I can't get Internet

Submitted by DeepGeek on Sun, 03/02/2008 - 02:39.

I can't get Internet!

More than a dozen years of providing Internet technical support fails to show DaGeek a more abused trouble report. Qualified technical support agents are quite aware of Internet access procedure, but remote descriptions of symptoms are often ambiguous. The afflicted user, however, describes an untechnical but quite personal understanding of their problem. Most resolutions require clear understandings by both parties.

The agent must assume the role of an expert interviewer. Ask insightful questions. Provoke illuminating answers. Define ambiguous vocabulary. A more successsful approach places "Internet" problems in layers by the OSI model. Using the OSI model will quickly determine where effective remedy to Internet dysfunction is applied.

Significant science is developed for the OSI model, and technical discussion may glaze uninitiated eyes. For the more shallowly interested readers, a quick guide to determining which layer is failing will be more useful. Truly sick readers might read through details of all seven layers and become effective technical support agents. Each layer will eventually link to more detail as this guide evolves. To help readers understand technical details of the extended guide, complimentary controls are planned for each section — just click "Simplify" when science is not needed or "Detail" when science is missing.

This guide evolves with time. Feel free to comment and question. Technical support agents solve many "can't get Internet" problems in a day … but you might have a previously unencountered problem. This guide serves both sides of the solution.

First, guidance for determining layers of failure is most helpful. Knowing points of failure is knowing what must change. Ask the question, "How is Internet not available?"

First, this article comes from the Internet. Perhaps you had to use an alternate computer. Perhaps you found a printed archive. What you have is better called Internet access limitation. Let's compile a list of limitations.

Workstation
Is the limitation on a single computer?
Does the same limitation happen on computers in other buildings?
Knowing, precisely, the scope of affected workstations is very useful to resolution. Connection problems may be for a single computer, a LAN, an ISP or even a peering point.
Routing
Do you have an IP address and netmask?
Do you have a default route?
Can you ping your gateway?
Can you trace a route beyond your gateway?
Routing is essential to Internet access. Find your IP address and default gateway. If you have an IP address, different from 127.0.0.1 (localhost), see if you can ping other addresses. If you can ping your gateway address, you have a connection on the Internet and could be able to reach other Internet locations. Try a traceroute for 12.122.81.97 and see if you reach that (very reliable) peering point.
Hosts
Does 12.122.81.97 respond to a ping request — what about ggr2.attga.ip.att.net?
Does google.com respond to a ping request — what about 64.233.167.99 and 64.233.187.99 and 72.14.207.99?
There is more than one way to connect two Internet hosts. Most people use named hosts (like google.com and youtube.com and amazon.com) but Internet hosts also use IP addresses. Check the local host files and named server configurations.
Application
Can you explore with a browser?
Can you look at e-mail?
Can you chat with messenger or IRC applications?
Does your VoIP telephone work?
Many applications depend on Internet connection. Browsers and e-mail clients are only the more recognized Internet applications. Messengers like ICQ and AIM use the Internet. VoIP uses the Internet. If some part of your Internet function is missing, it is possible that a firewall is misconfigured. Some ISP do not allow using port 25 (sending mail) except by their specified mail server. Peer to peer services like BearShare and Limewire and Kazaa are often blocked. Some workstations are disallowed connection to some websites; other workstations are only allowed a few specific web sites.
Detail
Can you access a web site, but your account services aren't available?
Are some web pages showing red "x" images?
These are signs of software configurations and forgotten passwords. Confirm settings and user credentials.

  1. The physical layer
    • Cables
    • modem
    • router
    • switch
    • NIC
  2. Data Link Layer
    The Data Link Layer includes the Logical Link Control Sublayer and the Media Access Control Sublayer.
    • error correction
    • network flow control
    • device driver
  3. Network Layer
    • connectionless service
    • address
    • accounting
    • routing
    • forwarding
    • firewall
  4. Transport Layer
    • connection-oriented service
    • input-output port management
    • NetBIOS
    • reliability
    • sequencing
    • terminal flow control
  5. Session Layer
    • authentication
    • authorization
  6. Presentation Layer
    The Presentation Layer includes the Common Application Service Element and the Specific Application Service Element sublayers.
    • encryption>
    • compression>
  7. Application Layer
    • web browser
    • messaging
      • AOL Instant Messenger
      • ICQ
      • mIRC
      • Trillian
      • YAHOO! Instant Messenger
    • e-mail client
    • peer-to-peer
      • BitTorrent
      • eDonkey
      • Napster
      • KaZaA
      • Gnutella
    • networked file system
      • NFS
      • SMB
      • FTP
    • VoIP
»