Networking

Other Network Schemes

• WINS • You might encounter • Was a microsoft version of TCP/IP for local networks • Based on NETBIOS • Not really used anymore since microsoft windows now fully supports TCP/IP • Netbios • Another service to allow computers to talk to each other over ethernet (and other mediums) • You might now see "netbios over TCP/IP" • Large organizations, businesses • IBM - netbui

Common Network Devices

• Wired Adapters • USB, PCIe • Up to 10 Gpbs • Wireless Adapters • USB, PCIe • Switches • Gateway/Firewall • Routers • Switch + gateway • Wireless Access Points • VOIP • Range Extenders/Bridges • NAS - network attached storage • Cameras

Folder Sharing

• You have files and folders on your computer that you want to make available to others on the network • 'Right-click' and click 'share' • Select specific users, everyone or homegroup • Select read only or read write permissions

Range and Speed

• You only get the rated speed at close distances with no walls and no interference • The farther the distance -> the slower the speed • Walls, furniture, objects affect range/speed • Some other devices interfere with wifi • Cordless phones • Microwave Ovens • Speed is continually auto-negotiated • Other wireless devices cause congestion • Wireless devices using the same access point • Other wireless access points • There are multiple channels but selection is not always automatic • Drops to 1Mbps or so before dropping completely

Share Names

• \\DSMITH3-PC visible on network • Should be able to go to file explorer look under network • The directory is visible

Star and Tree Topology

• Star Network • Better reliability, if wire fails only one node affected • Central node can broadcast to all other nodes or route to specific nodes • Limited Connections at the central hub • Most home networks resemble this • Tree Network • Nodes can talk to other nodes at the same level plus one node up and one node down • Multiple hops required to traverse the tree but it's better than the ring • Simultaneous conversations possible within the tree • Sophisticated home and business networks use this

IP Address Details

• Subnet Masks • Mechanism to separate the network address from the host computer address • A typical subnet mask is 255.255.255.0

Accessing Remote Computers

• Telnet • SSH • Putty • WinSCP • Remote Desktop • VNC • VPN

Tiers and Backbones

• Tier 1 Provider • High bandwidth between major nodes • Tier 2 • Major ISP (internet service provider) • Tier 3 • Smaller ISPs

Internet Topics

• Tiers and Backbones • Internet Connection Methods • Browser Security • Services and Programs

WEP and WPA2

• WEP (wired equivalent privacy) • Superseded by WPA • Older wireless networking equipment may only support WEP • Passkey used to generate a 40 or 64 bit encryption key • Can be cracked in about one minute with available tools • WPA2 • "WPA" was an early version, WPA2 now standard, some older equipment may only support WPA • 256 bit key (64 hex or 8 to 63 ASCII characters) • AES preferred over TKIP encryption algorithm • Short passphrases (less than 13 characters) susceptible to cracking • Wi-Fi Protected Setup • A simpler method for sharing/using passphrases • "push a button" or share a short PIN • Recently found to be breakable

Before we look at the details, let's look at how computers are connected

Bus Network • Only one node transmits at a time • Other nodes receive • Not very efficient but each node is adjacent to all other nodes • If a wire breaks => no network • Ring Network • Nodes can transmit simultaneously but only in one direction • Multiple hops required for one node to talk to another node • For large rings, nodes can be very far apart - require many hops • If a wire breaks => network fails

Network Organization A network typically isn't just a bunch of computers shouting at each other

Client/Server • A central computer acts as a resource for the client computer • The server stores files, handles computing tasks, serves as a gateway to the internet and other computers • Sharing is typically done between the server and client - not between clients • The router or home gateway in your home network is actually a computer running embdded linux and acting as a server • Peer to Peer • No central resource, sharing is peer to peer • There is a hub or switch buried in there but for networking

How do Computers "talk" to each other?

Email, files, data...

Services and Programs

HTTPS • Encrypts/decrypts packets between your browser and the server • Suggested on open wireless and public networks • FTP • A method for transferring files between computer and server or other computer • Filezilla or WINSCP • Telnet • Remote login to another computer (Superseded by SSH and other secure terminal methods - Putty) • VOIP (voice over IP) - telephone service • If you have phone service via cable company - it's actually VOIP • VPN (virtual private network) • Remote Desktop

Drive Mapping

Network Names Use the name reported during network discovery Use the local IP address for example \\192.168.1.25\Public

Powerline Networking

Up to 500 Mbps Older versions typically 5-10 Mpbs (not quite enough for HD video streaming) Newer versions typically 30-50 Mpbs

Common Network Devices

Wireless Routers Adapters Range Extenders Powerline Switches Firewalls Access Points Modems NAS VoIP Video

Typical home network

computer, phone jack, Cat5e Cable inside the wall,Wall plate 4 ethernet jacks, ethernet switch, cable or dsl modem, internet

Domain Names and Web Addresses

• "http://" means this is a web page request • As opposed to an FTP or email request • Names can have subdomains • www.example.com - routes to the server handling webpages • Mail.example.com - routes to the server handling mail • Up to 127 levels • TLDs or Top Level Domains • The rightmost label doesn't resolve to a computer server • Maps to a "root" zone • Used to be .com, .gov, .org and the various country domains .uk, .jp... • Many more now

Ethernet Frame

• 62 bits- Preamble used for bit synchronization • 2 bits- Start of Frame Delimiter • 48 bits- Destination Ethernet Address • 48 bits- Source Ethernet Address • 16 bits- Length or type • 46 - 1500 bytes- Data • 32 bits- Frame Check Sequence

NICs put out Frames or Packets

• A frame is like a addressed envelope

HomeGroup

• A home network feature offered by Microsoft • "easier" sharing among computers • Set a homegroup password and join • Standard directories are shared • If you can't see another computer on the network, it's often because that computer isn't part of the home group

Protocols Next Level Up

• Assembling Packets into meaningful things • Files, video streams, graphics streams.... • More meaningful computer names/addresses • Besides the physical MAC address • At the Operating System Level • TCP/IP • Transmission control protocol/Internet Protocol • It defines how data is formatted, addressed, transmitted and received between computers

DCHP and you

• DHCP from your broadband internet provider • Nearly always dynamic for consumers • It's a globally visible IP address - available to the entire internet • In practice it rarely changes but no guarantee so you can't attach a domain • Your internet router/gateway (or PC if directly attached) will automatically get an IP address from the provider's DHCP server • Businesses can pay extra for a static IP • You'll generally be given the numbers by the provider and you program into whatever router is being used • Sometimes the provider supplies the router hardware pre-programmed • DHCP inside your home/business • Typically you don't care what IP your router gives you • You may want fixed IP addresses for printers or other servers • Your router will let you specify a range for it's DHCP server • You can then manually assign a static IP (within your 192.168 subnet) to your resource and not worry about it being overriden by the DHCP server

Internet Connection Methods

• Dialup (analog modem and ISDN modem) • Dedicated • DSL • Runs with your regular phone line • Effective distance is at most 2 or 3 miles from the switching office or DLSAM • Upload/Download speeds ~ 1Mpbs/3Mbps • Cable • Shared with neighbors up to the service gateway • LAN (leased line) • Dedicated phone wires + routers/gateways • Fiber to the Home • Wireless • Wimax • Cellular • Long Range WiFi

Windows to/from Linux

• Difficult to view windows shares from linux • Possible with ubuntu • Easier to share folders hosted on a linux machine with windows computers • Samba • Client • Server

IPv4 Addresses

• Dotted-decimal notation example: 202.34.16.11 • Four fields - 32 bits total • Each field is 0 to 255 (one byte) • Separated into the address of a network and the address of a computer(host) • Address Classes - class A, B, C (and D & E) • Originally divided the internet up into big companies, medium companies, and other categories • Classless Inter-Domain Routing more recent way to organize IP addresses • IPv6 • IPv4 is running out of addresses • IPv6 uses 128 bits plus has various other new features • Most devices IPv6 capable but it's slowly being rolled out • It's there but your system may or may not be using it

Ports under TCP/IP

• Each computer with an address has 0 to 64K ports • Think of your house address as an IP address • A port is a door - front, back, side, garage.... • Visitors go to the front door • Deliveries to the back door • Cars to the garage door • TCP/IP Services are associated with specific ports • HTTP - web pages port 80 • Email - port 57 • Several hundred others

SSH & FTP

• Encryption • Authentication • FTP - file transfer protocol • Way to get/put files across a network

DNS and internet names

• Every connected device has an IP address • IP addresses are hard to remember • Web Addresses were invented • Domain Name System(Service) • Maps names to IP addresses • DNS is like a phone directory • Thirteen root nameservers hold the directory of names to IP addresses • Lots of sub-root nameservers and alternates • Anycast actually forwards requests to any one of several computer servers using the same root nameserver IP • Updated daily/hourly from domain name registrations and other sources • Your computer only needs to know the IP address of the nameserver • My home system has a DNS server of 75.75.75.75 (cndns01.comcast.net) • It passes the web address 'cnn.com' and gets back 157.166.255.19 • Sends a web page request to 157.166.255.19

How Does Data get From One Place to Another One Theory?

• Every device has a "network interface card" or NIC (pronounced 'nick') • Discrete Card • IC's on a motherboard • Wireless Interface • Every NIC has a MAC address • 'Media Access Control' • The 'Media' is the wire • Device controls access to the wire • Unique address for every NIC device in the universe • Form -> XX-XX-XX-XX-XX-XX

Home Network

• Everything downstream from the cable modem is ethernet • A different networking protocol is used to get to the ISP and internet though • Still a high speed serial interface • Packets/frames • A star topology • The home gateway has an ethernet switch • The switch has wired and wireless NICs • The switch keeps track of all connected devices via their MAC addresses

Mike's Four-Layer Model for troubleshooting

• First check hardware • Cables plugged in, activity and link lights • Cards installed properly (physically and drivers) • Protocols • Look for any problems with TCP/IP configurations • Check driver settings • Check IP addresses, gateways, dns settings • Network • Check other network resources • Is the router responding?, can you get to the internet?, use ping • Shared Resources • Check homegroup settings/password • Check sharing options

Router Control Panel

• From my home router • Automatically obtain IP address from provider • My external IP address is 67.171.161.140 • Can ping from anywhere in the world • My subnet mask is 255.255.240.0 • The network address is 1000011.10101011.1010 • Host computer address is 0001.10001100 • Gateway is 67.171.160.1 • That's where the router sends it's internet destined packets • Two DNS lookup hosts • 75.75.75.75 • 75.75.76.76

Details, Details Things you'll run into..

• Full Duplex vs Half Duplex • Some older NICs run half duplex • Half duplex -> means the NIC can't send and receive at the same time • MultiSpeed • Most NICs automatically negotiate with the NIC on the other end and test the capability of the wire • Some don't autonegotiate • Link Lights • One light to show a valid connection with the NIC on the other end (color often indicates speed) • One light to show activity

Fiber Optic Networking

• Further and more bandwidth • Light and electrons move at the same speed but... • Fiber immune to noise, static, magnetic effects • Twisted pair has a practical limit of 100 meters between NICs • Signals on fiber can go 2000 meters • Multimode Fiber • Multiple light signals

Sharing in Windows/linux

• Homegroup • Network • Public vs work vs home networks • Network discovery • SMB - sever message block • "SAMBA" - open source version • Firewall/router boundaries • Active Directory - windows servers

Topology

• How computers in a network are connected together Physical Topology • The physical wires and physical arrangements of computers

Wireless Ethernet

• IEEE 802.11 wireless ethernet standard • Present on phones, TVs, computers, touchpads, refrigerators,...... • Same packets, same client model as wired ethernet • Really just the physical layer (layer 1) is different • Radio signals instead of signals on twisted pair wiring • Physical Layer uses CSMA (collision sense and media access) • Receiver listens for other radios transmitting • Collision sense then back-off • Modes • Ad-hoc • Peer to peer • No wireless router needed • Infrastructure • WAP - wireless access point

Other Networking Systems

• IrDA • Older systems and some smartphones used infrared to communicate • Bluetooth • There is a networking protocol that supports PAN (personal area network) • Not meant for heavy duty • Cellular • Wireless USB • NFC (near field communication

TCP/IP Layers

• Link Layer - Ethernet • Internet Layer (IP) • Every connected device has an address • Transport Layer (TCP) - how data is exchanged • Application Layer • HTTP for example - how web pages work

Network Troubleshooting

• Loopback Testing • Need a loopback plug and diagnostic software (often available from the manufacturer) • You can buy or make the loopback plug • Tests the NIC hardware and the jack • Bad Cable • Use a cable tester • Plug/Unplug • Fixes many hiccups by forcing the hardware/software to reset and go through link, network discovery, DHCP... • Virus • Many computer viruses affect network connectivity

LAN

• MAC address • Private Network • 192.168.1.1 • Subnet only allows 255 clients • No gateway or local DNS

DHCP Dynamic Host Configuration Protocol

• MAC addresses are fixed to the device • IP addresses are above the MAC address and must be assigned • Static IP Addresses • You manually assign an unique IP address to each and every machine on a network • Can't have conflicts • Doesn't change • Dynamic IP address • A DHCP server keeps an IP table and assigns IP addresses • When you connect a computer to a network: • The computer sends a broadcast using port 67 across the network • The DHCP server responds with a "lease offer" • Your computer accepts the lease offer and sets the IP address and gets the gateway and DNS IP addresses • A lease is guaranteed for a length of time, when expired, the computer must ask again for an IP address

OSI seven layer model

• Mentioned in lecture for completeness • A good thing to memorize for the comptia exam or any data communications course • Very common when studying advanced networking and communications • Important to know • Physical is layer 1 - bits, wires, radio signals • Datalink is layer 2 - MAC addresses • Network is layer 3 - Packets, IP addresses • Transport is layer 4 - TCP, flow control, segmentation • Layers 5-7 are strictly software • Mike's four-layer model makes more practical sense for debugging

Installation and Configuration

• Most NICs are on the motherboard, not cards • You can add additional ethernet ports with PCI/PCIe cards • Not common, needs special configuration • Turns your computer into a router • Installation/Configuration is nearly automatic these days • Sometimes you may need a specific driver to be installed • TCP/IP is nearly automatic • Show TCP/IP configuration • "Not Connected" • 169.254.x.y • You have an IP address but it doesn't go anywhere

Wired Ethernet

• Most common networking standard in homes and businesses • Speeds • 10BaseT - 10 Mbps (IEEE 802.3i) • 100BaseT - 100 Mbps (IEEE 802.3u) • 1000BaseT - 1 Gbps (IEEE 802.3z) • 10GBaseT - 10 Gbps (IEEE 802.3an) • Other speeds/standards over fiber optic cables and other media • Star Configuration • Each wire has only one NIC at each end • NOT a bus topology • Older ethernet over coax cables was a bus topology • A hub or switch has multiple NICs inside • One for each port

Establishing a Link

• NICs get connected with a cable • "link" signals are sent back and forth • NICs recognize each other • MAC addresses are exchanged • Speeds are negotiated • Link is "UP"

Wires

• Network Cabling is manufactured to standards • CAT1 - simple phone wire • CAT3 - rarely seen anymore, used for 10 Mbps • CAT5 - common, for 100 Mbps • CAT5e - most common, for 1 Gbps • CAT6 - new installs, rated to 10 Gbps (Cat6a) • Wire is unshielded • Sometimes see shielded twisted pair in noisy areas • RJ45 is the standard connector • Cable Assembly • 4 pairs of wires per cable • Wires and connectors are color coded • The connector box comes with a color code chart

Wireless Security

• Open Mode • The default for many public wireless network is "open" • No authentication required to login to the wireless access point • Data can be "sniffed" with a commonly available program • Packet Encryption • WPA & WEP encrypt packets • Eavesdropper can't decrypt without key

Wifi Standards

• Other devices (phones, microwaves) interfere with 2.4 Ghz, 5Ghz is cleaner • Except for 802.11a devices, newer devices backwards compatible • Clear range is without walls/furniture/people/plants in the way • Some wifi vendors add technology for greater range/speed but only with that vendor's family of products • You'll get the standard compatibility at the regular speed/distance

Peer to Peer

• Peer to Peer • No central resource • Sharing is peer to peer • There is a hub or switch buried in there but for networking only • Windows Limitations • Practically limited to 15 peer to peer computers • Microsoft provides "workgroups" to organize computers

Linux Permissions

• Permissions apply to directories or folders • Need to know for sharing • Share folder should have permissions to allow "guests" or "others" to read/write files • "Public" directories

Windows TCP/IP tools

• Ping • Send a packet to the IP address or web address • Tells you if the computer on the other end is alive and connected • Tracert • Gives you the path through the routers • Not that useful to the average tech but interesting • Ipconfig • Your computer's settings • Tells you if you have a connection and your gateway is working • Nslookup • Maps internet names to IP addresses • Web based tools • www.network-tools.com + many, many others

Routers, switches and bridges

• Router • Receives and forwards data packets for multiple ports/devices • Routers range from the home wireless/wired router to backbone routers for the internet • Routers have tables and rules for routing IP addresses and ports • NAT (network address translation) • Takes your packet meant for the internet • Sends it out under it's IP address • Gets the response back and figures out which computer on your network to send it to • Typical SOHO (small office/home) switches • Layer 2 - learns the MAC addresses of attached devices and only forwards packets destined for those MAC addresses • A SOHO router includes switch functionality • Bridge (not that common anymore) • Layer 1 - also called a hub - repeats all packets to all ports

Security

• SSID broadcasting • Your router broadcasts "service set identifier" beacon • Google streetview cars and others collect SSIDs • You can turn it off so other systems don't know you are there • MAC address filtering • Set your wireless router to only accept certain MAC addresses • Have to know all MAC IDs of computers you want to connect • WEP • Packets are encrypted in transit • "breakable" • WPA - wi-fi protected access • WPA2 is standard • Authentication and encryption • Radius and other security methods

Even Lower Level At the Physical Layer or Wire

• Serial Interface over a pair of wires • Full Duplex • Transmit Wires • Receive Wires • '1's and '0's are sent • Assembled back into bytes • Bandwidth up to 10 Gbps (gigabits per second) for twisted pair wires • Higher for fiber optic links

Domain Based Networks

• Similar to client/server but much more controlled • Domain Controller provides services • Login to the network, not just the client computer • Security Policies • System names and policies • Directory services • PCC network (lab + office computers) are organized this way

Mesh Network

• Some or all computer nodes connected to each other • Redundancy - if one wire breaks there's always another path • Speed - in a full mesh, each node is one hop away from other node • Simultaneous conversations between all nodes • The global internet looks more like this

Map Network Drive

• Sometimes the other PC isn't visible under network • You want to assign a drive letter • Use "map network drive" • Type the name in and pick a drive letter

IP address Details

• Special Addresses • 127.0.0.1 - always interpreted by the computer as loopback to itself • Multicast and test addresses • Network Translation or Private Address • A gateway or router has a globally distinct IP address • Like the front door of a high rise apartment building • Computers behind the gateway have unique IP addresses within that private subnet • 10.0.0.0 to 10.255.255.255 -- large organizations (PCC) • 172.16.0.0 to 172.31.255.255 -- medium companies • 192.168.0.0 to 192.168.255.255 - individuals, small organizations • Private addresses are not globally unique • Example is your home network behind your router/gateway • Computers on your network have an address of 192.168.1.1 • Everyone's home network uses the same address behind their routers