CBSE UGC NET NETWORKING IMPORTANT POINTS

Important key points in networking:

• The connection points between the Network Layer and the Transport Layer is the IP number(s) whereas the connection points between the Transport Layer and the upper layers are called Ports which are represented by 16 bits in the TCP segment header.
• Unlike TCP the Transport Layer Protocol UDP is a connectionless protocol.
• The programmatic connection between the Network Layer and the upper (application) layers is usually established by small software running in Transport Layer. These are usually called Sockets.
• In a 802.3 LAN, IP to ethernet address translation is performed by/with ARP which stands for Address Resolution Protocol.
• In an IP address with CIDR standard a quad can range from 0 to 255.
• Bluetooth uses Time Division Multiplexing.
• A Bluetooth network with 7 active slaves is called a Piconet.
• Bluetooth standard specifies 13 applications which are called profiles.
• As modulation technology, Bluetooth employs FSK with 1M bps.
• The number of necessary OSI layers in a bridge is two
• Routers and Gateways are internetworking-connecting devices
• A networked computer must minimally have a host-IP, a netmask and default gateway-IP numbers set up in order to do IP-networking properly.
• An IP-address with all host bits set to 1 is called Broadcast address.
• A Class-B IP-range may have about 65000 hosts in it.
• IEEE-802.3 defines broadcast networks standards.
• The word ‗Base‘ in 10BaseT identifies the media as baseband.
• The letter ‗T‘ in 10BaseT indicates that it is a twisted-pair cable.
• An ethernet address with all bits set to 1 is called ethernet broadcast address.
• CIDR addressing scheme allows us to create subnets for efficient IP use.
• ARP is a process of obtaining ethernet addresses from IP-addresses.
• Performance of a network is usually measured by the amount of data transferred per unit time.
• Reliability of a network is usually measured by the frequency of failure (inverse of it).
• Logical to physical addressing conversion is done in the Network Layer.
• In stop and wait flow control method receiver ACKs each data frame received. The alternative to this is called sliding window.
• CSMA stands for “Carrier Sense Multiple Access” which is standardized in IEEE 802.3.
• The 10 Mbps twisted pair ethernet is usually designated by 10BaseT.
• Ethernet or NIC addresses are 48 bit unique numbers used to identify physical devices in CSMA/CD networks.
• Bridges divide the networks into smaller segments in order to reduce traffic.
• Repeaters and Bridges are networking connecting devices.
• In class-B IP-addresses 16 and 16 bits are reserved for host and network identification respectively.
• Topologically fully connected networks have the highest performance and the highest cost among the possible.
• In full-duplex transmission mode devices can transmit and receive simultaneously.
• For bit-rate to be three times the baud rate we need at least 8 constellations.
• Physical Layer deals with the physical and electrical specifications.
• The term point-to-point indicates the dedicated links between two nodes.
• Bus topology is the simplest and cheapest topology to implement in small networks.
• Full-Duplex transmission mode can be characterized simply as “two way simultaneous transmission/reception”.
• Performance of a network is usually measured by bits per second
• Switching/Routing is the job of Network Layer.
• Sliding Window line discipline where only some of the enquiries are acknowledged is more efficient then Stop-and-Wait.
• 10BaseT can have a maximum segment length of 100 meters.
• All NICs are manufactured having unique Hardware Address.
• Physical addressing, error control and access (to media) control are managed by the Data Link layer.
• An advantage of 10BaseT over 10Base2 is that 10Base2 is maintained easier than 10Base2.
• ‗Preamble‘ field at the beginning of an ethernet frame is used for synchronization.
• Bridges must have the following layers; Physical Layer 2 Data Link Layer.
• ‗Time To Live‘ field in an IP packet determines the number of hops (routers) it passes through before it is discarded.
• A host running in an IP-network on the ethernet must be assigned these three numbers properly in order for the networking software to operate correctly; IP address, 2. Netmask, 3. Gateway address.
• ARP is used on IEEE-802.3 networks in order to obtain ethernet addresses using the IP addresses.
• The field named as ‗Window Size‘ in a TCP segment header indicates the sliding window size.
• Standard TCP services use some standard TSAP numbers known as well known ports numbers.
• TCP is a connection oriented protocol while UDP is not.
• The three problems which limit a communication line are attenuation, distortion and noise.
• In order for a 2400 baud modem to achieve 9.6 kbps the constellation diagram must have at least 16 distinct points.
• The filter with a bandwidth of 300-3400 Hz at the end office for an ordinary voice phone line is removed for DSL operation.
• An ADSL modem and a splitter are the required equipment residing at the customer‘s premises for the ADSL system.
• Three of the BlueTooth profiles are Service Discovery, Serial Port, Cordless Telephony.
• In piconets of BlueTooth, Frequency Hopping Spread Spectrum technique is used with 1600
• hops/sec and hop sequence is dictated by the master.
• Pseudoternary encoding technique is used on T and S interfaces of ISDN system in order to maintain synchronization during the long sequences of zeros.
• PRI ISDN service carries 23 bearer and 1 data channels with a total of 1544 kbps.
• Bus topology usually requires terminators at both ends of the cable.
• In half-duplex transmission mode both station can transmit and receive but not at the same time.
• Logical addressing and routing is the function of network layer.
• Mail services are being made available by application layer.
• Manchester coding is one of the polar encoding techniques which effectively eliminate DC component of the signal.
• In Diff. Manchester, the transition in the middle is used for synchronization.
• The number of signal units per second is called baud-rate.
• In QAM both amplitude and phase of the carrier signal are varied.
• In stop-and-wait flow control technique, every frame is acknowledged.
• Physical Layer deals with the physical and electrical specifications.
• Full-duplex transmission mode can be characterized simply as “two way simultaneous transmission/reception”.
• All NICs are manufactured having unique ethernet address/MAC number.
• 10BaseT can have a maximum segment length of 100 meters.
• The words and numbers ’10’, ‗Base‘ and ‘T’ in 10BaseT respectively indicate 10 Mbps baseband and twisted pair.
• Carrier extension and Frame bursting are features added to 802.3 by the gigabit ethernet standards.
• 1000Base-T uses 4 pairs of Cat-5 UTP.
• Flooding is a packet routing method in which incoming packet is sent to every neighbor except where it came from.
• In Distance Vector Routing a router receives routing information from all of its neighbors and by using the knowledge about its distance to its neighbors it constructs its own routing table which in turn used by the router and distributed to the neighbors.
• Hierarchical Routing reduces the memory requirements at some penalty on the path optimality in large networks with large number of routers.
• If packets from a live audio/video source are to be distributed to multiple destinations we need to talk about Broadcast Routing.
• The 802.11 configuration in which no central coordination is used for is called Distributed Coordination Function
• Multipath Reception is a problem in wireless systems, which deteriorates the received signal at the receiver.
• When there is no central coordination is employed in 802.11, channel access privileges (who transmits when) are determined by a protocol called Carrier Sense Multiple Access / Collision Avoidance.
• In wireless ethernet, when stations directly talk to each other, a station wanting to transmit data when the channel is idle transmits Request To Send (RTS) frame first.
• The small clusters of stations communicating using Bluetooth are called Piconets.
• There can be only seven active slaves in a Bluetooth station cluster.
• The master station in a Bluetooth cluster employs Time Division Multiplexing in order to communicate with slaves and send commands to them.
• The destination address field in a Bluetooth frame is three bits
• Bluetooth operates on 2.4 GHz ISM band and its range is about 10 meters.
• The PSTN term Local Loop refers to the wiring between the customer and end office of the telecom company.