Merge pull request #32 from teach4hrs/main

cns fundamentals blog

blogs/Computer networks fundamentals.md

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+# Computer networks fundamentals
+
+
+
+**Introduction**
+
+a computer network is a set of nodes connected by communication links to perform the delivery of a set of information.
+
+**Nodes**: a node can be a computer, printer or any other devices capable of sending or receiving data generated by other nodes in the network.
+
+*example:* computer, server, printer, cctv, switches, bridges, routers etc.
+
+**Communication links**: a communication link can be wired or wireless links.
+
+- links carries the information.
+
+-------------fig---------
+
+- communication links can be wired or wireless link.
+- links carries the information.
+
+*examples*: links(medium)
+
+Wired-cable
+
+wireless- Air, Bluetooth etc.
+
+- computer network is used for resources sharing,
+
+  ---fig-----
+
+**Computer networks**
+
+------fig-------
+
+| End devices | Intermediate devices |
+| :---------: | :------------------: |
+|   printer   |        Router        |
+|     pc      |        cloud         |
+|   server    |   wireless router    |
+|   tablet    |      cell tower      |
+| smartphone  |                      |
+
+**Basics characteristics of a computer networks**
+
+- Fault tolerance
+- scalability
+- quality of services(qos)
+- security
+
+**Fault tolerance**
+
+- ability's to continue working desire failures
+- ensure no loss of services
+
+---fig--------------
+
+**scalability**
+
+- ability to grow based on the nodes
+- have good performances after growth.
+- if 10 computers re added to networks then again 10 computers can be added according to need and no decrement in performances.
+- scalable networks- the internet
+- scalability handles the loss as well as the priority of data.
+
+**Quality of services**
+
+- ability to
+- set priorities
+- manage data trafic to reduce data loss,delay etc.
+
+----fig-----
+
+**Security**
+
+- ability to prevent
+
+- unauthorized data
+
+- misuse
+
+- forgery
+
+- ability to provide
+
+  - confidentiality
+  - integrity
+  - availability
+
+  -------fig------
+
+  **Data communication**
+
+  data communication are the exchange of data between two nodes via some form of link(transmission medium) such as cable.
+
+  ------fig-------------
+
+  **Data flow**
+
+  - it means nodes are going to exchange the data.
+
+  - data is going to flow from one node to another node
+
+  - there are 3 forms of data flows.
+
+    1. Simplex
+    2. Half duplex
+    3. Full duplex
+
+
+
+    **Simplex**
+
+    - in simplex data flows, communication is always unidirectional.
+
+    - one devices can transmit and other devices will receive.
+
+      *example*s: keyboard, traditional monitors etc.
+
+      -------fig------------
+
+    **Half duplex**
+
+    - in half duplex, communication is in both directions but not at simultaneously.
+
+    - if one device is sending, the other devices can only receive & vice versa.
+
+      *examples*: walkies-talkies
+
+    **Full duplex**
+
+    - communication is in both directions
+
+
+
+