network communication overview – network functions

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Network Communication Overview – Network Functions

• Error control• Names and addresses• Prioritization and flow control• Segmentation• Synchronization

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Network Communication Overview – OSI Reference Model

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Network Communication Overview – OSI Reference Model

• Examples– Physical (Layer 1): RS-232

– Data link (Layer 2): Ethernet

– Network (Layer 3): IP

– Transport (Layer 4): TCP

– Session (Layer 5): RPC

– Presentation (Layer 6): MPEG

– Application (Layer 7): HTTP

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Network Communication Overview – OSI Reference Model

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Network Communication Overview – OSI Reference Model

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Network Communication Overview – OSI Reference Model

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Network Communication Overview – OSI Reference Model

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Network Devices

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Network Devices

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Network Addressing

• MAC addresses are used at Layer 2

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Network Addressing

• MAC addresses are used at Layer 2

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Network Addressing

• IP addresses are used in Layer 3

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Network Addressing

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Network Addressing

• TCP ports are used in Layer 4

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Network Addressing

• TCP ports– Ports 0 to 1023: Standard (also known as well-

known ports)– Ports 1024 to 49151: Registered ports– Ports 49152 to 65535: Dynamic ports (also known

as private or ephemeral)

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Network Addressing

• UDP ports are used in Layer 4

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Defense in Depth

• NAT• One Class A (10.0.0.0 - 10.255.255.255)• One Class B (192.168.0.0 -

192.168.255.255)• Several Class Cs (172.16.0.0 -

172.31.255.255)

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Defense in Depth

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Summary• Network communication systems provide five major

functions: naming and addressing, error control, prioritization and flow control, segmentation, and synchronization.

• The OSI reference model provides a standard framework for network communication.

• There are seven layers within the OSI model: physical, data link, network, transport, session, presentation, and application.

• The NIC, repeater, and hub operate at the Physical layer of the OSI reference model.

• Bridges and switches generally operate at the Data Link layer of the OSI reference model and help to reduce overall network congestion by directing traffic to specific hardware or MAC addresses.

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Summary

• Routers generally operate within the Network layer and are crucial devices in TCP/IP networks.

• Network protocols form standards to ensure that everyone on a network is speaking the same language.The Ethernet and TCP/IP protocols form the basis for most modern networks.

• Ethernet MAC addresses are 48-bit addresses usually expressed in hexadecimal format (e.g., 00-50-56-C0-00-08). IPv4 addresses are 32-bit addresses normally expressed in decimal format (e.g., 192.168.100.50).

• IP addressing comprises both an IP address and subnet mask. By applying the subnet mask to an IP address, routers can direct network traffic to the proper network and host ID.

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Summary

• TCP and UDP protocols operate within the Transport layer and provide another layer of functionality to the IP protocol.TCP is a connection-oriented protocol that helps to ensure proper delivery and reception of IP traffic. UDP is connectionless and thus less reliable than TCP; however, UDP offers greater delivery speeds of IP traffic.

• Networks should be protected by several layers of security protections. This “defense in depth” approach helps to ensure that the network is constantly protected, even if one defense is compromised. NAT, DMZs, and system firewalls are just a few technologies that can be applied to the network to help create security layers.