Study 1: Explain why the system of using IP

Survey 1:Explain why the system of utilizing IP references categories was considered suited for the Internet when it was foremost designed. Briefly describe two methods of guaranting that there are adequate Internet references for current usage.

Internet Protocol ( IP ) reference is a alone reference which is designated to devices in the cyberspace to be identified and pass on with each other. Originally, when there were merely few big webs such as ARPANET, the 32-bit IPv4 reference consisted of fixed web and host spot divider with 8-bit web figure field which specified the peculiar web a host was attached to, and a 24-bit host field which specified the reference of the host within that web. This resulted in merely 256 webs being available. With the coming of Local Area Networks ( LANs ) , internet began to turn which meant demand for more IP references. Hence classful turn toing strategies were introduced and they were considered suited for the undermentioned chief grounds:

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  1. The 32 spot address infinite was divided to supply three different sizes of web IDs and host IDs. This resulted in webs of different sizes being addressable, from a little figure of big webs to a big figure of little webs with an intermediate size in between, thereby suiting the growing of the Internet. The tabular array below summarized the three categories of turn toing where each category is distinguished by the taking spots of the reference. Two particular categories are those which start with 1110 used for multicast intent and those which start with

1111, which are reserved for future usage.

Class Leading Value in the 32-Bit Address Network ID Bits/ Number of addressable Networks Host ID Bits/ Number of Addressable Hosts
Class A 0 7 / 126 Networks 24 / 16,777,214 Hosts
Class B 10 14 / 16,384 Networks 16 / 65,534 Hosts
Class C 110 21 /2,097,152 Networks 8 / 254 Hosts

B ) Hierarchical classful reference infinite facilitated in aggregating the references into bunchs to be used in the routing tabular arraies. But for this, there would be tremendous figure of routing entries with the cyberspace growing.

Two methods of guaranting that there are adequate references for current usage are:

a ) Network Address Translation ( NAT ) & A ; Private Addresses – Large webs could utilize private references and have NAT to interpret the private references to globally routable IP reference. NAT hides an full web behind one individual IP reference, doing optimum use of the IP reference infinite.

B ) Using Classless Inter Domain Routing ( CIDR ) that permits the usage of bing category A, B and C

references in a classless mode, supplying for adaptable sized webs, in pattern. For case, see a web dwelling of 9 hosts which requires merely 4-bit of host-ID to stand for all hosts. A class-C reference which has the fewest hosts possible devotes 8 spots for the host which implies many references would travel fresh. With classless turn toing it is possible to sub-divide a individual category C reference into 16 references that each have a 28-bit web ID and 4-bit host ID which suits the web size of 9 hosts.

Survey 2:Compare ADSL with one other Internet Access engineering of your pick. Describe the of import parametric quantities of each engineering and list a few of the advantages and disadvantages of each.

Asymmetric Digital Subscribers Loop ( ADSL ) is a broadband entree engineering which provides digital services at high velocity over the distorted brace wiring that forms the local cringle of the parallel telephone system.

This is achieved by using frequences that are usually non used by a voice telephone call, in peculiar, frequencies higher than normal human hearing. This signal will non go really far over normal telephone overseas telegrams, so ADSL can merely be used over short distances, typically less than 5 kilometer. The service is asymmetric as the name suggests, with a higher spot rate downstream ( i.e, to the endorser ) than upstream ( i.e, from the endorser ) and the service is dedicated to the endorser. Therefore, ADSL engineering is optimized for typical users who receive more information than they send. Typical information rates available to the endorser on the ADSL nexus are 0.5 Mbps downstream and1.5 Mbps upstream.

Many options to ADSL engineering exist today and many are being researched. The primary motive for sing options to telephone local cringle arises from the built-in restrictions. The head job lies in the electrical features of the distorted brace wiring which poses an upper edge bound on how fast the informations can be transferred. Furthermore, the deficiency of screening makes the wiring susceptible to interference which can well degrade public presentation. One surrogate engineering which stands out peculiarly attractive because it offers higher velocity than telephone wiring, is less susceptible to interference and does non necessitate wholly new substructure is “Cable Modem Technology” .

Cable Modem engineering uses the overseas telegram telecasting web and commissariats digital informations via the overseas telegram web overseas telegrams and is a broadcast orientated system. This is an always-on service where endorsers portion the connexion which might present security concerns. The media consist of coaxal overseas telegram, which has high capacity and is immune to electromagnetic intervention. Cable systems are designed to transport many more telecasting signals than are presently available, the hardware has unused channels ( bandwidth ) that can be used to transport informations. The points enumerated below comparison advantages and disadvantages of the two entree engineerings.

Speed:Speed for ADSL varies from 128 kbps to 1.544 Mbps. It is besides a distance-sensitive engineering, and that complicates the public presentation image. The bandwidth available to a place user, for illustration, depends significantly on the length of telegraphing running from the place to the supplier ‘s installations every bit good as the electrical quality of that line. Cable modem has a typical mean velocity upto 2 MBps. But once more velocity can non be quantified because of the shared nature of the connexion. Today, overseas telegram modem retains a velocity advantage over ADSL.

Security:ADSL is more unafraid because of its dedicated service while overseas telegram modem fails when it comes to security because of its broadcast shared nature of operation.

Multi-dwelling installing:ADSL does non suit into this without major re-wiring, while overseas telegram modems are far easier to deploy.

Performance consistence:ADSL have guaranteed velocity and public presentation due to the dedicated nature of service where as with overseas telegram modem public presentation varies depending on figure of active endorsers.

In decision, both of these engineerings have their alone advantages and disadvantages and therefore are coexisting without being a major menace for each other.

Survey 3:Assume that you use myisp.com as your e-mail supplier. Explain how the Internet Protocol is involved in conveying an e-mail from your myisp e-mail history to your e-mail history on the LeedsMet waiter. You should depict the map of the IP bed and bespeak how data base on ballss to and from the IP bed informations at both the transmission and having hosts.

The diagram above indicates how a mail is transferred from the mysip.com web to LeedsMet web via the IP web.

Measure 1: User who uses the mysip.com service supplier initiates an electronic mail on a mail client such as mentality express to his history in the LeedsMet web. This electronic mail queues up at the Mail waiter of the mysip.com web such as mail.mysip.com.

Measure 2: The mail waiter at mysip.com web uses a mail transportation agent ( MTA ) [ If it is a unix-based waiter, sendmail is the most common MTA ] . Users don’t have to cover with the MTA, system decision maker sets up the MTA. Simple Mail Transfer Protocol ( SMTP ) is a mime-type protocol used by the MTA to reassign mails from the sender’s web to the receiver’s web.

Measure 3: After the receiver’s Mailer exchanger’s IP reference is derived utilizing the DNS waiter, MTA initiates a TCP port 25 connexion to the receiving system web. The electronic mail traverses the IP-based cyberspace as IP packets until it reaches the receiving system web

Measure 4: At the receiving system web, the MTA in the mail money changer accepts the TCP port 25 connexion and accepts the mail addressed to a user in its local web. Now, this electronic mail is queued in the user’s letter box residing in the mail waiter

Measure 5: Receiver initiates a mail client such as an mentality express and downloads the mails queued up in his letter box from the mail waiter.

Survey 4:Supply a sum-up of the method of congestion control used by TCP. You should guarantee that you define any other proficient footings used in your sum-up.

Transmission Control Protocol ( TCP ) provides dependable agencies of transporting informations between hosts. One other of import characteristic of TCP is the mechanism by which it tries to command congestion when multiple TCP connexions are sharing bandwidth of a engorged nexus. TCP must utilize end-to-end congestion control instead than network-assisted congestion control, since the IP bed provides no feedback to the terminal systems sing web congestion.

TCP operates by detecting the rate at which new packages should be injected into the web is the rate at which the recognitions are returned by the other terminal. TCP’s congestion control mechanism is termed as “Slow Start” TCP connexion controls its transmittal rate by restricting its figure of transmitted-but-yet-to-be acknowledged sections. Let us denote this figure of allowable unacknowledged sections astungsten, frequently referred to as the TCPwindow size.Slow start adds another window to sender’s TCP: the congestion window denoted bycwnd.When a new connexion is established with a host on another web,cwndis initialized to one section. Each frost an ACK is received, the congestion window is increased by one section. The transmitter can convey upto the lower limit of the congestion window. The congestion window is the flow control imposed by the transmitter. The transmitter starts conveying one section and waiting for its ACK. When that ACK is received, the congestion window is incremented fr0m one to two, and two sections can be sent. When each of these two sections is acknowledged, the congestion window is increased to four. This provides an exponential addition.

At some point, congestion would happen in the cyberspace nexus and the intermediate router will get down flinging packages. This tells the transmitter that its congestion window has gotten excessively big. Now, the TCP connexion reduces its congestion window to a safe-level and so begins examining once more for fresh bandwidth by easy increasing the congestion window.

Study 5: Compare the current functions of Ethernet and ATM within the Internet. Why is it improbable that ATM will be used on many LANs in the close hereafter?

Ethernet is a good known and widely used web engineering that employs bus topology. It was designed as one of the solutions to the multiple entree jobs in the wired-local country webs by mechanisms called bearer sense multiple entree and hit sensing ( CSMA/CD ) .

Presently Ethernet is the most widely deployed LAN engineering in endeavor webs, place networking metropolitan webs ( MAN ) and broad country webs ( WAN ) . This is due to ethernet’s high velocity, widespread interoperability and low cost. With the turning size and popularity of the cyberspace and Internet Protocol ( IP ) being the most preferable agencies of package conveyance, Ethernet is deriving huge range in the cyberspace.

Asynchronous Transfer Mode ( ATM ) was developed by telephone companies. An ATM web is formed from a switch to which multiple computing machines attach utilizing a brace of fibers one transporting informations in each way. ATM employs leading topology. They were designed for high-bandwidth with guaranteed quality of service webs potentially consolidative substructure that carries voice, picture and information. It is fundamentally a WAN engineering but besides deployed in LANs. ATM engineering is based on connexion oriented transmittal engineering, an thought adopted from the telephone webs and is packet shift, the thought being adopted from the cyberspace. ATM webs follow a different design doctrine when compared to the cyberspace and utilize their ain protocols. Large corporations and endeavors have deployed ATMs in their anchor webs.

Internet which is based on IP, represents a huge and of all time turning non-ATM web substructure. To be able to be widely accepted, ATM webs must interoperate with IP webs. Unfortunately, this interoperation is debatable, because ATM webs and IP webs have different design rules.

Internet is connectionless while ATM webs are connexion oriented. Internet emphasizes connectivity and best attempt service, while ATM webs emphasize on reserve and quality of service. Routing protocols in the cyberspace differ significantly from those in the ATM webs. In the visible radiation of these differences incorporating IP/ATM webs could be really complex. If the ATM webs are to be used by the huge bulk of IP users, they must suit user’s wants which is the challenge being faced by the interior decorators of the ATM protocol. Finally, although ATMs offer many advantages, jobs such as mentioned above and with undependable and expensive equipments, other higher velocity LAN engineerings such as Gbit Ethernet and FDDI have become more likely to be preferred and used as LAN technologies in close hereafter.

Survey 6:Briefly discuss the of import differences between a span and a router.

Both the span and the router are devices that perform package exchanging and send oning and have certain similarities. Packet shift is performed between interfaces. Both the devices have multiple interfaces that could either be similar or dissimilar. For eg: IEEE 802.3, Asynchronous consecutive interfaces, synchronal consecutive interfaces, etc on routers, IEEE 802.3, IEEE 802.11a/b/g on Bridgess

Outstanding differences between a span and a router can be summarized with the undermentioned points:

– Bridge performs exchanging and send oning at informations link bed, utilizing bed 2 references. Data nexus bed was designed such that nodes pass oning via the informations nexus protocol are attached to a common nexus. This hinders the span from operating in a multi-hop web. It provides a individual broadcast sphere ( send on a broadcast package received on one interface across all other ports ) whereas, a Router performs exchanging and forwards at the web bed utilizing web references. The web bed headings have hop count enabling the routers to run in a multi-hop web. Routers separate the broadcast domains cut downing the web traffic.

– Bridges use dynamically built forwarding tabular arraies and employ crossing tree protocol to observe alternate forwarding paths, if present. They do non modify the package in any manner while send oning. Routers use routing protocols to observe optimum waies. Packages at the web bed could be modified before forwarding.

– Entire figure of nodes that can be interconnected through Bridgess is limited and span reconfiguration after a topological alteration is a complex procedure. Entire figure of hosts that can be interconnected utilizing routers is practically limitless and router reconfiguration after a topological alteration is far simpler.

– Bridges must drop packages that are excessively big to frontward, while router has no such restraint. Reason being, web bed headings contain atomization and reassembly information while informations link layer heading does non.

– Bridges offer no firewall protection against broadcast storms while routers provide assorted entree filtering and firewall-like characteristics.

Apart from the above draw dorsums, Bridges besides offer few advantages over the routers:

  • Transparent Bridge is a stopper and drama web constituent, while router requires a batch of constellation and is complex to cover with.
  • Bridges have a better monetary value to public presentation ratio than routers. The ground being, routers holding to parse a more complicated web bed heading than a information nexus bed heading.

Mention:

[ 1 ] Forouzan, B.A. Data Communications ; A ; Networking ( 3rd Edition ) McGraw-Hill Higher Education, 2003. ISBN: 0-071-23241-9

[ 2 ] Kurose, J.F. ; A ; Ross, K.W. Computer Networking – A top-down attack having the Internet ( 2nd Edition ) Addison-Wesley, 2003. ISBN 0-201-97699-4

[ 3 ] hypertext transfer protocol: //bioif.kaist.ac.kr/~jskim/Home/research/network/cs441/congestion.html

[ 4 ] Steven, W.R, TCP/IP Illustrated Volume 1, Fourth Indian reissue, Addison Wesley, 2001, ISBN 81-808-101-6

[ 5 ] Comer, D.E, Computer Networks and Internets with Internet Applications, ( 3rdEdition ) , Prentice-Hall International, 2002

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