Transcript switch

TDC 461
Basic Communications
Systems
Local Area Networks
29 May, 2001
Agenda
• Local Area Networks
– Components
• Local Area Network
Technologies
– Topologies
– Ethernet
– Transmission Media
– Token Ring
– Network Interface Cards
(NICs)
– Network Operating System
software
• Client vs Server functions
• Peer-to-Peer vs. Serverbased
• LAN Interconnection
– LAN Switches
– Routers
What is a LAN?
• Key Elements:
–
–
–
–
–
LAN Components
• Workstations (PCs, etc.)
–
• Interconnecting Cable
–
• Network Operating System (NOS) Software
The Network Interface Card (NIC)
and Networking Software (NS) m us t
be com patible with each other and
with the com puter or device into
which they are ins talled.
Networking
Software
(NS)
Network Interf ace
Card (NIC)
NIC NS
NS
NS
Network Hub or
Wiring Center
NIC
Media
NIC
NIC NS
NIC NS
NIC
NS
NIC
Shared
Application
Serv er
GOLDMAN: LAN
FIG. 01-05
Shared Laser
Printer
LAN Topologies
• How are Workstations connected together?
–
–
–
Bus Topology
Bus Topology Example:
10Base5 Ethernet
Attachment
Unit Interface
(AUI Cable)
Terminating
Resister
Medium
Attachment
Unit (MAU)
Thick
Coaxial
Cable
Ring Topology
Dual Ring Example:
Fiber Distributed Data Interface (FDDI)
Dual-Attached Workstations in Normal Operation
Dual-attached
counter
rotating rings
Self healed after Link Failure
Self-healing
FDDI dual- link failure
attached
adapters
GOLDMAN: LAN
Star Topology
Star Topology Example:
10BaseT Ethernet
Twisted
Pair
10Base-T Hub
LAN Cable
• LAN Cable can be of several types:
–
–
–
Twisted Pair
• Unshielded Twisted Pair (UTP)
– Similar to telephone cable, but
• Usually 4-pair cable is used
• UTP Category ratings
– Category 3 - 10 Mbps up to 100 meters
– Category 4 - 16 Mbps up to 100 meters
– Category 5 - 100 Mbps up to 100 meters
• Shielded Twisted Pair (STP)
–
Coaxial Cable
• LAN coaxial cable is similar to Cable TV
cable (and can be identical)
– Construction
•
•
•
– Advantages
•
– Disadvantages
•
Coaxial Cable
Solid metal inner core Plastic insulator - Foil shield Braided shield/outer
Plastic or vinyl jacket
usually white
conductor
GOLDMAN: LAN
FIG. 08-17
Fiber Optic Cable
• Transmits data using light rather than
electricity
– Structure
•
•
– Advantages
•
•
– Disadvantages
•
diameters
Fiber Optic Cable
Glass core
Glass cladding
50 microns
62 microns
100 microns
Multimode
125 microns
125 microns
140 microns
2-8 microns
Singlemode
Plastic or vinyl jacket
Note: A micron is a millionth of a meter
GOLDMAN: LAN
FIG. 08-18
LAN Hardware
• Cabling and NIC card specs dictated by
standards document for the particular LAN
Access Method:
–
–
–
–
–
Ethernet
Token Ring
ARCNet
Fiber Distributed Data Interface (FDDI)
etc.
NIC Card Sales - 1Q 1998
(percentage of 10.9 millions units sold)
Fast
Ethernet
46%
Source: In-Stat
Other
FDDI
2%
1%
Ethernet
41%
Token Ring
10%
Network Operating Systems
• Popular NOSes:
–
–
–
• NOS determines workstation role:
–
–
Installed LAN Servers
2Q 1998
NetWare
36%
NT Server
17%
UNIX
42%
Other
5%
Source: Dataquest
New Servers Deployed
Jan-June 1998
NT Server
39%
NetWare
34%
UNIX
23%
Other
4%
Source: Network World
File Servers
• A File Server
• Shared files accessed via
–
–
•
•
Network Drives
Client
File Server
(PC w/ NOS software)
(PC w/ Server software)
Drive F:
C:\USERS\GREG
Security
• Login (Log on)
• Network Manager controls access rights for
each user to each resource.
Client
File Server
(PC w/ NOS software)
(PC w/ Server software)
Drive F:
C:\USERS\GREG
File Servers
•
•
Client
File Server
(PC w/ NOS software)
(PC w/ Server software)
Request
Response
Example: Get File
Open File
File Opened
Read Data
Data
Close File
File Closed
Client
File Server
NOS Types
• Peer-to-Peer NOS
–
–
• Dedicated Server NOS
–
–
–
Peer-to-Peer
All workstations are loaded with
the same Peer-to-Peer network
operating sy stem
Each workstation conf igured as
serv ice requester (client), serv ice
prov ider (serv er), or both.
Client/Server
Client workstations are loaded
with specialized client sof tware.
Serv er computers are loaded with
specialized serv er sof tware
designed to be compatible with
client sof tware.
Printer Serv er
GOLDMAN: LAN
FIG. 10-01
to other LANs
File Serv er with gateway
to other networks.
LAN Standards
• IEEE 802 Committee Standards
– 802.3 - Ethernet
– 802.5 - Token Ring
LAN Standards
• IEEE 802 Standards include
– Physical (Layer 1)
• Cable Types
• Maximum length restrictions
• Data rate and bit encodings
– Medium Access Control (Layer 2)
• Access control protocol (determines which device
can transmit when
• Frame header/trailer format
Ethernet
• Physical Standards:
– 10Base5 (1985)
• 10 Mbps Thick Coaxial Cable (Bus)
– 10Base2 (1988)
• 10 Mbps Thin Coaxial Cable (Bus)
– 10BaseT (1990)
• 10 Mbps Twisted Pair (Star)
Ethernet
• Physical Standards:
– 100BaseT (1995)
• 100 Mbps Twisted Pair (Star)
– 100BaseF (1995)
• 100 Mbps Fiber (Star)
– 1000BaseX (1998)
• 1 Gbps Fiber (Star)
Ethernet
• IEEE Naming System:
– <data rate><signal type><length of longest
cable in 100s of meters>
– Example: 10Base5
• 10 Mbps data rate
• Baseband signal type
• Longest cable length = 500 meters
Ethernet
• IEEE Naming System:
– <data rate><signal type><length of longest
cable in 100s of meters>
– Example: 10Base5
• 10 Mbps data rate
• Baseband signal type
• Longest cable length = 500 meters
10Base5 Ethernet
Attachment
Unit Interface
(AUI Cable)
Terminating
Resister
Medium
Attachment
Unit (MAU)
Thick
Coaxial
Cable
10Base2 Ethernet
Thin
Coaxial
Cable
10BaseT Ethernet
Twisted
Pair
10Base-T Hub
100BaseT Ethernet (Fast
Ethernet)
• Requires high-quality (Category 5) twisted
pair cabling
• Requires 100 Mbps NIC cards in PC
workstations
• Requires 100 Mbps hub
100BaseT Ethernet (Fast
Ethernet)
Twisted
Pair
100Base-T Hub
Switched Ethernet
• Switched vs. shared
• Bandwidth to desktop
• Additional hardware
– Switches
• Switched 10
• Switched 100
Gigabit Ethernet
• Requires fiber optic cabling
• Requires Gigabit NIC cards in PC
workstations
• Requires Gigabit Ethernet hub or Gigabit
Ethernet switch
1000BaseX Ethernet
Fiber
1000BaseX Hub
Ethernet MAC Protocol
• Medium Access Control (MAC) layer
protocol is identical for all Ethernets:
– Ethernet Frame format
– Carrier Sense Multiple Access with Collision
Detection (CSMA/CD) used to determine
which workstation can send at any given time.
Ethernet Frame Format
Preamble
Dest. Source Length
Address Address
Data
CRC
Ethernet Frame
• Header:
– Preamble - 8 bytes - alternating 1/0 bits for
clock synchronization
– Dest. Address - 6 bytes
– Source Address - 6 bytes
– Length - 2 bytes - Packet length
• Trailer:
– CRC - 4 bytes - Cyclic Redundancy Check
MAC Protocol
•
•
•
Carrier Sense Multiple Access with
Collision Detection
• To transmit data packet:
– First, listen to see if any other station is
transmitting (Carrier Sense)
•
– When network is quiet, start transmitting
•
•
Carrier Sense Multiple Access with
Collision Detection
• Station Backoff
– Each station involved in collision:
•
•
•
– As number of collisions grows, range of
random values (N) increases (“exponential
backoff”)
Ethernet Enhancements
• Switched Ethernet
–
• Full-duplex Ethernet
–
Ethernet Switches
• Ethernet Switch
–
–
–
Switches vs. Routers
• How is Switch different than a Router?
– Addressing
• Switch uses layer 2 MAC addresses
• Router uses layer 3 IP address
– Speed & security
• Switch forwards packets fast (~50-100 nsec).
• Router takes more time (~1-50 msec) and provides
other security features
Switched Ethernet
Twisted
Pair
Ethernet Switch
Switches vs. Hubs
• How is Switch different than a Hub?
– Broadcasting (and Security)
• Hub broadcasts every packet to every device
• Switch forwards packet out single port
– Matching Data Rates
• All ports on hub must run at same data rate
• Switch ports can run at different rates (can buffer
incoming packet at one data rate and re-transmit at
another data rate).
Full-Duplex Ethernet
• Full-Duplex Ethernet allows a workstation
to send and receive data simultaneously.
• Requirements
– Must have a full-duplex NIC card
– Must be connected to Ethernet switch
Switched Hierarchy
• Switches allow network manager to put
bandwidth where it is needed.
– Some users get 10 Mbps shared (hub)
– Some users get 10 Mbps dedicated (switch)
– Some users get 100 Mbps shared (hub)
– Some users get 100 Mbps dedicated (switch)
POWER USERS
DeskTop
Switch
10Base-T Hub
Backbone
Switch
100 Mbps
Ethernet
links
File
Server
File
Server
Token Ring
• Physical Layout:
– Dual Ring of Stars
• Medium Access Control Protocol
– Token Passing
Token Ring
• Advantages over Ethernet:
–
–
• Disadvantages over Ethernet:
–
–
Twisted
Pair
RO
RI
Multistation Access
Unit (MAU)
Ring In
Port
Patch Cable
(TP, STP, Fiber)
Multistation Access
Unit (MAU)
RO
Ring Out
Port
RI
Token Ring Frames
1. Token Frame
SD AC
ED
2. Data/Control Frame
SD AC
FC
Dest. Source
Address Address
SD -- Start Delimiter
AC -- Access Control
FC -- Frame Control
Data
CRC
ED -- End Delimiter
FS -- Frame Status
ED
FS
Access Control Byte
Access Control Byte
P P P T M R R R
Priority
Bits
Reservation
Bits
Token Monitor
Bit
Bit
Token Ring Operation
1
4
MAU
3
2