Networking with Remote Clients and Servers

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Chapter 7

• Networking with Remote Clients and Servers

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Remote Node

• Today remote nodes connect via ISDN, DSL, cable
  modem, and Virtual Private Networking (VPN)
  across the Internet, in addition to dialing up
  using the plain old telephone system (POTS).
• When connecting via remote node, a computer makes
  a connection through a public network to a remote
  access server (RAS).

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Remote Node

• The remote access server then acts as a router,
  exchanging traffic between the remote computer
  and the network.
• This enables the remote computer to act as though
  it is a network node, able to transfer files,
  access database information and applications, and
  print to network printers.

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Remote Node
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Remote Node

• Remote computing is typically slow!
• When the remote node accesses applications from a
  network location, the application must first
  download to the remote node before it is
  processed.
• Updates made to data must be uploaded across that
  slow link as well.
• A server handles requests the same way regardless
  of whether the node is local or remote.

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Remote Node

• Remote node computing is simply a point-to-point
  link. The remote node connects directly to a
  remote access server via an intervening network.

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Remote Node
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Remote Node

• Remote nodes differ from local nodes in only one
  way Data travels through a modem to access the
  network in a remote node when it uses a dialup
  connection.
• Data travels through a network interface card
  (NIC) to access the network in a local node.
  Therefore, a remote node simply treats its modem
  as though it were a NIC.

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Point-to-Point Connections with PPP

• When you create a dialup connection to RAS, you
  must use a protocol to communicate.
• The protocol most often used to create the
  point-to-point connection across the telephone
  network is the aptly named Point-to-Point
  Protocol (PPP).
• It is based on an older protocol know as the
  Serial Line Internet Protocol (SLIP).

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Point-to-Point Connections with PPP

• PPP offers several advanced capabilities.
• When it is used to connect with a remote network,
  it encapsulates the upper-layer protocols.
• This process enables a remote node to appear to
  be connected locally.
• PPPs link-control ability indicates when a
  connection is poor, providing for automatic
  termination and redialing.

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Point-to-Point Connections with PPP

• PPP supports both Password Authentication
  Protocol (PAP) and Challenge Handshake
  Authentication Protocol (CHAP), which both prompt
  users to log on to establish a connection using
  encryption or clear text passwords.

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Point-to-Point Connections with PPP
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Using DSL for Remote Node

• ADSL
• G.Lite (DSL lite)
• HDSL
• VDSL

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Remote Access Service (RAS)

• When you dial into a network as a remote node,
  you log into a remote access server.
• This is often the same server that provides
  remote node services across the Internet, via
  tunneling protocols.
• A variety of remote access servers is available.

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Remote Access Service (RAS)
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Tunneling to a Virtual Private Network (VPN)

• VPN describes remote nodes that access a network
  via the Internet in a secure fashion.
• That security is provided by tunneling protocols,
  along with encryption.
• Many encryption schemes can encode data with
  strengths up to 128 bits, an encryption strength
  that virtually prevents decryption altogether.

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Tunneling to a Virtual Private Network (VPN)

• VPN is available to clients who connect to the
  Internet through nearly any type of link.
• Whether the client connects via ISDN, DSL, cable
  modem, or dialup line, a VPN session can usually
  be created.
• VPN creates a virtual point-to-point connection
  to the RAS.
• Tunneling is driven by the need to protect that
  virtual point-to-point link from being
  interrupted or eavesdropped upon.
• Tunneling works by encapsulating data within IP
  packets in an encrypted format.

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Tunneling to a Virtual Private Network (VPN)
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Point-to-Point Tunneling Protocol (PPTP)

• Point-to-Point Tunneling Protocol (PPTP) takes
  its name from PPP because it uses PPP frames in
  its tunneling process.
• PPTP encapsulates PPP frames within IP datagrams,
  which are then transmitted across the Internet.

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Layer 2 Tunneling Protocol

• The Layer 2 Tunneling Protocol (L2TP) was
  developed to establish a viable alternative to
  PPTP as a standard.
• Like PPTP, L2TP is an extension of PPP that
  supports multiple protocols.
• Two servers provide an L2TP tunnel the first is
  an L2TP access concentrator (LAC), which is
  simply a RAS. The second is an L2TP network
  server (LNS), which provides the L2TP service.

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Remote Control

• Remote control was an early remote networking
  technology that enabled users to run applications
  on the network with fair performance.
• The user would create a remote control session
  with a computer that was connected directly to
  the LAN.
• On the remote computer, a window would appear
  with the remote computers desktop within it.
• All application processing and data remained on
  the LAN the only data that traveled to the LAN
  from the remote computer were keyboard and mouse
  clicks.
• The graphical user interface contained the data
  traveling back to the remote computer.

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Remote Control

• Remote control computing overcame some of the
  issues with remote node computing.
• Because the application ran only on the
  LAN-connected computer, the remote computer
  didnt need to be compatible with the network
  applications, nor did it require any additional
  hardware.

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Remote Control
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Independent Computing Architecture from Citrix

• Citrix developed its ICA protocol to facilitate
  remote control sessions.
• The protocol runs within the upper layers of the
  OSI reference model, including the application,
  presentation, and session layers.
• It establishes the session, maintains it, and
  terminates it.

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Independent Computing Architecture from Citrix

• During the session, ICA carries keystrokes, mouse
  clicks, and graphical data in the form of
  compressed draw commands.
• ICA is highly optimized in that it will update
  only the graphical data that has changed on the
  screen.
• The protocol also allows file transfers between
  the local and remote computers.

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Independent Computing Architecture from Citrix

• ICA requires very little bandwidth and can
  provide solid performance over a 20-Kbps
  connection.
• This means that the average computer using a
  56-Kbps modem connection will experience
  exceptional performance with an ICA session.

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Microsoft Remote Desktop Protocol (RDP)

• Remote Desktop Protocol (RDP) offers much the
  same type of service as ICA.
• It supplies the transport for keystrokes, mouse
  clicks, and display data for a server providing
  sessions to a thin client application.

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Microsoft Remote Desktop Protocol (RDP)

• RDP is limited in the protocols it will run
  across theres no direct dial method.
• RDP clients will operate only across a TCP/IP
  network.
• If you need to run remote sessions across a
  network that is solely IPX/SPX or NetBEUI, you
  would be required to use Citrix MetaFrame.