CHAP (Challenge Handshake Authentication Protocol)

CHAP is an authentication protocol used for remote logon, usually between a client and server or Web browser and Web server. A challenge/response is a security mechanism for verifying the identity of a person or process without revealing a secret password that is shared by the two entities. It is also referred to as a three-way handshake.

CIP (Classical IP Over ATM)

Classical IP over ATM, or CIP as it is informally called, defines how to transmit IP data grams over ATM networks. CIP was originally defined in  RFC 1577 (Classical IP and ARP over ATM,  January 1994). This RFC was made obsolete and replaced by RFC 2225 (Classical IP and ARP over ATM, April 1998). CIP is an IETF standard. Alternative methods for integrating ATM into legacy networks have been developed by the ATM Forum and are outlined under the heading “IP over ATM.”

Circuit-Switching Services

Circuit switching, as opposed to packet switching, sets up a dedicated communication channel between two end systems. Voice calls on the telephone networks are the best example.

Class of Service     

See CoS (Class of Service). 

Classification of Service, COS

 )802.1P Priority support (

The 802.1P protocol was created as a solution to network traffic congestion .Under ideal situations, a network should have enough bandwidth to cover everyone’s needs, but in reality, congestion often occurs and important traffic is blocked by other non-priority traffic.To ensure quality of service, the 802.1p give Layer 2 switches the ability to prioritize traffic.The Layer 2 switch does this by grouping incoming LAN packets into eight different classes depending on its priority, the higher the number the more important the traffic. Although network managers must determine actual priority assignments, it is recommended that the highest priority is seven, which might go to network-critical traffic such as Routing Information Protocol and Open Shortest Path First table updates. Values five and six might be for delay-sensitive applications such as interactive video and voice. Data classes four through one range from controlled-load applications such as streaming multimedia and business-critical traffic. The zero value is used as a best-effort default, invoked automatically when no other value has been set.In actual operation, the 802.1p reads the priority field from the packet and assigns bandwidth accordingly.

CLNP (Connectionless Network Protocol)

CLNP is the equivalent of the IP (Internet Protocol) for OSI (Open Systems Interconnection) networks, with the primary difference being the size of the address. CLNP’s address size is 20 bytes, as compared to IP’s 4 bytes; so CLNP has an advantage over IP, which is experiencing an address shortage. However, the OSI protocols have not gained worldwide acceptance and do not appear to be viable for anything other than a reference model at this writing. CLNP exists in the network layer of the OSI protocol stack. As the name implies, it provides connectionless datagram services over OSI networks.    

Collisions and Collision Domains 

 Ethernet networks use a collision-sensing protocol called CSMA/CD (carrier sense multiple access/collision detection). The protocol allows multiple devices connected to a shared network cable to use that cable by taking turns accessing it. The basic strategy goes like this:         

 1.A computer listens on the cable to see if another computer is transmitting, which is             

 indicated by a voltage change on the cable. If busy, the computer waits and listens.             

 2. When the cable is not busy, a computer attempts to transmit.                                     

 3. Another computer may attempt to transmit at the same time, which causes a collision. 

4.Both computers that attempted to transmit must back off, wait, and then attempt to transmit again.                                                              

COM (Component Object Model)

COM(Component Object Model)is a Microsoft specification that defines the interaction between components in the Windows environment .A  component is a self-contained coded module hat Model) provides  someservicetoothercomponentsinanobject-orientedenvironment.Thetopics“Technologies”and“DistributedObjectComputing”describethisconceptfurther.  

Connection-Oriented and Connectionless Services

Two distinct techniques are used in data communications to transfer data. Each has its own advantages and disadvantages. They are the connection-oriented method and the connectionless method:                              

*  Connection-oriented Requires a session connection (analogous to a phone call) be established before any data can be sent. This method is often called a “reliable” network service.

*  Connectionless Does not require a session connection between sender and receiver .The sender simply starts sending packets (called data grams) to the destination. This service does not have the reliability of the connection-oriented method, but it is useful for periodic burst transfers.

Connection Establishment

A connection is a link between two or more computer systems that need to exchange messages and data. On a shared network and internetwork, connections are usually virtual, meaning that a connection state is setup in software that tracks the exchange of data across what appears to be a

dedicated circuit to the application that is using it. These connections takeplace in the transport layer and are handled by TCP in the Internet protocol suite.

Constraint-Based Routing

Constraint-based routing is a QoS (Quality of Service) routing technique that has become important with the development of MPLS (Multi protocol Label Switching). However, RFC2702  ,Requirements for Traffic Engineering Over MPLS (September 1999) notes that QoS routing is really a subset of a more broadly defined constraint-based routing approach. MPLS is a protocol for carrier-based core networks that runs over MPLS-enabled IP routers   and ATM switches. Such devices are called MPLS LSRs (label switch routers ).

Core Network

A core network is a backbone network, usually with a mesh topology, that provides any-to-any connections among devices on the network. While the Internet could be considered a giant core network, it really consists of many service providers that run their own core networks, and

 those core networks are interconnected. A core network may consist of multiple ATM switches configured in a multilinked mesh topology, or it may consist of IP routers.

CoS (Class of Service)     

CoS—not to be confused with QoS (Quality of Service)—is a form of priority queuing that has been used in a number of communication and networking protocols. It is a way of classifying and prioritizing packets based on application type (voice, video, file transfers, transaction processing), the type of user (CEO, secretary), or other settings.

CoS is a queuing discipline while QoS covers a wider range of techniques to manage bandwidth and network resources.

CSMA/CD (Carrier Sense Multiple Access/Collision Detection)

CSMA is a network access method used on shared network topologies such as Ethernet to control access to the network. Devices attached to the network cable listen (carrier sense) before transmitting.

CSU/DSU (Channel Service Unit/Data Service Unit)

Because digital signaling on the telephone network is different than the digital signaling used by computer equipment, special devices are required to connect the two types of transmission facilities together. The CSU/DSU is part of the hardware you need to connect digital computer equipment to telephone company digital transmission lines (T1 and T3 lines). CSUs (channel service units) and DSUs (data service units) are actually two separate. devices, described next, but they are used in conjunction and often combined in to the same box.

Cut-Through Routing

Routers receive packets from one or more inputs and make forwarding decisions about where to send the packets. Traditional software routers (as opposed to routing switches) read each packet header and examine the fields to determine how the packet should be forwarded. This takes time and affects performance. Add multiple router hops into the path between source and destination, and the requirement to also filter packets, perform accounting, and encrypt data, and you come up with a low-performance network link. Some routers use caching techniques that detect a flow of packets and store the routing information of the first packet in memory. Subsequent routing decisions are made from the information in memory, thus boosting performance somewhat.