Branch Office Remote Access Technologies

1
Chapter 6

• Branch Office Remote Access Technologies

2
Topics

• Remote Access Strategies
• Leased Lines
• T1 Services
• ISDN
• Satellite Technology
• Optical Submarine Networks

3
Spanning the Globe

• Corporate offices span the globe
• The size and number of employees varies at each
  office
• Remote access must be easy for users and
  manageable for administrators

4
Remote Access Considerations

• Security
• Number of Users per location
• Number of Users Connected Simultaneously
• Number of Hours per day connected
• Type of Access required. I.E. e-mail.ftp
• Access is continuous or intermittent

5
Security Considerations

• Limit the number of entry points into a network
• Monitor and control access to the computer
  network
• Examine audit records and security logs
• Require strong passwords
• Change passwords every 30 days

6
What Works at One Location, May Not Work
Everywhere

• Due to Government Regulations Technology might
  not be exportable from United States
• Right of Ways may not be available may have to
  use wireless
• Equipment may not be available -
• Obsolete Technology

7
Leased Lines

• Permanent telephone connection between two points
• Organization owns the leased line not shared
  with anyone else
• Quality of service is assured
• Line access is assured
• Line is always active
• Fixed monthly fee
• Fees based on distance and speed of connection

8
Advantages of Leased Line

• Flexible level of connection based upon your
  business requirements
• Synchronous service where upstream and downstream
  speeds are the same
• Private network offers reduced security risks as
  it does not use the public network
• Service Level Agreement provides peace of mind
• Managed service

9
DTE and DCE

• A point-to-point connection has two pieces of
  Data Termination Equipment (DTE) at each end.
  I.E. computer, printer or terminal
• In between the DTE are two Data Communications
  Equipment (DCE), I.E. modem

10
Company access to POP

• Companies connect to branch offices, or use
  leased lines for Internet Access
• Point of Presence (POP) is an access point to the
  Internet
• Internet is an essential communication,
  collaboration, and marketing tool which users
  need 24/7
• Leased lines offer greater security than public
  links

11
Firewalls on Leased Lines

• Increased threats of Internet misuse has prompted
  companies to add firewalls to private leased
  lines to filter traffic coming into their network
• The firewall filters traffic based on rules
• Can block several types of attacks
• Can monitor network traffic
• Can not protect against virus attacks

12
Multidrop Connection

• Splitting usage of a single dedicated line is
  called a multidrop connection.
• Many DTEs can share one line with only two DTEs
  conversing at a time
• Without a multidrop, the organization would
  require a separate dedicated line for each site

13
Multipoint Connection

• Large companies use a combination of multidrop
  and multipoint connections
• Multipoint connections has many point-to-point
  connections and multipoint connections integrated
  into one large network

14
T-Carrier General Specifications

• Digital provides improved error performance
• Medium Independent UTP, STP, COAX, Microwave,
  Satellite, Ir, optical fiber not true for
  speeds greater than a T1
• Full-Duplex simultaneous 2 way traffic
• Symmetric same amount of bandwidth in each
  direction
• Four Wire
• Trunk Device

15
T1

• Leased line speeds vary from 64 Kbps to 45 Mbps
• T1 speed is 1.54 Mbps
• Can carry voice, data and multimedia traffic
• T1 can divide voice and data into different
  channels
• 24 channels
• Each channel is 64 Kbps a company can buy
  single channels (a fractional T1)

16
T1 Devices

• The 24 channels of a T1 are managed by a Time
  Division Multiplexer (TDM)
• Each channel is divided into a time slot I.E.
  there might be 12 time slots for voice, 6 time
  slots for data, 6 time slots for video
• Requires a CSU/DSU
• T3 45 Mbps also fractional T3

17
CSU

• The Channel Service Unit (CSU) is the
  demarcation point from the Telco and the customer
• CSU is the end point of the digital signal
• CSU converts customer data and voice signals into
  the format needed by the Telco for transmission
• Used by Telco for diagnostic loop back tests

18
DSU

• Converts data signals from other devices
• Often built into 1 device with CSU
• Converts data signals to the format required as
  input to CSU
• DSU converts signals from bridges, routers, and
  multiplexers to bipolar digital signals used by
  the T1 digital lines
• Not needed if voice only traffic
• CSU/DSU may be built into other devices I.E.
  multiplexers, routers and cards in a PBX

19
T1 Types
20
Other T-Carriers
21
Switched Bandwidth

• If high bandwidth is only required sporadically,
  switched bandwidth might fill the need
• If can be a combination of dedicated bandwidth
  and switched (dial on demand)
• A LAN is connected through an Etherswitch to the
  multiplexer so users can use the fractional T1
  line

22
ISDN

• Integrated Services Digital Network
• Digital service over twister pair copper
• Supports three simultaneous separate
  conversations
• Largely replaced by xDSL and Cable Modem services

23
DSL

• Digital Subscriber Line (DSL) uses two wire
  copper to provide always on Internet
• Limitation distance between Central Office and
  customer determines speed, distance cant be
  greater than a few miles
• Speed 144 Kbps 6 Mbps

24
ISDN BRI

• ISDN Basic Rate Interface (BRI) supports two
  channels (B channels) to carry conversations from
  telephone, computer, fax, or other device each
  channel 65 Kbps
• A D channel carries call setup information and
  signaling is carried, 16 Kbps

25
ISDN PRI

• Multiple BRIs combined into an IDSN Primary Rate
  Interface (PRI)
• Dedicate trunks used to connect corporate
  locations to the telco CO
• Can connect to a PBX, mainframe, LAN, WAN,
  multiplexers, ISDN controllers and video
  conferencing units
• 1.544 Mbps through T1, 23 B channels, 1 D channel
  for signaling, timing and diagnostic

26
ISDN Equipment

• A Network Termination Device (NTI) serves as the
  network interface for the BRI connection
  provides physical and electrical termination
  functions
• A Terminal Adapter (TA) is required for PC access
• Devices that support IDSN directly are called
  Terminal Equipment (TE1) I.E. digital phones,
  digital faxes, and intergrated voice/data
  terminals

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Benefits of ISDN PRI

• Reduce call setup time
• Reduce costs when compared to T1 leased line
• High-speed switched access to low-volume remote
  locations
• Use both local and interexchange carrier services
• Provides bandwidth on demand

28
PRI vs T1
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PRI vs T1
30
PRI vs T1
31
PRI vs T1
32
PRI vs T1
33
Communication Servers

• Communication Servers also known as Access
  Servers or Network Access Servers connect users
  to internetworks over normal telephone lines
• Purpose deliver to remote enterprise users
  internetwork-ready connections thru modems
  connected to serial telephone lines

34
Access Server Components

• Processor Cards plug in cards with a CPU, memory
  and a serial RS-232 port, w/o these each remote
  control session would require a separate PC
• SNMP (Simple Network Management Protocol) is
  built into the circuitry to provide remote
  management
• Controllers video, SCSI, EIDE, dual Ethernet,
  Serial, USB

35
Access Servers Services

• Terminal Service provide terminal emulation I.E.
  3270, UNIX rlogin
• Protocol Translation Service conversion between
  remove users virtual terminal protocol to
  another virtual terminal protocol
• Telecommuting Service PPP or SLIP
• Routing Service provide dial-on-demain routing
  (DDR) over dial-up phone lines

36
Access Server Features

• An Access Server is a collection of independent
  servers, each process card can run an Intel based
  Operating System I.E. Windows, Linux, Free BSD
  UNIX
• Processor cards are hot swappable
• Can host SQL databases, Web IIS servers, FTP
  access, firewall and proxy servers

37
Access Server Communication Features

• A digiboard is a serial card with multiple RS-232
  ports to provide analog access
• T1 access card for high speed
• ISDN access card

38
Windows 2000 Terminal Services

• Microsoft applications run from a server
• Remote users run software through browser, a
  Citrix Metaframe
• Access server becomes a thin client-server farms.
  Each dual processor card can support as many as
  200 (average) users
• Thin clients (Net PCs) have no floppy or CD-ROM
  and possible no hard drive

39
Unguided Media

• Electromagnetic wave transmission might simply an
  installation, I.E. dont have to dig up the
  street.
• Broadcast omni-direction
• Line of Sight, 3 types Microwave, Infrared and
  Laser (blocked by structures, limited distance
  due to curvature of the earth)
• Spread Spectrum Technology

40
Radio Broadcast

• Radio broadcast is omni-directional, signals are
  broadcast in all directions to provide a wide
  coverage
• Cellular phones use this technology
• Not secure, easily tapped

41
Microwave

• Microwave transmission is considered a form of
  radio and uses a high frequency range
• Susceptible to interference, jamming, and
  eavesdropping
• Uses dish antenna, horn antenna and waveguides
• Can be a health hazard

42
Infrared and Laser

• Light based technologies that operate on low
  power levels
• Used in LANs because the only operated over a
  limited distance
• Infrared built into PCs, Palm Pilots, Printers,
  Cellular Phones, Remote Controls

43
Spread Spectrum Technology

• Spread Spectrum Technology (SST) is used in LANs
• Resists jamming and hard to intercept, used in
  Military applications
• Frequency hopping is the easiest Spread Spectrum
  Technology to use
• Signals are spread over a very high frequency
  range, over 200 times the bandwidth of the
  original signal

44
Satellite Links

• Data can be transmitted via microwave over great
  distances via satellites
• Satellites are used for weather forecasting,
  television broadcast, Internet communications and
  GPS
• 3 orbit altitudes Geostationary, Low Earth
  Orbit, Middle Earth Orbit
• Life expectancy of 7 to 15 years, Solar panels
• Launch costs 15 Million each
• VSAT Very Small Aperture Terminal, Shell
  Installed them at over 5,000 Shell gas stations

45
Geostationary Satellites

• Used to transmit data and television signals
• Stationary in relation to a specific location on
  earth
• 22,238 miles above earth
• Data speeds up to 155 Mbps
• Propagation delay .25 to .50 seconds
• More than 100 communication satellites in orbit
• Most coverage of the earth, 1 satellite can see
  40 of earth, 3 satellites can cover globe

46
Low Earth Orbit

• LEO satellites are in orbit at a constant
  altitude a few hundred miles from earth
• Travel in orbit at 17,000 miles per hour, so
  gravity wont pull them down
• Data rates of 2.4 to 9.5 Kbps
• Used for mobile phones, PDA, automobile
  communication systems
• 400 to 1,000 miles from earths surface
• Lowest earth coverage, Iridium global phone uses
  66 LEO satellites to cover the globe

47
Middle Earth Orbit

• MEO satellites are used for global wireless
  communication
• Orbit earth in 2-12 hours
• Orbit at 8,000 miles
• Data rates of 9.6 to 38.4 Kbps
• Use modest size antenna

48
Submarine Networking

• 1858 first transatlantic cable installed for
  telegraph transmissions, worked only 30 days,
  they used 2,000 volts for transmission
• Optical cable is used for voice, data and
  Internet using Wave Division Multiplexing,
  optically amplified repeaters are installed along
  the ocean
• 8.4 terabits per fiber pair
• Trans-Atlantic coax cable from 1920 still used
• Over 116,000 miles of fiber was recently laid to
  Europe from North America

49
Submarine Networking

• Since 1988 20 new digital optical Trans-Atlantic
  cables have been installed
• Scouting ships survey the ocean bottom with sonar
  to determine a route with a soft ocean bottom and
  no wrecks
• Anywhere the water is less than 1 mile deep they
  will use a plow to dig a trench to bury the cable
  in the sand to keep the cable safe from anchors
  and fishing nets