MSIS 4523 Ch2.Network Models
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Transcript of MSIS 4523 Ch2.Network Models
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Data Communications SystemsCh 2: Network Models
JinKyu Lee, Ph.D.
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Topic List
Network Architecture/Reference Models OSI 7-Layer Model
TCP/IP Protocol Suite 5-Layer Model
Purpose of Layered Models
Encapsulation & Decapsulation Layer-to-Layer (peer-to-peer) Processing
Devices in Each Layer
Addressing in Each Layer
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Network Architectures
Reference model
Describes the layers of hardware and software
necessary to transmit data between two points or for
multiple devices / applications to interoperate
Necessary to increase the likelihood that different
components from different manufacturers will
converse Two architectures are required learning: The OSI
Model, and the TCP/IP protocol suite
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The Open Systems Interconnection (OSI)model
An ISO standard that
covers all aspects of
network communications
is the Open Systems
Interconnection (OSI)
model. It was first
introduced in the late
1970s.
Layered Architecture
ISO is the organization.
OSI is the model.
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TCP/IP PROTOCOL SUITE
The layers in the TCP/IP protocol suite do not
exactly match those in the OSI model. The original
TCP/IP protocol suite was defined as having fourlayers: host-to-network, internet, transport, and
application. However, when TCP/IP is compared to
OSI, we can say that the TCP/IP protocol suite is
made of five layers: physical, data link, network,transport, andapplication.
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TCP/IP Protocol Layers
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Summary of Duties
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Figure 2.16 TCP/IP and OSI model
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An exchange using the Internet model
Encapsulation
Decapsulation
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Peer-to-Peer Processes
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Physical layer
The physical layer is responsible fortransmitting individual bits from one
node to the next.
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Data link layer
The data link layer is responsible fortransmitting frames from
one node to the next.
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Node-to-node delivery Nodes
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Delivery in Data Link Layer
A node with physical (MAC) address 10 sends a frame to a
node with physical address 87. The two nodes are connected
by a link.
At the data link level this frame contains physical addresses
in the header. These are the only addresses needed.
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Network layer
The network layer is responsible for the
delivery of packets from the original sourceto the
final destination.
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Source-to-destination deliveryNodes
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Delivery in Network Layer
A node with a physical
address 10 wants to send datato a node with a physical
address 95, located on a
different network. Physical
addresses only have localjurisdiction. We need
universal addresses that can
pass through the LAN
boundaries. The network
(logical) addresses have this
characteristic.
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Transport layer
The transport layer is responsible for
delivery of a message from one process
to another.
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Delivery in Transport Layer
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Application layer
The application layer is responsible for
providing services to the user.
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Devices in Each Layer
Physical Layer Repeaters & Hubs
Data Link Layer Devices
Bridges & (Layer-2) Switches
Network Layer Device
Routers & Layer-3 Switches
Transport Layer Device
(Packet filtering, SPI, NAT) Firewalls Application Layer Device
Proxy servers, (Content filtering) Firewalls,Application Gateways
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Addressing
Each sub-network on a network requires aunique address within that network
Each computer on a sub-network requires aunique address on that sub-network
Each application requires a unique addresswithin the computer to allow support for multipleapplications (service access points, or SAP)
Service Access Points (SAPs)
Addresses for applications using transport services
Commonly known as Ports
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ADDRESSING
Four levels of addresses are used in an internet
employing the TCP/IP protocols: physical, logical,port, andspecific.
Addresses in TCP/IP
e.g., Email addresss& URLs
User friendly
Converted to alogical & portaddress
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Relationship of layers and addresses in TCP/IP