Merge pull request #8 from snowme34/docs

Docs

.travis.yml

@@ -1,5 +1,10 @@
 dist: trusty
 language: minimal
+branches:
+  except:
+  - master
+  - legacy
+  - experimental
 install:
   - rm -rf ./node_modules
   - nvm install node

cspell_dict_bash.txt

@@ -466,4 +466,8 @@ createtime
 centos
 rndc
 checkconf
-checkzone
+checkzone
+
+wifi
+connectionless
+Datagram

docs/source/reference/devops/bind-dns-server-setup.md

@@ -2,6 +2,12 @@
 
 To setup a basic master DNS server.
 
+This passage may contain some outdated information.
+
+Always read the latest official document first.
+
+Debian, for example, [Bind9 - Debian Wiki](https://wiki.debian.org/Bind9).
+
 ## BIND
 
 The most popular DNS server software.

docs/source/reference/network/OSI.xml

@@ -0,0 +1 @@
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docs/source/reference/network/osi-model.md

@@ -0,0 +1,190 @@
+# OSI Model
+
+Open Systems Interconnection (OSI) Model
+
+[Wikipedia](https://en.wikipedia.org/wiki/OSI_model)
+
+Use 7 layers to define basic functions of Internet.
+
+Published by ISO in 1984.
+
+The basic model for today's Internet.
+
+OSI is just a model, not any implementation.
+
+The most popular TCP/IP protocol is designed based on OSI model, or,
+an implementation of several layers of OSI.
+
+(Why include links? Repeating is meaningless. Here is just a summary)
+
+## Why
+
+* Reduces complexity
+* Standardizes interfaces
+* Facilitates modular engineering
+* Ensures interoperable technology
+* Accelerates evolution
+* Simplifies teaching and learning
+
+It defines standardized interfaces between different layers.
+So that all layers can be independent and can have different implementations.
+
+## Layers
+
+From bottom to top.
+
+```markdown
+7 Application
+6 Presentation
+5 Session
+4 Transport
+3 Network
+2 Data Link
+1 Physical
+```
+
+## 1 Physical Layer
+
+Bits
+
+The most basic physical transmission.
+
+"Is the wifi working?"
+
+Binary raw bit transmission.
+
+* electrical, mechanical, procedural, and functional specifications of the physical link
+
+From wikipedia:
+
+> The physical layer is responsible for the transmission and reception of unstructured
+> raw data between a device and a physical transmission medium.
+> It converts the digital bits into electrical, radio, or optical signals.
+
+[Wikipedia](https://en.wikipedia.org/wiki/Physical_layer)
+
+## 2 Data Link Layer
+
+Frames
+
+Defines basic format of data, how they are transmitted and denoted via the wires.
+
+2 sub-layers: logical link control (LLC) and media access control (MAC).
+
+* functional and procedural data transmission
+* error detection and correction
+
+[Wikipedia](https://en.wikipedia.org/wiki/Data_link_layer)
+
+## 3 Network Layer
+
+Packets
+
+Addressing and Routing
+
+1. Connectionless communication
+2. Host addressing (IP address)
+3. Message forwarding
+
+Data Delivery
+
+[Wikipedia](https://en.wikipedia.org/wiki/Network_layer)
+
+## 4 Transport Layer
+
+* TCP: segment
+* UDP: datagram
+
+host-to-host communication
+
+TCP/UDP
+
+How to transport data between 2 hosts reliably and effectively
+
+* connection-oriented communication
+* Same order delivery
+* reliability
+* flow control
+* Congestion avoidance
+* multiplexing
+
+* transportation issues handling
+* virtual circuits
+
+[Wikipedia](https://en.wikipedia.org/wiki/Transport_layer)
+
+## 5 Session Layer
+
+Basically, the top 3 layers, application presentation and session layers,
+can be regarded as the "Application" since they are all controlled by applications.
+
+Session layers manages different sessions between application processes between end-users
+
+> Establishes, manages, and terminates sessions between applications
+
+[Wikipedia](https://en.wikipedia.org/wiki/Session_layer)
+
+## 6 Presentation Layer
+
+data translation
+
+Also called "syntax layer".
+
+* Data conversion
+* Character code translation
+* Compression
+* Encryption and Decryption
+
+[Wikipedia](https://en.wikipedia.org/wiki/Presentation_layer)
+
+## 7 Application
+
+Different definitions for OSI and TCP/IP (actually same name, different layers).
+
+The applications are responsible for 5,6,7 three layers.
+Some applications might be simple, will only implement functionality of 7th layer.
+
+Network Processes to Application
+
+> defines user interface responsible for displaying received information to the user
+
+[Wikipedia](https://en.wikipedia.org/wiki/Application_layer)
+
+## Data Encapsulation
+
+applications generate data
+
+Data begin with 7th layer, the application layer.
+They will be transmitted from top to bottom.
+Each layer will include a HDR (header) to the data.
+Each layer stores its information in HDR.
+
+The process of "data going throughout 7 layers from top to lowermost one"
+in which each layer concatenates its header (or footer or both)
+is called data encapsulation.
+
+![osi-data-encapsulation](https://i.imgur.com/7vJObbO.png)
+
+Upon receiving, data will be "de-encapsulated".
+
+Each layer will check the information it is responsible for.
+
+From lowermost level to topmost layer.
+
+At the end only the original data will be transmitted to application.
+
+## TCP/IP Stack
+
+Now everyone uses TCP/IP. It is an implementation of OSI model.
+
+It has 4 layers.
+
+![TCP/IP-OSI](https://i.imgur.com/P1UaRNu.png)
+
+The most "important" ones are 3rd and 4th layer.
+
+## Summary
+
+For networking, it usually refers to the 4 low layers.
+
+For software engineering, people care the top 3 layers more.