Transcript Cables

Miscellaneous Network Info
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Brief history, WANs, LANs
Examples
Issues
Cabling
WAN – Wide Area Network
• Connect geographically separate networks
• ATM has played an important part in WAN
(not LAN)
LAN
LAN
WAN
LAN
LAN
WANs started with telephone (analog) lines.
Needed to send digital data over analog lines.
Wanted to use digital lines (e.g. FR, ATM)
instead.
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B
Analog lines
Digital lines
Modem
LANs were serial until 1984 or so.
Wiring was a big problem!
36/64/128 serial ports (local or dial)
VAX
• There were many network protocols e.g.
Appletalk, IPX, Decnet, OSI, SNA, IP
• Routers were needed to route each of
these
• Now, it’s pretty much an IP world
Why doesn’t ATM play a role in the
LAN?
• About 8 years ago ATM looked good,
scalable (T1, T2, T3)
• Every frame 53 byte cell size so HW could
be simple
• Had QOS feature built into the protocol
• Current Ethernet switches would’ve been
ATM switches
• BUT Ethernet kept ramping up, had an
installed base, and was simple
LAN Technology Battles
IEEE 802.3 or ethernet (DEC, Xerox, Intel)
IEEE 802.4 token bus (General Motors)
IEEE 802.5 token ring (IBM)
Issues:
Random access vs. deterministic approach
Installation
Hardware and cabling
Applications and protocols
Ethernet won
• Many hadn’t thought it would scale, but it did.
•To extend ethernet geographically, needed a bridge.
Spanning tree algorithm was major development.
Cabling System
IBM started building structured cabling plants.
Devised a better copper cable so got reasonable
distance for digital info.
CAT 5 was a major innovation - at every jack
guaranteed to work to 300 ft (100 m).
Future is fiber optic (cost still high).
Example: Network with Collapsed
Backbone
Traffic Collapses to the Core
Example:
Core is ATM (OC3)
Each floor in each building has a switch
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OC3
OC3
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To building floor
OC3
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• Collapsed Backbone is where routing is
• Could build in redundancy by putting
routers in buildings in case the backbone
has a problem
Example: To the Buildings…
• Optical fiber runs from backbone router to
building (in conduits)
• Optical fiber runs between floors in
building
• Point of presence on each floor
• From wiring closet on the floor, Category 5
(100Mbps) or Category 6 (1 Gbps), keep
lengths to 50 m just to be safe
• Ethernet used
Used to do this…
Bridge
Now can do this…
10BaseT – 10 Mbps
Spanning tree is in silicon.
Every port has spanning tree running on it.
Others don’t see conversation between ports.
In switched ethernet, every port is its own ethernet.
VLANs
Virtual LANs, VLANs, were important in switches
Not physically connected as a LAN.
HW can be programmed so each port belongs to a VLAN
(All belong to the same collision domain)
So all on VLAN see the ethernet packet.
Convergence
• Digitize all info & attach to a spigot so
data, voice, video are carried together
• Ethernet best effort service caused doubt
8 years or so ago
Private Branch Exchange
• Companies, enterprises use PBX for
internal phone service
• PBX is a circuit switch
• Digital
• Doesn’t go through telephone net
• Phone line to PBX not very demanding
(not like a data connection)
• Highly reliable
• Hosted/Virtual PBX now available
• IP PBX now available
• Still need to connect to POTS (Plain Old
Telephone System)
Voice Over IP
• Taking phones off PBX to do VoIP or
using IP PBX
• Some reliability issues in large
environments
• Over the WAN, it’s good & saves money
for individuals
Quality of Service
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QOS management needed
QOS being built into router ports
QOS can be built into switch ports
Need to control applications
Example:Network Management
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Performance
Fault
Configuration
Accounting
Security:
Performance
– Monitor activity of various types
– Use traffic shaper that monitors application
traffic and, when configured % exceeded,
drops packets
– Use Network Management platform to query
nodes via SNMP and retrieve performance
statistics
Fault
– Use SNMP to monitor switches, routers,
servers to see if they’re up or down
– Notify via paging, email if something is down
(e.g. ISDN lines go down if no activity so may
get errant message, then need to actively
send traffic on line to check). Need to avoid
storms.
– Knocking off a cable or making a change is
most likely reason for a node to be down.
Sometimes it’s the path to the node that’s
down.
– Remote reboot.
– Battery backups send low power traps.
Configuration
– Do some configuring using SNMP sets, but
often configure first then deploy
– Use Network Management platform to
discover nodes in network to make sure
nothing new is being attached or something
isn’t being taken away
Accounting
– Network manager specifies user and device
access to network resources.
– Assigns privileges to user
– No charge back
• Security
– Firewalls
– Monitoring
Some Link Layer Technologies
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Ethernet – CSMA/CD, 10 – 1000 Mbps
Fast Ethernet – 100 Mbps, needs Cat 5
Gigabit Ethernet – 1Gbps
LocalTalk – Apple, CSMA/CA
Token Ring – IBM, decreasing use
FDDI – Fiber Distributed Data, WAN
ATM – Asynchronous Transfer Mode,
WAN mostly
Protocol
Cable
Ethernet
twisted pair 10Mbps
coaxial
fiber
twisted pair 100Mbps
fiber
twisted pair .23Mbps
Fast
Ethernet
LocalTalk
Speed
Topology
Linear bus
star, tree
star
FDDI
Fiber
4 – 16
Mbps
100 Mbps
Linear bus,
star
Star-Wired
Ring
Dual ring
ATM
twisted pair 155 –
fiber
248Mbps
Linear bus,
star, tree
Token Ring Fiber
Ethernet card with RJ-45, AUI,
BNC connectors
Twisted Pair
Found in telephone applications, ethernet. Form of wiring in which two
conductors are wound together to cancel out electromagnetic interference
from external sources and crosstalk for neighboring wires.
• 8 wires
• Shielded Twisted Pair used in areas
susceptible to interference
• Unshielded Twisted Pair very common
UTP Categories
Type
Category 1
Category 2
Category 3
Category 4
Category 5
Use
Voice Only (Telephone Wire)
Data to 4 Mbps (LocalTalk)
Data to 10 Mbps (Ethernet)
Data to 20 Mbps (16 Mbps
Token Ring)
Data to 100 Mbps (Fast
Ethernet)
• Ethernet 10BaseT 10Mbps
• Ethernet 100BaseTX 100Mbps
• Cables connecting NIC cards are now
usually UTP with RJ-45 connectors
• For 100BaseTX, the cable must satisfy
Category 5 rating.
• Cat 5 has 4 pairs of twisted wires.
10BaseT and 100BaseTX Ethernet use
only 2 of the pairs
Twisted Pair – 2 Flavors
Use Crossover to connect
• 2 PCs
• 2 Routers
• 2 Hubs/Switch
Some hubs have an uplink port. Straight
through can be used between uplink port
of hub and regular hub port.
If UTP port on switch is MDI/MDI-X (Medium
Dependent Interface), either can be used
to connect to another
Use straight through to connect
• PC to router
• PC to Hub/Switch
Coaxial Cable
• Single copper conductor with plastic
insulation and braided metal shield
• Difficult to install but greater cable lengths
• Thick (10Base5) 500 meters
• Thin (10Base2) 2 is for 200 but goes 185
meters
BNC is most common connector for coax.
Used for video connections – analog and
digital. Were commonly used on 10base2
ethernet networks.
Fiber Optic
• Glass core surrounded by protective
materials (Ethernet is 10BaseF)
• Transmits light vs. electronic signals so
eliminates electrical interference
• Longer distance than coax or twisted pair
• Immune to moisture, lighting problem
• Faster
• Difficult to install
Fiber Optic Cable
Uses standard connector (FC, SC, ST, LC,
MTRJ)
AUI – Attachment Unit Interface
A 15 pin physical connector interface
between a NIC and an Ethernet cable
• Some AUI/RJ-45 transceivers have AUI
interface on one side and RJ-45 on the
other
• Becoming rarer because it’s common to
include Medium Attachment Unit (ethernet
transceiver) internally
Serial Connections
• Majority use RS-232
• RS-232 specifies 25-pin connector called
DB-25. 25-pins not always needed so
there are other connectors (DB-9, RJ-45)
Serial Connection for Router
Configuration
• One use is to connect router to PC
console port for configuration then use a
terminal emulation program (e.g. kermit) to
talk to the router
Serial Wan Connections
• Router may have one or more serial WAN
interfaces in addition to Ethernet
interfaces.
• Synchronous serial ports
• Can operate in full-duplex modes
• E.g. T1 line (1.544 Mbps)
• Framing may be Point-to-Point Protocol or
High Level Data Link (HDLC)
Cisco also uses proprietary DB-60
connector. To connect in lab, use
DB-60 crossover cable
Typical T1 WAN connection
DSU/CSU – Data Server Unit/Channel Service Unit
Miscellaneous Technologies
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ISDN Integrated Services Digital
Net (not telephone line)
DSL Digital Subscriber Line (same
cable as telephone)
T1 1.5 Mbps ~$800/month
T3 2nd fastest non-optical 45 Mbps
~15K/month
SONET Synchronous Optical
Networking uses laser or light
emitting diodes/LEDs to send
digital info
OC3 155.52 Mbps Optical size of
largest Internet backbone provider
OC12 fiber optic net 621.84 Mbps,
smaller backbones
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OC48 2488.32 Mbps/2.4 Gbps
(48x basic SONET signal 51.84
Mbps)
OC192 as of 2005 only large ISPs
9953.28 Mbps
OC768
802.11b 11 Mbps
802.11g 54 Mbps
Cable 10 – 20 Mbps ~$100/month
Satellite slower than DSL or cable
Broadband intranet access > 56K
dialup with cable modem and fiber
optic
10 Gigabit ethernet