Computer Networks

To create or to perform subnet addressing the local address should be divided into a number identifying the physical network and a number identifying the host on the subnet.

Then the senders route messages to the advertised network address, and the local system takes responsibility for routing messages to its subnets and their hosts. We need to consider the number of subnets and the number of hosts on the subnet at the time of deciding how to partition the local address into subnet address and host address.

5-4-3 rule is a guideline for Ethernet computer networks along with the number of repeaters and segments on shared-access.

The rule says that in an network there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated between any two points in the newtwork.

A bundle of virtual channels which share the same end point is known as virtual path.Each virtual path is identified by its unique virtual path identifier (VPI). All channels within a single path must have distinct channel identifiers but may have the same channel identifier as channels in different virtual paths.

Mail gateway is a means which connect two or more electronic mail system and helps in transfer of message between them. During complex mapping and translation there is a store and forward scheme where the message is received from one system completely before it is transmitted to the next system, after suitable translations.

Sending one packet of message to several destinations is known as multicast routing and algorithm which defines its route is known as multicast routing algorithm.

DNS Resource Record is Entry in database.Ex. user name

Short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren't generally necessary for personal computers.

If we have to choose f the four options provided would the answer be the network layer? since the network layer provides for the transfer of data between end systems over a communications network.

SD RAM:SDRAM is Single Data Rate meaning that SDRAM can accept one command and transfer one word of data per clock cycle. Typical speeds of SDRAM are 100 and 133 MHz.DDR SDRAM:DDR SDRAM transfers data twice per clock cycle hence the name double data rate. DDR clock speeds range between 200 MHz (DDR-200) and 400 MHz (DDR-400). DDR-200 transfers 1600 MB/s while DDR-400 transfers 3200 MB/s.DDR2 SDRAM:DDR2 SDRAM is twice as fast as DDR which means twice as much data is carried to the module for each clock cycle. Also consumes less power as compared to the DDR memory.

PINGIMCP echo request utility. This utility is excellent for rudimentary estimation of the round-trip time and packet loss rate between hosts.TRACEROUTE (Win32 and *NIX versions differ somewhat)UDP/ICMP utility which uses TTL as a mechanism to discover gateways between networks which are being traversed from point A to point B. TELNETTCP based application layer connectivity you can specify a port and look at banners, etc.

Proxy ARP is the technique in which one host, usually a router, answers ARP requests intended for another machine. By "faking" its identity, the router accepts responsibility for routing packets to the "real" destination. Proxy ARP can help machines on a subnet reach remote subnets without the need to configure routing or a default gateway.

If the following two conditions are simultaneously true:1. routing error leading to a loop2. the TTL field of the IP packet is not properly decremented at each hop

obviously it s time to live(TTL)it fixes up a time to reach,if it s not reached within that stipulated time,it is being killed by the auto timer...

To establish a connection, TCP uses a 3-way handshake. Before a client attempts to connect with a server, the server must first bind to a port to open it up for connections: this is called a passive open. Once the passive open is established then a client may initiate an active open. To establish a connection, the 3-way (or 3-step) handshake occurs:The active open is performed by sending a SYN to the server. In response, the server replies with a SYN-ACK. Finally the client sends an ACK back to the server. At this point, both the client and server have received an acknowledgement of the connection.

A network in which there are multiple network links between computers to provide multiple paths for data to travel.

LAN uses different ways of communicating. In some ways (like ETHERNET) data link layer is divided into two parts MAC and LLC (Logical Link Control).At LLC the data is known as Protocol Data Unit. It has 4 fields DSAP, SSAP, Control, Upper data layer.Its main function is to control the flow and error.

Directory:

In IT terminology Directory means a pouch where documents are kept. Like,director consists of files & Documnets etc.

Active Directory:

AD is related to servers.It is directory where all users, groups,computers, network resources, list of users Admins and specialised users are recorded. Like AD is Centralised database where the managable data is fed and all the database elements, objects and classes are managed