Networking BASICS

1
Networking BASICS

• Wide Area Networks
• Unit 3
• Lesson 9

2
Objectives

• Define a WAN and tell how it is used.
• List and describe different WAN technologies.
• Explain how to protect a WAN from unauthorized
  users.
• Define privacy.

3
Wide Area Network

• It connects computers and LANs over a larger
  geographical area.
• It crosses public thorough-fares such as roads,
  railroads, and water.

4
WAN vs. LAN

• Geography
• Ownership
• Management
• Speed
• Cost

5
Wired Analog Service

• It uses standard wired analog telephone lines.
• It requires a modem to convert digital signals to
  analog signals.
• Its top is speed 56 Kbps.
• Asymmetric Some modems are faster downloading
  than uploading.

6
Wired Analog Service
7
Digital Cellular

• It provides WAN data access to mobile users.
• Its coverage area is divided into smaller cells.
• Users roam into adjacent cells or handoff
  into remote networks.
• The current technology is 2.5G with a maximum
  speed of 384 Kbps.

8
Trunk-Based Leased Lines

• The same type of lines are used to connect the
  telephone companys switches.
• They provide always-on high-speed connections.
• The most common is T1, which oper-ates at 1.5
  Mbps over twisted pair wires.

9
Trunk-Based Leased Lines
10
Digital Subscriber Lines (DSL)

• They transmit at 1.5 Mbps over regular telephone
  lines.
• They use the higher unused frequencies to send
  data.
• Different versions of DSL ADSL, G.list, HDSL,
  HDSL2

11
Digital Subscriber Lines (DSL)
12
Cable Modem

• It uses the same coaxial cable that brings in
  cable TV signals.
• All cables for a neighborhood are connected to a
  neighborhood splitter.
• The connection is shared among all users in a
  neighborhood.
• Speed 300 Kbps 1.5 Mbps

13
Local Multipoint Distribution Service (LMDS)

• Transmits Maximum 155 Mbps downstream and 1.54
  upstream
• Range 2 5 miles
• It is a low-cost option to laying fiber optic
  cables.
• Its signals are susceptible to interference from
  rain or fog.

14
Multichannel Multipoint Distribution Service
(MMDS)

• It uses lower-frequency signals than LMDS.
• Range up to 35 miles
• Its signals are less susceptible to interference
  from rain or fog.

15
Satellites

• They have been used for over 40 years.
• They relay signals from one point on earth to
  another.
• They are classified according to the type of
  orbit.

16
Low Earth Orbiting (LEO)

• They orbit at an altitude of 200 900 miles.
• They circle the earth in 90 minutes.
• They have a small footprint.
• More satellites are needed to cover the entire
  earth.

17
Low Earth Orbiting (LEO)
18
Medium Earth Orbiting (MEO)

• They orbit at altitudes between 1,500 10,000
  miles.
• They circle the earth every 12 hours.
• They have a large footprint.
• Fewer are needed to cover the earth.

19
Remote Wireless Bridge

• It connects LANs located in different buildings.
• The distance between buildings can be up to 18
  miles at 11 Mbps.
• It has similar characteristics to a wireless LAN.

20
Free Space Optics (FSO)

• It transmits up to 1.25 Gbps at a distance of 2.5
  miles.
• It uses low-powered infrared beams.
• Its transmissions cannot be eavesdropped.

21
Virtual Private Network (VPN)

• It uses the public Internet to transmit private
  data.
• It encrypts data into a packet before sending.
• There is no cost for setting up or using a VPN.

22
Virtual Private Network (VPN)
23
Public Switched Data Networks (PSDN)

• Actual network itself
• X.25
• Frame Relay
• Asynchronous Transfer Mode (ATM)

24
Public Switched Data Networks (PSDN)

• Integrated Services Digital Network (ISDN)
• Synchronous Optical Network (SONET)
• Metro Ethernet Network (MEN)

25
Firewall

• It inspects incoming traffic.
• Packet-filter firewall Inspects header of each
  packet.
• Stateful packet-filter firewall Examines a
  packets source IP.
• Proxy firewall Examines the contents of a
  packet.

26
Network Address Translators (NAT)

• Disguises the internal IP by substituting a fake
  IP and port number.
• When a packet is returned, NAT replaces the fake
  numbers with the actual IP and port number.

27
Privacy

• Privacy is the right to be left alone to the
  degree that you choose.
• It is a difficult problem to keep personal data
  private.
• Identity theft is a major crime.

28
Summary

• The definition of a wide area network (WAN) is a
  network that connects computers and LANs over a
  large geographical area. Most industry experts
  consider a network to be a WAN if it crosses a
  public thoroughfare such as a road, highway,
  railroad, or body of water. There are several
  differences between WANs and LANs. WANs are a key
  component of the telecommunica-tions industry.
  This industry is made up of government agencies
  that regulate telecommunications and carriers,
  which provide the services consumers can
  purchase. WANs play a vital role in the world of
  business today. Businesses such as the airline
  and banking industries, investment services, and
  credit card services rely heavily on these
  networks to perform basic everyday operations.

29
Summary (continued)

• There are four general categories of WAN
  technologies and within each category are several
  different types of WANs. One of the original
  methods for connecting a computer to a WAN was
  using a standard wired analog telephone. In order
  for a computer to use a telephone dial-up line, a
  modem is needed. The top speed that data can be
  sent over a dial-up connection is about 56 Kbps.
  Digital cellular service transmits data in a
  digital format using cellular telephony. Digital
  cellular telephony today is called 2.5G and
  operates at a maximum speed of 384 Kbps. The
  future of digital cellular telephony is called
  Third Generation (3G). 3G is intended to be a
  uniform and global worldwide standard for
  cellular wireless communications.

30
Summary (continued)

• Leased data connections are permanent and
  dedicated lines between two sites. These
  connections can be leased from pub-lic telephone
  carriers or from private companies. Trunk-based
  leased lines provide always-on high-speed
  connections. A Digital Subscriber Line (DSL)
  transmits at 1.5 Mbps over regular telephone
  lines and has a low cost. Another carrier that
  can provide access to WANs is the local cable
  television operator. Multipoint distribution
  services refer to a technology that uses wireless
  high-frequency microwave radio signals to connect
  to a WAN.

31
Summary (continued)

• Local Multipoint Distribution Service (LMDS) can
  transmit from 51155 Mbps downstream and 1.54
  Mbps upstream. Because it uses low-powered radio
  frequency waves, these have a limited range. The
  coverage area for LMDS is between 25 miles.
  Multichannel Multipoint Distribution Service
  (MMDS) uses low-frequency signals that can travel
  farther, are less susceptible to interference
  from rain and fog, and are better able to
  penetrate buildings than high-frequency LMDS
  signals. MMDS can send data signals at 1.5 Mbps
  downstream and 300 Kbps upstream at distances of
  up to 35 miles. Satellites have been used for
  worldwide communications for over 40 years.
  Satellites relay signals from one point on the
  earth to another point.

32
Summary (continued)

• Satellite systems are classified according to the
  type of orbit they use. Low earth orbiting (LEO)
  satellites orbit the earth at an altitude of just
  200900 miles. Because they are in such a low
  orbit, their area of earth coverage (called the
  footprint) is small. Medium earth orbiting (MEO)
  satellites orbit the earth at alti-tudes between
  1,50010,000 miles and have a bigger earth
  footprint thus, fewer satellites are needed for
  total coverage.
• Leased data connections require that a certain
  amount be paid monthly or annually for the data
  connection. An alternative is to use private data
  connections. With a private data connection, a
  business purchases and owns the equipment, thus
  eliminating any leases for data connections.

33
Summary (continued)

• A remote wireless bridge is designed to connect
  two or more LANs that are located in different
  buildings. The distance be-tween buildings can be
  up to 18 miles when transmitting at 11 Mbps or up
  to 25 miles when transmitting at 2 Mbps. Free
  space optics (FSO) is an optical wireless
  point-to-point technology used to connect remote
  sites to create a WAN. FSO can trans-mit at
  speeds of up to 1.25 Gbps at a distance of 2.5
  miles. A virtual private network (VPN) uses the
  public Internet to transmit sensitive data, but
  does it in such a way that unauthorized
  indi-viduals cannot read the data, thus acting
  like a private network. VPN works by encrypting
  the data and then storing it in a packet (called
  encapsulating) before it is sent out through the
  Internet. The receiving computer then decrypts
  and extracts the data.

34
Summary (continued)

• A different solution than leasing or creating a
  free data connection is to use a public switched
  data network (PSDN). A PSDN is an actual network
  itself, whereas leased or public data connections
  are only the connections between networks. With a
  PSDN, each site needs only a single leased line
  circuit to con-nect it to the PSDN. X.25 was the
  first public switched data net-work (1960s) and,
  by todays standards, is considered to be very
  slow (9.664 Kbps). The most popular PSDN is
  Frame Relay. Unlike X.25, Frame Relay does not
  use an error-check-ing system instead, the
  sending and receiving devices are responsible for
  checking for errors. This lack of an
  error-check-ing system helps Frame Relay run
  faster, with speeds starting at 56 Kbps and
  running to a top speed of 40 Mbps.

35
Summary (continued)

• Asynchronous Transfer Mode (ATM) can support
  data, voice, and video all on one network. ATM
  uses small, fixed-length packets of only 53
  bytes, allowing the packets to be moved very
  quickly. ATM currently runs at speeds of 155 Mbps
  or 622 Mbps. Integrated Services Digital Network
  (ISDN) is a digital telephone line that can be
  used for either data or voice transmission.
  Syn-chronous Optical Network (SONET) uses fiber
  optic lines to transmit data, voice, or video at
  high speeds. SONET services are available at a
  variety of speeds. Metro Ethernet Network (MEN)
  transmits Ethernet LAN data across an
  Ethernet-based WAN. MEN eliminates the need to
  convert LAN data to another format before
  transmitting it over a PSDN WAN.

36
Summary (continued)

• Any computer connected to a WAN or to the
  Internet faces a serious security risk.
  Unauthorized users, sometimes called hackers, can
  use sophisticated tools and a knowledge of
  net-works to break into computer networks. A
  number of steps can be taken to reduce security
  risks. A firewall inspects incoming traffic and
  accepts or denies entrance to that traffic based
  on a set of predefined rules. A network address
  translator (NAT) disguises internal IP addresses
  by substituting fake IP numbers. On each packet
  going out to the WAN, the NAT removes the real
  source IP number and port number and replaces
  them with a fake IP address and fake port number.

37
Summary (continued)

• Privacy has been defined as the right to be left
  alone to the degree that you choose. Prior to
  WANs and the Internet, it was easy to limit the
  amount of information that another person could
  learn about you. However, today it is more
  difficult to keep information private. Industry
  experts recommend that consumers regularly review
  credit reports, use appropriate passwords on
  financial computer accounts, shred bills after
  they are paid, and use a firewall to protect
  personal computers.