Networking Essentials Notes

DEN'S Networking Essentials Notes

Coaxial Cable Types

RG-8 and RG-11	Thicknet (50 ohms)
RG-58 Family
RG-58 /U	Solid copper (50 ohms)
RG-58 A/U	Thinnet, Stranded copper (50 ohms)
RG-58 C/U	Thinnet, Military grade (50 ohms)
RG-59	Broadband/Cable TV (75 ohm) video cable
RG-62 A/U	ARCnet cable (93 ohm) RG-62 A/U is the standard ARCnet cable, but ARCnet can use fiber optic or twisted pair.

UTP/STP Category

Category (4 pairs)	Speeds
Cat 2	4 Mbps
Cat 3	10 Mpbs
Cat 4	16 Mbps
Cat 5	100 Mbps

Interrupt requests

IRQ 0	System Timer
IRQ 1	Keyboard
IRQ 2(9)	Video Card
IRQ 3	Com2, Com4
IRQ 4	Com1, Com3
IRQ 5	Available (Normally LPT2 or sound card )
IRQ 6	Floppy Disk Controller
IRQ 7	Parallel Port (LPT1)
IRQ 8	Real-time clock
IRQ 9	Redirected IRQ2
IRQ 10	Available
IRQ 11	Available
IRQ 12	PS/2 Mouse
IRQ 13	Math Coprocessor
IRQ 14	Hard Disk Controller
IRQ 15	Available

Cable Type Comparisons
Type	Speed	Distance	Installation	Interference	Cost	# of nodes per segment	# of nodes per network
10BaseT	10 Mbps	100 meters	Easy	Highly susceptible	Least expensive	1 computer
100BaseT	100 Mbps	100 meters	Easy	Highly susceptible	More expensive than 10BaseT
STP	16 to 155 Mbps	100 meters	Moderately Easy	Somewhat resistant	More expensive than Thinnet or UTP
10Base2	10 Mbps	185 meters	Medium Difficulty	Somewhat resistant	Inexpensive	30	1024
10Base5	10 Mbps	500 meters	More difficult than Thinnet	More resistant than most cable	More expensive than most cable	100	300
Fiber Optic	100 Mbps to 2 Gbps	2000 meters	Most difficult	Not susceptible to electronic interference	Most expensive type of cable

Signal Transmission

Baseband Transmission -- Digital

Baseband transmission uses digital signaling over a single frequency.

Entire communication channel is used to transmit a single signal.

Flow is bi-directional. Some can transmit and receive at the same time.

Baseband systems use repeaters to strengthen attenuated signals.

Broadband Transmission -- Analog

Broadband uses analog signaling over a range of frequencies.

Signals are continuous and non-discrete.

Flow is uni-directional and so two frequency channels or two separate cables must be used.

If enough bandwidth is available, multiple analog transmission systems such as cable TV AND network transmissions can be on the same cable at the same time. if this is the case, ALL devices must be tuned to use only certain frequencies

Uses amplifiers for signal regeneration.

IBM Cabling

Type 1	STP (Shielded twisted-pair)	used for computers and MAU's. 101 m	These three cable types can be used in Token Ring Networks	16 Mbps 260 computer limit
Type 2	STP, Voice and data	100 m
Type 3	UTP; Voice grade	45 m Most common Token Ring Cable		4 Mbps 72 computer limit
Type 5	Fiber-optic	industry standard
Type 6	STP; Data patch	used to connect MSAU's together used to extend Type 3 cables from one computer to the MSAU
Type 8	STP Flat; Carpet grade	Limited to 1/2 the distance of Type 1 cable
Type 9	STP; Plenum grade	used under floors or in ceiling space

Wireless Local Area Networks

Technique	Description	Limitations	Distances / Speed
Infrared	Broadband optical telepoint, as good as cable.	Line of sight	30 m
Laser		Direct line of sight
Narrow band radio	Single frenquency band	Cannot go through steel	4.8 Mbps
Spread spectrum radio	Signals over a range of frequency coded for data protection		250 Kbps
Point to point	Transfer data directly from a PC to PC.	Distance 200 feet indoor, 1/3 mile with line of site trnasmission.	1.2 to 38.4 Kbps
Multipoint Wireless bridge	Provides a data path between two buildings. Uses spread spectrum radio to create a wireless backbone.		3 miles
Long range wireless bridge	Uses spread spectrum technology to provide Ethernet and Token-Ring bridging.		25 miles
Mobile computing	Uses wireless public carriers to transmit and receive.

Base I/O port (Channel between CPU and hardware)

Specifies a channel through which information flows between the computer's adapter card and the CPU.
Each hardware device must have a different base I/O port

Base Memory address (Memory in RAM used for buffer area)

Identifies a location in the computer's RAM to act as a buffer area to store incoming and outgoing data frames.
Each device needs its own unique address.
Some cards allow you to specify the size of the buffer ( 16 or 32 k, for example)

Improving Network Card Performance

Direct Memory Access (DMA)

Data is moved directly from the network adapter card's buffer to computer memory.

Shared Adapter Memory

Network adapter card contains memory which is shared with the computer. The computer identifies RAM on the card as if it were actually installed on the computer

Shared System Memory

The network adapter selects a portion of the computer's memory for its use.

MOST common

Bus Mastering

The adapter card takes temporary control of the computer's bus, freeing the CPU for other tasks.

Moves data directly to the computer's system memory

Available on EISA and MCA

can improve network performance by 20% to 70%

RAM buffering

Ram on the adapter card acts as a buffer that holds data until the CPU can process it.

This keeps the card from being a bottleneck

On-board microprocessor

Enables the adapter card to process its own data without the need of the CPU

Remote-Boot PROMS (Programmable Read Only Memory)

Enables diskless workstations to boot and connect to a network.

Used where security is important.

OSI Model

Layer	Description	Device	Protocol
Application	Provides network access for applications, flow control and error recovery	Gateway	NCP, SMB, SMTP, FTP, SNMP, Telnet, Appletalk
Presentation	Performs protocol conversion, encryption and data compression	Gateway and redirectors	NCP, AFP, TDI
Session	Allows 2 applications to communicate over a network by opening a session and synchronizing the involved computers	Gateway	NetBios
Transport	Repackages messages into smaller formats, provides error free delivery and error handling functions	Gateway	NetBEUI, TCP, SPX, and NWLink
Network	Handles addressing, translates logical addresses and names to physical addresses, routing and traffic management.	Router and brouter	IP, IPX, NWLink, NetBEUI
Data Link	Packages raw bits into frames and includes a cyclical redundancy check(CRC). MAC Sublayer Communicates with network card and delivers error-free delivery between 2 computers. LLC Sublayer Defines service access points(SAPs) which are used to transfer information to the upper layers of the OSI model.	Switch, bridge and brouter	None
Physical	Transmits data over physical medium	Multiplexer and repeater	None

Protocols	Description
DDP (Delivery Datagram Protocol):	Apple's data transport protocol that is used in AppleTalk.
IP (Internet Protocol)	Part of the TCP/IP protocol suite that provides addressing and routing information.
IPX (Internetwork Packet Exchange)	Novell's netware protocol used for packet routing and forwarding
NetBEUI	It provides transport services for NetBIOS.
ATP (AppleTalk Transaction Protocol) and NBP (Name Binding Protocol)	AppleTalk's sessions and data transport protocols.
NetBIOS/NetBEUI	NetBIOS establishes and manages communications between computers; NetBEUI provides data transport services for that communication.
SPX (Sequenced Packet Exchange)	Novell's connection-oriented protocol that is used to guarantee data delivery.
TCP (Transmission Control Protocol)	The portion of the TCP/IP protocol suite that is responsible for reliable delivery of data.
AFP (AppleTalk File Protocol)		Apple's remote file management protocol.
FTP (File Transfer Protocol)		Another member of the TCP/IP protocol suite that is used to provide file transfer services.
NCP (Netware Core Protocol)		Novell's client shells and redirectors.
NFS (Network File System)		A client/server file system protocol primarily used to share directories with UNIX systems
SMB (Server Message Block)		A protocol that sits above the NetBEUI and NetBIOS that defines and formats commands for information passing between networked computers.
SMTP (Simple Mail Transfer Protocol)		Member of the TCP/IP protocol responsible for transfering mail.
SNMP (Simple Network Management Protocol)		Member of the TCP/IP protocol that is used to manage and monitor network devices.

The 802 project model

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802.1	Internet working
802.2	Division of Data Link Layer into sublayers LLC (Logical Link Control) Media Access Control (MAC)
802.3	CSMA/CD - Ethernet
802.4	Token Bus LAN (ARCnet)
802.5	Token Ring LAN
802.6	MAN (Metropolitan Area Network)
802.7	Broadband Technical Advisory Group
802.8	Fiber-Optic Technical Advisory Group
802.9	Integrated Voice/Data Networks
802.10	Network Security
802.11	Wireless Networks
802.12	Demand Priority Access Lan, 100 Base VG - AnyLAN

Protocols

NetBEUI	Fast, good error protection, ease of implementation, and low memory over-head. But it's not routable, it has very little support for cross-platform applications, and it has very few troubleshooting tools available.
TCP/IP	TCP/IP is able to span wide areas and is very flexible. It provides cross-platform support, routing capabilities, as well as support for the Simple Network Management Protocol (SNMP), the Dynamic Host Configuration Protocol (DHCP), the Windows Internet Name Service (WINS), the Domain Name Service (DNS), and a host of other useful protocols
AppleTalk	AppleTalk protocol is used for communication with Macintosh computers. By enabling AppleTalk, you allow Mac clients to store and access files located on a Windows NT Server, print to Windows NT printers, and vice versa. AppleTalk is routable.
APPC	The Advanced Program-to-Program Communication (APPQ protocol, developed by IBM, is a peer-to-peer protocol used in IBM's Systems Network Architecture (SNA) for use on AS/400-series computers.
X.25	X.25 is a set of wide-area protocols that are used in packet- switching networks. It was created to connect remote terminals to mainframes. Although many other wide-area communications types are available in the United States, X.25 is still widely used in Europe.
HDLC	High-level Data Link Control (HDLQ is a flexible, bit-oriented data link protocol that is based on IBM's Synchronous Data Link Control (SDLQ. It has been standardized by the ISO. HDLC can support half- or fullduplex transmission, circuit- or packet-switched networks, peer-to-peer or client/server networks, and transmission over cable or wireless media.
XNS	The Xerox Network System (XNS) was created by Xerox for use in Ethernet networks. XNS is the basis for Novell's IPX/SPX, but it is seldom found in today's networks.