ITM301 Notes PDF

Module 1 (Lecture 1) : Introduction to Networking Network Models ○ Topology: Describes how parts of a whole work together ○ Physical topology: Refers to a network’s hardware and how computers, other devices, and cables work toget...

Module 1 (Lecture 1) : Introduction to Networking Network Models ○ Topology: Describes how parts of a whole work together ○ Physical topology: Refers to a network’s hardware and how computers, other devices, and cables work together to form the physical network ○ Logical topology: Refers to how software controls access to network resources Includes how users and software initially gain access to the network ○ Network operating system (NOS): Controls access to the entire network NOS is required by client-server models Peer-2-peer Network model ○ In a peer-to-peer (P2P) model the OS of each computer on the network is responsible for controlling access to its resources No centralized control ○ Computers, called nodes or hosts, form a logical group of computers and users Each computer controls its own administration, resource and security Advantages Disadvantages ○ Simple configuration ○ Not scalable ○ Less expensive compared to other ○ Not necessarily secure network models ○ Not practical for large installation Client-Server Network Model ○ Resources managed by the NOS via centralized directory database ○ A Windows domain - is a logical group of computers that a windows server can control ○ Active directory (AD) - centralized directory database that contains user account information and security for the entire group of computers  ○ A user can sign on to the network from any computer on the network and gain access to the resources that AD allows Process is managed by Active Directory Domain Services (AD DS) ○ A computer making a request from another is called the Client ○ NOS is responsible for: Managing client data and other resources Ensuring authorized user access Controlling user file access Restricting user network access Dictating computer communication rules Supplying application communication rules ○ Servers that have NOS installed require: More memory, processing power, and storage capacity Equipped with special hardware to provide network management functions Client-Server Applications ○ Network services - resources a network makes available to its users Includes application and data provided by these applications ○ In client-server applications Client computer requests data or service from a second computer, called the server Network Services & Protocols ○ Protocol: Methods and rules for communication between networked devices ○ Primary network protocols: TCP - transmission control protocol IP - internet protocol ○ Popular client-server applications include Web server Email service  DNS service FTP service Database services Remote access service LANs & Hardware ○ LAN (Local Area Network): Usually contained in a small space ○ Switch: Receives incoming data from one of its ports and redirects it to another port or multiple ports A LAN can have several switches Sends data to intended destination ○ Physical topology used by this network is called a star topology ○ NIC (Network Interface Card): A network port used to attach a device a network (Called a network adapter) ○ Backbone: A central conduit that connects the segments (pieces) of a network ○ Router: A device that manages traffic between two or more networks Can help find best path for traffic to get from one network to another Routers can be used in small home networks to connect the home LAN to the internet Called a SOHO (small office-home office) network Industrial-grade routers can have several network ports, one for each network it connects to Difference between router & switch Router is like gateway between networks and belongs to two or more local networks A switch belongs only to its local network  MANs and WANs ○ WAN (Wide Area Network): A group of LANs that spread over a wide geographical area ○ MAN (Metropolitan Area Network): A group of connected LANs in the same geographical area Known as campus area network (CAN) ○ PAN (Personal Area Network): Smaller network of personal devices A network of personal devices such as your smartphone and your computer ○ Other network types: BAN - Body Area Network SAN - Storage Area Network WLAN - Wireless Local Area Network Safety Procedures & Policies ○ Network and computer technicians need to know how to protect themselves As well as protect sensitive electronic components ○ This section takes a look at some best practices for safety Electral and tool safety is generally by OSHA (Occupational Safety and Health Administration) Protecting Against static electricity ○ Computer components are grounded inside a computer case ○ Grounding means that a device is connected directly to the earth ○ Sensitive electronic components can be damaged by ESD (electrostatic discharge) ○ Static electricity can cause two types of damages Catastrophic failure - destroyed beyond use Upset failure - shorten the life of component ○ Before touching a component, ground yourself by: Wearing ESD strap around your wrist that clips onto chassis or computer case  Touching the case before touching any component inside the case Storing a component inside an antistatic bag ○ In addition to protecting against ESD, always shut down and unplug a computer before working inside it OSHA guidelines when using power tools ○ Wear PPE (personal protective equipment) ○ Keep all tools in good conditions and properly store tools not in use ○ Watch out for hazards ○ Use right tool for the right jobs Emergency Procedures ○ Know the best escape route or emergency exit ○ Fire Suppression Systems - have fire suppression system in the data center that includes Emergency alert system Portable fire extinguisher Emergency power-off switch ○ SDS (Safety Data sheet): Explains how to properly handle substances such as chemical solvents and how to dispose of them Includes information such as identification, first-aid measures, fire-fighting measures, accidental release measures, handling and storage guidelines, exposure controls, and physical and chemical properties Troubleshooting Network Problems 1. Identify the problem and its symptoms 2. Establish theory of probable cause 3. Test your theory to determine cause 4. Establish a plan for resolving the problem 5. Implement the solution or escalate the problem 6. Verify full functionality and implement preventative measures 7. Document findings, actions, outcomes Module 2 (Lecture 2 Part A): OSI Model Seven-layer OSI Model 01. Physical layer - Transmit raw bit stream over the physical medium 02. Data link layer - Defines the format of data on the network 03. Network layer - Decides which physical path the data will take 04. Transport layer - Transmits data using transmission protocol including TCP and UDP 05. Session Layer - Maintains connections and controls ports and session 06. Presentation layer - Ensures data is in a usable format and is where data encryption occurs 07. Application layer - Human-computer interaction layer, where applications can access the network services ○ A browser and web server communicate by way of the operating system and hardware Similar to how a letter is sent through the mail using postal services and the road system Layer 7: Application Layer ○ The application layer describes the interface between two applications on separate computer ○ Application layer protocols are used by programs that fail into two categories Provides services to a user, such as a browser and a web server Utility programs that provide services to the system, such as SNMP (simple network management protocol) programs that monitor and gather info about network traffic ○ Payload is the data that is passed between applications or utility programs and the OS Eg: Web Layer 6: Presentation Layer ○ The presentation layer is responsible for reformatting, compressing and/or encrypting data in a way that receiving application can read  Eg: An email message can be encrypted at the presentation latter by the email client or by the OS Eg: SSL, TLSV, PGP (pretty good privacy) Layer 5: Session Layer ○ The session layer describes how data between applications is synched and recovered if messages don’t arrive intact at the receiving application ○ The application, presentation, and session layer are intertwined Often difficult to distinguish between them ○ Most task are performed by the OS when an application makes an API (Application Programming Interface) call to the OS An API call is the method an application uses when it makes a request of the OS ○ Synchronization Layer 4: Transport Layer ○ The transport layer is responsible for transporting application layer payloads from one application to another → end to end ○ Two main transport layer protocol TCP (Transmission Control Protocol): makes a connection with the end host → checks whether data was received; called a connection-oriented protocol (Error handling) UDP (User Datagram Protocol): Does not guarantee delivery by the first connecting and checking whether data is received; called a connectionless protocol (No Error handling so it is faster than UDP) ○ Protocols add controls information in an area at the beginning of the payload (Called Header) ○ Encapsulation is the process of adding a header to the data inherited from the layer above ○ The transport layer header addresses the receiving application by a number called a port ○ If a message is too large, TCP divides it into smaller messages called segments In UDP, the message is called a datagram Layer 3: Network Layer ○ The network layer is responsible for moving messages from one node to another until they reach the destination host  ○ The principal protocol used by this layer is IP (internet protocol) ○ IP adds its own network layer header to the segment or datagram Entire network layer message is called a packet ○ An IP address is an address assigned to each node on a network IP’s are on the same network if the first number for both IP’s are the same Network layer uses it to uniquely identify each host IP address has 2 parts Net Address → postal code Host Address → home address Neighbour if first 4 numbers are the same ○ Eg: 192.168.12.1 & 192.168.12.84 are neighbours ○ IP relies on several routing protocols to find the best route for a packet to reach destination Eg: ICMP (Internet Control Messaging Protocol) and ARP ○ Network layer protocol will divide large packets into smaller packets in a process called fragmentation Layer 2: Data Link Layer ○ Layer 2 and 1 are responsible for interacting with physical hardware on the local network ○ Converts packets into frames of (0, 1) Protocols at these layers are programmed into firmware of a computer’s NIC and other hardware ○ Types of networking hardware or technology used on a network determine the data link layer protocol used Eg: Ethernet and wifi ○ Data link layer put control information in a data link layer header and at the end of the packet in a trailer Entire data link layer message is called a frame ○ LLC (Logical Link Protocol) → Frame of 0 and 1 ○ A MAC (media access control) address is also called a physical address, hardware address, or data link layer address It is embedded on every network adapter 48 bits, 12 Hexadecimal → B0-12-39-AF-C1-83 First 6 numbers is the manufacturer ID  The next 6 number is the device ID To test NIC → ping 127.0.0.1 Layer 1: Physical Layer ○ The physical layer is responsible for sending bits via a wired or wireless transmission (transmit 0’s and 1’s) → signal ○ Bits can be transmitted as: Wavelengths in the air Voltage on a copper wire Light (via fiber-optic cabling) Protocol Data Unit or PDU ○ Protocol data unit (PDU) is the technical name for a group of bits as it moves from one layer to the next and from one LAN to the next Technicians loosely call this group of bits a message or a transmission Module 2 (Lecture 2 Part B): Infrastructure Components of Structured Cabling ○ ANSI/TIA-568 Commercial building wiring standard Also known as structured cabling ○ The wiring standard describes the best way to install networking media to maximize performance and minimize upkeep Principles apply no matter what type of media, transmission technology, or networking speeds are involved ○ Structured cabling is based on hierarchical design and assume a network is based on the star topology  From the Demarc to a Workstation ○ Entrance facility in Building A: EF (entrance facility) - location where the incoming network (such as internet) connects with the school or corporate network Demarc (demarcation point) - The device that marks where telecommunications service providers network ends and the organization's network begins MDF (main distribution frame) - Centralized point of interconnection for an organizations LAN or WAN (called MC or main telecommunication point) Data room - Enclosed space that hold network equipment (called data closet, data center, equipment room, or telecommunication room Rack - Holds various network equipment Patch panel - Panel of data receptors which can be mounted to a wall or a rack Patch panel provides a central termination when many patch cables converge in a single location ○ Entrance Facility in Building A (Cont.) VoIP telephone equipment - VoIP (voice over IP) is the use of any network to carry voice signals using TCP/IP protocols In one or more data rooms you can find VoIP gateway VoIP PBX VoIP endpoints ○ Data Room in Building B: IDF (intermediate distribution frame) - provides an intermediate connection between the MDF and end-user equipment on each floor and in each building ○ Work Areas in All Three Buildings Work Area - Encompasses workstations, printers, and other network devices Wall Jacks - the ANSI/TIA standard calls for each wall jack to contain at least one voice and data outlet  ○ Rack Systems Racks come in two-post and four post varieties (six-post racks are also available) Racks may be wall or ceiling mounted, freestanding on the floor, or bolted to the floor Consider the following when purchasing racks Height - rack height is measured in rack units (RU or U) with the industry standard being 42U tall Width - equipment racks come in all standard 19 inch frame (19 inches wide) Depth - Rack depth vary between manufacturers In data centers containing multiple rows of racks, a hot aisle/cold aisle layout pulls cool air from vents in the floor or from low-lying wall vents into rows of racks Cabling ○ Types of cables Patch cable - A relatively short length of cabling with connectors at both ends Horizontal cabling - Connects workstation to the closest data room and switches housed in the room Backbone cabling - Consists of cables or wireless links that provide interconnection between the entrance facility and MDF and between MDF and IDFs  Pay attention to quality of cable connections and cable management ○ Cable Management Termination - When terminating twisted pair cabling, don’t leave more than one inch of exposed cable before a termination Bend Radius - Do not exceed cables prescribed bend radius; the radius is the maximum arc into which you can loop a cable without impairing data transmission Continuity - Use a cable tester to verify each cable segment transmit data reliably Loosely cinch cables Cable covering and conduits - avoid laying cables across a floor and use cord covers if they must be exposed EMI sources - Install cable at least 3 ft away from fluorescent lights or other source of EMI (electromagnetic interference) Plenum cabling - If running cable in the plenum (area above the ceiling tile or below subflooring) make sure cable sheath is plenum-rated Grounding - Pay attention to grounding requirements Slack in cable runs Cable trays - Use cable management devices such as cable trays, braided sleevings, and furniture grommets Patch Panels - Use patch panels to organize and connect lines Company standards and inventory  Documentation Keep cable plant documentation Label every data jack or port , patch panel and connector Use color-coded cables for different purposes Update documentation as you make changes to network Monitoring the Environment and Security ○ Data rooms are often serviced by HVAC systems separate from the rest of the building ○ Specialized products can monitor the critical factors of data closets environment: Unacceptable temperature Humidity Airflow condition ○ Every data room should be locked with only IT personnel having keys Network Documentation ○ Having up-to-date detailed documentation of your network is essential for the following reasons Makes connection with coworkers efficient Speeds up troubleshooting efforts Puts information at the fingertips when facing similar problem in the future Network Diagrams ○ Network diagrams are graphical representations of a networks device amd connections They may show physical layout, logical topology, IP address reserves, name of major network devices, and types of transmission media ○ Network mapping - The process of discovering and identifying the devices on a network NMAP - one of the most popular tools used for network mapping Zenmap - Nmap’s GUI option ○ Cisco systems set the standard for diagram symbols used to represent network devices  ○ Network diagrams provide broad snapshots of a network’s physical or topology Useful for planning where to insert a new switch or determining how a particular router, gateway, or firewall interact ○ Wiring schematic is a graphical representation of a network’s wired infrastructure In detailed form, it shows every wire necessary to interconnect network devices ○ Rack diagram is a drawing that shows devices stacked in a rack system Operating Procedures ○ Essential documentation Logical and physical connection on a network Inventory management IP address utilization Vendors Internal operating procedures Policies Standards  ○ Many corporations establish SOPs (standard operating procedures) to ensure consistency ○ An organization could provide an internal website or database to hold this information Inventory Management ○ System life cycle (SLC) - is the process of designing, implementing, and maintaining an entire network ○ SLC includes: Removal and disposal of outdated assets Addition of compatible, updated devices ○ Inventory management - is the monitoring and maintaining of all assets that make up a network Simplifies maintaining and upgrading a network Provides network administrators with information about the costs and benefits of certain types of hardware or software Labeling and Naming Conventions ○ Tips for labeling and naming conventions Use names that are descriptive as possible Only include fields that are essential in identifying the device Don't over complicate the name with useless or redundant information Use established naming conventions Think big-picture-down-to-details Consider any security risks from details included in your naming convention Use color-coded cables and use cable tags to identify each cable’s purpose Label the ports and jacks that cables connect to Where labels won’t fit on the device, draw a simple diagram of each device that indicates how each port is used Use labels that are durable and are designed to stick to plastic and metal Business Documents ○ Standard business documents you may encounter RFP (request for proposal) - is a request to vendors to submit a proposal for a product or service your company wants to purchase  MOU (memorandum of understanding) - Documents the intentions of two or more parties to enter into a binding agreement, or contract SOW (Statement of work) - documents in detail the work that must be completed for a particular project SLA (service-level agreement) is a legally binding contract or part of a contract that defines the aspects of a service provided to a customer Eg: the service provided by an ISP ○ Standard business documents you may encounter MSA (master service agreement) - A contract that defines terms of future contracts between parties MLA (master license agreement) - Grants a license from a creator, developer, or producer to a third party for the purpose of marketing or sub licensing, or distributing the product to consumers Change Management ○ Managing change while maintaining networks efficiency and availability requires good planning Network users need to know when to expect certain network resources to be unavailable ○ Common software and hardware changes range from installing patches to replacing network backbone ○ You may also need to know the change management documentation that might be required for an enterprise-scale network Software and Hardware Changes ○ Four types of software changes: Installation - new software to be installed on relevant devices and incorporated with network resources Patch - A correction, improvement, or enhancement Upgrade - a major change to a software package that enhances the functionality and feature of the software Rollback - Called backleveling or downgrading Process of reverting to a previous version ○ Hardware changes could include adding new security cameras, replacing workstations, installing new printers, and upgrading hardware ○ The same change management principles apply to any type of change  Process change through proper channels Minimize negative impacts on business procedures\ Plan thoroughly to maximize the chances of successful change on the first attempt Document each change throughout the process Change Management Documentation ○ Generally the larger an organization the more documentation required when making changes ○ You may need to do the following Submit A change request document Understand and follow the approval process Follow project management procedures Provide additional documentation that could include; Network config IP utilization Additions to the network Physical location changes Close the change Module 3 (Lecture 3 Part A): Network Addressing Addressing Overview ○ There are four addressing method Data link layer (MAC) address is 48 bits, written as six pairs of hex numbers separated by colons MAC is called physical address also MAC address are embedded on every NIC (Network Interface Card) in the world Network layer IP (internet access) address can be used to find any computer in the world IPv4 addresses can have 32 bits and are written as four decimal numbers called octets IPv6 addresses have 128 bits and are written as eight blocks of hexadecimal number  Transport layer port number are used to find applications Application layer FQDN, computer names, and host names FQDN - Fully Qualified Domain Name is a unique character-based name MAC Address ○ Traditional MAC addresses contain two parts The first 24 bits are known as the OUI )Organizationally Unique Identifier) or manufacturer-ID This part is assigned by the IEEE The last 24 bits make up the extension identifier or device ID Manufacturer's assigns each NIC to a unique device ID ○ Switches use MAC addresses to identify devices on the local area network (LAN) IP Addresses ○ Static IP addresses are assigned manually by the network administrator ○ Dynamic IP addresses are automatically assigned by a DHCP server ○ There are two types of IP addresses: IPv4 32-bit address IPv6 128-bit address IPv4 Addresses ○ A 32-bit IPv4 address is organized into four groups of 8 bits each (known as octets) Each of the four octets can be any number from 0 to 255 Some IP addresses are reserved Eg: 72.56.105.12 ○ Classful addressing The dividing line between the network and host portions is determined by the numerical range the IP address falls in 127 → loopback (test NIC card) Eg: 127.0.0.1 ○ Classful IPv4 addresses are divided into five classes Class A: 1-126 Class B: 128-191 Class C: 192-223 Class D: 224-243 Multimedia class Class E: 244-254 (experimental class) ○ To separate a net address from a given IP we use subnet mask ICANN Class A subm= 255.0.0.0 Eg: 114.12.18.19 ○ net address: 114 ○ Host address: 12.18.19 Class B subm= 255.255.0.0 Eg: 180.12.100.210 ○ Net address: 180.12 ○ Host address: 100.210 Class C subm = 255.255.255 Eg: 192.168.1.200 ○ Net address: 192.168.1 ○ Host address: 200 ○ Class A, B, and C licensed IP addresses are available for use on the internet and only class A, B, and C ave a submask not class D and E Called public IP addresses ○ A company can use private IP addresses on its private networks ○ The IANA recommends the following IP addresses be used for private networks: 10.0.0.0 through 10.255.255.255 → Class A 172.16.0.0 through 172.31.255.255 → Class B 192.168.0.0 through 192.168.255.255 → Class C 168.254.255.255 → APIPA; assigned by DHCP  ○ Classless Addressing - allows the dividing line between network and host portions to fall anywhere along the string of binary bits in an IP address ○ CIDR (Classless Interdomain Routing) notation - takes the network ID or host’s IP address and follows it with a forward slash (/) followed by the number of bits that are used for the network ID ○ Network Address Translation (NAT) - is a technique designed to conserve public IP addresses needed by a network ○ Address translation is process where a gateway device substitutes the private IP addresses with its own public address When these computers need access to other networks or internet ○ Port Address Translation (PAT) is the process of assigning a TCP port number to each ongoing session between a local host and internet host; faster than NAT and each WS is assigned a port # ○ Two variation of NAT to be aware of: SNAT (Source Network Address Translation) - The gateway assigns the same public IP address to a host each time it makes a request to access the internet DNAT (Dynamic Network Address Translation) - The gateway has a pool of public address that it is free to assign to a local host when it makes a request to access the internet IPv6 Addresses ○ IPv6 address has 128 bits written as eight blocks of hexadecimal numbers separated by colons Eg: 2001:0000:0B80:0000:00D3:9C5A:00CC ○ Each block is 16 bits ○ Leading zeros in a four character hex block can be eliminated ○ If blocks contain all zeros, they can be written as double colons (::) only one set of double colons is used in an IP address ○ Therefore the example above can be written in two ways 2001:B80:0000:0000:D3:9C5A:CC 2001:0000:B80::D3:9C5A:CC  The second way is the preferred method because it contains the fewest zeros ○ IPv6 terminology A link (sometimes called local link) is any LAN bounded by router Neighbors are two or more nodes on the same link Dual stacked is when a network is configured to use IPv4 and IPv6 Tunneling is a method used by IPv6 to transport IPv6 packets through or over an IPv4 network Interface ID is the last 64 bits or four blocks of an IPv6 address that identify the interface Types of IPv6 Addresses ○ Unicast Address - specifies a single node on a network Global address can be routed on the internet Link local address can be used for communicating with nodes in the same link Loopback address can be used to test that an interface an supporting protocol stack are functioning properly ○ Multicast address - delivers packets to all nodes on a network ○ Anycast address - can identify multiple destinations with packets delivered to the closest destination ○ IPv6 autoconfiguration IPv6 addressing is designed so that a computer can autoconfig its own link local IP address This process is called SLACC (stateless address autoconfiguration) Step 1: computer creates it IPv6 address ○ Uses FE80:://64 as the first 64 bit (called prefix) ○ The last 64 bits are generated from the network adapters MAC address  Step 2: The computer checks to make sure its IP address is unique on the network Step 3: The computer asks if a router on the network can provide configuration information ○ The message is called an RS (router solicitation) message Ports and Sockets ○ A port is a number assigned to a process that can receive data A port number ensure data is transmitted to the correct process among multiple processes running on a single device Port 21 → FTP (download/upload file) Port 22 → SSH (secure shell) Port 23 → Telnet POrt 25 → SMTP (send email) POrt 79→ Finger (locate a pc) Port 80 → HTTP Port 110 → POP3 (read email) Port 143 → IMAP Port 200 → IMAP3 Port 161 → SNMP Simple network management pro Port 389 → LDAP (lightweight, directory, access, protocol Port 443 → HTTPS (SSL, TLL) ○ A socket consists of host’s IP address and the port number of an application running on the host A colon separates the two values Eg: 10.43.3.87:23 ○ Port numbers are divided into three types: Well- known ports: 0 to 1023 Registered ports: 1024 to 49151 Dynamic and private port: 49152 to 65535 Domain Names and DNS ○ Character-based names are easier to remember than numeric IP addresses  ○ A URL (uniform resource locator) is an addressing scheme that identifies where to find a particular resource on a network ○ Last part of an FQDN is called the Top-level domain (TLD) ○ Domain names must be registered with an internet naming authority that works on behalf of ICANN ICANN restricts what type of hosts can be associated with.arpa,.mil,.int,.edu, and.gov ○ Name resolution is the process of discovering the IP address of a host when you know the FQDN ○ DNS os an application layer client-server system of computers and databases made up of these elements Namespace - The entire collection of computer names and their associated IP addresses stored in databases on DNS name servers around the globe Name servers - hold databases, which are organized in a hierarchical structure Resolvers - A DNS client that requests information from DNS name servers Namespace Database ○ Each organization that provides host services is responsible for providing and maintaining its own DNS authoritative servers for public access An authoritative name server is the authority on computer names and their IP addresses for computers in their domains ○ The domains that the organization is responsible for managing are called a DNS zone Name Servers ○ Four common types of DNS servers: Primary DNS server - The authoritative name server for the organization Holds the authoritative DNS database for the organization’s zone Secondary DNS server - backup authoritative name server for the organization Caching DNS server - accesses the public DNS data and caches the DNS information it collect  Forwarding DNS server - Receives queries from local clients but doesn’t work to resolve the queries ○ Any of these DNS server types can co-exist on the same machine ○ DNS name servers are organized in a hierarchical structure ○ At the root level, 12 clusters of root DNS servers hold information used to locate top-level domain (TLD) servers ○ Ways the resolution process can get more complex: A caching server typically is not the same machine as the authoritative server The caching server exists only to resolve names for its own local clients Name servers within a company might not have access to root servers A TLD name server might be aware of an intermediate name server rather than the authoritative name server Two types of DNS requests: Recursive lookups: a query that demands a resolution or the answer “it can’t be found” Iterative lookup: A query where the local server issues queries to other servers ○ Other servers only provide information if they have it ○ Do not demand a resolution Resource Records in a DNS Database ○ Several types of records, called resources records are kept in a DNS database: SOA (start of authority) record: give information about the zones  A (address) record: Stores the name-to-address mapping for a host AAAA (address) record: Holds the name-to-address mapping, the IP address is an IPv6 type IP address CNAME (canonical name) record: holds alternative names for a host PTR (pointer) record: used for reverse lookups NS (name server) record: indicates the authoritative name server for a domain MX (mail exchanger) record: identifies a mail server and is used for email traffic SRV (service) record: Identifies the hostname and port of a computer that hosts a specific network services besides email TXT (text) record): Holds any type of free-form text DNS Server Software ○ BIND ( Berkeley Internet Name Domain( is the most popular DNS server software Open source - the term for software whose code is publicly available for use and modification ○ Microsoft DNS server is a built in DNS service in the Windows Server OS ○ Windows server is capable of split brian or split horizon deployment which is used to handle internal clients and external clients Troubleshooting Tools ○ Command-line tools are a great resource to troubleshoot network problems ○ Ping (packet internet Groper) utility is used to verify that TCP/IP is: Installed Bound to the NIC Configured correctly Communicating with the network ○ The ping utility sends out a signal called an echo request to another device (request for a response) Other computer responds in the form of an echo reply ○ ICMP (Internet Control Message Protocol) is the protocol used by the echo request/reply to carry error messages and information about the network ○ IPv6 networks use a version of ICMP calledICMPv6  Ping6 - On linux computers, use ping6 to verify whether an IPv6 host is available Pink -6 on windows computers, use ping with the -6 switch to verify connectivity on IPv6 ○ For the ping6 and ping -6 commands to work over the internet, you must have access to the Ipv6 internet ○ The ipconfig command shows current TCP/IP addressing and domain name information on a windows computer Use ipconfig/all to see a more complete summary of TCP/IP addressing information ○ Use the ip utility to view and manage TCP/IP settings ○ The ip utility is only available on UNIX and Linux systems ○ Any ip commands that change the state of a link require elevated privileges This is accomplished by logging in as the root user or temporarily elevating the current user’s privileges with the sudo commands ○ Ifconfig is a similar utility used to view and manage TCP/IP settings ○ The nslookup (namespace lookup) utility allows you to query the DNS database from any computer on a network To find the hostname of a device by specifying its IP address or vice versa It is useful for verifying a host is configured correctly or for troubleshooting DNS resolution problems ○ Reverse DNS lookup - to find the hostname of a device whose IP address you know Nslookup 69.23.208.74 ○ The nslookup utility is available in two modes Interactive → test multiple DNS servers at one time Noninteractive → test a single DNS server ○ You ca change DNS servers from within interactive mode with the server subcommand and specifying the IP address of the new DNS server ○ To exit nslookup interactive mode enter exit ○ The dig (domain information groper) utility is available on linus and macOS Provides more detailed information than nslookup abd uses more reliable source of information to output its result  ○ Use dig to query DNS nameservers for information about host addresses and other DNS records ○ An IP scanner can be used to gather information about all devices connected to a network Common Network Issues ○ Incorrect time Check a domain computer’s time source from a command prompt window by entering w32tm /query / source ○ DHCP issues IF you are getting DHCP errors or if multiple clients are having trouble connecting to the network try the following: Check the settings on your DHCP server Make sure the DHCP scope is large enough to account for the number of client the network must support Consider implementing a shorter lease time on larger networks ○ Network Connection Configuration Issues Common configuration errors: Incorrect IP address Duplicate IP address Incorrect subnet mask Incorrect gateway Incorrect DNS or DNS issue When a computer is struggling to establish a network connection Check its TCP/IP configuration settings IF the computer is not obtaining an IP address and related information from a DHCP server Static settings might be using the wrong information Try switching to DHCP Module 4 (Lecture 3 Part B): Protocols TCP/IP Core Protocol ○ TCP/IP is a suite of protocols including TCP, IP (IPv4 and IPv6), UDP, ARP, etc  ○ TCP/IP protocols add a header to data inherited from the layer above it ○ Layer 7, 6, and 5 - data and instruction, known as payloads are generated by applications running on source host ○ Layer 4 - A transport layer protocol, usually TCP or UP adds a header to the payload Includes a port number to identify the receiving app ○ Layer 3 - network layer adds its own header and becomes a packet ○ Layer 2 - packet is passed to data link layer on NIC, encapsulates data with its own header and trailer, creating a frame ○ Layer 1 - Physical layer on the NIC receives the frame and places the transmission on the network ○ The receiving host decapsulates the message at each layer in reverse order and presents payload to the receiving application In transit, transmissions might pass through a number of connectivity devices Connectivity devices are specialized devices that allow two or more networks or multiple parts of one network to connect and exchange data Known by the highest OSI layer they read and process TCP (Transmission Control Protocol) ○ TCP operates in the transport layer of OSI model ○ Three characteristics of TCP: Connection-oriented: TCP ensures that a connection or session is established by using  three-step processing called a three-way handshake Sequencing and checksums: TCP sends a character string called a checksum that is checked by the destination host along with a sequence number for each segment Flow control: Gauges rate of transmission based on how quickly recipient can accept data ○ The TCP three-way handshake establishes a session before TCP transmit actual data Three transmission are sent before data transmission: Step 1: A request for a connection (SYN) Step 2: A response to the request (SYN/ACK) Step 3: A connection is established (ACK) After the three initial messages, the payload or data is sent Sequences numbers will increase by number of bits included in each received segment Confirms the correct length of message was received UDP (User Datagram Protocol) ○ UDP is an unreliable, connectionless protocol No three-way handshake is performed UDP does not guarantee delivery of data ○ UDP provides no error checking, sequencing, or flow control This makes UDP more efficient than TCP ○ Useful for live audio or video transmission over the internet ○ More efficient for carrying messages that fit with one data packet ○ A UDP header contains only four fields: Source port, Destination port, Length, and Checksum Use of Checksum field in UDP is optional in IPv4 but required in IPv6 IP (internet protocol) ○ IP operates at the network layer of the OSI model Specifies where data should be delivered Identifies the data’s source and destination IP addresses  ○ IP enables TCP/IP to internetwork To transverse more than one LAN segment and more than one type of network through a router ○ IP is an unreliable, connectionless protocol That means that IP does not guarantee delivery of data and no session is established before data is transmitted ○ IP depends on TCP to ensure messages are put back together in the right order and to ensure each message reaches the correct application on the receiving host ○ IPv6 Packets IPv6 uses a different packet format than IPv4 Ipv6 can accommodate the much longer IPv6 addresses There is no fragment offset field IPv6 hosts adjust their packet sizes to fit the requirements of the network before sending IPv6 messages ICMP (Internet Control Message Protocol) ○ ICMP is a core network layer protocol that reports on the success or failure of data delivery ○ ICMP can indicate the following: When part of a network is congested When data fails to reach its destination When data has been discarded because the allotted TTL has expired ○ ICMP announces transmission failures to the sender but does not correct errors it detects ○ It provides critical information for troubleshooting network problems ○ It provides critical information for troubleshooting network problems ○ ICMPv6 on IPv6 networks performs the functions of ICMP and ARP on IPv4 networks  ARP (Address Resolution Protocol) on IPv4 Networks ○ ARP works in conjunction with IPv4 to discover the MAC address of a host or node on the local network And to maintain a database that maps IP addresses to MAC addresses on the local network ○ ARP is a layer 2 protocol that uses IP in layer 3 and relies on broadcasting Operates only within its local network ○ ARP table can contain two types of entities: Dynamic : Created when a client makes an ARP request that could not be satisfied by data already in the ARP table Static : Those someone entered manually using ARP utility (arp command) ○ To view a Windows workstations ARP table enter → arp -a NDP (Neighbor Discovery Protocol) ○ IPv6 devices learn about other devices on their networks through a process called neighbor discovery ○ NDP (Neighbor Discovery Protocol): info carrier in ICMPv6 messages automatically detects neighboring device and automatically adjust when nodes fail or are removed ○ NDP offers several ICMPv6 message types: RA (router advertisement) RS (router solicitation) Redirect NS (neighbor solicitation) NA (neighbor advertisement) Ethernet ○ Ethernet is the most important data link layer standard Capable of running on variety of network media Ethernet offers excellent throughput at a reasonable cost Most popular network technology used on modern LANs ○ Ethernet II is the current standard ○ Ethernet adds both a header and trailer to the payload Creates a frame around payload (this includes the MAC address of the sender)  ○ Header and FCS make up the 18-byte “frame” around the data ○ Data portion of an ethernet frame may contained from 46 to 1500 bytes ○ MTU (maximum transmission unit) the largest size that routers in a message’s path will allow at network layer Encryption Protocols ○ Encryption protocols use a mathematical code, called a cipher, to scramble data into a format that can be read only by reversing the cipher ○ Purpose of encryption is to keep info private ○ Encryption methods are evaluated by 3 benchmarks Confidentiality Integrity Availability ○ The principles above from the standard security model called the CIA triad Key Encryption ○ A key is a random string of characters woven into original data’s bits Generates unique data block called cipher text Key is created according to a specific set of rules (algorithms) ○ Key encryption can be separated into two categories: Public key encryptions Private key encryptions IPsec (internet Protocol Security) ○ IPsec is an encryption protocol suite that defines rules for encryption, authentication, and key management for TCP/IP transmission ○ IPsec creates secure connections in five steps: IPsec initiation Key management Security negotiations Data transfer Termination ○ Operates in two modes: Transport mode Tunnel mode SSL (Secure Sockets Layer) & TLS (Transport Layer Security) ○ Both SSL and TLS are methods of encrypting TCP/IP transmissions  ○ Both protocols work side by side and widely known as SSL/TLS or TLS/SSL ○ When a client and server establishes SSL/TLS connection, they establish a unique session which is an association between client and server Session is defined by an agreement on a specific set of encryption techniques A session is created by an SSL handshake protocol ○ THe handshake protocol allows client and server to authenticate Handshake is similar to TCP three way handshake Remote Access Protocols ○ Remote access is service that allows a client to connect with and log on to a server, LAN, or WAN in a different geographical location ○ Remote access requires a types of RAS (remote access server) ○ There are two type of RAS: Dedicated devices Software running on a server ○ Types of remote access include: Remote File Access FTP (file transfer protocol) - provides remote file access Three related technologies include: ○ FTPS (FTP secure or FTP over SSL) - offers an added layer of protection for FTP using SSL/TLS ○ SFTP (Secure FTP) - File-transfer version SSH that includes encryption and authentication for transferring files ○ TCTP (Trivial FTP) - Simple protocol similar to FTP but it includes no authentication or security for transferring files Terminal emulation, aka remote virtual computing A terminal emulator is software that allows a user on one computer (client) to control another computer (host of computer) ○ Eg: remote desktop for windows Telent is a terminal emulation utility that allows an administrator or other user to control a computer remotely ○ Provides little security for establishing a connection ○ Provides no security for transiting data  SSH (secure Shell) is a collection of protocol that provides for secure authentication and encryption ○ Guards against number of security threats Unauthorized access to a host IP spoofing Interception of data in transit DNS spoofing ○ Secure connection requires SSH running on both client and server ○ Allows for password authentication using public and private key generation RDP (Remote Desktop Protocol): A microsoft proprietary protocol used to connect to and control remote computer VNC (Virtual Network computing): Uses the cross-platform protocol RFB (remote frame buffer) to remotely control a workstation or server Out-of-brand management relies on a dedicated connection between the network administrators computer and each network device VPN A VPN is a network connection encrypted from end to end that creates a private connection to a remote network ○ Referred to as a tunnel Can be classified according to three models: ○ Site to site ○ Client to site ○ Host to host To ensure VPNs can carry all types of data securely, special protocols encapsulate high-layer protocols in a process known as tunneling Many VPN tunneling protocols operate at data link layer to encapsulate the VPN frame into network layer packets Some VPN tunneling protocols work at layer 3 which enables additional features and options  Most tunneling protocols rely on an additional encryption protocol to provide data security Common VPN tunneling protocols include: ○ L2TP ○ GRE ○ Open vpn ○ IKEv2 Cisco developed a proprietary protocol called mGRE that allows the configuration of multiple tunnel destinations on a single interface Type of enterprise VPN using Cisco devices is called DMVPN ( Dynamic multipoint VPN) DMVPN dynamically creates VPN tunnel between branch locations as needed rather than requiring constant, static tunnels for site-to-site connections Remote Access Policies ○ Common requirements of a good remote access policy: Remote access devices must be up to date with patches, anti-malware software, and a firewall Device access must be controlled by a strong password or biometric measures Passwords must be strong and must be changed periodically The device’s internal and external storage devices must be encrypted Company and customer data must be kept secure The loss or theft of any devices used for remote access must be reported immediately Encrypted VPN software must be used to remotely access company network resource While remotely connected to the company network, the device must not be connected to the open Internet or any other network not fully owned or controlled by the employee Remote sessions must be terminated when not in use  Troubleshooting Network Issues ○ Netstat display TCP/IP statistics and details about TCP/IP components /connections on a host ○ Information that can be obtained from the netstat command includes: The port on which a TCP/IP service is running Which network connections are currently established for a client How many messages have been handled by an interface since it was activated How many data errors have occurred on a particular network interface ○ Tracert or traceroute ○ Windows tracert utility uses ICMP echo requests to trace the path from one networked node to another, identifying all intermediate hops between the nodes ○ Linux, UNIX, and OS X system use the traceroute utility to send UDP messages to a random port on the destination node (concept is the same as tracert ○ Tcpdump is a free command-line packet sniffer that runs on linux and other unix OS Captures traffic that crosses a computer's network interface Output can be saved to a file that you can filter or play back You must either use the sudo command or log in as root to access tcpddump Solving Common Network Problems ○ Duplicate MAC Addresses Two devices on the same network with the same MAC address is a problem MAC addresses can be impersonated, which is a security risk called spoofing It happens most often when managing multiple virtual devices on a large network Most switches will detect the problem and produce helpful error messages  Then it’s a matter of tracking down which virtual devices have the same MAC address and update each device’s configuration ○ Hardware Failure - when a router, switch, NIC, or other hardware goes down: Use tracert or traceroute to track down malfunctioning routers and other devices on larger networks Get more accurate trace feedback on a questionable router by targeting a node on the other side of that router, rather than aiming for that router itself Use ping to test for network connectivity Module 5 (Lecture 4 Part A): Cabling Transmission Basics ○ Transmission techniques in use on today’s network are complex and varied ○ This section covers Measurements that indicate network efficiency Obstacles to good network performance Frequency, Bandwidth, and Throughput ○ Frequency - Typically measured in MHz or GHz which indicated the number of times in a second that an electrical signal can change states ○ Bandwidth - amount of data that could be theoretically transmitted during a given period of time ○ Throughput - Measure of how much data is actually transmitted during given time period New technologies such as modulation (sending data over an analog signal) and encoding (converting data into a digital signal for transmission) offer methods for increasing theoretical bandwidth and effective data throughout given the same maximum frequency Transmission Flaws ○ Noise is any undesirable influence degrading or distorting signal Noise is measured in dB (decibels) ○ Two common sources of noise include EMI (Electromagnetic interface) - caused by motor, power lines, tvs, copiers, fluorescent lights  Cross-talk - Occurs when the signal on one wire infringes on adjacent wire signal Alien cross-talk - Occur between two cables Near end cross-talk (NEXT) - occurs near source Far end cross- talk (FEXT) - occurs at the far end ○ Attenuation - Loss of signal’s strength as it travels away from source ○ Signals can be boosted using a repeater which regenerates a digital signal in its original without noise previously accumulated ○ Latency - the delay between signal transmission and receipt Latency may cause network transmission errors ○ The length of the cable affects latency, as does the existence of any intervening device ○ RRT (round trip time) - Is the time for packet to go from sender to receiver, then back from receiver to sender ○ If the packets experience varying amounts of delay they can arrive out of order Problem commonly called jitter or PVD (packet delay variation) Duplex, Half-Duplex, and Simplex ○ NIC settings include the direction in which signals travel over the media and the number of signals that can traverse the media at any given time These two settings are combined to create different methods of communication ○ Full-duplex - Signals travels in both directions over a medium simultaneously ○ Half-duplex - signals may travels in both direction but only in one direction at a time ○ Simplex - Signals may travel in one direction and is sometimes called one-way or unidirectional, communication ○ In windows, use device manager to configure a NIC, including speed and duplex settings  Multiplexing ○ Is form of transmission that allows multiple signals to travel simultaneously over one medium ○ To carry multiple signals, the medium channel is logically separated into smaller channels or subchannels ○ Multiplexer (mus) is a device that combines many channel signals Required at the transmitting end of the channel ○ A demultiplexer (demux) separates the combined signals on the receiving end ○ Three types of multiplexing are used on copper lines: TDM (time division multiplexing): divides a channel into multiple time intervals STDM (statistical time division multiplexing): Assigns slots to nodes according to priority and need FDM (frequency division multiplexing): Assigns different frequency band for each communication subchannel ○ Three types of multiplexing are used on fiber-optic cables WDM (wavelength division multiplexing): carriers multiple light signals simultaneously by dividing a light beam into different wavelength colors DWDM (dense wavelength division multiplexing): increase the number of channels provided by normal WDM CWDM (Coarse wavelength division multiplexing): Lowers cost by spacing frequency bands wider apart to allow for cheaper transceiver equipment  Coaxial Cable and Twinaxial Cable ○ Coaxial cable - called “coax” was the foundation for ethernet networks in the 1980s Coax has been replaced by newer media types A form of coax is still used cable internet, cable TV, and some multimedia connection types ○ Coax has central metal core surrounded by an insulator, a braided metal shielding, and an outer cover called the sheath or jacket ○ Two types of coax, RG-6 and RG-59 can terminate with one of two connector types: F -connector BNC connector ○ Twinaxial cable - called “twinax” looks similar to a coax except there are two cores ○ The two cores cooperate in a half-duplex fashion to transmit data This makes it capable of supporting much higher throughput than coax ○ Twinax is made from 26 or 28 AWG copper so it is resistant to damage from rough handling ○ The Type of twinax cable determines its maximum supported distance Passive is sufficient for the shortest distances of less than about 5 or 7 meters Active contains internal electrical components to strengthens signals up to 10 meters Twisted-Pair Cable ○ Twisted-pair cable consists of color-coded insulated copper wire each with a 0.4 to 0.8 mm diameter Every two wires are twisted together to form pairs encased in a plastic sheath ○ Twisted-pair cabling in ethernet networks contain four wire pairs Fast ethernet: uses one pair to send data and one pair to receive data Networks using gigabit ethernet use all four pairs for both sending and receiving ○ Most common twisted pair types include the following Category (cat) 3, 5, 5e, 6, 6a, 7, 7a, and 8  CAT 5e or higher used in modem LANs ○ All twisted-pair cable falls into one of two classifications: Shielded twisted pair (STP) Unshielded twisted pair (UTP) STP (Shielded Twisted Pair) ○ Wires in STP cable are individually insulated and may also be surrounded by metallic substance shielding (foil) Shielding acts as a barrier to external electromagnetic forces ○ The shielding must be grounded to enhance its protective effects ○ Effectiveness of STP’s shield depends on the following: Level and type of environmental noise Thickness and material used for the shield Grounding mechanism Symmetry and consistency of the shielding ○ Newer types of cable, such as CAT 8 incorporate more sophisticated shielding materials, more tightly twisted wires, higher bandwidth to offer data rates rivaling fiber-optic cable at short distances UTP (Unshielded Twisted Pair) ○ UTP cabling consists of one or more insulated wire pairs encased in plastic sheath ○ UTP does not contain additional shielding Makes UTP less expensive and less resistant to noise than STP ○ Historically UTP was more popular than STP Modern cable prices have dropped low enough that STP prices are becoming more reasonable STP vs UTP ○ STP and UTP similarities and differences include the following:  Throughput - STP and UTP can transmit are same rates Cost - STP and UTP vary in cost STP is typically more expensive Noise immunity STP is more noise resistant Size and scalability Maximum segment length for both is 100 meters on ethernet networks that support data rates from 1 Mbps and 10 Gbps ○ Some categories of STP require shorter segment lengths to achieve maximum throughput Cables Pinouts ○ Proper cable termination is a requirement for two nodes on a network to communicate Poor termination can lead to loss or noise in a signal ○ TIA/EIA specifies two methods of inserting wires into RJ-45 TIA/EIA 568A TIA/EIA 568B ○ There is no functional difference between the two standards Just make sure you s=use the same standard on every RJ-45 plug and jack ○ Most common type of networking cable is a straight-through cable (also called patch cable) Create one, terminate RJ-45 plugs at both ends identically ○ Rollover cable (also called console cable) are used to connect a computer to the console part of the router All wires are reversed Terminations are a mirror image of each other PoE (Power over Ethernet) ○ PoE is an IEEE 802.3af standard which specifies a method for supplying electrical power over twisted pair ethernet connections ○ Amount of power provided is 15.4 watts for standard PoE devices and 25.5 watts for newer PoE+ devices (802.3at standard) ○ PoE standard specifies two types of devices PSE (power sourcing equipment)  PDs (powered devices) ○ PoE requires Cat 5 or better copper cable ○ The PSE device first determines whether a node is PoE-capable before attempting to supply it with power Ethernet Standards for Twisted-Pair Cable ○ A cables category determines the fastest network speed it can support Layer 1 characteristic ○ A device’s NIC is rated for maximum network speeds ○ Most LANs today use devices and NICs that can support fast ethernet and gigabit ethernet Devices can auto-negotiate for the fastest standard they have in common ○ The fastest ethernet standard currently is 100GBASE-T ○ Two new standard were raffled by IEEE: 2.5GBASE-T 5GBASE-T ○ These new standards provide intermediate steps between gigabit ethernet and 10-gigabit ethernet ○ Maximum segment length for ethernet networks is 100 meters Fiber-Optic Cable ○ Fiber-optic cable - also called fiber contains one or more glass or plastic fibers at its center (core) ○ Data is transmitted via a pulsing light sent from laser or LED through central fibers ○ Surrounding the fibers is a layer of glass or plastic called cladding  Cladding is less dense than the glass or plastic in the strands and so reflects light back to the core in patterns This reflection allows the fiber to bend ○ Outside the cladding, a plastic buffer protects the cladding and core The buffer is opaque, absorbs escaping light Surrounded by kevlar (polymeric fiber) strands ○ Fiber-optic cabling offers the following benefits over copper cabling: Extremely high throughput Very high noise resistance Excellent security Able to carry signals for longer distances ○ Drawbacks More expensive than twisted pair cable Requires special equipment to splice SMF (Single Mode Fiber) ○ SMF consists of a narrow core (8-10 microns in diameter) Laser-generated light travels over one path, reflecting very little The light does not disperse as the signal travels ○ SMF can carry signals many miles before repeating is required ○ SMF is rarely used for shorter connections due to high costs ○ The internet backbone depends on SMF MMF (Multimode Fiber) ○ MMF contains a core with a larger diameter than single mode fiber Common size are 50-62.5 microns ○ Laser or LED generated light pulses travel at different angles through MMF ○ Signals traveling over MMF experience greater attenuation than SMF ○ Common use include: Cables connecting routers,switches, and servers on the backbone of a network Cables to connect a desktop workstation to the network ○ The transition between SMF and MMF might occur at an fiber distribution panel (FDP) Fiber Connectors ○ MMF connectors can be classified by the number of fibers they connect  ○ SMF connectors are classified by size and shape of the ferrule ○ Ferrule is the extended tip of a connector that makes contact with the receptacle in the jack ○ Shapes and polishes used by SMF ferrules to reduce back reflection include: Ultra Polished Connector (UPC) Angle Polished Connector (APC) ○ SMF connectors are typically available with a 1.25 mm ferrule or a 2.5 mm ferrule Most common 1.25 mm connector is the LC (local connector) Two 2.5 mm connectors are the SC (standard connector) and ST (Straight Tip) ○ Most common MMF connector is the MTRJ (mechanical transfer-registered jack) Media Converters ○ Media converters - is hardware that enables networks or segments running on different media to interconnect and exchange signals ○ The media converter completes the physical connection and converts electrical signals from copper cable to light wave signals Can also be used to convert networks using MMF with networks using SMF Fiber Transceivers ○ Some switches allow you to change and upgrade its interface They contain sockets where one of many types of modular interfaces, called transceivers can be plugged in GBIC, pronounced jee-bick was a standard type of transceiver designed for gigabit ethernet connection Newer transceivers have made the GIBC obsolete include: SFP (small form factor pluggable) XFP ( 10 gigabit small form factor pluggable) SFP+ QSFP (quad small form factor pluggable) QSFP+ CFP (Centum form factor pluggable) ○ To avoid using the incorrect transceiver you must pair these devices based on supported speeds and protocols  ○ Installing a transceiver can be achieved by sliding the transceiver into a socket on the back of the connectivity device Most transceivers come with a tab or latch system and keyed so that they will slide into the socket when aligned properly Ethernet Standards for Fiber-Optic Cable ○ Important details about ethernet include: 100BASE-SX is a low-cost solution for Fast Ethernet and uses a short 850-nanometer wavelength light signal 100BASE-FX also offers Fast Ethernet speeds, uses a longer wavelength, and is rated up to 2 kilometers 1000BASE-SX is a form of Gigabit Ethernet and uses short wavelengths of 850 nanometers 1000BASE-LX is the more common fiber version of Gigabit Ethernet and uses long wavelengths or 1300 nanometers 10GBASE-SR is the “short range” standard for 10-Gigabit Ethernet 10GBASE-LR uses lasers emitting 1310 nanometer light Common Fiber-Cable Problems ○ Fiber type mismatch - Actually more of a fiber core mismatch Even same-mode cables can be mismatch if the cores have different widths ○ Wavelength mismatch - occurs when transmission are optimized for one type of cable but sent over a different type of cable ○ Dirty Connectors - If fiber connectors get dirty, signal loss and other errors can start to cause problems ○ Link loss - The power of a light signal emitted at one end of a connection is subjected to many losses along its way to the other end Include losses from distance along the cable, losses from multiplexing and losses from imperfect connections, patches, or splices Cable Troubleshooting Tools ○ You can start troubleshooting a network connection problem by checking the network connection LED status indicator lights Stead light = connectivity Blinking light = activity  Red or amber light = problem ○ If cabling issue is suspected, you need to know which tools are designed to analyze and isolate problems Toner and Probe kit ○ Tone generator (toner) is small electronic device that issues a signal on a wire pair ○ Tone locator (probe) is a device that emits a tone when electrical activity detected ○ Probe kit or toner probe is a generator and locator combination, sold as a set ○ Tone Generators and tone locators are used to determine where wired pair terminated Cannot be used to determine a cable Multimeter ○ Multimeter - measures electric circuit characteristics such as resistance, voltage, and impedance ○ Use a multimeter to do the following: Measure voltage to verify cable is conducting electricity Check for the presence of noise Test for short or open circuit in the wire A short circuit is unwanted connection A open circuit is one where needed connections are missing Cable Continuity Tester ○ Tests whether a cable carrier a signal to destination ○ Copper-based cable tested consists of two parts Base unit → generates voltage Remote unit → detects voltage ○ Most cable testers provide a series of lights and some emit an audible tone They are used to signal pass/fail ○ Some continuity testers verify UTP, STP wires are paired correctly Not reversed, crossed, or split ○ Fiber optic continuity testers issue light pulses on the fiber and determine whether pulses reach the other end ○ Most testers are portable, lightweight, and are inexpensive  Cable Performance Tester ○ Line tester, or certifier perform similarly to continuity testers but can be used to Measure distance to connectivity device, termination point, or cable fault Measure attenuation Measure NEXT (near end cross-talk) Measure termination resistance and impedance Issue pass/fail ratings for Cat 3-7 standards Store and print results or save to a computer database Graphically depict attenuation and cross-talk ○ TDR (time domain reflectometer) - issues a signal then measures the way the signal bounces back to the TDR Indicates distance between nodes Indicated whether terminators are properly installed and functional ○ OTDRs (Optical time domain reflectometers) - measure fiber length Determine faulty splice locations, breaks, connectors, bends, and measure attenuation over cable They can measure attenuation over the cable Can be expensive OPM (Optical Power Meter) ○ Also called a light meter, measures the amount of light power transmitted on a fiber-optic line ○ An OPM must be calibrated precisely, following highly accurate optical power standards The surrounding room temp, connection type, and the skill of the technicians all affect the final test result 802 - define LAN/MAN/WAN 802.1 - Bridge (MAC) 802.2 - Layer 2 -LLC 802.3 - defines Ethernet (stars, bus, topology) Key point: CSMA/CD carrier sense multiple access/collision detection 802.5 - Token Ring (IBM), no collision (Expensive; used by airports, banks, medical) 1) To send data a WS must grab a token 2) There is only one token 802.8 - fiber optic network called FDDI (Fiber Distributed Data Interface) 802.10 Network sec 802.11 Wireless (wifi) 802.15 WPAN 802.15.1 Bluetooth 802.15.3a,b Ultrawide bandwidth - IoT 802.15.4 Zigbee (IoT) 802.16 - Broadband wireless (WiMax) Bridge: a "switch" that converts 2 topologies signals. The middle man - is a translator; a bridge is a MAC-based device a) Baseband: Baseband network carriers only one type of signal b) Broadband system: carriers multiple types of signals c) Signal: a signal carriers a voltage light or wave notes: the # of signals/sec is called frequency Eg: 10 GHz d) Computer network with digital signal; to do so, we need an analog-to-digital or digital-to-analog converter Module ? (Lecture 5): Transmission Media Transmission Basics ○ Transmission techniques in use on today’s network are complex and varied  ○ This section covers Measurements that indicate network efficiency Obstacles to good network performance Structural cabling Throughput and Bandwidth ○ Bandwidth - The amount of data that could be theoretically transmitted during a given period of time ○ Throughput - Measure of how much data is actually transmitted during given time period ○ Both are commonly expressed as bits transmitted per second, called bit rate  File System is measured by Byte (8 bits, one character) Network Equipment in Commercial Buildings ○ One of the main tasks of an infrastructure administrator is to identify the best practices for managing networks and cabling equipment in commercial buildings and work areas  ○ We need to understand issues related to managing power and the environment in which networking equipment operates as well as troubleshoot network devices ○ Structural Cabling - Most organizations follow a cabling standard Popular standar is TIA/EIA’s joint 568 commercial building wiring standard, AKA: structured cabling, for uniform, enterprise-wide, multivendor cabling system Structural Cabling ○ Structural cabling includes the following components Entrance facilities MDF (Main Distribution Frame) Cross-connect facilities IDF (Intermediate distribution frame) Backbone wiring Telecommunication closet Horizontal wiring Work area Cable Management ○ Recommendation Do not exceed the cable’s prescribed bend radius (fiber optic) Use a cable tester to verify that each cable segment transmit data reliably Avoid laying cables across a floor and use cord covers if they must be exposed Avoid electromagnetic interference (EMI) PAy attention to grounding requirements Leave some slack in cable runs Use patch panels to organize and connect lines Keep your cable plant documents accessible Label every data jack or port, patch panel, and connector Use colour-coded cables for different purposes Update your documentation as you make changes to the network  Monitoring the Environment and Security ○ Data rooms are often serviced by heating, ventilation, and air conditioning (HVAC) systems separate from the rest of the building ○ Specialized products can monitor the critical factors of data closet’s environment: Unacceptable temperature Humidity Airflow conditions ○ Every data room should be locked with only limited IT personnel having keys Cameras are suggested Transmission Flaw ○ Noise: Any undesirable influence degrading or distorting signal Measured in dB (decibels) ○ Type of noise EMI (electromagnetic interference): Caused by motors, power lines, tv, copiers, fluorescent lights, etc One type of EMI is RFI (radio frequency interference) ○ Cross-talk Signal on one wire infringes on adjacent wire signal Alien cross-talk occurs between two cables Near end cross-talk (NEXT) occurs near source Far end cross-talk (FEXT) occurs at the far end ○ Attenuation Loss of signal’s strength as it travels away from source ○ Signals can be boosted: Repeater - Regenerates a digital signal in its original form Without noise previously accumulated Repeater is a physical layer device  ○ Latency: Delay between signal transmission and receipt May cause network transmission errors ○ Latency causes: Cable length Intervening connectivity device ○ Round trip time (RTT) Time for packet to go from sender to receiver, then back from receiver to sender ○ If packets experience varying amounts of delay: They can arrive out of order A problem commonly called jitter or PDV (packet delay variation) Baseband and Broadband ○ Baseband: is a transmission form in which (typically) digital signals are sent through direct current (DC) pulses applied to the wire. The direct current requires exclusive use of the wires capacity As a result, baseband systems can transmit only one signal, or one channel, at a time Every device on a baseband system share the same channel ○ Broadband: Form of transmission in which signals are modulated as radio frequency (RF) analog waves that use different frequency ranges Broadband is used to bring cable TV to your home Broadband systems can span longer distances than baseband While a baseband system can only carry one type of signal, the broadband systems can carry multiple types of signals simultaneously (eg: cable TV) Modulation ○ The process of embedding data signal into carrier signal (for transmission purposes) called modulation Modulation is done at the sender side ○ Process of separating data signal from a carrier signal (at receiver side) is called demodulation Demodulation is done at the receiver side ○ A device capable of modulation and demodulation is called a modem  Session Communication ○ Session communication via media ○ Full-duplex - called duplex Signals travel in both directions over a medium simultaneously ○ Half-duplex Signals may travel in both directions but only in one direction at a time Eg: walkie-talkie ○ Simplex Signals may travel in only one direction and is sometimes called one-way or unidirectional, communication Eg: FM Radio Multiplexing ○ Multiplexing A form of transmissions that allows multiple signals to travel simultaneously over one medium ○ Subchannels Logical multiple smaller channels ○ Multiplexer (MUX) Combines many channel signals Required at the transmitting end of the channel ○ Demultiplexer (DEMUX) Separates the combined signals Module 6 (Lecture 5): Wireless Networking Characteristics of wireless transmissions ○ Wireless networks (WLANs) are networks that transmit signals through the air via RF (radio frequency) waves ○ Wired and wireless signals share many similarities including use of the same layer 3 and higher protocols ○ Nature of the atmosphere makes wireless transmission different from wired transmission Wireless Spectrum ○ Wireless spectrum - is the frequency range of electromagnetic waves used for data and voice communications Wireless spectrum spans frequency ranges or bands between 9 kHz and 300 GHz ○ RFID (Radio Frequency Identification) uses electromagnetic fields to store data on a small chip in an RFID tag, which includes an antenna that can transmit and receive, and possibly a battery  RFID is commonly used for inventory management ○ NFC (near-field communication) - is a form of RFID that transfers data wirelessly over very short distances Singlas can be transmitted one way by an NFC tag or smart tag NFC tag collects power from the smartphone or other device by magnetic induction ○ Z-Waves - Smart home protocol that provides two basic functions Signaling to manage wireless connections and control to transmit data and commands between devices A Z-wave network controller (called a hub) receives commands from a smartphone or computer and relays the commands to various smart devices on its network ○ Zigbee - Is a low-powered , battery-conserving wireless technology Designed to handle small amount of data Zigbee is used in IoT devices for purposes such as building automation, HVAC control, AMR (automatic meter reading) and fleet management ○ Bluetooth - Technology unites separate entities under single communication standard Hops between frequencies within that band to help reduce interference Most bluetooth devices requires close proximity to form connection, with the exact distance requirements depending on the class of bluetooth devices ○ Ant+ - technology based on the ANT protocol, which is an ad-hoc wireless protocol operating at 2.4 Ghz ANT+ gathers and tracks info from sensors embedded in heart rate monitors, GPS, and other activity monitoring devices Can also sync data from multiple devices for the same activity Eg: smartwatches, smartphone ○ IR (infrared) - Technology used to collect data through various sensors Exists just below spectrum viable to the human eye IR sensors are used to collect info such as: Pr