Networking Fundamentals

Networking Fundamental

Objectives

• Describe the function and operation of a hub, a switch and a router 

• Describe the function and operation of a firewall and a gateway 

• Describe the function and operation of Layer 2 switching, Layer 3 switching, and routing 

• Identify the layers of the OSI model 

• Describe the functionality of LAN, MAN, and WAN networks

• Identify the possible media types for LAN and WAN connections

What is a Network?

• A network refers to two or more connected computers that can share resources such as data, a printer, an Internet connection, applications, or a combination of these resources.

Types of Networks

Local Area Network (LAN)

Metropolitan Area Network (MAN)

Wide Area Network (WAN)

WAN Technologies 

Leased Line

Circuit-switched

Frame-Relay

Broadband Access

Network Topologies:

Bus Topology 

Star Topology

Extended Star Topology

The OSI Model— Why a Layered Network Model?

• Reduces complexity 

• Standardizes interfaces 

• Facilitates modular engineering 

• Ensures interoperable technology 

• Accelerates evolution

• Simplifies teaching and learning

The Seven Layers of the OSI Model

Application Layers (Upper Layers): 

• Network Processes to Applications 

• Data Representation 

• Inter Host Communication

End To End Connections:

• Handles transportation issues between hosts
• Ensures data transport reliability
• Establishes, maintains and terminates virtual circuits
• Provides reliability through fault detection and recovery
• Information flow control

Data Delivery:

• Provides connectivity and path selection between two host systems
• Routes data packets
• Selects best path to deliver data
• The Network layer prioritizes data known as Quality of Service (QoS)

Access to Media:

• Defines how data is formatted for transmission and how access to the network is controlled

Binary Transmission:

• Defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link

Physical Media Types

Physical Media Comparison

	Twisted Pair	Coaxial	Fiber Optic	Wireless LAN
Bandwidth	Up to 1 Gbps	10- 1-- Mbps	Up to 10 Gbps or Higher	Up to 54 Mbps
Distance	Up to 100 m	Up to 500 m	Up to 60 km	Up to 100 m
Price	Least expensive	Inexpensive	Most expensive	Moderate

Hub or Repeater

A hub (concentrator) is a device that repeats the signals it
receives on one port to all other ports. It is a central
connection point for several network devices.

Network Interface Card

WAN—Physical Layer Implementations

• Physical layer implementations vary
• Cable specifications define speed of link

Cisco	PPP	Frame Relay	ISDN BRI (with PPP)	DSL Modem	Cable Modem
EIA/TIA-232 EIA/TIA-449 X.21 V.24 V.35 HSSI	Up to 1 Gbps	fg	RJ-48 Note: ISDN BRI cable pinouts are different than the pinouts for Ethernet. The RJ-48 and RJ-45 look the same, but the pinouts are different.	RJ-11 Note: Works over telephone line	BNC Note: Works over Cable TV line

WAN

Data Link Layer

• Data Link layer protocols create, transmit, and receive packets. This layer is also responsible for logical MAC addressing and LLC processing, creating logical topologies, and controlling media access.

MAC Address

• The network interface card address, called the hardware address, is protocol-independent and is usually assigned at the factory. This address is technically called the media access control address (MAC) because it is found on the MAC sub layer of the Data Link layer.

Data Link Devices

• The Data Link layer is manipulated by two devices: bridges and switches. These are more complex and more expensive than their Physical layer counterparts, but they do have advantages.

Switch

• When a switch receives data the switch examines the data link header for the MAC address of the destination station and forwards it to the correct port. This opens a path between ports that can use the full bandwidth of the topology.

Network Layer

• The network layer provides connectivity and path selection between two host systems that may be located on geographically separated networks

• IP is a standard that defines the manner in which the network layers of two hosts interact. IP addresses are 32 bit long, hierarchical addressing scheme

Network Layer Devices

The devices that operate at the Network layer are routers and Layer 3 Switches

Routers

Routers facilitate communication within this internet work. It decides how to send packets within the network so that they arrive at their destination.

Layer 3 Switches

The Layer 3 switch functions at the Network layer and performs the multiport, virtual LAN, data pipelining functions of a standard Layer 2 switch. It can also perform basic routing functions between virtual LANs.

Multilayer Switching

Combines functionality of:

– Layer 2 switching

– Layer 3 switching

– Layer 4 switching

• High-speed scalability

• Low latency compared to routers

Transport Layer Implementations

The Transport layer is charge of the reliable/unreliable transport of data. It can be implemented as TCP or UDP.

Gateway

A gateway is a combination of hardware and software that connects dissimilar network environments. It performs translations at multiple layers of the open system interconnection (OSI) model.

Firewalls

A firewall is a system or group of systems that manages access between two or more networks

Summary

This lesson covered the following main topics:

• The function and operation of a hub, a switch, and a router

• The function and operation of Layer 2 switching, Layer 3 switching, and routing

• The OSI model

• Functionality of LAN, MAN and WAN networks

• Possible media types for LAN and WAN connections

• The function and definition of firewalls and gateways