Terminologies you need to know Graph Theory Concepts Getting familiar with Graphs in python Analysis on a dataset Graphs and their applications Let us look at a simple graph to understand the concept. Look at the image below — Consider that this graph represents the places in a city that people generally visit, and the path that was followed by a visitor of that city. Let us consider V as the places and E as the path to travel from one place to another.
It is part of the larger OSI model upon which most data communications is based. For manageability, the data is usually split into multiple pieces or packets each with its own error detection bytes in the control section or header of the packet.
The remote computer Intro to networking receives the packets and reassembles the data and checks for errors. It then passes the data to the program that expects to receive it.
How does the computer know what program needs the data? Each IP packet also contains a piece of information in its header called the type field. This informs the computer receiving the data about the type of layer 4 transportation mechanism being used.
This is explained in more detail later. TCP keeps track of the packets sent by giving each one a sequence number with the remote server sending back acknowledgment packets confirming correct delivery.
Programs that use TCP therefore have a means of detecting connection failures and requesting the retransmission of missing packets. TCP is a good example of a connection-oriented protocol. Someone knocks on the door to a house, the person inside asks "Who is it?
Both persons knew who was on the other side of the door before it opened and now a conversation can now begin. TCP acts in a similar way. The communication then continues with a series of segment exchanges, each with the ACK bit set. The communication terminates with a final ACK from the server that wanted to end the session.
This is Intro to networking equivalent of ending a conversation by saying "I really have to go now, I have to go for lunch", to which the reply is "I think I'm finished here too, see you tomorrow Here is a modified packet trace obtained from the tethereal program discussed in Chapter 4, "Simple Network Troubleshooting".
You can clearly see the three way handshake to connect and disconnect the session.
So in the first line, a random value of was assigned to the first byte and all subsequent bytes for the connection from this host will be sequentially tracked. This makes the second byte in the segment numberthe third number etc.
The acknowledgment number or Ack, not to be confused with the ACK bit, is the byte serial number of the next segment it expects to receive from the other end, and the total number of bytes cannot exceed the Win or window value that follows it.
If data isn't received correctly, the receiver will re-send the requesting segment asking for the information to be sent again. The TCP code keeps track of all this along with the source and destination ports and IP addresses to ensure that each unique connection is serviced correctly.
Data is sent on a "best effort" basis with the machine that sends the data having no means of verifying whether the data was correctly received by the remote machine. UDP is usually used for applications in which the data sent is not mission-critical.
It is also used when data needs to be broadcast to all available servers on a locally attached network where the creation of dozens of TCP connections for a short burst of data is considered resource-hungry. Certain programs are assigned specific ports that are internationally recognized.
Ports below are reserved for privileged system functions, and those above are generally reserved for non-system third-party applications. Usually when a connection is made from a client computer requesting data to the server that contains the data: The client selects a random previously unused "source" port greater than and queries the server on the "destination" port specific to the application.
When the Web server software replies to the client, it tells the TCP application to respond back to port of the client using a source port of port The client keeps track of all its requests to the server's IP address and will recognize that the reply on port isn't a request initiation for "NFS", but a response to the initial port 80 HTTP query.
The server sending the packet sets the initial TTL value, and each network device that the packet passes through then reduces this value by 1. If the TTL value reaches 0, the network device will discard the packet. This mechanism helps to ensure that bad routing on the Internet won't cause packets to aimlessly loop around the network without being removed.
TTLs therefore help to reduce the clogging of data circuits with unnecessary traffic. Remember this concept as it will be helpful in understanding the traceroute troubleshooting technique outlined in Chapter 4, " Simple Network Troubleshooting ", that covers Network Troubleshooting.Summary I n Unit 2, we looked at the signals a network carries, network topologies that determine the flow of those signals, and physical transmission media used to build those topologies.
We learned that data can be carried by two types of signals: analog and digital. Jul 01, · (this article was originally posted on ashio-midori.com). Networking and security automation — and specifically the use of on-demand services — will continue to play a more significant role as NSX (and network virtualization in general) continues to become more and more prominent.
Cisco Press is the sole authorized publisher of books that support the Cisco Networking Academy curricula. Find out about new learning products, special offers, and instructor and student resources that will help you along the way.
Introduction to Networking with Network + is the cornerstone for your networking curriculum. It is built around the new Network+ framework.
It is based upon the CompTIA Network+ certification and covers the most recent exam objectives. A network is a group of computers (or a group of smaller networks) that are connected to each other by various means, so that they may communicate with each other.
Servers and Clients . In networking there are always two computers in the connection. The server and the client. The server listens and waits for clients to connect to it and the client connects to the server.