Network + Part 1

Open Systems Interconnection Reference Model. Describes how traffic moves from one part of the network to another.

Application Presentation Session Transport Network Data Link Physical

Please Do Not Throw Sausage Pizza Away

All People Seem To Need Data Processing

The physical Layer, Signaling, cables and connectors.

The Data Link Layer. Uses MAC (Media Access Control) addresses on the internet. Switches live here. Frames are made here. Extended Unique Identifiers.

Network Layer. Associated with IP addresses, routers, packets, fragmenting frames for other networks.

• The Transport Layer.
• Associated with post offices, describes how a webpage is broken into frames (pieces) and how it is put back together. TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) live here.

• Session Layer.
• Communication Management between devices. Such as start, stop, restart. Control protocols, tunneling protocols.

• Presentation.
• Character encoding. Takes data and puts it in a form we understand. Encryption. SSL and TTL.

• Application.
• The layer users actually see.

• Secure Sockets Layer
• SSL is standard technology for securing an internet connection by encrypting data sent between a website and a browser (or between two servers). It prevents hackers from seeing or stealing any information transferred, including personal or financial data.

Time to Live refers to the amount of time or “hops” that a packet is set to exist inside a network before being discarded by a router.

An application that shows all 7 layers on a data packet.

HTTPS, IMAP, SSH are associated with Layers 5-7

• Protocol Data Unit
• Transmission Units for each group of data at different OSI layers.

• The header identifies the payload and control information.
• SYN - Synchronize sequence numbers
• PSH - Push the data to the application without buffering
• RST - Reset the connection
• FIN - Last packet from the sender

Maximum Transmission Unit. Designated the size of the data allowed to be sent without fragmented. Standard is 1,500 bytes.

Internet Protocol (IP) process that breaks packets into smaller pieces (fragments), so that the resulting pieces can pass through a link with a smaller maximum transmission unit (MTU) than the original packet size. The fragments are reassembled by the receiving host. Fragments are always in multiples of 8.

Ping with DF and force a maximum size of 1472 bytes. 1500 total. 8 byte ICMP header. 20 bytes IP address.

Also called hub and spoke. All devices are connected to a central device like a star.

A circle of connected nodes. Data can be looped in case of a break.

A straight line, usually a coaxial cable that branches off into nodes. One break can disable the entire network.

Multiple connections to each site. Includes redundancy, fault tolerance, and load balancing. Used in WAN to ensure internet connectivity.

A combination of 2 or more topologies.

All devices communicate through an access point. The most common wireless communication mode.

Devices communicating with each other without pre-existing infrastructure.

All devices are clients and servers. Easy to deploy and low cost. Difficult to administer and secure.

Central server that the clients talk to. Clients do not communicate directly with each other. Performance and administration bonus. Does have cost and complexity issues.

Local Area Network. High speed connectivity. Ethernet and 802.11 wireless are mostly used here.

• Metropolitan Area Network
• A network covering a city. Usually larger than a LAN but smaller than a WAN. An example is the MTA. The government also uses these.

Wide area Network. Can be worldwide and tends to be slower.

• Wireless LAN. Called 802.11 / wifi.
• Limited Geographical Area but can be extended with multiple access points.

Personal Area Network. Your own private network. Bluetooth, IR (infrared), NFC, health and headsets are examples.

Campus Area Network. Can also be associated with a corporate city. LAN expanded.

Network attached storage. Shared storage device across the network with file level access.

Storage Area Network. Feels like a local storage device. Offers block level access and is very efficient at reading and writing. Requires more bandwidth.

Multiprotocol Label Switching. Learning from ATM and Frame Relay. Packets through the WAN have labels that help make routing decisions. Any transport medium or protocol inside such as IP packets and Ethernet frames. Labels are put on and taken off at the edge routers.

Multipoint Generic Router Encapsulation. Used extensively for dynamic multipoint VPN (DMVPN). Common on Cisco routers. The remote sites communicate with each other, and the VPN builds itself. Tunnels are built dynamically, a dynamic mesh.

Software Defined Networking Wide Area Network. WAN build for the cloud. Cloud based applications communicate directly to the cloud without a need for a central point.

The point where you connect with the outside world. Usually the WAN Provider, Internet Service Provider, is also called the demarc. The provider can’t provide services on your side (customer premises).

A NIU (network interface unit) is a device that determines the demarcation point. Can be a circuit card in a chassis. The customer can see warning lights, but the provider has access.

Network function virtualization. Replace physical network devices with virtual versions that are managed by a hypervisor. Same functionalities as physical devices such as routing, switching, load balancing, firewalls.

Virtual Machine Manager that manages the virtual platform and guest operating systems.

Virtual Switch.

Virtual Network Interface Card.

Communication via satellites. High cost and High latency. Vulnerable to weather.

Inexpensive, easy to install and maintain. Slower than fiber.

Asymmetric Digital Subscriber Lines. The ingoing and outgoing speeds are different. Faster if it is closer to the Central Office.

Transmission across multiple frequencies. Broad range of activities such as TV, Phone, and internet.

High speed data communication over light. Can be used over long distances. Costly, difficult to repair.

Also called Metro E. Contained in a regional area. Higher speeds on a local network.

Layers 5-7