Chapter 7

Network Architectures

Describing a Network Architecture

• Overall network structure
• Physical media
• Topology
• Channel access method

Network Architecture Standards

• Ethernet
• Token Ring
• AppleTalk
• ARCnet
• FDDI
• ATM

Ethernet

• Most popular architecture
• Ease of installation, Low cost
• Frames, Baseband, CSMA/CD
• 10/100Mbps
• NIC ROM address MAC address

IEEE 10Mbps

• 10BASE-5 Thicknet coaxial
• 10BASE-2 Thinnet coaxial
• 10BASE-T Unshielded twisted pair
• 10BASE-F Fiber-optic cable

10BASE-5

• Standard Ethernet
• 500 meters (1640ft)
• Transceivers, vampire taps, 50 meter
• 500 meters/segment 5 segments
• Frozen yellow garden hose
• 5-4-3 rule

5-4-3 Rule

10BASE-2

• 185 meters (607ft)
• Thinnet, not TV coax
• Transceiver built into NIC
• BNC connector, terminators
• Bus topology,
• 5-4-3 rule applies

10BASE-T

• Most popular, Star topology
• UTP, STP twisted pair, 100 meters (328ft)
• Low cost of media and equipment
• 5-4-3 doesn't apply
• Active hubs act as repeaters

10BASE-T Hub Connection

10BASE-F

• Fiber-optic cable
• 2000 meters (6561ft)
• 10BASE-FL fiber to the desktop
• 10BASE-FP passive hubs 500 meters per segment
• 10BASEFB Fiber backbone between hubs
• All use star topology

100Mbps IEEE Standards

• 100VAnyLAN, 100BASE-T
• Fast Ethernet
• Suited for video
• CAD computer aided drafting
• CAM computer aided manufacturing
• Imaging

100VG-AnyLAN

• Demand priority
• Cascaded hubs
• Star topology
• Root or parent hub
• 100BASE-VG, 100VG, VG, AnyLAN

100BASE-T

• Category 5 UTP, Cascading hubs
• Star topology, Modified 802.3
• 100BASE-T4 4 pair Cat. 3,4,5 UTP
• 100BASE-TX 2 pair Cat. 5UTP
• 100BASE-FX 2 strand fiber-optic

Gigabit Ethernet

• 1000BaseX
  • Based on standards for fiber optic
  • Full duplex mode operation
  • Up to 5000 meters (16,404ft)
  • 1000BaseLX
  • 1000BaseSX
  • 1000BaseCX
• 1000BaseT
  • 100 meter segments of Cat5
  • requires all 4 pairs

FourEthernet Frame Types

• Ethernet 802.3
• Ethernet 802.2
• Ethernet SNAP
• Ethernet II

Ethernet 802.3 Frame

• IPX/SPX
• Usually only Novell NetWare 2.X 3.X
• Ethernet raw
• Start Frame Delimiter (SFD)
• Cyclic Redundancy Check (CRC)

Ethernet 802.2

• 802.3 Ethernet standard compliant
• Logical Link Control (LLC) OSI layer
• Has 3 additional LLC fields
• IEEE 802.2 group was LLC focused
• Novell had chosen Ethernet raw for 802.3

Ethernet SNAP

• SubNetwork Address Protocol
• AppleTalk Phase II
• Enhanced 802.2 frame
• Includes a "type" field
• Network protocol in data portion

Ethernet II

• Used in TCP/IP networks
• SFD field included in preamble
• Type field replaces length field
• Type field identifies protocol

Segmentation

• Increasing numbers of computers
• Increasing network traffic
• Network slows down
• Break network into smaller pieces
• Add bridge or router

Token-Ring

• Developed by IBM
• IEEE 802.5 standard
• Physically cabled as a star; operates
• gically as a ring
• Token passing channel access method

How Token-Ring works

• Token passes around ring
• Received from: Nearest Active Upstream Neighbor (NAUN)
• Transmitted to: Nearest Active Downstream Neighbor (NADN)
• Each computer reads the token
• Acts upon if addressed to it
• Sends to NADN if not or;
• Attaches data if token is empty
• "To" addressee verifies reception

Beaconing

• Automatic Token-Ring fault isolation
• First computer is active monitor
• Every 7 seconds transmits packet
• Travels ring collecting addresses
• Ring reconfigures avoiding inactive computers

Token-Ring Hardware

• Hub is the IBM Multistation Access Unit (MAU) or Smart MAU (SMAU)
• Ten connections, eight computers
• Ring IN, Ring Out (RI/RO) ports

Token-Ring Cabling

• American Wire Gauge standards (AWG)
• Larger AWG means smaller wire diameter
• Types 1, 2, 3, 5, 6, 8, 9

AppleTalk

The AppleTalk Environment

• Simple, easy to implement
• Uses dynamic addressing scheme
• Protocols
  • EtherTalk
  • TokenTalk
  • Local talk

Local Talk

• Uses STP
• Bus topology
• Share devices, data in small number
• Tree structure
• Connection is with three connectors

EtherTalk & TokenTalk

• EtherTalk is AppleTalk protocols running on 802.3 Ethernet 10Mbps network
• TokenTalk is AppleTalk protocols running on a Token-Ring 4Mbps or 16 Mbps network

ARCnet

ARCnet Environment

• Attached Resource Computer Network
• Up to 2.5 Mbps
• Token-passing channel access
• Operates in a virtual ring
• Wired as bus, star, or both

ARCnet Environment

• Tokens are passed based on SID (Station Identifiers)
• NIC addressee is set by dip switches
• SID for next station in line NID (Next Station Identifier)
• 1-255 nodes receive token

ARCnet Hubs

• Active hubs are generally 8 ports
  • Regenerate signal
  • Hub to hub < 600 meters
• Passive hubs are generally 4 ports
  • Pass signal only from port to port
  • Passive to active hub < 30 meters

ARCnet Cabling

• RG-62 A/U 93 ohm coaxial
• BNC connectors
• Bus or star topology
• UTP up to 121 meters (400ft)
• Fiber-optic up to 3,485 meters (11,500ft)

FDDI

• Fiber Distributed Data Interface
• Token-passing channel access
• 100Mbps, 500 nodes, 100 km (60 miles)
• Physical ring, no hubs
• Dual counter rotating rings

Other Network Alternatives

• Broadband technology
  • Analog, Internet, cable modems
• Broadcast technology
  • Satellite home reception, Internet
• Gigabit technology
  • 1,000 Mbps, 802.3z/D2 for UTP