Pertemuan_3 Internet and Internetworking.pptx

SISTEM DISTRIBUSI DAN KOMPUTASI
PARALEL
Dwi Pratiwi, S.T.,M.T.

Networking and Internetworking
• Introduction
• Types of Networks
• Networks Principles
• Internet Protocols

• Distributed systems use local area networks, wide area networks and internetworks
for communication. The performance, reliability, scalability, mobility and quality of
service characteristics of the underlying networks impact the behaviour of distributed
systems and hence affect their design.
• The networks used in distributed systems are built from a variety of transmission
media, including wire, cable, fibre and wireless channels; hardware devices, including
routers, switches, bridges, hubs, repeaters and network interfaces; and software
components, including protocol stacks, communication handlers and drivers.
• The computers and other devices that use the network for communication purposes
are referred to as hosts. The term node is used to refer to any computer or switching
device attached to a network.
• A subnet is a unit of routing (delivering data from one part of the Internet to
another); it is a collection of nodes that can all be reached on the same physical
network.

3.1 Networking issued for distributed system
1.
Performance
2. Scalability 3. Reliability
4. Security 4. Mobility
5. Quality of
Service
(QoS)
6.
Multicasting

1. Performance
• The network performance parameters that are of primary interest for our purposes are
those affecting the speed with which individual messages can be transferred between
two interconnected computers. These are the latency and the point to- point data
transfer rate:
• Latency is the delay that occurs after a send operation is executed and before data starts
to arrive at the destination computer. It can be measured as the time required to transfer
an empty message.
• Data transfer rate is the speed at which data can be transferred between two computers
in the network once transmission has begun, usually quoted in bits per second.

• The total system bandwidth of a network is a measure of throughput – the total volume
of traffic that can be transferred across the network in a given time.
• local area network technologies, such as Ethernet, the full transmission capacity of the
network is used for every transmission and the system bandwidth is the same as the
data transfer rate.
• wide area networks messages can be transferred on several different channels
simultaneously, and the total system bandwidth bears no direct relationship to the
transfer rate. The performance of networks deteriorates in conditions of overload –
when there are too many messages in the network at the same time
• The precise effect of overload on the latency, data transfer rate and total system
bandwidth of a network depends strongly on the network technology.
• On the Internet, round-trip latencies are in the 5–500 ms range, with means of 20–200
ms depending on distance [www.globalcrossing.net], so requests transmitted across the
Internet are 10–100 times slower than those sent on fast local networks.

2. Scalability
• Computer networks are an indispensable part of the infrastructure of
modern societies. In Figure beside we showed the growth in the number of
host computers and web servers connected to the Internet over a 12-year
period ending in 2005. The growth since then has been so rapid and diverse
that it is difficult to find recent reliable statistics. The potential future size of
the Internet is commensurate with the population of the planet. It is realistic
to expect it to include several billion nodes and hundreds of millions of
active hosts.

3. Reliability
• The end-to-end argument further supports the view that the
communication subsystem need not provide totally error-free
communication; the detection of communication errors and their correction
is often best performed by application-level software
• The reliability of most physical transmission media is very high. When errors occur they
are usually due to failures in the software at the sender or receiver (for example, failure
by the receiving computer to accept a packet) or buffer overflow rather than errors in
the network.

4. Security
• Firewall creates a protection boundary between the organization’s intranet and the rest
of the Internet.
• The purpose of the firewall is to protect the resources in all of the computers inside the
organization from access by external users or processes and to control the use of
resources outside the firewall by users inside the organization.
• A firewall runs on a gateway – a computer that stands at the network entry
point to an organization’s intranet. The firewall receives and filters all of the
messages travelling into and out of an organization. It is configured
according to the organization’s security policy to allow certain incoming and
outgoing messages to pass through it and to reject all others.

5. Mobility
• Mobile devices such as laptop computers and Internet-capable mobile phones are
moved frequently between locations and reconnected at convenient network
connection points or even used while on the move. Wireless networks provide
connectivity to such devices, but the addressing and routing schemes of the Internet
were developed before the advent of these mobile devices and are not well adapted to
their need for intermittent connection to many different subnets.

6. Quality of Service
• we defined quality of service as including the ability Quality of service to meet
deadlines when transmitting and processing streams of real-time multimedia data.
• This imposes major new requirements on computer networks. Applications that
transmit multimedia data require guaranteed bandwidth and bounded latencies for the
communication channels that they use.

7. Multicasting
• Most communication in distributed systems is between pairs of Multicasting processes,
but there often is also a need for one-to-many communication. While this can be
simulated by to several destinations, that is more costly than necessary and may sends
not exhibit the fault-tolerance characteristics required by applications.

3.2 Types of Network
• Most communication in distributed systems is between pairs of Multicasting processes,
but there often is also a need for one-to-many communication. While this can be
simulated by to several destinations, that is more costly than necessary and may sends
not exhibit the fault-tolerance characteristics required by applications.

1. Personal Area Network (PANs)
• PANs are a subcategory of local networks in which Personal area networks (PANs) the
various digital devices carried by a user are connected by a low-cost, low-energy
network.

2. Local Area Network (LANs)
• LANs carry messages at relatively high speeds between computers connected by a single
communication medium, such as twisted copper wire, coaxial cable or optical fibre.
• The total system bandwidth is shared between the computers connected to a segment.
Larger local networks, such as those that serve a campus or an office building, are
composed of many segments interconnected by switches or hubs.
• In local area networks, the total system bandwidth is high and latency is low, except
when message traffic is very high..
• There is a very large installed base of local area networks, serving virtually all working
environments that contain more than one or two personal computers or workstations.

2. Wide Area Network (WANs)
• WANs carry messages at lower speeds between nodes that are often in different
organizations and may be separated by large distances. They may be located in different
cities, countries or continents. The communication medium is a set of communication
circuits linking a set of dedicated computers called routers.
• For example, the propagation delay for a signal to travel from Europe to Australia via a
terrestrial link is approximately 0.13 seconds and signals via a geostationary satellite
between any two points on the Earth’s surface are subject to a delay of approximately
0.20 seconds. Bandwidths available across the Internet also vary widely. Speeds of up to
600 Mbps are commonly available, but speeds of 1–10 Mbps are more typically
experienced for bulk transfers of data.

3. Metropolitan Area Network (MANs)
• This type of network is based on the highbandwidth copper and fibre optic cabling
recently installed in some towns and cities for the transmission of video, voice and other
data over distances of up to 50 kilometres. A variety of technologies have been used to
implement the routing of data in MANs, ranging from Ethernet to ATM.

4. Internetworks
• An internetwork is a communication subsystem in which several networks are linked
together to provide common data communication facilities that overlay the technologies
and protocols of the individual component networks and the methods used for their
interconnection.

3.3 Protocols
• The term Protocols is used to refer to a well-known set of rules and formats to be used
Protocol for communication between processes in order to perform a given task. The
definition of a protocol has two important parts to it:
• a specification of the sequence of messages that must be exchanged;
• a specification of the format of the data in the messages.
• Protocol Layer Network software is arranged in a hierarchy of layers. Each layer presents
an interface to the layers above it that extends the properties of the underlying
communication system.

• Protocol suites is A complete set of protocol layers is referred to as a protocol suite or a
protocol stack, reflecting the layered structure. In figure Above shows a protocol stack
that conforms to the seven-layer Reference Model for Open Systems Interconnection
(OSI) adopted by the International Organization for Standardization (ISO)

• Packet assembly The task of dividing messages into packets before transmission and
reassembling them at the receiving computer is usually performed in the transport
layer.
• Ports The transport layer’s task is to provide a network-independent message
transport service between pairs of network ports. Ports are software-defined
destination points at a host computer. They are attached to processes, enabling data
transmission to be addressed to a specific process at a destination node.
• Addressing • The transport layer is responsible for delivering messages to
destinations with transport addresses that are composed of the network address of a
host computer and a port number. A network address is a numeric identifier that
uniquely identifies a host computer and enables it to be located by nodes that are
responsible for routing data to it. In the Internet every host computer is assigned an IP
number,

• Packet delivery There are two approaches to the delivery of packets by the network layer:
• Datagram packet delivery: The term ‘datagram’ refers to the similarity of this delivery
mode to the way in which letters and telegrams are delivered. The essential feature of
datagram networks is that the delivery of each packet is a ‘one-shot’ process; no setup is
required, and once the packet is delivered the network retains no information about it.
• Virtual circuit packet delivery: Some network-level services implement packet
transmission in a manner that is analogous to a telephone network. A virtual circuit must
be set up before packets can pass from a source host A to destination host B. The
establishment of a virtual circuit involves the identification of a route from the source to
the destination, possibly passing through several intermediate nodes. At each node along
the route a table entry is made, indicating which link should be used for the next stage of
the route.

Pertemuan_3 Internet and Internetworking.pptx

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