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||CAIDA (Cooperative Association for Internet Data Analysis) provides tools and analyses promoting the engineering and maintenance of a robust, scalable global Internet infrastructure. It is a collaborative undertaking among commercial, government, and research organizations with a strong interest in keeping primary Internet capacity and usage efficiency in line with ever-increasing demand.
||Cantenna - yagi antenna design for 802.11b wireless applications, constructed from Pringles, or other type of cans :) Yes, they work too, you can make a 12db gain cantenna in 30 min.
||CAT5 (Category 5 ethernet cable) is an widely used EIA/TIA Ethernet cable standard. CAT5 cables contain 4 twisted pairs of copper wire and support 100 Mbps Fast Ethernet. CAT5 cable runs are limited to a maximum recommended length of 100m (328 feet).
||CAT5e (Category 5 enhanced) is a CAT5 variation that supports short-run Gigabit Ethernet (1000 Mbps) networking by utilizing all four wire pairs in a CAT5 cable, and is backward-compatible with ordinary CAT5.
||CAT6 (Category 6) is the 6th generation of twisted pair Ethernet cabling. It is a standard superseeding CAT5e in its support for Gigabit Ethernet. Unlike CAT5, it utilizes all four twisted pairs. CAT6 supports communications at more than twice the speed of CAT5e, the other popular standard for Gigabit Ethernet cabling.
||CAT7 (Category 7) is the new generation of cabling that is still in the works. Generally when CAT6 was introduced there were actually two proposals, 200MHz and 600MHz one. When study began on those two proposals, a decision was made to develop both generations in parallel. The CAT7 standard is not yet finalized, besides at some point it might be cheaper to use fiber than to "stretch" the UTP copper any further.
||CCCM (CPE Controlled Cable Modem) is a project covered under the DOCSIS CMCI Specification.
It provides an architectural overview of a CPE Controlled Cable Modem (CCCM), introducing the basic functions residing in both the CCCM hardware and the CCCM software running on the host CPE.
||CCMP (Counter-Mode Cipher Block Chaining Message Authentication Code Protocol). It is a specific mode of AES which is implemented in the 802.11i standard and WPA2.
||Code-Division Multiple Access - a digital cellular technology, that uses spread spectrum techniques. Each channel in CDMA uses the full spectrum (unlike comppeting technologies, such as GSM or TDMA), and individual conversations are encoded with a random digital sequence.
||cellular refers to a communicatins system that divides geographic regions into sections called cells. The purpose of this division is to make the most out of a limited number of transmission frequencies (total of ~1000) required by each separate call. Cellular systems allocate a set number of frequencies to each cell, and such frequencies can only be reused by other non-adjacent cells.
GSM and CDMA are some of the more popular cellular systems in use today.
||Central Office (CO) is the office of your local carrier (LEC) closest to your location. Your circuit will be terminated to the CO closest to you and then connected to the closest Point of Presence (POP) of your chosen ISP.
||checksum is a value calculated by aplying a specific algorithm to a file or datagram. The algorithm is designed so that even a single bit change in the source file/data causes a completely different checksum value.
Checksums are fixed length (32 bits for CRC32, 128 bits for MD5, etc.) regardles of the size of the file or datagram they are applied to.
See also: CRC
||CIDR (Classless Inter-Domain Routing) is an IP addressing scheme that allows network administrators to subdivide a block of IP addresses to create more usable address space. CIDR IP addresses are normally noted in the format of a normal IP address except that it ends with a slash followed by a number, called the IP network prefix: 188.8.131.52/27. In this case, /27 indicates that the first 27 bits are used to identify the unique network, and the remaining 5 bits (5 binary digits, or 32 addresses) have been allocated to the client.
CIDR addresses reduce the size of routing tables and make more IP addresses available within organizations. CIDR is also called supernetting. CIDR currently uses prefixes anywhere from 13 to 27 bits:
CIDR - # hosts (Class C equivalent)
/27 - 32 hosts (1/8th of a Class C)
/26 - 64 hosts (1/4th of a Class C)
/25 - 128 hosts (1/2 of a Class C)
/24 - 256 hosts (1 Class C )
/23 - 512 hosts (2 Class C)
/22 - 1,024 hosts (4 Class C)
/21 - 2,048 hosts (8 Class C)
/20 - 4,096 hosts (16 Class C)
/19 - 8,192 hosts (32 Class C)
/18 - 16,384 hosts (64 Class C)
/17 - 32,768 hosts (128 Class C)
/16 - 65,536 hosts (256 Class C = 1 Class B)
/15 - 131,072 hosts (512 Class C)
/14 - 262,144 hosts (1,024 Class C)
/13 - 524,288 hosts (2,048 Class C)
||block ciphers - method for encrypting plain text in chunks. Common block sizes are 64 and 128 bits.
stream ciphers - method for encrypting plain text one byte (or bit) at a time. A stream cipher can be thought of as a block cipher with a really small block size.
Generally, block ciphers are more efficient for computers than stream ciphers.
Examples: DES is a block sipher with a 64-bit block size. RSA is a block cypher with a variable block size. RC4 (WEP, WPA, TKIP) and A5 (the algorightm used to encrypt GSM) are stream ciphers.
||CIR (Committed Information Rate) is a specified amount of guaranteed bandwidth (measured in bits per second).
Typically, when purchasing a Broadband Internet service, the ISP can specify the CIR level they wish. The vendor basically guarantees that a certain bandwidth will be delivered. It's possible that additional traffic may also be delivered, but it's not guaranteed.
||In telecommunications, a circuit is a physical path between two or more points along which signals (data or voice) can be carried. It consists of one or more wires or wireless paths, and possibly intermediate switching points. It represents a persistent, dedicated connection established for transmitting information.
||CLEC (Competitive Local Exchange Carrier) is a company that competes with established local telephone business (local exchange carriers, or simply LEC) by providing its own network and switching.
The term arises from the Telecommunications Act of 1996, which was intended to promote competition among providers.
||CMTS (Cable Modem Termination System) is a system of devices located at the head-end (the local cable TV company office) that exchanges digital signals with cable modems on a cable network. All cable modems can exchange signals only with the CMTS, and not directly with other modems.
One TV channel is used for upstream signals from cable modems to the CMTS, and another channel for downstream signals from the CMTS to cable modems. The CMTS is responsible for converting received signals into IP packets, which are then sent to an IP router for transmission across the Internet. When a CMTS sends signals to a cable modem, it modulates the downstream signals for tranmission to the cable modem via coax cable.
||CODEC - a hardware device or software program that converts analog information streams into digital signals, and vice versa; generally used in audio and video communications where compression and other functions may be necessary and provided by the CODEC as well.
||CoDel (controlled delay) is a network scheduler algorithm designed to overcome bufferbloat in network links, such as routers by setting limits on the delay network packets can suffer because of buffering. It only affects congested links, and helps improve overall latency by dropping the slowest packets on links that are overloading the buffers.
CoDel improves on the performance of the RED algorithm by better recognizing bufferbloat. CoDel distinguishes between two types of packet queues, "good queues" that exibit no buffer bloat, and "bad queues" that exibit some buffer bloat (more than 5ms delay because of buffers). CoDel only comes into effect when the network buffers fill up, and the minimum delay for the TCP Window is exceeded, it then treats "bad queues" by dropping slowest packets to control link rates.
CoDel is available in the Linux kernel since version 3.5. It is also available with various open source router firmwares, such as CeroWrt, OpenWrt, dd-wrt, and AsusWrt-Merlin firmware.
||In a network, a packet collision is the result of two devices atteprting to transmit data at the same time. Collisions are common in Ethernet networks. Collisions cause packets to be retransmitted and can impede the performance of the network when in large quantities. Using switches (rather than hubs) can reduce the number of collisions/retransmissions.
See also: CSMA/CD
||CoS (Class of Service, or 802.1p) is a 3 bit field within an Ethernet frame header when using 802.1Q tagging. The field specifies a priority value between 0 and 7 that can be used by Quality of Service (QoS) disciplines to differentiate traffic.
Some switches/routers use CoS to internally classify traffic for QoS purposes.
||CPE (customer premises equipment) - any piece of equipment in a communication system that resides within the home or office of the customer. Examples include Cable/DSL modems, TV set-top boxes, telephones, etc.
||cps (characters per second) is a measure of speed used to describe the number of characters passing a designated point per second.
Usually used in measuring the speed of dot-matrix and daisy-wheel printers, where one character is printed at a time.
||cracker - an intruder who breaks into someone else's computer system, often (incorrectly) referred to as a hacker.
The term cracker is also widely used to describe a person who breaks copy protection in software applications in order to keep or distribute free/pirated copies.
Hacker is a term used by some to mean "a clever programmer" and by others, especially journalists or their editors, to mean "someone who tries to break into computer systems.". Please note hacking is the process of cleverly solving a programming problem, not necessarily associated with crackers.
||CRC (Cyclic Redundancy Check/Code) is a method of checking for errors in data that has been transmitted over a network.
The sending device applies a 16 or 32 bit polynomial division to a datagram (Ethernet uses 32-bit CRC) and appends the resulting CRC before transmitting it. The receiving end applies the same polynomial to the data, compares the CRC results and determines whether the data has been received successfully, or it needs to be retransmited.
See also: checksum
||A type of Ethernet cable in which the "send" and "receive" pairs are crossed, so it can be used to connect similar network devices (such as swithches, or PCs without a hub/switch between them) directly.
In a crossover cable, the inside wires are arranged differently (crossed over) in the RJ45 plugs on either end. It has the same effect as (and can substitute for) an uplink port in a hub/switch.
See also: How to make Network Cables
||crosstalk is an interference along a circuit or a cable pair. When such crosstalk occurs, a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.
In essence, one signal disrupts a signal in an adjacent circuit and can cause the signals to cross over and interfere with each other.
||CSMA/CD (Carrier Sense Multiple Access / Collision Detection) is a standard set of rules determining how network devices detect and respond when a packet collision occurs in a network, such as Ethernet. In essense, after detecting a collision, a device waits a random delay time and then attempts to re-transmit the data.
||CSU (Channel Service Unit) receives and transmits signals from and to the WAN line and provides a barrier for electrical interference from either side of the unit. The CSU can also echo loopback signals from the phone company for testing purposes.
Often combined with a DSU into a single CSU/DSU (Channel Service Unit/Data Service Unit) device.
||CSU/DSU (Channel Service Unit/Data Service Unit) - a hardware device that converts a digital data frame from the communications technology used on a LAN into a frame appropriate to a WAN and vice versa.
A CSU/DSU is typically an external hardware device that sits at the customer premise at the termination point of a digital line. The CSU/DSU then connects to the customer network, normally through a router. The CSU/DSU bridges the customer network and the LEC network by performing line coding, line-conditioning, and equalization functions, and responds to loopback commands sent from the central office.
||CTCP (Compound TCP) is a newer TCP congestion control algorithm designed to aggressively adjust the sender's TCP Window to optimize TCP for connections with higher bandwidth and latency.
The algorithm is generally an improvement over the more traditional slow-start and congestion avoidance TCP algorithms. It is especially effective with broadband internet connections, or any connection with a high bandwidth * delay product.
CTCP has been implemented in Windows Vista/2008, and is also available for Windows 2003 server, and XP(64-bit) via hotfixes. The algorithm has been ported to Linux as well.
||CTIA Cellular Telecommunications and Internet Association (www.ctia.org). Formerly the Cellular Telecommunications Industry Association.
The CTIA is a membership organization, involved with regulatory and public affairs issues in the wireless industry. It represents all elements of wireless communication, including cellular, mobile satellite services and personal communications services. The CTIA deals with taxation, roaming, safety, fraud and evolving technologies.
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