Network Architecture

Overall structure:
topology
physical media
speed
channel access method

Major Architectures and Standards

Architecture	Standard
Ethernet and AppleTalk	IEEE 802.3
Token Ring	IEEE 802.5
FDDI	ANSI X3T9.1
100VG-AnyLAN	IEEE 802.12
ARCNet	IEEE 802.4 like

Most popular architecture.(1997, 83% of market)
• Economical
• Easy to install
• Available for multiple media.

Two major Ethernet speeds

10 Mbps including 10base5, 10base2, 10baseT, or 10base F.
10base 5 is the original Ethernet Classic
100 Mbps as 100baseXX. Fast Ethernet

Faster than Fast Ethernet

Gigabit Ethernet standards have recently been approved.
The new standard is called IEEE Std 802.3ab.
1,000 Mbs using CSMA/CD and standard Ethernet frames.

Ethernet Characteristics

Contention Access Method
CSMA/CD or CSMA/CA
Burned in MAC address
Multiple media i.e. TWP, Coax, or Fiber

Ethernet History

Developed from work done by Bob Metcalf at PARC
Aloha Net
Further developed by a consortium that included Digital, Intel, and Xerox(DIX).
In 1990, became IEEE standard 802.3.

Ethernet 5-4-3 Rule

Applies to all Coaxial Cable based Ethernet Networks.
A coaxial Ethernet can consist of a maximum of five segments with four repeaters, with devices attached to three of the segments.
Latency
Insertion loss

Transceivers

Transceivers convert internal parallel signals to serial signals
Thicknet utilizes external transceivers with AUI connectors.
All other forms of Ethernet utilize internal transceivers.

10base5 Ethernet

Thicknet cable. (RG-8)
Difficult to work
Expensive
50 Ohm impedance
Runs up to 500 meters
External transceivers with Vampire Taps.
AUI (DX15) connectors

10base2 Ethernet

Thinnet cable. (RG-58)
Relatively easy to work
Most economical coax
50 ohm impedance
Runs up to 185 meters
Internal transceivers with BNC connectors.

10baseT Ethernet

Twisted pair cable. UTP or STP (Cat 3 or Cat 5)
Most economical form of Ethernet
Most widely implemented form of Ethernet
RJ-45 connectors
Runs up to 100 meters
Each computer is an end node on the cable.
Eliminates major Coax vulnerability.

10base F Ethernet

Can run up to 2000 meters.

100baseXX Ethernet

100baseT (Fast Ethernet)
Uses CSMA/CD
Can use a variety of cable configurations.

Ethernet Frame Types

Ethernet supports four frame types.
Each frame type is unique
With NT, unless manually specified, each frame type will not work with other frame types.
Communications requires frame type specifications that match exactly.

Four Ethernet Frame Types

Frame Type	Utilization
802.3	IPX/SPX Novel 2.X and early 3.X
802.2	IPX/SPX Novel 3.12 and 4.X
SNAP	Used by Ethertalk and in mainframes
Ethernet II	Used by TCP/IP

Segmentation

In an Ethernet based net, increasing computers increases contention.
Segmentation is a process that divides the network reducing contention.
Segmenting a network effectively multiplies bandwidth.

Token Ring

Cabled as a physical star but functions electrically (logically) as a ring.
IEEE 802.5, Originally, 4 Mbs, now 16 Mbs.
Can use much larger packets than Ethernet.
MAC address burned into NIC.
Active Technology that passes a token around the ring. (NAUN to NADN)

Token Ring Hubs

Called Multistation Access Units (MAUs) and Smart Multistation Access Units (SMAUs).
Each hub can accommodate 8 computers.
Allows for 33 hubs in a net.

Fault tolerant -- Should the token become damaged, the network can recover through a process called Beaconing.

Token Ring Cable

While Token Ring uses UTP or STP, IBM has their own cabling system.
Most networks use IBM Type 3 cabling.
Uses RJ-45 or RJ-11 connectors.
Type 6 cables for patch panels

Token Ring Beaconing

Beaoning is the process of signaling computers on a ring that token passing has been interrupted.
Provides ring networks with a limited ability to repair themselves.

AppleTalk and ARCNet

AppleTalk is a simple, easy to implement network architecture designed for use with Macintoshes.
Phase 2 of Appletalk is called EtherTalk.

Using Token passing and is similar to IEEE802.4.
Not widely employed.

FDDI Fiber Distributed Data Interface

Token passing with dual counter rotating rings.
Can use a primary and a secondary ring.
Can be configured to automatically switch to secondary ring in the event of primary ring failure. (dual connect devices)
Hubs are called concentrators.
Copper version available for short distances (CUDDI)

Higher Speeds

Broadband with Cable modems.
ADSL from the phone companies
Broadcast technology. (Satellite)