Friends,
I am posting some notes on different important terms of Networking. Based on your feedback, I will add more posts on Networking and other topics
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ETHERNET: Ethernet frames must carry a minimum payload of 46 bytes, which ensures that a valid Ethernet frame is 512-bits long (considering bits of header section also). The shortest Ethernet frame is 64 bytes in length, which carry Control messages.
Ethernet frames don't have a way to indicate end-of-frame, but an inter-frame gap (of time required to send 96 bit of data, i.e. 9.6 microsec.) is used.
Slot Time: It is twice the time it takes for an electronic pulse to travel the maximum distance between two nodes. Thus Propagation delay takes half of the time of slot time since it is only the measure of the time required for signal to reach from node A to B. Slot time is used for half-duplex Ethernet network operation. It is 512 bit times for Ethernet networks operating below 1 Gbit/s, and 4096 bit times for Gigabit Ethernet. To reliably detect collisions, the minimum transmission time for a complete frame must be at least one slot time, whereas the round-trip propagation delay must be less than a slot time (half of slot time).
Back-off Algorithm: Once a collision is detected by simultaneous transmitters, they will follow a backoff algorithm, which requires each transmitter to wait an integral number of slot times (51.2 µs) before attempting a new transmission sequence. The integer is determined by the equation:
0<=r<2 power k where k = min (n, 10)
The variable k is actually the number of collisions capped at a maximum of 10. Therefore, r can range from 0 to 1023. The actual value for r is determined by a random process within each Ethernet node. As the number of consecutive collisions increases, the range of possible backoff times increases exponentially. The number of possible retries is max. 16.
There are no collisions with a full-duplex link, where each node is paired with a port on the hub.
Collision Domain: a section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters, in particular.
The 5-4-3 rule: A system can have up to five segments in series, with up to four repeaters and no more than three mixing segments (a segment that may be connected to more than two transceivers).
The FCS field in Ethernet frame provides only bit-level error detection, no error recovery.
UDP is also known as laissez-faire protocol.
TCP is used for unicast addresses only, so multicast applications must use the UDP transport protocol.
In asynchronous transmission, the Start bit always has a value of 0 (a Space). The Stop Bit always has a value of 1 (a Mark). This means that there will always be a Mark (1) to Space (0) transition on the line at the start of every word.
Application layer is free to send any size of data, there is no upper limit defined by standards. The lower layers divides the data if needed.
A channel with x bps may not necessarily transmit data at x rate, since protocols, encryption, and other factors can add may overheads.
The asymptotic bandwidth (formally asymptotic throughput) for a network is the measure of maximum throughput for a greedy source (a traffic generator that generates data at the maximum rate possible and at the earliest opportunity possible).
CIDR: Classless Inter-Domain Routing, known as supernetting, is a solution to limited address space problem in a network. It allocates address space to ISPs and end users on any address bit boundary, instead of on 8-bit segments (which is class based addressing). It appends to the IP address a slash character and the decimal number as routing prefix, e.g., "192.168.2.0/24" for IPv4, and 2001:db8::/32 for IPv6. The value after / indicates how many bits are used for the network prefix, leaving the remaining bits to identify the specific host.
CIDR currently uses prefixes anywhere from 13 to 27 bits. This solution fits an organization's specific needs. It helps in reducing number of entries in global routing tables. It is the concept of subnetting within the internet itself.
The industrial, scientific and medical (ISM) radio bands are radio bands (portions of the radio spectrum) reserved internationally for industrial, scientific and medical purposes other than communications. These are for unlicensed operations. Cordless phones, Bluetooth devices, near field communication (NFC) devices, and wireless computer networks all use frequencies allocated to low power communications as well as ISM.
Hartley's law: "The maximum data rate of a physical communication link is proportional to its bandwidth in hertz, which is sometimes called frequency bandwidth, spectral bandwidth, RF bandwidth, signal bandwidth or analog bandwidth."
A Baud Rate represents the number of bits that are actually being sent over the media, not the amount of data that is actually moved from one DTE device to the other. That means, baud rate decides the actual bit rate. For example, the bit rate is 9600
The Intelligent Network (IN) is the standard network architecture which allows telecom operators to differentiate themselves by providing value-added services in addition to the standard telecom services. The intelligence is provided by network nodes on the service layer (a conceptual layer within a network service provider architecture. It aims at providing middleware that serves third-party value-added services and applications at a higher application layer.)
The Internet protocol suite ( TCP/IP Model), occasionally known as the DoD model due to the foundational influence of the ARPANET. The TCP/IP model and related protocols are maintained by the Internet Engineering Task Force (IETF).
PORT: Each process that wants to communicate with another process identifies itself to the TCP/IP protocol suite by one or more ports. Application Layer talks with Transport layer through ports. A port number helps the transport layer protocols (like TCP) to know the type of content residing inside the packet.
A port is a 16-bit number, used by the host-to-host protocol to identify to which higher level protocol or application program (process) it must deliver incoming messages. There are two types of ports. Well-known port numbers(0-1023) are typically odd, because early systems using the port concept required an odd/even pair of ports for duplex operations.
The well-known ports are controlled and assigned by the Internet Assigned Number Authority (IANA) and on most systems can only be used by system processes or by programs executed by privileged users. Ephemeral ports are opposite to well-known ports. Such port number are used by clients and are contained in the UDP datagrams sent to the server.
Normally, a server will use either TCP or UDP, but there are exceptions. For example, domain name servers use both UDP port 53 and TCP port 53.
SOCKET: A socket is a special type of file handle, which is used by a process to request network services from the operating system. A socket address is the triple: <protocol, local-address, local-process>. For example, in the TCP/IP suite:
<tcp, 193.44.234.3, 12345>
An association is the 5-tuple that completely specifies the two processes that comprise a connection:
<protocol, local-address, local-process, foreign-address, foreign-process>. In the TCP/IP suite, the following could be a valid association:
<tcp, 193.44.234.3, 1500, 193.44.234.5, 21>
Two processes communicate via TCP sockets. The socket model provides a process with a full-duplex byte stream connection to another process.
UDP: UDP is basically an application interface to IP. It adds no reliability, flow-control, or error recovery to IP. It simply serves as a multiplexer/demultiplexer for sending and receiving datagrams, using ports to direct the datagrams. It requires the application to take responsibility for error recovery and so on.
Slow-start is one of the algorithms that TCP uses to control congestion inside the network. It is also known as the exponential growth phase.
Broadband means "having instantaneous bandwidths greater than 1 MHz and supporting data rates greater than about 1.5 Mbit/s." In telecommunication, Broadband refers to a communication bandwidth of at least 256 kbit/s. Each channel is 6 MHz wide.
I am posting some notes on different important terms of Networking. Based on your feedback, I will add more posts on Networking and other topics
********************************************************
ETHERNET: Ethernet frames must carry a minimum payload of 46 bytes, which ensures that a valid Ethernet frame is 512-bits long (considering bits of header section also). The shortest Ethernet frame is 64 bytes in length, which carry Control messages.
Ethernet frames don't have a way to indicate end-of-frame, but an inter-frame gap (of time required to send 96 bit of data, i.e. 9.6 microsec.) is used.
Slot Time: It is twice the time it takes for an electronic pulse to travel the maximum distance between two nodes. Thus Propagation delay takes half of the time of slot time since it is only the measure of the time required for signal to reach from node A to B. Slot time is used for half-duplex Ethernet network operation. It is 512 bit times for Ethernet networks operating below 1 Gbit/s, and 4096 bit times for Gigabit Ethernet. To reliably detect collisions, the minimum transmission time for a complete frame must be at least one slot time, whereas the round-trip propagation delay must be less than a slot time (half of slot time).
Back-off Algorithm: Once a collision is detected by simultaneous transmitters, they will follow a backoff algorithm, which requires each transmitter to wait an integral number of slot times (51.2 µs) before attempting a new transmission sequence. The integer is determined by the equation:
0<=r<2 power k where k = min (n, 10)
The variable k is actually the number of collisions capped at a maximum of 10. Therefore, r can range from 0 to 1023. The actual value for r is determined by a random process within each Ethernet node. As the number of consecutive collisions increases, the range of possible backoff times increases exponentially. The number of possible retries is max. 16.
There are no collisions with a full-duplex link, where each node is paired with a port on the hub.
Collision Domain: a section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters, in particular.
The 5-4-3 rule: A system can have up to five segments in series, with up to four repeaters and no more than three mixing segments (a segment that may be connected to more than two transceivers).
The FCS field in Ethernet frame provides only bit-level error detection, no error recovery.
UDP is also known as laissez-faire protocol.
TCP is used for unicast addresses only, so multicast applications must use the UDP transport protocol.
In asynchronous transmission, the Start bit always has a value of 0 (a Space). The Stop Bit always has a value of 1 (a Mark). This means that there will always be a Mark (1) to Space (0) transition on the line at the start of every word.
Application layer is free to send any size of data, there is no upper limit defined by standards. The lower layers divides the data if needed.
A channel with x bps may not necessarily transmit data at x rate, since protocols, encryption, and other factors can add may overheads.
The asymptotic bandwidth (formally asymptotic throughput) for a network is the measure of maximum throughput for a greedy source (a traffic generator that generates data at the maximum rate possible and at the earliest opportunity possible).
CIDR: Classless Inter-Domain Routing, known as supernetting, is a solution to limited address space problem in a network. It allocates address space to ISPs and end users on any address bit boundary, instead of on 8-bit segments (which is class based addressing). It appends to the IP address a slash character and the decimal number as routing prefix, e.g., "192.168.2.0/24" for IPv4, and 2001:db8::/32 for IPv6. The value after / indicates how many bits are used for the network prefix, leaving the remaining bits to identify the specific host.
CIDR currently uses prefixes anywhere from 13 to 27 bits. This solution fits an organization's specific needs. It helps in reducing number of entries in global routing tables. It is the concept of subnetting within the internet itself.
The industrial, scientific and medical (ISM) radio bands are radio bands (portions of the radio spectrum) reserved internationally for industrial, scientific and medical purposes other than communications. These are for unlicensed operations. Cordless phones, Bluetooth devices, near field communication (NFC) devices, and wireless computer networks all use frequencies allocated to low power communications as well as ISM.
Hartley's law: "The maximum data rate of a physical communication link is proportional to its bandwidth in hertz, which is sometimes called frequency bandwidth, spectral bandwidth, RF bandwidth, signal bandwidth or analog bandwidth."
A Baud Rate represents the number of bits that are actually being sent over the media, not the amount of data that is actually moved from one DTE device to the other. That means, baud rate decides the actual bit rate. For example, the bit rate is 9600
The Intelligent Network (IN) is the standard network architecture which allows telecom operators to differentiate themselves by providing value-added services in addition to the standard telecom services. The intelligence is provided by network nodes on the service layer (a conceptual layer within a network service provider architecture. It aims at providing middleware that serves third-party value-added services and applications at a higher application layer.)
The Internet protocol suite ( TCP/IP Model), occasionally known as the DoD model due to the foundational influence of the ARPANET. The TCP/IP model and related protocols are maintained by the Internet Engineering Task Force (IETF).
PORT: Each process that wants to communicate with another process identifies itself to the TCP/IP protocol suite by one or more ports. Application Layer talks with Transport layer through ports. A port number helps the transport layer protocols (like TCP) to know the type of content residing inside the packet.
A port is a 16-bit number, used by the host-to-host protocol to identify to which higher level protocol or application program (process) it must deliver incoming messages. There are two types of ports. Well-known port numbers(0-1023) are typically odd, because early systems using the port concept required an odd/even pair of ports for duplex operations.
The well-known ports are controlled and assigned by the Internet Assigned Number Authority (IANA) and on most systems can only be used by system processes or by programs executed by privileged users. Ephemeral ports are opposite to well-known ports. Such port number are used by clients and are contained in the UDP datagrams sent to the server.
Normally, a server will use either TCP or UDP, but there are exceptions. For example, domain name servers use both UDP port 53 and TCP port 53.
SOCKET: A socket is a special type of file handle, which is used by a process to request network services from the operating system. A socket address is the triple: <protocol, local-address, local-process>. For example, in the TCP/IP suite:
<tcp, 193.44.234.3, 12345>
An association is the 5-tuple that completely specifies the two processes that comprise a connection:
<protocol, local-address, local-process, foreign-address, foreign-process>. In the TCP/IP suite, the following could be a valid association:
<tcp, 193.44.234.3, 1500, 193.44.234.5, 21>
Two processes communicate via TCP sockets. The socket model provides a process with a full-duplex byte stream connection to another process.
UDP: UDP is basically an application interface to IP. It adds no reliability, flow-control, or error recovery to IP. It simply serves as a multiplexer/demultiplexer for sending and receiving datagrams, using ports to direct the datagrams. It requires the application to take responsibility for error recovery and so on.
Slow-start is one of the algorithms that TCP uses to control congestion inside the network. It is also known as the exponential growth phase.
Broadband means "having instantaneous bandwidths greater than 1 MHz and supporting data rates greater than about 1.5 Mbit/s." In telecommunication, Broadband refers to a communication bandwidth of at least 256 kbit/s. Each channel is 6 MHz wide.
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