Networking Theory 101: Introduction to Networking

(An Evolving Online Research for Peer Review)

by Michael Egan

Purpose: The purpose of this paper is to provide some networking information for people that wish to better understand it.

To facilitate this abstract topic's disassembly into a more tangible form more easily quantified, this review is broken into multiple parts or sections.

Terms: (Incomplete: being written) This paper includes a few semi-technical words that are partially defined on this link's page. A general user unfamiliar with these words may want to examine this section to prepare themselves with the meaning of most of the technical words used here.
Networking Models (Rough First Drafts in progress) can be reviewed, and would provide an initial reference for understanding the topics that will come later in this document below this point. (This includes a simple review of the ISO OSI 7 Layer Reference Model for networking and an attempt to push TCP/IP into a 5 Layer Model using some of the thoughts and ideas expressed in the earlier 7 layer model.)

Now that you have been able to encounter the ISO OSI 7 Layer Reference Model for Networking, the rest is likely to get easier.

OSI Physical Layer (Will be moved out when work starts, but topics include:)
- Visual
- Voice/Spoken
- Written/Drawn
- Unshielded Twisted Pair
- Shielded Twisted Pair
- Fiber Optics
- Wireless
- ...
OSI Data Link Layer(Will be moved out when work starts, but topics include:)
- Brodcast vs. Point-to-point communication with examples. Exampes include one each for Simplex, Half-Duplex, and Full-Duplex types of communcations.
- Ethernet (Broadcast Example)
  - LLC
  - MAC
  - CSMA/CD
  - 10 Base T
  - 10 Base 2
  - 10 Base 5
  - Fiber Optic
  - 100 Base T
  - ...
- PPP (Point-to-point Example)
- TokenRing here (Token Passing Example)
- LocalTalk here
  - CSMA/CA
- EtherTalk
- ATM
- xDSL
  - ADSL
  - SDSL
  - HDSL
  - VDSL
  - ...
- ISDN
- 100VG-AnyLAN (Demand Priority Example)
OSI Network Layer (Will be moved out when work starts, but topics include:)
- From the TCP/IP suite of protocols: a partial list of common packets and/or protocols associated with the TCP/IP suite. (See an rfc which is also a tutorial on tcp/ip: rfc1180.)
  - Network Layer: IP Packet: An examination of a routed protocol packet can help to explain what information a firewall system has available to use in allowing for networking policies. In this case a review of a Network Layer protocol packet like IP is a good standard candidate.
  - ICMP Packet: A control packet that may also run over IP but is often considered to be part of the Network layer by most people since it may alter routes (as well as other things.) Some function does however make it appear as though it could be a Transport Layer protocol...
- From the IPX/SPX suite of protocols:
  - IPX
  - RIP
- From AppleTalk:
  - something here NBP? hmmmm
OSI Transport Layer (Will be moved out when work starts, but topics include:)
- From the TCP/IP suite of protocols:
  - TCP Packet: An examination of a Transport Layer protocol packet can help to explain what information a firewall system has available to use in allowing for networking policies. In this case a review of TCP is a good standard candidate for this.
  - UDP Packet: An examination of another Transport Layer protocol packet can help to explain what information a firewall system has available to use in allowing for networking policies. In this case a review of UDP is a good choice for seeing how little information exists in a UDP header for analysis. Also, with less information in the packet, you may think that UDP is less secure than TCP and you would be correct.
  - Other Packets: A cursory examination of other Transport Layer protocol packets and Network Layer protocol payloads of IP packets helps to demonstrate the information that is available to a firewalling filter. (These are not examined in great detail.)
- From the IPX/SPX suite of protocols:
  - SPX here
- Appletalk:
  - ZIP?
  - ...
OSI Session Layer (Will be moved out when work starts, but topics include:)
- IPX/SPX:
  - NetBIOS? p169 MS hmmm odd.
OSI Presentation Layer (Will be moved out when work starts, but topics include:)
OSI Application Layer (Will be moved out when work starts, but topics include:)
- Application Layer Protocols: This offers some systems even more information on what kinds of data to allow passed a firewall. (Most of the discussion of Application Layer protocols may be discussed in the Applications section.)
- OSI Application Layer, Presentation Layer, Session Layer Transport Layer, and Network Layers have examples here in the following TCP/IP Session examination from a real-world sniffed session:
  - Sample TCP/IP packet: This can be used to examine a sample TCP/IP packet that has been broken down.
  - Copy of an interactive session: This is an example of a telnet session where I logged into a remote machine from a network.
  - A sample captured telnet session in packet form converted by hand to HTML: This is just the raw data in packet form.
  - An analysis of the packets sent and received: This is one way to understand the process for TCP/IP based interactive connections. This is an analysis of the session you can review above.
IPX/SPX from Novell Netware Application Layer (Much like the TCP/IP Application Layer by the 5 layer system in assigned tasks for layers:
- OSI Application Layer, Presentation Layer, Session Layer: NDS/NCP
- OSI Application Layer, Presentation Layer, Session Layer: SAP
- Apple File-sharing Protocol
Firewall Theory for TCP/IP Suite protocols (Will be moved out when work continues, but topics include:):
- Integration of above information with theory: This may help to introduce the uninformed user on how the information contained in the above mentioned packets may be used in a firewalling system with policies to act as a firewall.
- Summary: Bringing all of the ideas together into a generalized and conceptual understanding while avoiding detailed examinations is the purpose of this section.
History of some related communications (Will be moved out when work starts, but topics include:)
Bibliography / Reference documents and books: (Being expanded as new resources are found) Most of the information contained in here is from memory or documents read. I try to include a list of most of the documents I used here.

Comments and/or suggestions for this?: Email me at: dugan@passwall.com
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