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What is a network?
- • The definition of a network is simple.
- -A network is created when you have two or more hosts connected together so that they can communicate and share resources.
- • A host can be any device which has a “network interface” which allows it to connect to other devices on a network.
- • Some examples of resources which can be shared are documents and printers.
What are some of the different types of networks?
LAN –Local Area Network
–Typically refers to a network contained within a building
What are some of the different types of networks?
LAN –Local Area Network
–Typically refers to a network contained within a building.
•MAN – Metropolitan Area Network
–A network spread between multiple noncontiguous buildings within the single metropolitan area.
How Do We Make Connections?
- •Network hosts communicate with each other by
- sending bits of information across network media.
- • Network media can be wire or wireless.
- • Examples of wire media are copper and fiber optic.
• Examples of wireless media are RF and infra-red.
• We will discuss all the different forms of media in detail later in this course.
What is a Protocol?
•The definition of a protocol is a set of rules and procedures for communication.
• In order for hosts to communicate on a network they must agree to use a common set of rules and procedures or in other words, must use the same network protocol.
• Some of the common network protocols used today are TCP/IP, IPX/SPX, NetBEUI, and AppleTalk.
Introduction to Addressing
• All hosts on a network must be identified with an address on that network.
- • Addressing in computer networks is similar to how addressing works with the postal network or telephone
• The most typical types of addresses used in computer networking are MAC addresses and IP addresses.
• There are both private and public forms of addressing.
- – Private addressing is used to keep communications safe within the boundaries of a private secure network.
- – Public addressing is used to allow communications with the outside world, most typically known as the Internet.
Wired Media – Twisted Pair
•CAT 3: 10 Mbps
•CAT 5: 100 Mbps
•CAT 5e: 1000 Mbps
•CAT 6: 1000 Mbps
•All categories can travel up to100 meters before suffering from decrease in signal.
•UTP: Unshielded Twisted Pair
–Susceptible to EMI
•STP: Shielded Twisted Pair
– Differs from UTP in that it has a foil jacket that helps prevent cross talk. Cross talk is signal overflow from an adjacent wire .
–Uses an RJ-45 Connector
What the Heck is the Plenum?
- • An enclosed space used for airflow.
• Usually thought of as the space above a drop ceiling or below a raised floor.
• Plenum grade cable should always be used in a plenum space.
LAN Technology Types-Ethernet
- • Ethernet is known as the 802.3 standard.
- • Ethernet uses the CSMA/CD access method.
•Ethernet is the most widely-installed local area network ( LAN) technology.
•Specified in a standard, IEEE 802.3.
- •Early ethernet networks uses coaxial connections. The most common types currently use twisted pair cabling,
- however, fiber optic cabling is becoming much more common as standards and speeds increase
LAN Technology Types
•CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
–In the early days of ethernet, when two hosts would send packets at the same time, a collision would occur.
–A standard had to be created that would have the hosts follow rules relating to when they could send data and when they could not.
–This standard is Carrier Sense Multiple Access with Collision Detection, referred to as CSMA/CD. CSMA/CD forces computers to “listen” to the wire before sending in order to make sure that no other host on the wire is sending.
–If a collision is detected, both of the senders will send a jam signal over the Ethernet.
–This jam signal indicates to all other devices on the Ethernet segment that there has been a collision, and they should not send data onto the wire.
The TCP/IP Protocol Suite
• TCP/IP stands for the Transmission Control Protocol/Internet Protocol.
•It is the basic communication protocol of the Internet.
• Although it was designed to be an Internet protocol, it can also be used as a communication protocol in a private network.
• The TCP/IP architecture is based off the 4 layer DARPA model. Each layer of the DARPA model corresponds to one or more of the layers of the 7 layer OSI model.
• Each of the 4 layers have individual protocols which all work together to form a protocol stack.
Transport Layer Protocols
• TCP – Transmission Control Protocol
–TCP breaks data into manageable packets and tracks information such as source and destination of packets.
–It is able to reroute packets and is responsible for guaranteed delivery of the data.
– Reliable Communication
• UDP – User Datagram Protocol
–A connectionless, datagram service that provides an unreliable, best-effort delivery.
Internet Layer Protocols
• IP – Internet Protocol
–This is a connectionless protocol, which means that a session is not created before sending data.
- –IP is responsible for addressing and routing of packets between computers.
- –It does not guarantee delivery and does not give acknowledgement of packets that are lost or sent out of order as this is the responsibility of higher layer protocols such as TCP.
- • ARP – Address Resolution Protocol
- –Provides IP-address to MAC address resolution for IP packets.
–A MAC address is your computer's unique hardware number and appears in the form 00-A0-F1-27-64-E1 (for example).
–Each computer stores an ARP cache of other computers ARP-IP combinations.
Internet Layer Protocols
• ICMP – Internet Control Message Protocol
–Internet Control Message Protocol
enables systems on a TCP/IP network to share status and error information such as with the use of PING and TRACERT utilities.
– PING & TRACERT are used for diagnostic and error reporting
• IGMP – Internet Group Management Protocol
–Internet Group Management Protocol
is used to manage Internet Protocol multicast groups.
- –IP hosts and adjacent multicast routers use IGMP to establish multicast group memberships.
- –IGMP is only needed for IPv4 networks, as multicast is handled differently in IPv6 networks.
Working with IP Addresses
•What is an IP Address?
- –A 32 bit address that is used to uniquely identify a computer on a
–The Network ID portion of the IP Address identifies the network where the computer sits.
–The Host ID portion of the IP Address uniquely identifies the computer on its network.
- IP Address: 192.168.10.1
- Network ID Host ID
Planning an IP Addressing Scheme
• How to Plan an IP Addressing Scheme
–How many IP Addresses do you need today?
–How many IP Addresses will you need in the future?
–Are you dealing with a pre-existing IP scheme?
Rules for IP Addressing
• Each of the 4 numbers in an IP Address is called an octet (8 bits).
• A bit is a 1 or a 0.
• Each octet can only have a number from 0 to 255
- –00000000 = 0
- –11111111 = 255
•The first octet cannot be 127.
–The 127 range has been reserved for diagnostics.
–127.0.0.1 is known as the loopback address. (It is sometimes also referred to as local host.)
• The Host ID cannot be all 0s or all 255s.
- –All 0s represents the Network ID
- –All 255s is the broadcast address
–192.168.10.0 is a Network ID–192.168.10.255 is the broadcast address for the 192.168.10.0 network
Private vs. Public IP Addressing
• Private IP ranges which have been reserved from Public
- – 10.0.0.0 – 10.255.255.255
- – 172.16.0.0 – 172.31.255.255
- – 192.168.0.0 – 192.168.255.255
- – 169.254.0.0 – 169.254.255.255
- •Hosts assigned private IP Addresses can get to the Internet through a technology called Network Address Translation (NAT)
•Most of today’s companies use private IP addresses on their private networks
What is NAT?
•NAT stands for Network Address Translation and is a commonly used IP translation and mapping technology.
• Using a device (such as a router) or piece of software that implements NAT allows an entire home or office network to share a single internet connection over a single IP address.
- • A single cable modem, DSL modem, or even 56k modem could connect all the computers to the internet
• Additionally, NAT keeps your home network fairly secure from hackers.
• NAT is built in to the most common InternetConnection sharing technologies.
How Computers get IP Addresses
• From a DHCP Server
–The Dynamic Host Configuration Protocol or (DCHP) is used for assigning dynamic IP addresses to devices on a network.
• Using APIPA
–Stands for Automatic Private Internet Protocol Addressing.
–Client systems that are configured for automatic IP address assignment / dynamic IP assignment will attempt to use DHCP to make a request for an IP address lease for a given network. When the DHCP server is unavailable the service on the client will automatically configure the system with an APIPA IP address in the 169.254.0.1 through 169.254.255.254 address range with a subnet mask of 255.255.0.0.
• What is a Router?
–A router is a device that forwards data packets along networks.
- –A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network.
- –Routers are located at gateways, the places where two or more networks connect, and are the critical device that keeps data flowing between networks and keeps the networks connected to the Internet.
–When data is sent between locations on one network or from one network to a second network the data is always seen and directed to the correct location by the router.
–They accomplish this by using headers and forwarding tables to determine the best path for forwarding the data packets, and the use protocols such as ICMP to communicate with each
What is a Default Gateway?
• Computers can only communicate directly with other computers on the same network.
• The only way for a computer to communicate with a computer on a different network is through a router. (Internetworking)
• The Default Gateway represents the IP Address of a router that a computer uses to communicate outside of its network
What is Subnetting?
- •Subnetting is the process of taking a large network and dividing it into
- smaller networks to increase efficiency and manageability.
•IP addresses can be class A, B or C.
•Class A addresses are for networks with a large number of hosts.
–The first octet is the netid and the 3 remaining octets are the hostid.
•Class B addresses are used in medium to large networks.
–The first 2 octets making up the netid and the remaining 2 are the hostid.
•Class C is for smaller networks.
–The first 3 octets making up the netid and the last octet comprising the hostid. The Network ID and the Host ID are determined by a subnet mask.
What if You Wanted More Than 1 Subnet?
•Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network.
•If you don't subnet, you will only be able to use one network from your Class A, B, or C network.
•When subnetting is employed, the multiple networks are connected with a router which enables data to find its way between networks.
•On the client side, a default gateway is assigned in the TCP/IP properties. The default gateway tells the client the IP address of the router that will allow their computer to communicate with clients on other networks.
What is IPv4
•Every IP address can be broken down into 2 parts, the Network ID(netid) and the Host ID(hostid).
• All hosts on the same network must have the same netid.
• Each of these hosts must have a hostid that is unique in relation to the netid.
IP addresses are divided into 4 octets with each having a maximum value of 255.
• We view IPv4 addresses in decimal notation such as 220.127.116.11, but it is actually utilized as binary data.
Disadvantages of IPv4
• Not Enough Addresses
- • Cluttered the Internet Routing Tables
- • Difficult to Configure
• Security is Optional
What is IPv6
•The previous information on TCP/IP has referred to IPv4, however, this addressing scheme has run out of available IP addresses due to the large influx of internet users and expanding networks.
•As a result, the powers that be had to create a new addressing scheme to deal with this situation and developed IPv6.
- •This new addressing scheme utilizes a 128 bit address (instead of 32) and utilizes a hex numbering method in order to avoid long addresses such as 18.104.22.168.22.214.171.124.126.96.36.199.188.8.131.52
- •The hex address format will appear in the form of 3FFE:B00:800:2::C as an example.
• Plenty of Addresses
• Simplified the Internet Routing Tables
• Easy and Automated Configuration
• Security is Required
Types of IPv6 Addresses
• Unicast (One to One)
–Sending of information packets to a single network node.
–This type of network transmission is used where a private or unique resource such as media servers are being requested for two way connections that are needed to complete the network communication.
–So in the media server example, a client system may make the request for streaming content from the single source and the responding system may leverage unicast as part of the response to the session request to deliver the content.
•Multicast (One to Many)
- –Single source address responding to multiple destination addresses with information to be sent.
- –In a media server example, the single source address may need to send the data to multiple clients; it does this by sending the data with multiple destination IP addresses.
- • FTP
- • TFTP
- • HTTP
- • HTTPS
- • NTP
- • POP3
- • IMAP4
- • SMTP
- •The File Transfer Protocol provides connection oriented file transfer between a client and a server.
•It was originally used to transfer files between UNIX systems, and is now the most popular file transfer protocol on the Internet.
•Must resolve host name to IP address to establish communication.
•It is connection oriented (i.e. verifies that packets reach destination).
• FTP uses TCP port 21 for control
and TCP port 20 for data transport.
- •The Trivial File Transfer Protocol provides connectionless file transfer functions.
•TFTP is a simple and small protocol, which makes it suitable for transferring small amounts of data.
- •It is primarily used for updating devices such as routers and switches.
- •Another common use is transferring the data required to boot a diskless system over the network.
•TFTP uses UDP port 69.
- • The Hypertext Transfer Protocol was originally designed for transferring World Wide Web documents and has been extended to transfer other types of files as well.
•Its most common use is transferring web pages between a web browser and a web server.
•It is the protocol controlling the transfer and addressing of HTTP requests and responses.
HTTP uses TCP port 80 by default
•HTTPS is used in exactly the same way as the HTTP protocol.
•The difference is that HTTPS uses SSL (Secure Sockets Layer) to send data in an encrypted form and to authenticate the server.
•For example, when you buy something online using a credit card HTTPS uses TCP port 443 by default.
- •The Dynamic Host Configuration Protocol is used for assigning dynamic IP addresses to devices on a network.
•DHCP simplifies network administration by keeping track of IP addresses in a database rather than an administrator having to manage and assign them manually.
•When a client is configured to receive an IP address automatically, it will send out a broadcast to the DHCP server requesting an address.
•The server will then issue a "lease" and assign it to that client. DHCP uses UDP ports 67 & 68.
Benefits of DHCP
•Prevents users from making up their own IP addresses.
•Prevents incorrect gateway or subnet masks from being entered.
•Decreases amount of time spent configuring computers especially in environments where computers get moved around all the time.
• The Domain Naming System is a standard name service that allows your computer to register and resolve domain names.
- • DNS uses TCP port 53 for zone transfers and UDP port 53 for
Telnet is a terminal emulation protocol that allows remote access to a system.
•Telnet can also refer to software which can be used by a client to remotely connect to and configure operating systems and network devices.
•Provides a virtual terminal or remote login across the network that is connection-based.
- •The remote server must be running a Telnet service for clients to connect.
- • Telnet uses TCP port 23.
Bridges & Switches
–Network device that filters and forwards packets between LAN segments and ensures that data goes straight from its origin to its proper destination.
–Switches remember the address of every node on the network, and anticipate where data needs to go.
- –A switch only operates with the computers on the same LAN.
- –This reduces competition for bandwidth between devices on the network.
–It isn't smart enough to send data out to the internet, or across a WAN. These functions require a router.
–Functions the same as a repeater, but can also divide a network in order to reduce traffic problems.
–A bridge can also connect unlike network segments (ie. token ring and ethernet).
–Bridges create routing tables based on the source address.
Bridges & Switches
- •Bridges (Cont’d)
- –If the bridge can't find the source address it will forward the packets to all segments.
•Transparent - Only one bridge is used.
•Source-Route - Bridging address tables are stored on each PC on the network
•Spanning Tree - Prevents looping where there exists more than one path between segments
Advanced Switch Functionality
- •Power over Ethernet (PoE) is used to transfer electrical power, along with data, over standard twisted pair cable.
- •The Spanning Tree Algorithm (STA) is used by switches to determine the best route when there is more than one connection to a node.
•Virtual LANs (VLANs) can be created in order to emulate multiple broadcast domains using switches.
•Trunking is when a switch presents more than one VLAN configuration over a single connection to another switch or a router.
•Port Mirroring is used to send a copy of network data to a second (mirrored) connection usually for the purposes of monitoring.
•Port Authentication is used to restrict access based upon authentication information. Typically used in 802.1x network.
Firewalls & Proxy Servers
- –Either a hardware or software entity (or a combination of both) that protects a network by stopping network traffic from passing through it.
- –In most cases, a firewall is placed on the network to allow all internal traffic to leave the network (email to the outside world, web access, etc.), but stop unwanted traffic from the outside world from entering the internal network.
–This is achieved by granting and denying access to resources based on a set of configurable rules
–Firewalls are used to protect private networks from external intrusion.
–Firewalls can control what data is allowed in or out of a network.
–Firewalls can be created with hardware or software.
- •Proxy Servers
- –A proxy server acts as a middle-man between clients and the Internet providing security, administrative control, and caching services.
–When a user makes a request for an internet service and it passes filtering requirements, the proxy server looks in its local cache of previously downloaded web pages.
–If the item is found in cache, the proxy server forwards it to the client. This reduces bandwidth through the gateway.
–If the page is not in the cache, the proxy server will request the page from the appropriate server.
- –Nowadays, the functions of proxy servers are often built into firewalls.
- –Serve 3 main purposes.
– Disguise an end users actual identity using NAT.
– Cache requests to save bandwidth.
– Control content permitted to be requested from the Internet.
Load Balancer & Bandwidth Shaper
- •Load Balancer
- –A load balancer is a hardware and/or software solution that provides load balancing services.
- –Load balancing is used to distribute workloads evenly across two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, minimize response time, and avoid overload.
–Using multiple components with load balancing, instead of a single component, may increase reliability through redundancy.
- •Bandwidth Shaper drew
- –Describes the mechanisms used to control bandwidth usage on the network.
–Bandwidth shaping is typically done using software installed on a network server.
–From this server, administrators can control who uses bandwidth, for what, and when.
–Bandwidth shaping establishes priorities to data traveling to and from the Internet and within the network
–A bandwidth shaper essentially performs two key functions: monitoring and shaping.
•Monitoring includes identifying where bandwidth usage is high and at what time of day. After that information is obtained, administrators can customize or shape bandwidth usage for the best needs of the network.