division Multiplexors are data link Layer 2 tools. Thus, the typical DWDM
machine does not perform any switching, routing or protocol conversion.
Networking Terminology Tutorial for Business Continuity Planners 5Channel
Extenders
DWDM
SONET
PtP, DSn, OCn
Frame Relay
PVCs, SVCs
LANE-CIP
Channel Extenders: These devices take a data center protocol (typically Fibre Channel,
ESCON, FICON, or Fibre Channel) and convert it to WAN protocols for transmission to its
companion machine at the remote site, where the signal is then converted the signal back
to its original form.
For SAN Distance extension (that is, Fibre Channel), there are many vendors and
Business Partners. See the System Storage™ Proven Web page at:
http://www-03.ibm.com/systems/storage/proven/index.html
Media Access Control (MAC): A data link functionality which defines how the computer in
question participates or is identified in the network from a hardware standpoint; the best
known example of a MAC address is the firmware unique hardware address.
Logical Link Control (LLC): A data link functionality which defines how the computer in
question participates or is identified in the network from a network address standpoint.
The most prevalent LLC protocol you have probably seen labeled as IEEE 802.2.
OSI layer 3 - network layer
Figure 4 shows the OSI data link layer 3 and the logical network protocols that reside within it.
N N3- Network 3- NetworkH H
Internet Protocol (IP)
TR shared & switched; 4 & 16 Mbps ATM
LLC LLC
L L L LEthernet shared & switched;
H T T H2-Data Link 2-Data Link10-Base2, 10-Base5, 10-BaseT,
MAC 10-BaseF, 100-BaseT, 100-BaseF, MAC
1000-BaseT, 1000-BaseF . . . . . . .
1- Physical 1- Physical
LAN - Campus
MAN - WAN
Network
Figure 4 OSI layer 3 - network layer
You can think of the OSI layer 3 network layer as being the actual logical language that the
two communicating computers use to talk to each other. Let us illustrate with an example
using a telephone call as an analogy (this is only an analogy for explanation purposes):
Layer 2 Data Link: You are in San Jose, you pick up a telephone, you get dial tone, you
dial Kuwait, and someone answers. This is an analogous example of a successful OSI
layer 2 data link connection using the telco's OSI layer 1 physical connection.
Layer 3 Network Link: Now, you start speaking English. The other person starts speaking
Arabic. Neither of you understand each other. This is a failed layer 3 Network Link. If
either of you switches to a language you both understand, that is a successful layer 3
Network Link.
6 Networking Terminology Tutorial for Business Continuity Planners
Wireless
IBM SNA
Network
IBM
Coax thick thin
NetBUI
UTP 3,4,5,6
IBM
Video APPN
Coax cable
MicroSoft
TV
NetBios
Multi Mode
Novell
Fiber - Light
IPX
Single Mode
Apple
Fiber - Laser
local talk
Free Space
DEC
Optics FSO
DecNet
Microwave
Banyon
Vines
others
SatelitesWith this as an example, the layer 3 network link logical protocols include (but are not limited
to):
IBM SNA: IBM Systems Network Architecture logical protocol, heavily used in the past, for
example in 3270/VTAM/NCP networks
IBM NetBEUI: An IBM PC LAN logical protocol
IBM APPN: IBM Advanced Program to Program Networking, an older IBM logical protocol
for program to program communication
Microsoft® NetBios: Microsoft LAN networking logical protocol
Novell IPX: Novell LAN networking logical protocol
Apple LocalTalk: Apple LAN networking logical protocol
DEC DecNet: DEC LAN and inter-DEC computer logical protocol
Banyan Vines: Banyan LAN logical protocol
IP: Internet Protocol is the best known and most widely used logical protocol today, and it
is the logical protocol that TCP/IP and the Internet use
Layer 3 note: IP is not a hard requirement. However, IP is shown as overlaying all
protocols because it has become the de facto world standard in the campus and network.
Often these other logical protocols listed are encapsulated within IP message frames to
exploit IP’s position as the de facto world standard.
Note: While each OSI functionality layer is distinctly identified, any individual network
component is likely to have some overlap of functionality across layers. For example, a
layer 3 switch is probably going to have aspects of layer 2 or layer 4 in it also.
Understanding the architectural functions of a layer allows you to decode what a vendor or
technician really means when they use terminology such as layer 2 switch, router, bridge,
or hub.
Networking Terminology Tutorial for Business Continuity Planners 7Channel
Extenders
MS Exchange
DWDM
SONET
other...
PtP, DSn, OCn
Frame Relay
Tivoli
PVCs, SVCs
LANE-CIP
Video
Voice VoIP
Voice PSTN
DB2, Oracle
SAP
E-MAIL
WWW
HTML
OSI layers 4, 5, 6, 7 - Transport, session, presentation, application layers
Figure 5 illustrated the additional layers of transport, session, presentation, and application.
Workstation Workstation
……...
……...
……...
……...
A 7- Application 7- Application A
DATA Data……...H H
……...
6- Presentation 6- PresentationP P
H H
5- Session 5- SessionS S
H H
T T
H H4- Transport 4- Transport
N N3- Network 3- NetworkH H
Internet Protocol (IP)
TR shared & switched; 4 & 16 Mbps ATM
LLC LLCL L L LEthernet shared & switched;
H T T H2-Data Link 2-Data Link10-Base2, 10-Base5, 10-BaseT,
MAC 10-BaseF, 100-BaseT, 100-BaseF, MAC
1000-BaseT, 1000-BaseF . . . . . . .
1- Physical 1- Physical
LAN - Campus
MAN - WAN
Network
Figure 5 OSI layers 4, 5, 6, 7 - transport, session, presentation, and application
From a networking perspective, the main action happens at the lower layers: 1, 2, 3. In
general, you can safely assume that if you can connect at the OSI layer 3 level, then from
there the software can provide the additional logic to transverse the other layers.
OSI layer 4 - transport layer general comment
TCP or Transmission Control Protocol (the TCP portion of TCP/IP) is in the OSI layer 4
transport layer. In this layer, TCP/IP data packets undergo:
Flow and congestion control
Reassembly of received -out-of-order packets
CRC error checking
8 Networking Terminology Tutorial for Business Continuity Planners
Wireless
IBM SNA
Network
IBM
Coax thick thin
NetBUI
UTP 3,4,5,6
IBM
Video
APPN
Coax cable
MicroSoft
TV
NetBios
Multi Mode
Novell
Fiber - Light
IPX
Single Mode
Fiber - Laser Apple
local talk
Free Space
Optics FSO DEC
DecNet
Microwave
Banyon
Vines
others
SatelitesInterfacing different networks
With the OSI model now understood, we turn next to the need and methods of interfacing
between two networks. There are four basic types of network interface devices, as illustrated
in Figure 6:
Repeaters
Hubs and bridges
Switches
Routers
7- Application 7- Application
6- Presentation 6- Presentation
5- Session 5- Session
Peer-to-Peer Communication
4- Transport 4- Transport
3- Network 3- NetworkNetwork Network
2-Data Link Data Link 2-Data LinkData Link
Physical Physical1- Physical 1- Physical
Figure 6 Interfacing networks using repeaters, hubs and bridges, switches, and routers
As shown with the vertical arrows in the diagram, determining which device to use depends
on which layer of the OSI model is interfaced. Some basic guidelines for device use include:
Repeaters are used when the highest level of network interconnection is fundamentally at
the OSI layer 1 physical connection level.
Hubs and bridges are used when the highest level of network interconnection is
fundamentally at the OSI layer 2 data link level.
Switches are used when the highest level of network interconnection is fundamentally at
the more basic levels of the OSI layer 3 network level.
Routers are used when the highest level of network interconnection is fundamentally deep
within the OSI layer 3 network level.
Obviously, there is no hard and fast line between these four types of interconnection devices.
Vendors all have varying levels of technology, and that technology can and does span layer
interconnections.
Networking Terminology Tutorial for Business Continuity Planners 9
Repeaters
Hubs / Bridges
Switches
RoutersFigure 7 is another example of where repeaters, hubs and bridges, switches, and routers can
typically be used.
7- Application 7- Application
6- Presentation 6- Presentation
5- Session 5- Session
Peer-to-Peer Communication
4- Transport 4- Transport
3- Network 3- NetworkNetwork Network
2-Data Link Data Link 2-Data LinkData Link
Physical Physical1- Physical 1- Physical
Network A Network B
Ethernet 10 Base T (shared) RepeaterEthernet 10 Base F (shared)
Ethernet 10 Base T (Shared/Switched) Ethernet 100 Base F (Shared/Switched) Bridge
Token-Ring 4 Mbps (Shared/Switched) Token-Ring 16 Mbps (Shared/Switched) Bridge
Token-Ring 4/16 Mbps (Shared/Switched) Ethernet 100 Base T (Shared/Switched) BridgeIP Subnet
IP Subnet xx.xx.xx.xx yy.yy.yy.yy Router
Internet Protocol (IP) Novell IPX Router
Microsoft NetBios Digital Equipment DecNet Router
ATM (LANE & CIP) ATM WAN (PVCs) Switch
ATM WAN (PVCs)Frame Relay Switch
PtP, DSn - OCn SONET Switch
SONET DWDM Switch
ATM (LAN, MAN and WAN) Switch
Figure 7 Another example of where repeaters, hubs and bridges, switches, and routers can be used
10 Networking Terminology Tutorial for Business Continuity Planners
LAN - Campus
MAN - WAN
Repeaters
Hubs / Bridges
Switches
Routers

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