Welcome to network+

Cisco ( CCNA, CCNP, CCIE, … ) Comptia (Network+, Server+, Linux+, Security+, e-Biz+, A+ ) Microsoft (MCP, MCSE, MCSD,MCITP, ….) Redhat Red Hat Certified Technician (RHCT). SUN Solaris

A requisite for CCNA Course Passing the Network+ Exam and get the certification Representing a solid background of networking knowledge regarding Network+ standard course

Basic Networking Fundamentals

What is a Computer Network ? = What is a Computer Network ? Two or more computers connected together, having the ability to use shared resources on each other. Two computers that are connected with a Network Cable through their network cards are an example of a simple network.

Something to share ( Data ) Physical Pathway ( Transmission medium ) Interfaces for communication ( Network Interface ) Rules of Communication ( Protocols )

What are some of the different types of the network? In a clinent/server network each host will act Specifically as a Server (the provider of resources) or a Client (the receiver of resources)

What are some of the different types of the network? Peer to peer In a peer to peer network every host will act as a client AND a server

What are some of the different types of the network? LAN –Local Area Network Typically refers to a network contained whitin a building

MAN – Metropolitan Area Network A network spread between non-contiguous Buildings within a single metropolitan area.

WAN –Wide Area Network A network spread over a wide area ,typically covering multiple cities and countries.

Network Types ( 2 ) Network Topologies : 1 – Bus 2 – Star 3 – Ring 4 – Mesh (Full mesh Vs. Partial mesh) 5 -Tree 6 - Hybrid

Bus Topology

Star Topology

Ring Topology

Mesh Topology

Tree Topology

Hybrid Topology

Network Types Transmission Methods : Circuit switching Dedicated path is created between two nodes Packet switching Message is broken into small packets

Circuit Switching A circuit is established, an end-to-end connection must exist to transfer data The actual data transfer After data transmitted, connection is terminated

Packet Switching Message is broken into small packets. Allows interactive exchanges because of small packets. Uses messages that are all the same length (called packets)

Network Terminology (1) Client Server Host Workstation Peer

Network Terminology (2) Backbone A part of a network that all segments and servers connect. (Gigabit Ethernet, FDDI, Thicknet) Segment Any short section of the network that is connected to the backbone

Network Terminology (3) Half-duplex A bi-directional communication but only one direction at a time, such as walkie-talkie Full-duplex Allows communications in both directions simultaneously.

Network Terminology (4) Broadband Vs. Baseband With baseband the whole bandwidth of the cable is used for each signal (channel), but in broadband the bandwidth is divided into descrete bands

PHYSICAL MEDIA

Physical Media )

Copper Coaxial Cable - Thick or Thin Unshielded Twisted Pair Optical Fiber Multimode Singlemode Wireless Short Range Medium Range (Line of Sight) Satellite

Copper Media: Coaxial Cable Coaxial cable is a copper-cored cable surrounded by a heavy shielding and is used to connect computers in a network. Outer conductor shields the inner conductor from picking up stray signal from the air. High bandwidth but lossy channel. Repeater is used to regenerate the weakened signals. Category Impedance Use RG-59 75 W Cable TV RG-58 50 W Thin Ethernet RG-11 Thick Ethernet

Copper Media: Twisted Pair Twisted-pair is a type of cabling that is used for telephone communications and most modern Ethernet networks. A pair of wires forms a circuit that can transmit data. The pairs are twisted to provide protection against crosstalk, the noise generated by adjacent pairs. There are two basic types, shielded twisted-pair (STP) and unshielded twisted-pair (UTP).

Shielded Twisted Pair (STP)

Unshielded Twisted Pair (UTP)

Unshielded Twisted Pair (UTP) Consists of 4 pairs (8 wires) of insulated copper wires typically about 1 mm thick. The wires are twisted together in a helical form. Twisting reduces the interference between pairs of wires. High bandwidth and High attenuation channel. Flexible and cheap cable. Category rating based on number of twists per inch and the material used CAT 3, CAT 4, CAT 5, Enhanced CAT 5 and CAT 6.

EIA/TIA 568A vs 568 B

Fiber Media Optical fibers use light to send information through the optical medium. It uses the principal of total internal reflection. Modulated light transmissions are used to transmit the signal.

Total Internal Reflection

Fiber Media Light travels through the optical media by the way of total internal reflection. Modulation scheme used is intensity modulation. Two types of Fiber media : Multimode Singlemode Multimode Fiber can support less bandwidth than Singlemode Fiber. Singlemode Fiber has a very small core and carry only one beam of light.

Single and Multimode Fiber Single-mode fiber Carries light pulses along single path Uses Laser Light Source Multimode fiber Many pulses of light generated by LED travel at different angles

Network Terminology (5) Fiber-Optic Cable Contains one or several glass fibers at its core Surrounding the fibers is a layer called cladding

Fiber Optic Cable FO Cable may have 1 to over 1000 fibers

Fiber optic connectors ST (Straight Tip) Connector

Fiber optic connectors . SC Connector

Fiber optic connectors MT-RJ LC

Wireless Media Very useful in difficult terrain where cable laying is not possible. Provides mobility to communication nodes. Right of way and cable laying costs can be reduced. Susceptible to rain, atmospheric variations and Objects in transmission path.

Installation type Infrastructor

Installation type Ad-hoc

Unidirectional antennas

Type of Transmission Unicast Multicast Broadcast

Type of Transmission

Broadcast Domain A group of devices receiving broadcast frames initiating from any device within the group Routers do not forward broadcast frames

Collision The effect of two nodes sending transmissions simultaneously in Ethernet. When they meet on the physical media, the frames from each node collide and are damaged. Exam Watch Make sure you understand the mechanics of Ethernet: CSMA/CD. No device has priority over another device. If two devices transmit simultaneously, a collision occurs. When this happens, a jam signal is generated and the devices try to retransmit after waiting a random period.

Collision Domain The network area in Ethernet over which frames that have collided will be detected. Collisions are propagated by hubs and repeaters Collisions are Not propagated by switches, routers, or bridges If two or more machines simultaneously sense the wire and see no frame, and each places its frame on the wire, a collision will occur. In this situation, the voltage levels on a copper wire or the light frequencies on a piece of fiber get messed up. For example, if two NICs attempt to put the same voltage on an electrical piece of wire, the voltage level will be different than if only one device does so. Basically, the two original frames become unintelligible (or undecipherable). The NICs, when they place a frame on the wire, examine the status of the wire to ensure that a collision does not occur: this is the collision detection mechanism of CSMA/CD. If the NICs see a collision for their transmitted frames, they have to resend the frames. In this instance, each NIC that was transmitting a frame when a collision occurred creates a special signal, called a jam signal, on the wire, waits a small random time period, and senses the wire again. If no frame is currently on the wire, the NIC will then retransmit its original frame. The time period that the NIC waits is measured in microseconds, a delay that can’t be detected by a human. Likewise, the time period the NICs wait is random to help ensure a collision won’t occur again when these NICs retransmit their frames. The more devices you place on a segment, the more likely you are to experience collisions. If you put too many devices on the segment, too many collisions will occur, seriously affecting your throughput. Therefore, you need to monitor the number of collisions on each of your network segments. The more collisions you experience, the less throughput you’ll get. Normally, if your collisions are less than one percent of your total traffic, you are okay. This is not to say that collisions are bad—they are just one part of how Ethernet functions.

Networking device

Objectives Explain the uses, advantages, and disadvantages of repeaters Explain the uses, advantages, and disadvantages of hubs Define wireless access points Define network segmentation Explain network segmentation using bridges

Objectives (continued) Explain network segmentation using switches Explain network segmentation using routers Brouters is a term

Repeaters Length of cable used influence the quality of communication Repeaters repeat signals Repeaters only work with the physical signal Cannot reformat, resize, or manipulate the data Physical layer (layer 1) device

Repeaters (continued)

Repeaters (continued)

Hubs Generic connection device Physical layer Connect several networking cables together Active hubs Multiport repeaters Passive hubs Hubs and topology

Hubs (continued)

Advantages And Disadvantages Of Repeaters And Hubs Advantages of using repeaters Extend network physical distance Do not seriously affect network performance Disadvantages of using repeaters Cannot connect different network architectures Token Ring and Ethernet Cannot reduce network traffic

Advantages And Disadvantages Of Repeaters And Hubs (continued) Disadvantages of using repeaters Do not segment the network Repeat everything without discrimination Number of repeaters must be limited Repeaters are part of a collision domain

Hubs & Collision Domains More end stations means more collisions. CSMA/CD is used. Tk-10-7

Wireless Access Points Wireless local area networks (WLANs) Wireless access points provide cell-based areas Contains radio transceiver Function like a hub Bandwidth is shared May also function as a wireless repeater Wireless clients

Wireless Access Points (continued)

Network Segmentation Problems occur with too many nodes on the same network segment or collision domain

Network Segmentation (continued)

Bridges Operate at the Data Link layer Forward or drop frames Cannot filter broadcasts MAC to segment # table

Bridges (continued)

Advantages And Disadvantages Of Bridges Advantages of using a bridge Reduce network traffic with minor segmentation Creates separate collision domains Reduce collisions

Advantages And Disadvantages Of Bridges (continued) Disadvantages of using bridges Slower due to filtering Do not filter broadcasts More expensive

Switches Operate at the Data Link layer Increase network performance Virtual circuits between source and destination Micro segmentation

Devices On Layer 2 (Switches & Bridges) Data-Link OR 1 2 3 4 1 2 Each segment has its own collision domain. All segments are in the same broadcast domain.

Switches Switch Each segment is its own collision domain. Memory Each segment is its own collision domain. Broadcasts are forwarded to all segments. TK16-15

MAC Address Table Initial MAC address table is empty. Slide 1 of 3 Emphasize: The 1900en max MAC address table size is 1024. Once the table is full, it will flood all new addresses until existing entries age out. The command to change the MAC address table aging time is, as follows: wg_sw_a(config)#mac-address-table aging-time ? <10-1000000> Aging time value The default is 300 sec. The MAC address table is also referred to as the CAM table (Content Address Memory) on some switches. Initial MAC address table is empty.

Learning Addresses Station A sends a frame to station C. Slide 2 of 3 Station A sends a frame to station C. Switch caches the MAC address of station A to port E0 by learning the source address of data frames. The frame from station A to station C is flooded out to all ports except port E0 (unknown unicasts are flooded).

Learning Addresses (Cont.) Slide 3 of 3 Emphasize: Once C replies, the switch will also cache station C’s MAC address to port E2, as shown in the next slide. Station D sends a frame to station C. Switch caches the MAC address of station D to port E3 by learning the source address of data frames. The frame from station D to station C is flooded out to all ports except port E3 (unknown unicasts are flooded).

Filtering Frames Station A sends a frame to station C. Destination is known; frame is not flooded.

Broadcast and Multicast Frames Station D sends a broadcast or multicast frame. Broadcast and multicast frames are flooded to all ports other than the originating port.

Forward/Filter Decision When a frame arrives at a switch interface, the destination hardware address is compared to the forward/ filter MAC database. If the destination hardware address is known and listed in the database, the frame is sent out only the correct exit interface If the destination hardware address is not listed in the MAC database, then the frame is flooded out all active interfaces except the interface the frame was received on. If a host or server sends a broadcast on the LAN, the switch will flood the frame out all active ports except the source port.

Switches (continued) Advantages of switches Increase available network bandwidth Reduced workload, computers only receive packets intended for them specifically Increase network performance Smaller collision domains

Switches (continued) Disadvantages of switches More expensive than hubs and bridges Does not filter broadcast traffic

Method of Switching - Cut Through Mode Much faster Cannot detect corrupt packets Can propagate the corrupt packets to the network Best suited to small workgroups

Method of Switching - Store and Forward Mode Read the whole packet before transmit Slower than the cut-through mode More accurate since corrupt packets can be detected using the FCS More suit to large LAN since they will not propagate error packets Facilitate data transfer between segments of different speed DB 100Mbps 10Mbps

Using Switches to Create VLANs Switches can logically group together some ports to form a virtual local area network (VLAN) SW1 VLAN1 VLAN2 Hub SW2 Hub Switches can be configured to communicate only within the devices in the group SW3 Hub

Switches (continued)

Routers Provide filtering and network traffic control Used on LANs and WANs Connect multiple segments and networks Multiple routers create an “internetwork” Operate at the Network layer

Routers (continued) Create a table to determine how to forward packets Filtering and traffic control base on logical addresses

Physical Versus Logical Addresses MAC addresses Data Link layer application Used by switches, bridges, and routers Used for directly connected devices Logical addresses Network and transport protocols dictate the format of the logical network layer address TCP/IP, IPX/SPX IP addresses are assigned manually or by software

Physical Versus Logical Addresses (continued)

Advantages And Disadvantages Of Routers Can connect networks of different architecture Token Ring to Ethernet Choose best path through or to a network Create smaller collision domains Create smaller broadcast domains

Advantages And Disadvantages Of Routers (continued) Only work with routable protocols More expensive than hubs, bridges, and switches Routing table updates consume bandwidth Increase latency due to a greater degree of packet filtering and/or analyzing

Advantages And Disadvantages Of Routers (continued)

Static and Dynamic Routers

Layer-3 Switches Why Layer-3 switches? Layer-3 switches operate in both layer 2 (data link layer) and 3 (network layer) Can perform both MAC switching and IP routing A combination of switch and router but much faster and easier to configure than router Why Layer-3 switches? Traffic of LAN is no longer local Speed of LAN is much faster Need a much faster router, however, very expensive

Summary Repeaters are the least expensive way to expand a network, but they are limited to connecting two segments Bridges function similar to repeaters, but can understand the node addresses Switches can be considered as multiport bridges, can divide a network into some logical channels Routers interconnect networks and provide filtering functions. They can determine the best route

Remote Access Devices 1. Modems

Cannot send digital signal directly to telephone line Sending end: MODulate the computer’s digital signal into analog signal and transmits Receiving end: DEModulate the analog signal back into digital form

ADSL ADSL stands for Asymmetric Digital Subscriber Line Particularly suitable for high speed multimedia communications, general Internet applications Asymmetric - downstream 1.5 to 6.1Mbps upstream 16 to 640kbps Digital - mainly for transmitting digital data still require modulation and demodulation Subscriber line - make use of the analog connection between household and COB

ADSL Illustration 2 to 3 miles subscriber line Telephone Company Splitter local loop low speed data high speed

Why Asymmetric? In general Internet applications, downstream often requires a higher data rate than upstream Downstream - file download, video playback Upstream - click a link, send a form Reducing the resource for upstream can provide more resource for downstream

ADSL exploits the unused analogue bandwidth available in the wires ADSL works by using a frequency splitter device to split a traditional voice telephone line into two frequencies PSTN Downstream Upstream

Architecture of ADSL Services Network Terminology (5) DSL Voice Switch ISP Central Office Subscriber premises