- Introduction to Internet and its Applications
January-2004 [18]
7. Explain how Domain Names are allocated with special
reference to special domain names.
[18]
July-2004 [22]
1.
e) Write a note on how Domain Name
System (DNS) Servers work. [4]
ANS
:- 
If you've ever used the Internet,
it's a good bet that you've used the Domain
Name System, or DNS,
even without realizing it. DNS is a protocol within the set of standards for
how computers exchange data on the Internet and on many private networks, known
as the TCP/IP protocol suite. Its basic job is to turn a user-friendly domain name like
"howstuffworks.com" into an Internet
Protocol (IP) address like 70.42.251.42 that computers use to
identify each other on the network. It's like your computer's GPS for the
Internet.Computers and other network devices on the Internet use an IP address to route your request to the site you're trying to reach. This is similar to dialing a phone number to connect to the person you're trying to call. Thanks to DNS, though, you don't have to keep your own address book of IP addresses. Instead, you just connect through a domain name server, also called a DNS server or name server, which manages a massive database that maps domain names to IP addresses.Whether you're accessing a Web site or sending e-mail, your computer uses a DNS server to look up the domain name you're trying to access. The proper term for this process is DNS name resolution, and you would say that the DNS server resolves the domain name to the IP address. For example, when you enter "http://www.howstuffworks.com" in your browser, part of the network connection includes resolving the domain name "howstuffworks.com" into an IP address, like 70.42.251.42, for HowStuffWorks' Web servers. You can always bypass a DNS lookup by entering 70.42.251.42 directly in your browser (give it a try). However, you're probably more likely to remember "howstuffworks.com" when you want to return later. In addition, a Web site's IP address can change over time, and some sites associate multiple IP addresses with a single domain name.Without DNS servers, the Internet would shut down very quickly. But how does your computer know what DNS server to use? Typically, when you connect to your home network, Internet service provider (ISP) or WiFi network, the modem or router that assigns your computer's network address also sends some important network configuration information to your computer or mobile device. That configuration includes one or more DNS servers that the device should use when translating DNS names to IP address.So far, you've read about some important DNS basics. The rest of this article dives deeper into domain name servers and name resolution. It even includes an introduction to managing your own DNS server. Let's start by looking at how IP addresses are structured and how that's important to the name resolution process.
3.
b) What
are the essential functions that the router must perform to achieve
internetworking among dissimilar subnetworks?
[6]
ans :-- Understanding IP Addresses
An IP address is an address used in order to uniquely identify a device on an IP network. The address is made up of 32 binary bits, which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary.Here is how binary octets convert to decimal: The right most bit, or least significant bit, of an octet holds a value of 20. The bit just to the left of that holds a value of 21. This continues until the left-most bit, or most significant bit, which holds a value of 27. So if all binary bits are a one, the decimal equivalent would be 255 as shown here:
1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255)
Here is a sample octet conversion when not all of the bits are set to 1.0 1 0 0 0 0 0 1
0 64 0 0 0 0 0 1 (0+64+0+0+0+0+0+1=65)
And this is sample shows an IP address represented in both binary and decimal.10. 1. 23. 19 (decimal)
00001010.00000001.00010111.00010011 (binary)
These octets are broken down to provide an addressing scheme that can
accommodate large and small networks. There are five different classes of
networks, A to E. This document focuses on addressing classes A to C, since
classes D and E are reserved and discussion of them is beyond the scope of this
document.Note: Also note that the terms "Class A, Class B" and so on are used in this document to help facilitate the understanding of IP addressing and subnetting. These terms are rarely used in the industry anymore because of the introduction of classless interdomain routing (CIDR).
Given an IP address, its class can be determined from the three high-order bits. Figure 1 shows the significance in the three high order bits and the range of addresses that fall into each class. For informational purposes, Class D and Class E addresses are also shown.
In a Class A address, the first octet is the network portion, so the Class A example in Figure 1 has a major network address of 1.0.0.0 - 127.255.255.255. Octets 2, 3, and 4 (the next 24 bits) are for the network manager to divide into subnets and hosts as he/she sees fit. Class A addresses are used for networks that have more than 65,536 hosts (actually, up to 16777214 hosts!).
In a Class B address, the first two octets are the network portion, so the Class B example in Figure 1 has a major network address of 128.0.0.0 - 191.255.255.255. Octets 3 and 4 (16 bits) are for local subnets and hosts. Class B addresses are used for networks that have between 256 and 65534 hosts.
In a Class C address, the first three octets are the network portion. The Class C example in Figure 1 has a major network address of 192.0.0.0 - 233.255.255.255. Octet 4 (8 bits) is for local subnets and hosts - perfect for networks with less than 254 hosts.
Network Masks
A network mask helps you know which portion of the address identifies the network and which portion of the address identifies the node. Class A, B, and C networks have default masks, also known as natural masks, as shown here:Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0An IP address on a Class A network that has not been subnetted would have an address/mask pair similar to: 8.20.15.1 255.0.0.0. To see how the mask helps you identify the network and node parts of the address, convert the address and mask to binary numbers.
8.20.15.1 = 00001000.00010100.00001111.00000001
255.0.0.0 = 11111111.00000000.00000000.00000000Once you have the address and the mask represented in binary, then identifying the network and host ID is easier. Any address bits which have corresponding mask bits set to 1 represent the network ID. Any address bits that have corresponding mask bits set to 0 represent the node ID.
8.20.15.1 = 00001000.00010100.00001111.00000001
255.0.0.0 = 11111111.00000000.00000000.00000000
-----------------------------------
net id | host id
netid = 00001000 = 8
hostid = 00010100.00001111.00000001 = 20.15.1
Understanding Subnetting
Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network. If you do not subnet, you are only able to use one network from your Class A, B, or C network, which is unrealistic.Each data link on a network must have a unique network ID, with every node on that link being a member of the same network. If you break a major network (Class A, B, or C) into smaller subnetworks, it allows you to create a network of interconnecting subnetworks. Each data link on this network would then have a unique network/subnetwork ID. Any device, or gateway, connecting n networks/subnetworks has n distinct IP addresses, one for each network / subnetwork that it interconnects.
In order to subnet a network, extend the natural mask using some of the bits from the host ID portion of the address to create a subnetwork ID. For example, given a Class C network of 204.17.5.0 which has a natural mask of 255.255.255.0, you can create subnets in this manner:
204.17.5.0 - 11001100.00010001.00000101.00000000
255.255.255.224 - 11111111.11111111.11111111.11100000
--------------------------|sub|----
By extending the mask to be 255.255.255.224, you have taken three bits
(indicated by "sub") from the original host portion of the address
and used them to make subnets. With these three bits, it is possible to create
eight subnets. With the remaining five host ID bits, each subnet can have up to
32 host addresses, 30 of which can actually be assigned to a device since
host ids of all zeros or all ones are not allowed (it is very important to
remember this). So, with this in mind, these subnets have been created.204.17.5.0 255.255.255.224 host address range 1 to 30
204.17.5.32 255.255.255.224 host address range 33 to 62
204.17.5.64 255.255.255.224 host address range 65 to 94
204.17.5.96 255.255.255.224 host address range 97 to 126
204.17.5.128 255.255.255.224 host address range 129 to 158
204.17.5.160 255.255.255.224 host address range 161 to 190
204.17.5.192 255.255.255.224 host address range 193 to 222
204.17.5.224 255.255.255.224 host address range 225 to 254
Note: There are two ways to denote these masks. First, since you
are using three bits more than the "natural" Class C mask, you can
denote these addresses as having a 3-bit subnet mask. Or, secondly, the mask of
255.255.255.224 can also be denoted as /27 as there are 27 bits that are set in
the mask. This second method is used with CIDR.
With this method, one of these networks can be described with the notation
prefix/length. For example, 204.17.5.32/27 denotes the network 204.17.5.32
255.255.255.224. When appropriate the prefix/length notation is used to denote
the mask throughout the rest of this document.The network subnetting scheme in this section allows for eight subnets, and the network might appear as:
Notice that each of the routers in Figure 2 is attached to four subnetworks, one subnetwork is common to both routers. Also, each router has an IP address for each subnetwork to which it is attached. Each subnetwork could potentially support up to 30 host addresses.
This brings up an interesting point. The more host bits you use for a subnet mask, the more subnets you have available. However, the more subnets available, the less host addresses available per subnet. For example, a Class C network of 204.17.5.0 and a mask of 255.255.255.224 (/27) allows you to have eight subnets, each with 32 host addresses (30 of which could be assigned to devices). If you use a mask of 255.255.255.240 (/28), the break down is:
204.17.5.0 - 11001100.00010001.00000101.00000000
255.255.255.240 - 11111111.11111111.11111111.11110000
--------------------------|sub |---
Since you now have four bits to make subnets with, you only have four bits
left for host addresses. So in this case you can have up to 16 subnets, each of
which can have up to 16 host addresses (14 of which can be assigned to
devices).Take a look at how a Class B network might be subnetted. If you have network 172.16.0.0 ,then you know that its natural mask is 255.255.0.0 or 172.16.0.0/16. Extending the mask to anything beyond 255.255.0.0 means you are subnetting. You can quickly see that you have the ability to create a lot more subnets than with the Class C network. If you use a mask of 255.255.248.0 (/21), how many subnets and hosts per subnet does this allow for?
172.16.0.0 - 10101100.00010000.00000000.00000000
255.255.248.0 - 11111111.11111111.11111000.00000000
-----------------| sub |-----------
You are using five bits from the original host bits for subnets. This allows
you to have 32 subnets (25). After using the five bits for
subnetting, you are left with 11 bits for host addresses. This allows each
subnet so have 2048 host addresses (211), 2046 of which could be
assigned to devices.Note: In the past, there were limitations to the use of a subnet 0 (all subnet bits are set to zero) and all ones subnet (all subnet bits set to one). Some devices would not allow the use of these subnets. Cisco Systems devices allow the use of these subnets when theip subnet zero command is configured.
Examples
Sample Exercise 1
Now that you have an understanding of subnetting, put this knowledge to use. In this example, you are given two address / mask combinations, written with the prefix/length notation, which have been assigned to two devices. Your task is to determine if these devices are on the same subnet or different subnets. You can do this by using the address and mask of each device to determine to which subnet each address belongs.DeviceA: 172.16.17.30/20
DeviceB: 172.16.28.15/20Determining the Subnet for DeviceA:
172.16.17.30 - 10101100.00010000.00010001.00011110
255.255.240.0 - 11111111.11111111.11110000.00000000
-----------------| sub|------------
subnet = 10101100.00010000.00010000.00000000 = 172.16.16.0
Looking at the address bits that have a corresponding mask bit set to one,
and setting all the other address bits to zero (this is equivalent to
performing a logical "AND" between the mask and address), shows you
to which subnet this address belongs. In this case, DeviceA belongs to subnet
172.16.16.0.Determining the Subnet for DeviceB:
172.16.28.15 - 10101100.00010000.00011100.00001111
255.255.240.0 - 11111111.11111111.11110000.00000000
-----------------| sub|------------
subnet = 10101100.00010000.00010000.00000000 = 172.16.16.0
From these determinations, DeviceA and DeviceB have addresses that are part
of the same subnet.Sample Exercise 2
Given the Class C network of 204.15.5.0/24, subnet the network in order to create the network in Figure 3 with the host requirements shown.
Looking at the network shown in Figure 3, you can see that you are required to create five subnets. The largest subnet must support 28 host addresses. Is this possible with a Class C network? and if so, then how?
You can start by looking at the subnet requirement. In order to create the five needed subnets you would need to use three bits from the Class C host bits. Two bits would only allow you four subnets (22).
Since you need three subnet bits, that leaves you with five bits for the host portion of the address. How many hosts does this support? 25 = 32 (30 usable). This meets the requirement.
Therefore you have determined that it is possible to create this network with a Class C network. An example of how you might assign the subnetworks is:
netA: 204.15.5.0/27 host address range 1 to 30
netB: 204.15.5.32/27 host address range 33 to 62
netC: 204.15.5.64/27 host address range 65 to 94
netD: 204.15.5.96/27 host address range 97 to 126
netE: 204.15.5.128/27 host address range 129 to 158
VLSM Example
In all of the previous examples of subnetting, notice that the same subnet mask was applied for all the subnets. This means that each subnet has the same number of available host addresses. You can need this in some cases, but, in most cases, having the same subnet mask for all subnets ends up wasting address space. For example, in the Sample Exercise 2 section, a class C network was split into eight equal-size subnets; however, each subnet did not utilize all available host addresses, which results in wasted address space. Figure 4 illustrates this wasted address space.
Figure 4 illustrates that of the subnets that are being used, NetA, NetC, and NetD have a lot of unused host address space. It is possible that this was a deliberate design accounting for future growth, but in many cases this is just wasted address space due to the fact that the same subnet mask is being used for all the subnets.
Variable Length Subnet Masks (VLSM) allows you to use different masks for each subnet, thereby using address space efficiently.
VLSM Example
Given the same network and requirements as in Sample Exercise 2 develop a subnetting scheme with the use of VLSM, given:netA: must support 14 hosts
netB: must support 28 hosts
netC: must support 2 hosts
netD: must support 7 hosts
netE: must support 28 hostDetermine what mask allows the required number of hosts.
netA: requires a /28 (255.255.255.240) mask to support 14 hosts
netB: requires a /27 (255.255.255.224) mask to support 28 hosts
netC: requires a /30 (255.255.255.252) mask to support 2 hosts
netD*: requires a /28 (255.255.255.240) mask to support 7 hosts
netE: requires a /27 (255.255.255.224) mask to support 28 hosts
* a /29 (255.255.255.248) would only allow 6 usable host addresses
therefore netD requires a /28 mask.
The easiest way to assign the subnets is to assign the largest first. For
example, you can assign in this manner:netB: 204.15.5.0/27 host address range 1 to 30
netE: 204.15.5.32/27 host address range 33 to 62
netA: 204.15.5.64/28 host address range 65 to 78
netD: 204.15.5.80/28 host address range 81 to 94
netC: 204.15.5.96/30 host address range 97 to 98This can be graphically represented as shown in Figure 5:
Figure 5 illustrates how using VLSM helped save more than half of the address space.
CIDR
Classless Interdomain Routing (CIDR) was introduced to improve both address space utilization and routing scalability in the Internet. It was needed because of the rapid growth of the Internet and growth of the IP routing tables held in the Internet routers.CIDR moves way from the traditional IP classes (Class A, Class B, Class C, and so on). In CIDR , an IP network is represented by a prefix, which is an IP address and some indication of the length of the mask. Length means the number of left-most contiguous mask bits that are set to one. So network 172.16.0.0 255.255.0.0 can be represented as 172.16.0.0/16. CIDR also depicts a more hierarchical Internet architecture, where each domain takes its IP addresses from a higher level. This allows for the summarization of the domains to be done at the higher level. For example, if an ISP owns network 172.16.0.0/16, then the ISP can offer 172.16.1.0/24, 172.16.2.0/24, and so on to customers. Yet, when advertising to other providers, the ISP only needs to advertise 172.16.0.0/16.
For more information on CIDR, see RFC 1518
and RFC 1519 .Appendix
Sample Config
Routers A and B are connected via serial interface.Router A
hostname routera
!
ip routing
!
int e 0
ip address 172.16.50.1 255.255.255.0
!(subnet 50)
int e 1 ip address 172.16.55.1 255.255.255.0
!(subnet 55)
int t 0 ip address 172.16.60.1 255.255.255.0
!(subnet 60) int s 0
ip address 172.16.65.1 255.255.255.0 (subnet 65)
!S 0 connects to router B
router rip
network 172.16.0.0
Router B
hostname routerb
!
ip routing
!
int e 0
ip address 192.1.10.200 255.255.255.240
!(subnet 192)
int e 1
ip address 192.1.10.66 255.255.255.240
!(subnet 64)
int s 0
ip address 172.16.65.2 (same subnet as router A's s 0)
!Int s 0 connects to router A
router rip
network 192.1.10.0
network 172.16.0.0
Host/Subnet Quantities Table
Class B Effective Effective
# bits Mask Subnets Hosts
------- --------------- --------- ---------
1 255.255.128.0 2 32766
2 255.255.192.0 4 16382
3 255.255.224.0 8 8190
4 255.255.240.0 16 4094
5 255.255.248.0 32 2046
6 255.255.252.0 64 1022
7 255.255.254.0 128 510
8 255.255.255.0 256 254
9 255.255.255.128 512 126
10 255.255.255.192 1024 62
11 255.255.255.224 2048 30
12 255.255.255.240 4096 14
13 255.255.255.248 8192 6
14 255.255.255.252 16384 2
Class C Effective Effective
# bits Mask Subnets Hosts
------- --------------- --------- ---------
1 255.255.255.128 2 126
2 255.255.255.192 4 62
3 255.255.255.224 8 30
4 255.255.255.240 16 14
5 255.255.255.248 32 6
6 255.255.255.252 64 2
*Subnet all zeroes and all ones included. These
might not be supported on some legacy systems.
*Host all zeroes and all ones excluded.
6. Write short notes on any three of
the following:
iii) Working
of Client/Server architecture [6]
- Client applications are not responsible for performing any data processing. Client applications can concentrate on requesting input from users, requesting desired data from the server, and then analyzing and presenting this data using the display capabilities of the client workstation or the terminal (for example, using graphics or spreadsheets).
- Client applications can be designed with no dependence on the physical location of the data. If the data is moved or distributed to other database servers, the application continues to function with little or no modification.
- Oracle exploits the multitasking and shared-memory facilities of its underlying operating system. As a result, it delivers the highest possible degree of concurrency, data integrity, and performance to its client applications.
- Client workstations or terminals can be optimized for the presentation of data (for example, by providing graphics and mouse support) and the server can be optimized for the processing and storage of data (for example, by having large amounts of memory and disk space).
- If necessary, Oracle can be scaled. As your system grows, you can add multiple servers to distribute the database processing load throughout the network (horizontally scaled). Alternatively, you can replace Oracle on a less powerful computer, such as a microcomputer, with Oracle running on a minicomputer or mainframe, to take advantage of a larger system's performance (vertically scaled). In either case, all data and applications are maintained with little or no modification, since Oracle is portable between systems.
- In networked environments, inexpensive, low-end client workstations can be used to access the remote data of the server effectively.
- In networked environments, client applications submit database requests to the server using SQL statements. Once received, the SQL statement is processed by the server, and the results are returned to the client application. Network traffic is kept to a minimum because only the requests and the results are shipped over the network.
iv) Digital
Subscriber lines [6]
ANS :-- Digital subscriber line (DSL) is a family of technologies that provides digital
data transmission over the wires of a local telephone
network. DSL originally stood for digital subscriber loop. In
telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line
(ADSL), the most commonly installed DSL technology. DSL service is delivered
simultaneously with wired telephone service on the same telephone
line. This is possible because DSL uses higher frequency
bands for data separated by filtering. On the customer premises, a DSL filter
on each outlet removes the high frequency interference, to enable simultaneous
use of the telephone and data.The data bit rate
of consumer DSL services typically ranges from 256 kbit/s to 40 Mbit/s in the
direction to the customer (downstream), depending on DSL technology,
line conditions, and service-level implementation. In ADSL, the data throughput
in the upstream direction, (the direction to the
service provider) is lower, hence the designation of asymmetric service.
In Symmetric Digital Subscriber Line
(SDSL) services, the downstream and upstream data rates are equal. 
Telephones are connected to the telephone exchange via a local loop, which is a physical pair of wires. Prior to the digital age, the use of the local loop for anything other than the transmission of speech, encompassing an audio frequency range of 300 to 3400 Hertz (voiceband or commercial bandwidth) was not considered. However, as long distance trunks were gradually converted from analog to digital operation, the idea of being able to pass data through the local loop (by utilizing frequencies above the voiceband) took hold, ultimately leading to DSL.
For a long time it was thought that it was not possible to operate a conventional phone-line beyond low-speed limits (typically under 9600 bit/s). In the 1950s, ordinary twisted-pair telephone-cable often carried four megahertz (MHz) television signals between studios, suggesting that such lines would allow transmitting many megabits per second. One such circuit in the UK ran some ten miles (16 km) between Pontop Pike transmitter and Newcastle on Tyne BBC Studios. It was able to give the studios a low quality cue feed but not one suitable for transmission.[citation needed] However, these cables had other impairments besides Gaussian noise, preventing such rates from becoming practical in the field. The 1980s saw the development of techniques for broadband communications that allowed the limit to be greatly extended.
The local loop connecting the telephone exchange to most subscribers has the capability of carrying frequencies well beyond the 3.4 kHz upper limit of POTS. Depending on the length and quality of the loop, the upper limit can be tens of megahertz. DSL takes advantage of this unused bandwidth of the local loop by creating 4312.5 Hz wide channels starting between 10 and 100 kHz, depending on how the system is configured. Allocation of channels continues at higher and higher frequencies (up to 1.1 MHz for ADSL) until new channels are deemed unusable. Each channel is evaluated for usability in much the same way an analog modem would on a POTS connection. More usable channels equates to more available bandwidth, which is why distance and line quality are a factor (the higher frequencies used by DSL travel only short distances). The pool of usable channels is then split into two different frequency bands for upstream and downstream traffic, based on a preconfigured ratio. This segregation reduces interference. Once the channel groups have been established, the individual channels are bonded into a pair of virtual circuits, one in each direction. Like analog modems, DSL transceivers constantly monitor the quality of each channel and will add or remove them from service depending on whether they are usable.
One of Lechleider's[4] contributions to DSL was his insight that an asymmetric arrangement offered more than double the bandwidth capacity of symmetric DSL. This allowed Internet Service Providers to offer efficient service to consumers, who benefited greatly from the ability to download large amounts of data but rarely needed to upload comparable amounts. ADSL supports two modes of transport: fast channel and interleaved channel. Fast channel is preferred for streaming multimedia, where an occasional dropped bit is acceptable, but lags are less so. Interleaved channel works better for file transfers, where the delivered data must be error free but latency incurred by the retransmission of errored packets is acceptable.
Because DSL operates above the 3.4 kHz voice limit, it cannot pass through a load coil. Load coils are, in essence, filters that block out any non-voice frequency. They are commonly set at regular intervals in lines placed only for POTS service. A DSL signal cannot pass through a properly installed and working load coil, while voice service cannot be maintained past a certain distance without such coils. Therefore, some areas that are within range for DSL service are disqualified from eligibility because of load coil placement. Because of this, phone companies endeavor to remove load coils on copper loops that can operate without them, and conditioning lines to avoid them through the use of fiber to the neighborhood or node (FTTN).
The commercial success of DSL and similar technologies largely reflects the advances made in electronics over the decades that have increased performance and reduced costs even while digging trenches in the ground for new cables (copper or fiber optic) remains expensive. Several factors contributed to the popularity of DSL technology:
- Until the late 1990s, the cost of digital signal processors for DSL was prohibitive. All types of DSL employ highly complex digital signal processing algorithms to overcome the inherent limitations of the existing twisted pair wires. Due to the advancements of Very-large-scale integration (VLSI) technology, the cost of the equipment associated with a DSL deployment lowered significantly. The two main pieces of equipment are a Digital subscriber line access multiplexer (DSLAM) at one end and a DSL modem at the other end.
- A DSL connection can be deployed over existing cable. Such deployment, even including equipment, is much cheaper than installing a new, high-bandwidth fiber-optic cable over the same route and distance. This is true both for ADSL and SDSL variations.
- In the case of ADSL, competition in Internet access caused subscription fees to drop significantly over the years, thus making ADSL more economical than dial up access. Telephone companies were pressured into moving to ADSL largely due to competition from cable companies, which use DOCSIS cable modem technology to achieve similar speeds. Demand for high bandwidth applications, such as video and file sharing, also contributed to popularize ADSL technology.
Once upstream and downstream channels are established, a subscriber can connect to a service such as an Internet service provider.
January-2005 [23]
2.
b) Write
and Explain the procedure for translating a domain name into an equivalent IP
address. What are two performance optimizations techniques used by DNS
server? [9]
ans :-- The
introduction of the domain name into the world of virtual reality brought some
transformation not only in such dimension but even to the lives of most people.
Today, many people are looking for some ways that will help them get their own
domain names. And as years go by, many companies and individuals are into it.
Some of them are purchasing domain names, and the others are selling it, and some
are even finding answers on how to translate a domain name to IP address. But
despite this fact, still many people are not aware that this thing exists in
the real world. So to let them know the nature behind this thing, this article
is written.
Speaking on how to translate a domain name to IP address, it is very important that the concept of the Domain Name System plays a large role here. The DNS is such a powerful tool that really contributes a vital part in translating a domain name to IP address, for the fact that it is the primary function of the Domain Name System – to translate a domain name to IP address. So if you are asking how the domain name is translated to an IP address, the answer mainly lies on the operation of the Domain Name System.
Speaking of the Internet Protocol or IP address, it is noted as a 32-bit integer. So if somebody wishes to send a message, it is important to include the destination address, but most of the people today rather prefer to assign machines pronounceable and easily remembered domain names. For such reason, the Domain Name System is largely used. Aside from translating a domain name to IP address, the Domain Name System also allows independence from knowing the physical location of a host. And speaking of a host, it can be moved to a various network while the users are still using the same logical name.
In the process of translating a domain name to IP address, it is then necessary to remember that the Domain Name System is a distributed database by the TCP/IP applications to map a domain name to IP address. It is also noted that it serves to provide electronic mail routing information. With that, each site on the web whether it is university department, company, campus, or even department within a company, for example, holds it own database of details and thus runs a server program that other systems across the internet can query. By translating a domain name to IP address, the clients and servers will be able to communicate with each other.
And through the process of translating a domain name to IP address, it is considered that the system then accesses the DNS through a resolver. The resolver then gets the domain name and then puts back the IP address or get the IP address and search for the domain name. The translation of a domain name to IP address then involves the functioning of the TCP for opening a link or sending a datagram by using the UDRP. Thus in the translation of a domain name to IP address, everything is in control and everything is in use.
3.
c) Explain the differences between
Routing and Switching? [6]
ans :-- Switches
A switch does essentially what a hub does, but more efficiently. By paying attention to the traffic that comes across it, it can "learn" where particular addresses are.Initially, a switch knows nothing and simply sends on incoming messages to all ports:
That means that subsequent messages destined for machine "A" need only be sent to that one port:
Routers
A router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes - from the small, four-port broadband routers that are very popular right now to the large industrial strength devices that drive the internet itself.A simple way to think of a router is as a computer that can be programmed to understand, possibly manipulate, and route the data that it's being asked to handle. Many routers today are, in fact, little computers dedicated to the task of routing network traffic.
As far as simple traffic routing is concerned, a router operates exactly as a switch, learning the location of the computers on its connections and routing traffic only to those computers.
Consumer grade routers perform at minimum two additional and important tasks: DHCP and NAT.
DHCP - Dynamic Host Configuration Protocol - is the way dynamic IP addresses are assigned. A device asks for an IP address to be assigned to it from "upstream" and a DHCP server responds with an IP address assignment. A router connected to your ISP-provided internet connection will typically ask your ISP's server for an IP address; this will be your IP address on the internet. Your local computers, on the other hand, will ask the router for an IP address and these addresses are local to your network.
A side effect of NAT is that machines on the internet cannot initiate communications to local machines - they can only respond to communications initiated by those local machines.
The net effect is that the router then also acts as a firewall:
All routers include some kind of user interface for configuring how the router will treat traffic. The really large routers include the equivalent of a full-blown programming language to describe how they should operate as well as the ability to communicate with other routers to describe or determine the best way to get network traffic from point A to point B.
6.
c) Home
based Internet services can be established using analog modems, IDSN, cable
modems, ADSL and hi-speed wireless links. Compare their advantages and
disadvantages [8]
July-2005 [50]
1.
d) Write any three features of intranet
that differences it largely from Internet. [4]
c) Write
a short note on baseband technology and broadband technology, with a special
reference to advantages and the latest status of broadband in India.
[6]
3. State the difference between any three of the following in brief:
4. Expand and explain in detail any three of the following acronyms:
5.
7.
a) With
reference to various applications of Internet in our daily life, explain, how
Internet has revolution the area of Learning?
[8]
b) Suppose a network uses distance
vector routing. What happens if the router sends a distance vector with all
0’s(Zero)?
[5]
January-2006 [19]
1.
f) What is Domain Name System?
Explain. [4]
2.
a) What is Internet? Describe the
Architecture of Internet. Explain how a router works. [6]
3.
a) What
is Client/Server architecture? Explain the advantages and disadvantages of
two-tier and three-tier architecture in detail.
[9]
July-2006 [16]
1.
f) Which
transport technique is most appropriate for multimedia service: packet
switching, circuit switching or ATM cell switching. Why? [4]
4.
b) What
does DNS stand for? What is its main purpose? [6]
6.
a) Explain
the following terms:
ii) Router [2]
c) What
is xDSL technology? [4]
January-2007 [16]
1.
e) Explain the significance of DNS
server. [4]
4.
a) What
is ATM? Discuss the four types of services provided by it. [6]
5.
b) Differentiate
between multi-protocol router and a traditional single-protocol router. [6]
July-2007 [18]
2.
b) Write
a short note on Baseband Technology and Broadband Technology, with a special
reference to advantages and the latest status of Broadband in India. [6]
4.
a) Explain
whether an ATM cell carries a source or destination address in its header or
not. [6]
5.
a) The
fundamental property of the DNS is caching. DNS server caches the information
when a name server receives information about a mapping. What is the purpose of
it and how does it work? [6]
January-2008 [34]
1.
d) Explain
the client server model of communication? What is the difference between client
server architecture and web architecture?
[4]
2.
b) What
are the advantages of ATM that uses small the fixed length packets? [6]
4.
a) What
are the benefits of DSL? How can a DSL line be shared among multiple users? [6]
c) What
is Domain Name System? What does it mean to “register” a domain name? What’s
the difference between forward lookup and reverse lookup in DNS? [6]
5.
b) Discuss
how a user gets connected to the Internet using an ISP. [6]
c) Write
a short note a Baseband Technology and Broadband Technology, with a special
reference to advantages and the latest status of Broadband in India. [6]
July-2008 [30]
2.
c) What is meant by
upstream and downstream? [6]
4.
a) What is the difference
between an Ethernet switch and an Ethernet hub? Which is more suitable for a
network with a high traffic load, a switch or a hub? Explain. [6]
b)
Compare DSL with the following:
* 56 Kbps analog modems
* T.1 line
* ISDN [6]
c) When
a DNS server receives a request, what are the possible actions that it can
take? [6]
7.
a) What is Virtual circuit network?
What are its advantages and disadvantages? Name some network technologies that
use virtual circuits. [6]
January-2009
[14]
1.
a) What is Domain Name System (DNS)? Differentiate
between forward lookup and
reverse in DNS. [4]
g) How do ports on host machine enable
communication between them? [4]
7. Write short notes on (any three):
d) Integrated Services Digital Network (ISDN) [6]
July-2009
[26]
1.
a) What is the difference between the
Basic Rate Interface(BRI) and Primary Rate Interface (PRI) services on ISDN?
[4]
c) Describe the difference between
client server system and peer to peer system. [4]
2.
b) What do you mean by term xDSL? Which
DSL technology is mainly deployed in residential areas? [6]
3.
a) What is a resolver? How does it help
in Mapping the Domain name onto an IP address? [6]
7. Write short notes on any three of the
following:
c) Satellite Communication [6]
January-2010 [26]
4.
c) Explain ATM
in detail. Also discuss the services provided by it. [6]
5.
b) What is DSL?
Discuss its benefits? Differentiate between upstream and downstream. “DSL line
can be shared between multiple computers”. Is this statement true or false?
Justify your answer. [9]
July-2010 [16]
1.
b) An
internet service provider (ISP) is a company that offers its customer access to
the internet. What types of connection can it provide to users? [4]
3.
c) Integrated Services Digital Network
(ISDN) [6]
ans
:-- The Integrated Services Digital Network was the first
telecommunications service designed specifically for digital data
communication. ISDN was designed to run over standard voice digital telephone
systems already in place. Consequently ISDN conforms to specifications found in
the telecom's digital voice network. However, it took so long for ISDN to be
standardized that it was never fully deployed in the telecommunications
networks it was intended for. CHANNEL TYPES
ISDN uses two bearer channels and one data channel.
Bearer Channels
The first channel type is a
'bearer' channel or 'B' channel. These are the channels that carry the
end-user's actual data. Bearer channels are always 64kbps in the US, and 56kbps
elsewhere.
Data Channels
To confuse things, the telcos
called the second channel type the 'data' channel or 'D' channel. This channel
contains the data THEY consider important such as signalling errors, framing
and various control and managment signals. The D channel's speed is 16 kbps for
a BRI, and 64 kbps for a PRI.
SERVICE TYPES
ISDN provides two types of service, Primary Rate Interface (PRI) and Basic Rate Interface (BRI). These speed and number of channels for these two types of service vary depending upon whether you are in the United States or are elsewhere.
Primary Rate Interface
In the US, a PRI consists of 23,
64kbps 'B' channels and one 64kbps 'D' channel for a total of 1.544 Mbps.
Elsewhere in the world a PRI consists of 30 'B' channels running at 56kbps and
one 'D' channel also running at 64kbps. The reason for this difference is that
overseas systems use a 7-bit word (7 bits x 8000 sample rate = 56,000 bps) and
no echo cancellation. The US
uses an 8-bit word (8 bits x 8,000 sample/second rate = 64,000 bps) with echo
cancellation in the voice network.
Basic Rate Interface
BRI's consist of two bearer
channels and one data channel. The Bearer channels are either (US) 64 or 56
kbps (elsewhere) and the data channel is 16 kbps, providing up to 144 kbps of
data transmitted and 128 kbps of usable user data.
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