NET-101
This entry tracks my progress towards more advanced knowledge of
computer networking. Content is structured according to this learning
pattern:
- Subject
- Problem
- Solution
- Results
"Subject" is the broad area of knowledge. "Problem" is a statement of
my incomprehension of something within the subject. "Solution" are
theoretical steps towards gaining sufficient knowledge to resolve the
problem. Results are any work I have done towards implementing the
solution.
TCP/IP Protocol Suite
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I don't know how TCP streams compare across the application protocols
I routinely use (IMAP, Gopher, HTTP, IRC, SSH).
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Solution
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Run and capture packet data for three to four application protocols
that use TCP. Capture the data while performing a few common uses of
these applications. Explain and summarize how this data was captured
(and how, writing down any pcap rules) and what can be observed in the
streams. Identify remarkable attributes of each packet stream such as
TCP options used, number of packets sent, and contents of the
application data. Annotate, cross-reference, and augment your
observations with reference to the RFC for your selected protocols.
Resources used: rfc-editor.org, tcpdump(1), pcap-filter(7), Wireshark
I don't know how and why application protocols are planned, designed,
and implemented.
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Solution
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Choose two application protocols (using TCP or UDP, doesn't
matter). Research and summarize each protocol's purpose, originating
context, and historical precedent. Find an open-source program that
implements each protocol (you can choose one program for one protocol,
or one program for both protocols). Capture snippets of code from the
program(s) showing how the protocol is implemented. Research and
explain two to three flaws, weakness, and/or vulnerability in each
protocol (these can be historical--and thus obselete--or relevant
today.) Where applicable, indicate how these negative attributes are
inherent in the protocol's design.
I haven't had the experience of building my own application protocol
onto of TCP or UDP.
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Solution
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Design a new application protocol suited to some purpose of your own
conception. Research and understand the RFC format, then write your
protocol using the RFC format: describe motivation, requirements, and
include a brief outline of the protocol. The purpose of the protocol
is up to you. As an example, it could include mechanisms for
initiating an initial handshake and reconnection handshake, sending
payloads with 2 or more attributes, and checking client and server
health (response time, availability). Build a small program that
implements some part of your protocol.
Networking tools and their use
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I don't know the workflow for capturing and introspecting arbitrary
packet data for monitoring, defensive security, or debugging perposes.
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Solution
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Use `tcpdump' to create a packet capture of a workstation or (ideally)
server over a few days. Use `tshark' to parse and organize the large
pcap file into smaller, filtered pcap files. Each files should contain
only the packets for a given application protocol. Choose these
filters based on protocols you commonly use (HTTP/HTTPS, Gopher, SSH,
IRC). Research and summarize three common packet analysis methods and
processes in Wireshark. Then perform these processes on the filtered
pcap files. Document your findings (or lack thereof).
I don't understand how an internet arrives to my house, gets router to
my computer and back out again.
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Solution
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Investigate and summarize the infrastructure and technology used to
initiate and carry an internet connection into your house. Describe
this process with relation to the OSI model: summarize the purpose of
each layer and annote it with details of the layer's implementation
for you.
I don't know how to setup a network
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TBD...
analysi