Inter networking and Internet Protocols

7/29/2019 Inter networking and Internet Protocols

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Internetworking & Internet Protocols 2013

Sarvjeet Singh Sohal (1269922)1

OUTLINE

oOSI and TCP/IP Model.oFDDI (Fiber Distributed Data Interface).o Internetwork and Its Architectural Modal.oFunction of TCP protocol.oToken Ring Protocol.oEthernet.oMetropolitan Area Network (MAN) & Wide Area

Network (WAN)


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congestion of data packets.

Data link layer: The data link layer packages raw bits from the physical layer into frames

(logical, structured packets for data). This layer is responsible for transferring frames from

one computer to another, without errors. After sending a frame, it waits for an

acknowledgment from the receiving computer.

Physical layer: The physical layer transmits bits from one computer to another and regulates

the transmission of a stream of bits over a physical medium. The layer defines how the cable

is attached to the network adapter and what transmission technique is used to send data over

the cable

The Internet Protocol Suite also known as TCP/IP is the set of communications protocols

used for the Internet and other similar networks. It is named from two of the most important

protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which

were the first two networking protocols defined in this standard. IP networking represents asynthesis of several developments that began to evolve in the 1960s and 1970s, namely the

Internet and LANs (Local Area Networks), which emerged in the mid- to late-1980s, together

with the advent of the World Wide Web in early 1990s.

The Internet Protocol Suite, like many protocol suites, may be viewed as a set of layers. Each

layer solves a set of problems involving the transmission of data, and provides a well-defined

service to the upper layer protocols based on using services from some lower layers. Upper

layers are logically closer to the user and deal with more abstract data, relying on lower layer

protocols to translate data into forms that can eventually be physically transmitted.

The main differences between the two models are as follows:

1. OSI is a reference model and TCP/IP is an implementation of OSI model.2. TCP/IP Protocols are considered to be standards around which the internet has

developed. The OSI model however is a "generic, protocol independent standard."

3. TCP/IP combines the presentation and session layer issues into its application layer.4. TCP/IP combines the OSI data link and physical layers into the network access layer.5. TCP/IP appears to be a simpler model and this is mainly due to the fact that it has

fewer layers.

6. TCP/IP is considered to be a more credible model- This is mainly due to the factbecause TCP/IP protocols are the standards around which the internet was developed

therefore it mainly gains creditability due to this reason. Whereas in contrast networks

are not usually built around the OSI model as it is merely used as a guidance tool.

7. The OSI model consists of 7 architectural layers whereas the TCP/IP only has 4layers.

8. In the TCP/IP model of the Internet, protocols are deliberately not as rigidly designedinto strict layers as the OSI model.[6] RFC 3439 contains a section entitled "Layering

considered harmful." However, TCP/IP does recognize four broad layers of

functionality which are derived from the operating scope of their contained protocols,


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namely the scope of the software application, the end-to-end transport connection, the

internetworking range, and lastly the scope of the direct links to other nodes on the

local network.

9. The presumably strict consumer/producer layering of OSI as it is usually describeddoes not present contradictions in TCP/IP, as it is permissible that protocol usage doesnot follow the hierarchy implied in a layered model. Such examples exist in some

routing protocols (e.g., OSPF), or in the description of tunnelling protocols, which

provide a Link Layer for an application, although the tunnel host protocol may well

be a Transport or even an Application Layer protocol in its own right.

10.The TCP/IP design generally favours decisions based on simplicity, efficiency andease of implementation.

FDDI (Fiber Distributed Data Interface).

FDDI is another popular local area networking technology that provides a data rate of 100

Mbps (i.e., the same data rate as Fast Ethernet). Unlike Ethernet and other LAN technologies

that use copper cables to carry electrical signals, FDDI is designed to use optical fiber. Data

is encoded in pulses of light.

FDDI defines use of two types of fiber:single mode (sometimes called mono mode) and

multimode. Modes can be thought of as bundles of light rays entering the fiber at a particular

angle. Single-mode fiber allows only one mode of light to propagate through the fiber, while

multimode fiber allows multiple modes of light to propagate through the fiber. Because

multiple modes of light propagating through the fiber may travel different distances(depending on the entry angles), causing them to arrive at the destination at different times (a

phenomenon called modal dispersion), single-mode fiber is capable of higher bandwidth and

greater cable run distances than multimode fiber. Due to these characteristics, single-mode

fiber is often used for interbuilding connectivity, while multimode fiber is often used for

intrabuilding connectivity. Multimode fiber uses light-emitting diodes (LEDs) as the light-

generating devices, while single-mode fiber generally uses lasers.

Dual-counter-rotating token ring architecture one ring is primary and the other secondary. Up


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to 500 stations with a maximum distance of 2 km between any pair of stations for multimode

fiber with single-mode fiber the distance can be up to 40 km Maximum ring length is 100 km

(total fiber length is 200 km for two rings) and uses 4b/5b encoding.

Architectural model of FDDI:

Media Access Control(MAC): Defines how the medium is accessed, including frame format,

token handling, addressing, algorithm for calculating a cyclic redundancy check value, anderror recovery mechanisms.

Physical Layer Protocol(PHY): Defines data encoding/decoding procedures, clocking

requirements, framing, and other functions.

Physical Layer Medium (PMD): Defines the characteristics of the transmission medium,

including the fiber-optic link, power levels, bit error rates, optical components, and

connectors.

Station Management(SMT): Defines the FDDI station configuration, ring configuration,and ring control features, including station insertion and removal, initialization, fault isolation

and recovery, scheduling, and collection of statistics.

FDDI Frame Format:

The fields of an FDDI frame are as follows:

Preamble: Prepares each station for the upcoming frame.

Start delimiter: Indicates the beginning of the frame. It consists of signalling patterns that

differentiate it from the rest of the frame.


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Frame control: Indicates the size of the address fields, whether the frame contains

asynchronous or synchronous data, and other control information.

Destination address: Contains a unicast (singular), multicast (group), or broadcast (every

station) address. As with Ethernet and Token Ring, FDDI destination addresses are 6 bytes.

Source address: Identifies the single station that sent the frame. As with Ethernet and Token

Ring, FDDI source addresses are 6bytes.

Data: Contains either information destined for an upper-layer protocol or control

information.

Frame check sequence (FCS): Filled by the source station with a calculated cyclic

redundancy check(CRC) value dependent on the frame contents (as with Token Ring and

Ethernet). The destination station recalculates the value to determine whether the frame may

have been damaged in transit. If so, the frame is discarded.

End delimiter: Contains non data symbols that indicate the end of the frame.

Frame status: Allows the source station to determine if an error occurred and if the frame

was recognized and copied by a receiving station.

Advantages of FDDI over token ring:

High bandwidth (10 times more than token ring) Larger distances between FDDI nodes because of very low attenuation ( 0.3 db/km)

in fibers

Improved signal-to-noise ratio because of no interference from external radiofrequencies and electromagnetic noise

Token ring protocol cannot work if a link or a station fails. So, it is vulnerable to linkand station failure but FDDI does works even.

Very difficult to tap signals form a fiber cable


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Internetwork and Its Architectural Modal

An internetwork is a collection of individual networks, connected by intermediate networking

devices, that functions as a single large network. Internetworking refers to the industry,

products, and procedures that meet the challenge of creating and administering internetworks.

Figure below illustrates some different kinds of network technologies that can be

interconnected by routers and other networking devices to create an internetwork.

The words internetwork and internet are simply a contraction of the phrase interconnected

network. However, when written with a capital I, the Internet refers to the worldwide set of

interconnected networks. Therefore, the Internet is an internet, but the reverse does not apply.

The Internet is sometimes called the connected Internet.

Architectural Modal of Internetwork:

The Internetwork consists of the following groups of networks:

1. Backbones: Large networks that exist primarily to interconnect other networks. Alsoknown as network access points (NAPs) or Internet Exchange Points (IXPs).

Currently, the backbones consist of commercial entities.

2. Regional networks connecting, for example, universities and colleges.3. Commercial networks providing access to the backbones to subscribers, and networks

owned by commercial organizations for internal use that also have connections to the

Internet.

4. Local networks, such as campus-wide university networks.Another important aspect of internetworking is the creation of a standardized abstraction


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of the communication mechanisms provided by each type of network. Each physical

network has its own technology-dependent communication interface, in the form of a

programming interface that provides basic communication functions (primitives). TCP/IP

provides communication services that run between the programming interface of a

physical network and user applications. It enables a common interface for theseapplications, independent of the underlying physical network. The architecture of the

physical network is therefore hidden from the user and from the developer of the

application. The application need only code to the standardized communication

abstraction to be able to function under any type of physical network and operating

platform.

In Figure, to interconnect two networks, we need a computer that is attached to both networks

and can forward data packets from one network to the other; such a machine is called a

router. The term IP router is also used because the routing function is part of the Internet

Protocol portion of the TCP/IP protocol suite

To be able to identify a host within the internetwork, each host is assigned an address, called

the IP address. When a host has multiple network adapters (interfaces) such as with a router,

each interface has a unique IP address. The IP address consists of two parts:

IP address =

The network number part of the IP address identifies the network within the internet and is

assigned by a central authority and is unique throughout the internet. The authority for

assigning the host number part of the IP address resides with the organization that controls

the network identified by the network number.


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Function of TCP protocol

Functions Performed By TCP

o Addressing/Multiplexing: TCP is used by many different applications for theirtransport protocol. Therefore, like its simpler sibling UDP, an important job for TCPis multiplexingthe data received from these different processes so they can be sent out

using the underlying network-layer protocol. At the same time, these higher-layer

application processes are identified using TCP ports. The section on TCP/IP transport

layer addressing contains a great deal of detail on how this addressing works.

o Connection Establishment, Management and Termination: TCP provides a set ofprocedures that devices follow to negotiate and establish a TCP connection over

which data can travel. Once opened, TCP includes logic for managing connections

and handling problems that may result with them. When a device is done with a TCP

connection, a special process is followed to terminate it.

o Data Handling and Packaging: TCP defines a mechanism by which applications areable to send data to it from higher layers. This data is then packaged into messages to

be sent to the destination TCP software. The destination software un packages the

data and gives it to the application on the destination machine.

o Data Transfer: Conceptually, the TCP implementation on a transmitting device isresponsible for the transfer of packaged data to the TCP process on the other device.

Following the principle of layering, this is done by having the TCP software on the

sending machine pass the data packets to the underlying network-layer protocol,

which again normally means IP.

o Providing Reliability and Transmission Quality Services: TCP includes a set ofservices and features that allow an application to consider the sending of data using

the protocol to be reliable. This means that normally, a TCP application doesn't

have to worry about data being sent and never showing up, or arriving in the wrong

order. It also means other common problems that might arise if IP were used directly

are avoided.

o Providing Flow Control and Congestion Avoidance Features: TCP allows the flow ofdata between two devices to be controlled and managed. It also includes features to

deal with congestion that may be experienced during communication between

devices.

TCP Header Format:

The Transmission Control Protocol (TCP) header is the first 24 bytes of a TCP segment that

contains the parameters and state of an end-to-end TCP socket. The TCP header is used to

track the state of communication between two TCP endpoints. Since TCP segments are

inserted (encapsulated) in the payload of the IP packet the TCP header immediately follows
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the IP header during transmission. TCP does not need to keep track of which systems are

communicating, it only needs to track which end to end sockets are currently open. Internet

Protocol handles the logical addressing, routing and host-to-host connectivity.

TCP uses port numbers on each side of the connection to track the connection endpoints, state

bits such as SYN, ACK, RST, FIN, sequence numbers and acknowledgement numbers to

track the communication at each step in transmission.


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Token Ring Protocol

Token ring: a number of stations connected by transmission links in a ring topology.

Information flows in one direction along the ring from source to destination and back to

source.

Medium access control is provided by a small frame, the token that circulates around the ring

when all stations are idle. Only the station possessing the token is allowed to transmit at any

given time.

Token Ring Operation

When a station wishes to transmit, it must wait for token to pass by and seize thetoken.

One approach: change one bit in token which transforms it into a start-of-frame sequence and appends frame for transmission.

Second approach: station claims token by removing it from the ring. Frame circles the ring and is removed by the transmitting station. Each station interrogates passing frame, if destined for station, it copies the frame into

local buffer. {Normally, there is a one bit delay as the frame passes through a

station.}

Features:

4 and 16 Mbps using twisted-pair cabling with differential Manchester line encoding. Maximum number of stations is 250. Waits for last byte of frame to arrive before reinserting token on ring {new token after

received}.

8 priority levels provided via two 3-bit fields (priority and reservation) in data andtoken frames.

Permits 16-bit and 48-bit addresses. Under light loaddelay is added due to waiting for the token. Under heavy loadring is round-robin The ring must be long enough to hold the complete token. Advantagesfair access Disadvantagesring is single point of failure, added issues due to token maintenance.


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Frame format:

Token Ring and IEEE 802.5 support two basic frame types: Tokens Data/command frames.

Tokens are 3 bytes in length and consist of a start delimiter, an access control byte,and an end delimiter.

Data frames carry information for upper-layer protocols Command frames contain control information and have no data for upper-layer

protocols.

Token Frame contains three fields, each of which is 1 byte in length:

Start Delimiter Access Control Ending delimiter

Start delimiter (1 byte): Alerts each station of the arrival of a token (or data/command

frame). This field includes signals that distinguish the byte from the rest of the frame by

violating the encoding scheme used elsewhere in the frame.

Access-control (1 byte): Contains the Priority field (the most significant 3 bits) and the

Reservation field (the least significant 3 bits), as well as a token bit (used to differentiate a

token from a data/command frame) and a monitor bit (used by the active monitor to

determine whether a frame is circling the ring endlessly).

End delimiter (1 byte): Signals the end of the token or data/command frame. This field alsocontains bits to indicate a damaged frame and identify the frame that is the last in a logical

sequence.

Data/command frames have the same three fields as Token Frames, plus several others. The

Data/command frame fields are described below:

Frame-control byte (1 byte): Indicates whether the frame contains data or controlinformation. In control frames, this byte specifies the type of control information.

Destination and source addresses (2-6 bytes): Consists of two 6-byte address fields that

identify the destination and source station addresses.

Data (up to 4500 bytes): Indicates that the length of field is limited by the ring token holding

time, which defines the maximum time a station can hold the token.

Frame-check sequence (FCS- 4 byte): Is filed by the source station with a calculated value

dependent on the frame contents. The destination station recalculates the value to determine

whether the frame was damaged in transit. If so, the frame is discarded.

Frame Status (1 byte): This is the terminating field of a command/data frame. The Frame

Status field includes the address-recognized indicator and frame-copied indicator.

Start

Delimiter

Access

Control

Frame

Control

Destination

address

Source

addressData

Frame

check

sequence

End

Delimiter

Frame

Status


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ETHERNET

Ethernet is a well-known and widely used network technology that employs bus topology.

IEEE802.3 working group controls the Ethernet standards.

The original Ethernet hardware operated at a rate of 10 Mbps A later version known as Fast Ethernet operates at 100 Mbps. The most recent version, which is known as Gigabit Ethernet operates at 1000 Mbps

or 1 Gigabit per second (Gbps).

10Gbps on copper will soon be availableEthernet uses a bus topology; Ethernet requires multiple computers to share access to a single

medium.

While transmitting a frame, a computer has the exclusive use of the cable. A sender transmits a signal, which propagates from the sender toward both ends of the cable.

Sharing in local area networks technologies does not mean that multiple frames from

different computers are being sent at the same time. Instead, the sending computer has

exclusive use of the entire cable during the transmission of a given frame other computers

must wait.

Only one computer can transmit at any time. After the computer finishes transmitting oneframe, the shared cable becomes available for another computer to use.

Ethernet has several different variations, each of which uses different cable types, topologies,

and distance limitations.

The different types are:

10 Base-5 (Thick Ethernet) 10 Base-2 (Thin Ethernet)

10 Base-T (UTP Ethernet)


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10 Base-FL 100 Base-T 100 Base-F Gigabit Ethernet 10-Gigabit Ethernet

Thick Ethernet, officially known as 10 Base-5

10 Base-5 is laid out in a bus topology, with a single coaxial cable connecting all nodes

together. At each end of the coaxial cable is a terminator. Each node on the network

physically connects to the coaxial cable through a device called a transceiver and an AUI

cable is connected between the node and the transceiver.

A single 10 Base-5 segment may be up to 500 meters (1650 feet)in length and may have up to

255 nodes connected to it. Each node must be at least 2.5 meters (8.25 feet) apart.

Advantage and Disadvantage of 10 Base-5

Advantage:

Long Distances Possible: 10 Base-5 allows distances up to 500 meters (1650 feet). This

makes it very useful as a "backbone" technology for wiring together multiple locations within

a building without the use of repeaters

Noise Immunity: Since 10 Base-5 uses a very heavily shielded cable, it can be used in

electrically noisy environments which can cause other network types to fail.

Conceptually Simple: Since all devices on a 10 Base-5 network are simply chained together

on a common coaxial cable, it is a simple matter to plan the routing of the cable.

Disadvantage:

Inflexible: 10 Base-5 networks do not lend themselves well to installations where the setup of

the network will change much after the initial installation. It can be very difficult to add or

move a node once it is connected to the coaxial cable.

Fault Intolerant: Since 10 Base-5 uses a common physical cable to interconnect all the


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nodes, the failure of any part of the coaxial cable or any node has the ability to cause the

collapse of the entire network.

Susceptible to Ground Loops: A ground loop occurs when a network cable is used to

interconnect devices which are powered from different sources, and therefore a difference in

voltage exists between two points on the network. The result is an electrical current flowing

through the shields of the cable, which causes considerable noise to be introduced into the

center conductor.

Very Difficult Troubleshooting: As mentioned above, a failure anywhere on a 10 Base-5

segment has the ability to drop the entire network. Troubleshooting such a failure can be

extremely frustrating, as the only way to do it is to check each node and the cabling between

them one at a time. This is very time consuming, and can be expensive if a company's entire

business relies on the network to be up.

Metropolitan Area Network (MAN) & Wide Area Network (WAN)

Metropolitan Area Network (MAN)

A MAN (metropolitan area network) is a high-speed network covering widerdistances than LAN.

A MAN spans distances of approximately 100 miles; therefore, it is suitable forconnecting devices and LANs in a metropolitan area.

MAN speeds are typically 100 Mbps or higher. The most commonly implemented MAN is the fiber distributed data interface (FDDI).

It operates at 100 Mbps over fiber optic cable for distances up to 200 kilometers.

Wide Area Network (WAN)

A WAN is the oldest type of network. WANs generally span a wide geographic area like a state, province, country, or

multiple countries. However, some WANs are confined to a limited geographic area,

like a LAN.

A WAN in a limited geographic area could be easily extended over a wide area usingthe same technologies. The same is not true of a LAN.


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Inter networking and Internet Protocols