What is Mail Gateway?
It is a system that performs a protocol translation between different electronic mail delivery protocols
What is wide-mouth frog?
Wide-mouth frog is the simplest known key distribution center (KDC) authentication protocol.
What are Digrams and Trigrams?
The most common two letter combinations are called as digrams. e.g. th, in, er, re and an. The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ion.
What is silly window syndrome?
It is a problem that can ruin TCP performance. This problem occurs when data are passed to the sending TCP entity in large blocks, but an interactive application on the receiving side reads 1 byte at a time.
What is region?
When hierarchical routing is used, the routers are divided into what we will call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions
What is multicast routing?
Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.
What is traffic shaping?
One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.
What is virtual channel?
Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.
What is logical link control?
One of two sublayers of the data link layer of OSI reference model, as defined by the IEEE 802 standard. This sublayer is responsible for maintaining the link between computers when they are sending data across the physical network connection.
What is the difference between routable and non- routable protocols?
Routable protocols can work with a router and can be used to build large networks. Non-Routable protocols are designed to work on small, local networks and cannot be used with a router
Friday, October 15, 2010
Basic Networking Questions-2
What does the Mount protocol do ?
The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message is sent to the client from the server after reception of a client's request.
What is anonymous FTP and why would you use it?
Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP uses a login called anonymous or guest, with the password usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on the host without having to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas an anonymous user can access.
What is the Network Time Protocol?
The Network Time Protocol is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. NTP uses UDP port 123 as its transport layer. It is designed particularly to resist the effects of variable latency (Jitter).NTP is one of the oldest Internet protocols still in use (since before 1985).
What is a pseudo tty?
In Unix, a pseudo terminal is a pseudo-device pair that provides a text terminal interface without associated virtual console, computer terminal or serial port hardware. Instead, a process replaces the role of the underlying hardware for the pseudo terminal session.For each pseudo terminal, the operating system kernel provides two character devices: a master device and a slave device.The master and slave devices, in their most common deployment, form an association between a Unix shell and a terminal emulation program or some sort of network server.The slave device file, which generally has a nomenclature of /dev/ttyp*, has the appearance and supported system calls of any text terminal. Thus it has the understanding of a login session and session leader process (which is typically the shell program).The master device file, which generally has a nomenclature of /dev/ptyp*, is the endpoint for communication with the terminal emulator. It receives the control requests and information from the other party over this interface and responds accordingly.
What is External Data Representation?
eXternal Data Representation (XDR) is an IETF standard from 1995 of the presentation layer in the OSI model. XDR allows data to be wrapped in an architecture independent manner so data can be transferred between heterogeneous computer systems. Converting from the local representation to XDR is called encoding. Converting from XDR to the local representation is called decoding. XDR is implemented as a software library of functions that is portable between different operating systems and is also independent of the transport layer.
What is the difference between interior and exterior neighbor gateways?
Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.
What are 10Base2, 10Base5 and 10BaseT Ethernet LANs ?
10Base2—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling, with a contiguous cable segment length of 100
meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling, with 5 continuous segments not exceeding 100
meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling and twisted pair cabling.
BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its IP address and the location of its operating system boot files ?
BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address. The same message might contain the name of the machine that has the boot files on it. If the boot image location is not specified, the workstation sends another UDP message to query the server
What protocol is used by DNS name servers ?
DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course, transmission reliability suffers with UDP.
Which are the three types of routing tables ?
The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network administrator, although the table's contents can change without the administrator being aware of the change.
The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message is sent to the client from the server after reception of a client's request.
What is anonymous FTP and why would you use it?
Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP uses a login called anonymous or guest, with the password usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on the host without having to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas an anonymous user can access.
What is the Network Time Protocol?
The Network Time Protocol is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. NTP uses UDP port 123 as its transport layer. It is designed particularly to resist the effects of variable latency (Jitter).NTP is one of the oldest Internet protocols still in use (since before 1985).
What is a pseudo tty?
In Unix, a pseudo terminal is a pseudo-device pair that provides a text terminal interface without associated virtual console, computer terminal or serial port hardware. Instead, a process replaces the role of the underlying hardware for the pseudo terminal session.For each pseudo terminal, the operating system kernel provides two character devices: a master device and a slave device.The master and slave devices, in their most common deployment, form an association between a Unix shell and a terminal emulation program or some sort of network server.The slave device file, which generally has a nomenclature of /dev/ttyp*, has the appearance and supported system calls of any text terminal. Thus it has the understanding of a login session and session leader process (which is typically the shell program).The master device file, which generally has a nomenclature of /dev/ptyp*, is the endpoint for communication with the terminal emulator. It receives the control requests and information from the other party over this interface and responds accordingly.
What is External Data Representation?
eXternal Data Representation (XDR) is an IETF standard from 1995 of the presentation layer in the OSI model. XDR allows data to be wrapped in an architecture independent manner so data can be transferred between heterogeneous computer systems. Converting from the local representation to XDR is called encoding. Converting from XDR to the local representation is called decoding. XDR is implemented as a software library of functions that is portable between different operating systems and is also independent of the transport layer.
What is the difference between interior and exterior neighbor gateways?
Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.
What are 10Base2, 10Base5 and 10BaseT Ethernet LANs ?
10Base2—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling, with a contiguous cable segment length of 100
meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling, with 5 continuous segments not exceeding 100
meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling and twisted pair cabling.
BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its IP address and the location of its operating system boot files ?
BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address. The same message might contain the name of the machine that has the boot files on it. If the boot image location is not specified, the workstation sends another UDP message to query the server
What protocol is used by DNS name servers ?
DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course, transmission reliability suffers with UDP.
Which are the three types of routing tables ?
The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network administrator, although the table's contents can change without the administrator being aware of the change.
Basic Networking Questions-1
What is source-route bridging algorithm ?
The source-route bridging (SRB) algorithm was developed by IBM and was proposed to the IEEE 802.5 committee as the means to bridge between all LANs. SRBs are so named because they assume that the complete source-to-destination route is placed in all inter-LAN frames sent by the source. SRBs store and forward the frames as indicated by the route appearing in the appropriate frame field. Assume that Host X wants to send a frame to Host Y. Initially, Host X does not know whether Host Y resides on the same LAN or a different LAN. To determine this, Host X sends out a test frame. If that frame returns to Host X without a positive indication that Host Y has seen it, Host X assumes that Host Y is on a remote segment. To determine the exact remote location of Host Y, Host X sends an explorer frame. Each bridge receiving the explorer frame copies the frame onto all outbound ports. Route information is added to the explorer frames as they travel through the internetwork. When Host X's explorer frames reach Host Y, Host Y replies to each individually, using the accumulated route information. Upon receipt of all response frames, Host X chooses a path based on some predetermined criteria. Host X must select one of these two routes. The IEEE 802.5 specification does not mandate the criteria that Host X should use in choosing a route, but it does make several suggestions, including the following:
•First frame received
•Response with the minimum number of hops
•Response with the largest allowed frame size
•Various combinations of the preceding criteria
In most cases, the path contained in the first frame received is used.
What is Transparent Bridge ?
Transparent bridges were first developed at Digital Equipment Corporation (Digital) in
the early 1980s. Transparent bridges are so named because their presence and operation are transparent to network hosts. When transparent bridges are powered on, they learn the workstation locations by analyzing the source address of incoming frames from all attached networks. For example, if a bridge sees a frame arrive on port 1 from Host A, the bridge concludes that Host A can be reached through the segment connected to port 1. Through this process, transparent bridges build a table. The bridge uses its table as the basis for traffic forwarding. When a frame is received on one of the bridge's interfaces, the bridge looks up the frame's destination address in its internal table. If the table contains an association between the destination address and any of the bridge's ports aside from the one on which the frame was received, the frame is forwarded out the indicated port. If no association is found, the frame is flooded to all ports except the inbound port. Broadcasts and multicasts also are flooded in this way. Transparent bridges successfully isolate intrasegment traffic, thereby reducing the traffic seen on each individual segment. This is called filtering and occurs when the source and destination MAC addresses reside on the same bridge interface. Filtering usually improves network response times, as seen by the user. The extent to which traffic is reduced and response times are improved depends on the volume of intersegment traffic relative to the total traffic, as well as the volume of broadcast and multicast traffic.
What is the basic difference between transparent bridges and source-route bridges relative to the forwarding processes ?
In a transparent bridged environment, bridges determine whether a frame needs to be forwarded, and through what path based upon local bridge tables. In an SRB network, the source device prescribes the route to the destination and indicates the desired path in the RIF.
What is Switched Multimegabit Data Service ?
Switched Multimegabit Data Service (SMDS) is a high-speed, packet-switched, datagram-based WAN networking technology used for communication over public data networks (PDNs). SMDS can use fiber- or copper-based media. SMDS networks consist of several underlying devices to provide high-speed data service. These include customer premises equipment (CPE), carrier equipment, and the subscriber network interface (SNI). CPE is terminal equipment typically owned and maintained by the customer. CPE includes end devices, such as terminals and personal computers, and intermediate nodes, such as routers, modems, and multiplexers. Intermediate nodes, however, sometimes are provided by the SMDS carrier. Carrier equipment generally consists of high-speed WAN switches that must conform to certain network equipment specifications. These specifications define network operations, the interface between a local carrier network and a long-distance carrier network, and the interface between two switches inside a single carrier network.
Where is SMDS Interface Protocol used ?
The SMDS Interface Protocol (SIP) is used for communications between CPE (Customer premises equipment) and SMDS (Switched Multimegabit Data Service) carrier equipment. SIP provides connectionless service across the subscriber network interface (SNI), allowing the CPE to access the SMDS network.
What is Data-Link Switching ?
Data-link switching (DLSw) provides a means of transporting IBM Systems Network Architecture (SNA) and network basic input/output system (NetBIOS) traffic over an IP network. It serves as an alternative to source-route bridging (SRB), a protocol for transporting SNA and NetBIOS traffic in Token Ring environments that was widely deployed before the introduction of DLSw. In general, DLSw addresses some of the shortcomings of SRB for certain communication requirements—particularly in WAN implementations. This chapter contrasts DLSw with SRB, summarizes underlying protocols, and provides a synopsis of normal protocol operations. The three primary functions of DLSw are :
•The Switch-to-Switch Protocol (SSP) is the protocol maintained between two DLSw nodes or routers.
•The termination of SNA data-link control (DLC) connections helps to reduce the likelihood of link layer timeouts across WANs.
•The local mapping of DLC connections to a DLSw circuit.
What is Banyan VINES ?
Banyan Virtual Integrated Network Service (VINES) implements a distributed network operating system based on a proprietary protocol family derived from the Xerox Corporation's Xerox Network Systems (XNS) protocols. VINES uses a client/server architecture in which clients request certain services, such as file and printer access, from servers.
What is Enhanced Interior Gateway Routing Protocol ?
The Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP. This evolution resulted from changes in networking and the demands of diverse, large-scale internetworks. EIGRP integrates the capabilities of link-state protocols into distance vector protocols. Additionally, EIGRP contains several important protocols that greatly increase its operational efficiency relative to other routing protocols. One of these protocols is the Diffusing update algorithm (DUAL). DUAL enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers. EIGRP provides compatibility and seamless interoperation with IGRP routers. An automatic-redistribution mechanism allows IGRP routes to be imported into EIGRP, and vice versa, so it is possible to add EIGRP gradually into an existing IGRP network. Because the metrics for both protocols are directly translatable, they are as easily comparable as if they were routes that originated in their own autonomous systems (ASs). In addition, EIGRP treats IGRP routes as external routes and provides a way for the network administrator to customize them.
Name the four key technologies that are used by EIGRP ?
EIGRP employs four key technologies, including neighbor discover/recovery, Reliable Transport Protocol (RTP), Diffusing Update ALgorithm (DUAL) finite-state machine, and a modular architecture that enables support for new protocols to be easily added to an existing network.
Why EIGRP is more efficient in operation than IGRP ?
Unlike most other distance vector routing protocols, EIGRP does not mandate a periodic update of routing tables between neighboring routers. Instead, it employs a neighbor discovery/recovery mechanism to ensure that neighbors remain aware of each other's accessibility. As long as a router receives periodic hello packets from its neighbors, it can assume that those neighbors remain functional. More importantly, it can assume that all of its routes that rely upon passage through those neighbors remain usable. Thus, EIGRP is much more efficient than conventional distance vector routing protocols because it imposes much less overhead on routers and transmission facilities during normal operation.
What is Interior Gateway Protocol ?
IGRP is a distance vector Interior Gateway Protocol (IGP). Distance vector routing protocols mathematically compare routes using some measurement of distance. This measurement is known as the distance vector. Routers using a distance vector protocol must send all or a portion of their routing table in a routing-update message at regular intervals to each of their neighboring routers. As routing information proliferates through the network, routers can identify new destinations as they are added to the network, learn of failures in the network, and, most importantly, calculate distances to all known destinations.
The source-route bridging (SRB) algorithm was developed by IBM and was proposed to the IEEE 802.5 committee as the means to bridge between all LANs. SRBs are so named because they assume that the complete source-to-destination route is placed in all inter-LAN frames sent by the source. SRBs store and forward the frames as indicated by the route appearing in the appropriate frame field. Assume that Host X wants to send a frame to Host Y. Initially, Host X does not know whether Host Y resides on the same LAN or a different LAN. To determine this, Host X sends out a test frame. If that frame returns to Host X without a positive indication that Host Y has seen it, Host X assumes that Host Y is on a remote segment. To determine the exact remote location of Host Y, Host X sends an explorer frame. Each bridge receiving the explorer frame copies the frame onto all outbound ports. Route information is added to the explorer frames as they travel through the internetwork. When Host X's explorer frames reach Host Y, Host Y replies to each individually, using the accumulated route information. Upon receipt of all response frames, Host X chooses a path based on some predetermined criteria. Host X must select one of these two routes. The IEEE 802.5 specification does not mandate the criteria that Host X should use in choosing a route, but it does make several suggestions, including the following:
•First frame received
•Response with the minimum number of hops
•Response with the largest allowed frame size
•Various combinations of the preceding criteria
In most cases, the path contained in the first frame received is used.
What is Transparent Bridge ?
Transparent bridges were first developed at Digital Equipment Corporation (Digital) in
the early 1980s. Transparent bridges are so named because their presence and operation are transparent to network hosts. When transparent bridges are powered on, they learn the workstation locations by analyzing the source address of incoming frames from all attached networks. For example, if a bridge sees a frame arrive on port 1 from Host A, the bridge concludes that Host A can be reached through the segment connected to port 1. Through this process, transparent bridges build a table. The bridge uses its table as the basis for traffic forwarding. When a frame is received on one of the bridge's interfaces, the bridge looks up the frame's destination address in its internal table. If the table contains an association between the destination address and any of the bridge's ports aside from the one on which the frame was received, the frame is forwarded out the indicated port. If no association is found, the frame is flooded to all ports except the inbound port. Broadcasts and multicasts also are flooded in this way. Transparent bridges successfully isolate intrasegment traffic, thereby reducing the traffic seen on each individual segment. This is called filtering and occurs when the source and destination MAC addresses reside on the same bridge interface. Filtering usually improves network response times, as seen by the user. The extent to which traffic is reduced and response times are improved depends on the volume of intersegment traffic relative to the total traffic, as well as the volume of broadcast and multicast traffic.
What is the basic difference between transparent bridges and source-route bridges relative to the forwarding processes ?
In a transparent bridged environment, bridges determine whether a frame needs to be forwarded, and through what path based upon local bridge tables. In an SRB network, the source device prescribes the route to the destination and indicates the desired path in the RIF.
What is Switched Multimegabit Data Service ?
Switched Multimegabit Data Service (SMDS) is a high-speed, packet-switched, datagram-based WAN networking technology used for communication over public data networks (PDNs). SMDS can use fiber- or copper-based media. SMDS networks consist of several underlying devices to provide high-speed data service. These include customer premises equipment (CPE), carrier equipment, and the subscriber network interface (SNI). CPE is terminal equipment typically owned and maintained by the customer. CPE includes end devices, such as terminals and personal computers, and intermediate nodes, such as routers, modems, and multiplexers. Intermediate nodes, however, sometimes are provided by the SMDS carrier. Carrier equipment generally consists of high-speed WAN switches that must conform to certain network equipment specifications. These specifications define network operations, the interface between a local carrier network and a long-distance carrier network, and the interface between two switches inside a single carrier network.
Where is SMDS Interface Protocol used ?
The SMDS Interface Protocol (SIP) is used for communications between CPE (Customer premises equipment) and SMDS (Switched Multimegabit Data Service) carrier equipment. SIP provides connectionless service across the subscriber network interface (SNI), allowing the CPE to access the SMDS network.
What is Data-Link Switching ?
Data-link switching (DLSw) provides a means of transporting IBM Systems Network Architecture (SNA) and network basic input/output system (NetBIOS) traffic over an IP network. It serves as an alternative to source-route bridging (SRB), a protocol for transporting SNA and NetBIOS traffic in Token Ring environments that was widely deployed before the introduction of DLSw. In general, DLSw addresses some of the shortcomings of SRB for certain communication requirements—particularly in WAN implementations. This chapter contrasts DLSw with SRB, summarizes underlying protocols, and provides a synopsis of normal protocol operations. The three primary functions of DLSw are :
•The Switch-to-Switch Protocol (SSP) is the protocol maintained between two DLSw nodes or routers.
•The termination of SNA data-link control (DLC) connections helps to reduce the likelihood of link layer timeouts across WANs.
•The local mapping of DLC connections to a DLSw circuit.
What is Banyan VINES ?
Banyan Virtual Integrated Network Service (VINES) implements a distributed network operating system based on a proprietary protocol family derived from the Xerox Corporation's Xerox Network Systems (XNS) protocols. VINES uses a client/server architecture in which clients request certain services, such as file and printer access, from servers.
What is Enhanced Interior Gateway Routing Protocol ?
The Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP. This evolution resulted from changes in networking and the demands of diverse, large-scale internetworks. EIGRP integrates the capabilities of link-state protocols into distance vector protocols. Additionally, EIGRP contains several important protocols that greatly increase its operational efficiency relative to other routing protocols. One of these protocols is the Diffusing update algorithm (DUAL). DUAL enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers. EIGRP provides compatibility and seamless interoperation with IGRP routers. An automatic-redistribution mechanism allows IGRP routes to be imported into EIGRP, and vice versa, so it is possible to add EIGRP gradually into an existing IGRP network. Because the metrics for both protocols are directly translatable, they are as easily comparable as if they were routes that originated in their own autonomous systems (ASs). In addition, EIGRP treats IGRP routes as external routes and provides a way for the network administrator to customize them.
Name the four key technologies that are used by EIGRP ?
EIGRP employs four key technologies, including neighbor discover/recovery, Reliable Transport Protocol (RTP), Diffusing Update ALgorithm (DUAL) finite-state machine, and a modular architecture that enables support for new protocols to be easily added to an existing network.
Why EIGRP is more efficient in operation than IGRP ?
Unlike most other distance vector routing protocols, EIGRP does not mandate a periodic update of routing tables between neighboring routers. Instead, it employs a neighbor discovery/recovery mechanism to ensure that neighbors remain aware of each other's accessibility. As long as a router receives periodic hello packets from its neighbors, it can assume that those neighbors remain functional. More importantly, it can assume that all of its routes that rely upon passage through those neighbors remain usable. Thus, EIGRP is much more efficient than conventional distance vector routing protocols because it imposes much less overhead on routers and transmission facilities during normal operation.
What is Interior Gateway Protocol ?
IGRP is a distance vector Interior Gateway Protocol (IGP). Distance vector routing protocols mathematically compare routes using some measurement of distance. This measurement is known as the distance vector. Routers using a distance vector protocol must send all or a portion of their routing table in a routing-update message at regular intervals to each of their neighboring routers. As routing information proliferates through the network, routers can identify new destinations as they are added to the network, learn of failures in the network, and, most importantly, calculate distances to all known destinations.
Thursday, October 14, 2010
Basic questions
What is MAC address?
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.
What is cladding?
A layer of a glass surrounding the center fiber of glass inside a fiber-optic cable.
How Gateway is different from Routers?
A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats
What is passive topology?
When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way. Example for passive topology - linear bus.
What is SAP?
Series of interface points that allow other computers to communicate with the other layers of network protocol stack.
What is subnet?
A generic term for section of a large networks usually separated by a bridge or router.
What is IP?
IP is Internet Protocol. It is the network protocol which is used to send information from one computer to another over the network over the internet in the form of packets
What’s the meaning of ARP in TCP/IP?
The “ARP” stands for Address Resolution Protocol. The ARP standard defines two basic message types: a request and a response. a request message contains an IP address and requests the corresponding hardware address; a replay contains both the IP address, sent in the request, and the hardware address.
What is data link layer in the OSI reference model responsible for?
Data link layer is located above the physical layer, but below the network layer. Taking raw data bits and packaging them into frames. The network layer will be responsible for addressing the frames, while the physical layer is reponsible for retrieving and sending raw data bits.
What is binding order?
The order by which the network protocols are used for client-server communications. The most frequently used protocols should be at the top.
How do cryptography-based keys ensure the validity of data transferred across the network?
Each IP packet is assigned a checksum, so if the checksums do not match on both receiving and transmitting ends, the data was modified or corrupted.
What is UTP?
UTP — Unshielded twisted pair 10BASE-T is the preferred Ethernet medium of the 90s. It is based on a star topology and provides a number of advantages over coaxial media.
It uses inexpensive, readily available copper phone wire. UTP wire is much easier to install and debug than coax. UTP uses RG-45 connectors, which are cheap and reliable.
What is a router? What is a gateway?
Routers are machines that direct a packet through the maze of networks that stand between its source and destination. Normally a router is used for internal networks while a gateway acts a door for the packet to reach the ‘outside’ of the internal network
What is Semaphore? What is deadlock?
Semaphore is a synchronization tool to solve critical-section problem, can be used to control access to the critical section for a process or thread. The main disadvantage (same of mutual-exclusion) is require busy waiting. It will create problems in a multiprogramming system, where a single CPU is shared among many processes.
Busy waiting wastes CPU cycles.
Deadlock is a situation when two or more processes are waiting indefinitely for an event that can be caused by only one of the waiting processes. The implementation of a semaphore with a waiting queue may result in this situation
What MAU?
In token Ring , hub is called Multistation Access Unit(MAU).
What is difference between baseband and broadband transmission?
In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.
What are the important topologies for networks?
BUS topology:In this each computer is directly connected to primary network cable in a single line.
Advantages:Inexpensive, easy to install, simple to understand, easy to extend.
STAR topology:In this all computers are connected using a central hub.
Advantages:Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems.
RING topology:In this all computers are connected in loop.
Advantages:All computers have equal access to network media, installation can be simple, and signal does not degrade as much as in other topologies because each computer regenerates it
What is the difference between TFTP and FTP application layer protocols?
The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP.The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offer by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.
What are the data units at different layers of the TCP / IP protocol suite?
The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media.
What are the different type of networking / internetworking devices?
Repeater:Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.
Routers:They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission.
Gateways:They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.
What is Project 802?
It is a project started by IEEE to set standards to enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN
protocols.It consists of the following:
802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols.
802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs.
Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product being used.
The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5).
802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.
What are the types of Transmission media?
Signals are usually transmitted over some transmission media that are broadly classified in to two categories.
a)Guided Media:These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
b) Unguided Media: This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.
What is Bandwidth?
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth
Difference between bit rate and baud rate.
Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits.
baud rate = bit rate / N ,where N is no-of-bits represented by each signal shift.
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.
What is cladding?
A layer of a glass surrounding the center fiber of glass inside a fiber-optic cable.
How Gateway is different from Routers?
A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats
What is passive topology?
When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way. Example for passive topology - linear bus.
What is SAP?
Series of interface points that allow other computers to communicate with the other layers of network protocol stack.
What is subnet?
A generic term for section of a large networks usually separated by a bridge or router.
What is IP?
IP is Internet Protocol. It is the network protocol which is used to send information from one computer to another over the network over the internet in the form of packets
What’s the meaning of ARP in TCP/IP?
The “ARP” stands for Address Resolution Protocol. The ARP standard defines two basic message types: a request and a response. a request message contains an IP address and requests the corresponding hardware address; a replay contains both the IP address, sent in the request, and the hardware address.
What is data link layer in the OSI reference model responsible for?
Data link layer is located above the physical layer, but below the network layer. Taking raw data bits and packaging them into frames. The network layer will be responsible for addressing the frames, while the physical layer is reponsible for retrieving and sending raw data bits.
What is binding order?
The order by which the network protocols are used for client-server communications. The most frequently used protocols should be at the top.
How do cryptography-based keys ensure the validity of data transferred across the network?
Each IP packet is assigned a checksum, so if the checksums do not match on both receiving and transmitting ends, the data was modified or corrupted.
What is UTP?
UTP — Unshielded twisted pair 10BASE-T is the preferred Ethernet medium of the 90s. It is based on a star topology and provides a number of advantages over coaxial media.
It uses inexpensive, readily available copper phone wire. UTP wire is much easier to install and debug than coax. UTP uses RG-45 connectors, which are cheap and reliable.
What is a router? What is a gateway?
Routers are machines that direct a packet through the maze of networks that stand between its source and destination. Normally a router is used for internal networks while a gateway acts a door for the packet to reach the ‘outside’ of the internal network
What is Semaphore? What is deadlock?
Semaphore is a synchronization tool to solve critical-section problem, can be used to control access to the critical section for a process or thread. The main disadvantage (same of mutual-exclusion) is require busy waiting. It will create problems in a multiprogramming system, where a single CPU is shared among many processes.
Busy waiting wastes CPU cycles.
Deadlock is a situation when two or more processes are waiting indefinitely for an event that can be caused by only one of the waiting processes. The implementation of a semaphore with a waiting queue may result in this situation
What MAU?
In token Ring , hub is called Multistation Access Unit(MAU).
What is difference between baseband and broadband transmission?
In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.
What are the important topologies for networks?
BUS topology:In this each computer is directly connected to primary network cable in a single line.
Advantages:Inexpensive, easy to install, simple to understand, easy to extend.
STAR topology:In this all computers are connected using a central hub.
Advantages:Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems.
RING topology:In this all computers are connected in loop.
Advantages:All computers have equal access to network media, installation can be simple, and signal does not degrade as much as in other topologies because each computer regenerates it
What is the difference between TFTP and FTP application layer protocols?
The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP.The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offer by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.
What are the data units at different layers of the TCP / IP protocol suite?
The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media.
What are the different type of networking / internetworking devices?
Repeater:Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.
Routers:They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission.
Gateways:They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.
What is Project 802?
It is a project started by IEEE to set standards to enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN
protocols.It consists of the following:
802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols.
802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs.
Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product being used.
The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5).
802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.
What are the types of Transmission media?
Signals are usually transmitted over some transmission media that are broadly classified in to two categories.
a)Guided Media:These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
b) Unguided Media: This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.
What is Bandwidth?
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth
Difference between bit rate and baud rate.
Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits.
baud rate = bit rate / N ,where N is no-of-bits represented by each signal shift.
Subscribe to:
Posts (Atom)