Introduction to Data Communications
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5c. Breaking The Big Picture up!

The Big Picture still doesn't give us a good idea of the placement of the many protocols involved in networking and telecommunications. The Big Picture can be broken up into the following 4 areas:

1. Local Loop
2. LANs
3. MANs
4. WANs.
5. Telecommunications components

i. The Local Loop

The Local Loop is often called "the last mile" and it refers to the last mile of analog phone line that goes from the central office (CO) to your house. Typical local loop protocols are:

• Voice lines
• Modem connections ­ 56 kbps
• ISDN (Integrated Services Digital Network) ­ 2 x 64 kbps digital lines
• ADSL (Asymmetrical Digital Subscriber Line) ­ up to 8 Mbps
• Cable Modems ­ up to 30 Mbps

Note: Cable modems are not part of the Local Loop but do fall in the category of "the last mile" or how to get high speed digital communication to the premise (home). It would incredibly expensive to replace the existing cabling structure. All of these protocols are used to overcome the existing cabling limitations in the local loop and provide high speed digital data tranmission. The existing cabling was designed for voice communications and not digital.

ii. LANs

Local Area Networks (LANs) are networks that connect computers and resources together in a building or buildings close together. The computers share resources such as hard-drives, printers, data, CPU power, fax/modem, applications, etc... They usually have distributed processing - means that there is many desktop computers distributed around the network and that there is no central processor machine (mainframe).

Components of a LAN

The components used by LANs can be divided into cabling standards, hardware and protocols.

Examples of cabling standards used on LANs are:

• Cat 3, 4 and 5 cables
• IBM Type 1­9 cabling standards
• EIA568A and 568B
• Ethernet cabling standards: IEEE 802.3 (10Base5), IEEE 802.3a (10Base2), IEEE 802.3i (10BaseT)
• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP)
• Connectors: RJ45, RJ11, Hermaphroditic connectors, RS232, DB25, BNC

Examples of hardware devices are:

• Network Interface Cards NICs
• Repeaters
• Ethernet Hubs or multiport repeaters
• Token Ring MultiStation Access Units (MSAUs), Control Access Units (CAUs) and Lobe Access Modules (LAMs)
• Bridges
• Brouters
• Routers
• Gateways
• Print servers
• File servers
• Switches

Examples of LAN protocols are:

• Ethernet frame types: Ethernet_II, Ethernet_SNAP, Ethernet_802.2, Ethernet_802.3
• Media Access Control layer (MAC layer)
• Token Ring: IBM and IEEE 802.5
• Logical Link Control Layer (LLC) IEEE 802.2
• TCP/IP
• SMB, NetBIOS and NetBeui
• IPX/SPX
• Fiber Distributed Data Interchange (FDDI)
• Asynchronous Transfer Mode (ATM)

Introduction to Data Communications
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