Transcript hosts
3: Connecting to the Network Networking for Home & Small Business What’s a Network? • Make a phone call, watching TV, radio, Internet, Gaming – All depend on a reliable network • Group of connected devices able to communicate with each other Networks Basic Network Components • 4 categories of components – Hosts – Shared peripherals – Networking devices – Networking media Hosts – They send & receive data – Have an IP Address Shared Peripherals – Shared devices that ARE connected to a host – Print Sharing Networking devices • Interconnect hosts • Move & control traffic Networking media • Connects Devices Activity Handout • Complete Client-Server • Hosts have an IP Address • Can act as a client or server – Server provides services to other hosts – One server can provide many services – Clients request & display info from servers Popular Client-Server Network • World of Warcraft • Players from all over the world connect & play Peer-to-Peer Networks • One computer can sometimes act as the server & the client • Simplest: 2 connected devices – Uses a crossover cable • Multiple PC’s connect with a hub Peer-to-Peer Networks • Large businesses have lots of traffic – Dedicated servers to handle requests Famous Peer-to-Peer • LimeWire – Exchanging MP3’s with another device Client, Server, or Both Physical Topology • Layout/Map of network • Shows where each host is located, wiring, network devices Logical Topology • Groups hosts by how they use the network – Not physical location • Host names, addresses, group info & applications can be recorded Lab 3.1.5 • Building a Peer-to-Peer Network Review • What does SOHO stand for? – Small office home office • What interconnects hosts & controls traffic? – Network devices • Which cable connects 2 PC’s together? – Crossover cable • Hosts are devices that have what? – IP Addresses • Describe client-server. End of Part 1 Principles of Communication • The Message • Source or Sender • Destination or Receiver • Channel or Pathway • Protocol or Rules Human Communication • What are our rules of communication? Protocols • Rules of Communication over a medium • Protocols define the details of how the message is transmitted, and delivered. • This includes issues of: Message Encoding • Encoding • • Thoughts into words Proper encoding for that medium • • Light, electricity, or radio waves Destination will decode the message Encapsulation • Putting a letter in an envelope • Encapsulated in a frame before sent over the network – The frame acts as the envelope – Has addresses of source and destination • If not formatted correctly, they will not be delivered! Handout • Complete Review • What 4 things do you need for communication? – Source, destination, channel, protocol • Describe encoding. – Bits into electricity, light, or radio waves • A message is encapsulated in what? – Frame • Which 2 address are in the frame? – Source & destination MAC address Message Size • You talk in sentences. – Length will vary depending on what can be processed or understood by the listener • Messages sent across networks are broken into smaller pieces – Size of a frame Message Timing • People use timing to determine when to speak, how fast or slow to talk, and how long to wait for a response. These are the rules of engagement. • Access Method • Flow Control • Response Timeout Message Timing • Access Method – When to begin sending & how to respond to errors – Collision if two talk at same time • Flow Control – Sender can transmit messages faster than the destination can receive & process – Use flow control to negotiate correct timing for successful communication • Response Timeout – How long to wait for responses & what to do Unicast Message Pattern • Unicast – 1 to 1 single message Multicast Message Pattern • Multicast – 1 to a group message Broadcast Message Pattern • Broadcast – 1 to all Activity Review • What is it called when one message format is placed in another message format? – Encapsulation • Bob is talking to Sally. Which type of message pattern is this? – Unicast • Which address is used in a frame? – MAC address (source & destination) Review • Which message is one to all? – Broadcast Importance of Protocols • Computers need rules to communicate • Local network devices MUST speak same language • Most common wired protocol is ETHERNET Early Days of Computing • Each vendor had their own rules • Standards had to be created Standardizing • IEEE maintains standards approvals – Assigned a # – 802.3 is Ethernet – 100Base-T • 100 megabit Ethernet • Baseband Transmission • Twisted Pair Cabling Physical Addressing • Remember encapsulating frames? – Source & destination address needed • Each host on Ethernet has a physical address (MAC Address) – Burned into NIC • NIC encapsulates source & dest. MAC • Host that receives frame reads dest. MAC – If it contains its own MAC, it will process it – If not, it ignores it Example Lab 3.3.3 • Determine the Mac Address • Ipconfig /all Ethernet Frame Structure • Frames are also called PDU’s – Protocol Data Units Activity Hierarchical Design Structure • MAC Address is like your name – Doesn’t tell where you are on the network – Not efficient by itself – Imagine if all hosts on Internet could only be identified by a MAC address • Ethernet is a broadcast technology – Sent to all in a network – Too much traffic & collisions • Separate into smaller networks Hierarchical in Life Hierarchical Design in Networks • Dividing your network into smaller groups or layers – Keeps local traffic local – Only data intended for other networks will move on to other layers • Access Layer – Provides connections to hosts in a local Ethernet network. • Distribution Layer – Interconnects the smaller local networks. • Core Layer – A high-speed connection between distribution layer devices. 3 Layer Model IP Addressing • Your name doesn’t change but where you live might – MAC stays on NIC – Doesn’t change no matter where you move • IP Address is like your address – It is logical, not physical • Needed to go beyond your network – Stay local or go elsewhere??? IP Addressing • 2 parts – Identify the network – Identify the host • Network portion is same for all devices on a local network • 209.120.5.72 IP Network Example Lab 3.3.6 • Determine the IP Address of the Computer • Let’s do this together • How do we find the IP Address through the command prompt? – Ipconfig /all • Why is an IP address important? Handout • 3 Layer Model & Addressing Activity Review 1. What is the process of placing one format into another (like a letter into an envelope to be sent in the mail)? – Encapsulation 2. Which device is typically at the Distribution Layer? – Router 3. When a PC receives a message, which address is used to determine if it for that PC? – Destination MAC Review 1. Which organization creates & maintains the standards? – IEEE – Why? 2. A frame contains which 2 addresses? – Source & Destination MAC 3. What does FCS stand for & what does it do? – Frame Check Sequence, checks for errors Hubs • At Access Layer • Simple Device (DUMB) – Message in one port, out all others – Does not send to specific device – Sends one message at a time • • • • Collisions can occur They wait for silence, & then resend randomly Too many collisions slow the network Keep these collision domains SMALL Pictures of Hubs Hub Example Hub & Collision Domain Handout • Hubs Switches • Access Layer • Connects multiple hosts like a hub – Forwards a message to a specific host! – Reads the destination MAC • Has a MAC address table – Ports & MAC addresses on them • Creates a virtual circuit to destination • No bandwidth sharing between hosts • No collisions! How a switch works More about Switches… • What if destination MAC is NOT in the table? – Floods message out all ports, except one it came in on – Compare the destination MAC in frame – Correct one processes the message Switch Table • How does the switch add the MAC address to its table? – It examines the source MAC & port it came in on – When it responds to a message, it adds it • Updates table for every message Example • Go to Slide 3.4.3-2 • Look at example What else about Switches? • Hub attached to switch port scenario • Separate collision domains for each switch port Switch Handout Review 1. Hubs & Switches are at which design layer? – Access Layer 2. Which device creates a virtual circuit from the source to destination? – Switch 3. Which device sends data in one port & out all ports regardless of the destination? – Hub Review 1. Which address does a NIC read when deciding if the message is for itself? – Destination MAC 2. In 100Base-T, what does the 100 mean? – 100Mbps – How about the T? • Twisted Pair Cabling 3. If a switch receives a frame & doesn’t have the dest. MAC in its table, what happens? – Floods it out all ports, except one it came in on Broadcasts • One host can send messages to all other LOCAL hosts – Find info from others – Tell others something • One destination MAC in a frame only – There’s a special MAC address that all hosts will receive & process – 48 bits, all binary 1’s – In hexadecimal, FF:FF:FF:FF:FF:FF • Look at 3.4.4 Broadcast Domain • Too many hosts in a domain, causes traffic backup – This is why you divide into smaller LAN’s Let’s Practice Together • Slide 3.4.5 MAC & IP • What if you want to send data, but only know their IP address and not their MAC? – ARP (Address Resolution Protocol) ARP • Host sends out a broadcast frame w/ the IP address of the destination host – FF:FF:FF:FF:FF:FF • Each host receives & compares the IP address to see if it is their own • Matching host sends its MAC address back to source • Source then adds it to its ARP table • Then it can send the message ARP Example ARP Example Review 1. A broadcast frame contains which MAC address? – All F’s 2. How many bits is a MAC address? – 48 3. Describe a broadcast 4. What separates broadcasts? Distribution Layer • Separates & connects your small networks – Connects your Access Layer networks – Can filter traffic & provide security Routers • Distribution Layer • Connects different local networks • Reads the packet encaps. in frame – Destination IP Address (network portion) – Subnet Mask • Finds best path to that destination network Routers- The Path… • Each port connects a different local network • Rips open to find destination IP • Looks in Routing Table – In the table: • Encapsulates in new frame • Sends it out port towards or connected to that destination • Routers DO NOT forward broadcasts! Path Example- H1 to H4 Default Gateway • When sending a message on your local network you use ARP to find dest. MAC • When sending a message on another network – You encapsulate: • • • • • • Source IP Source MAC Destination IP You don’t know the destination MAC! So you include the MAC of the router port! Router will receive & process this MAC, BUT NOT THE ARP MAC broadcast! Default Gateway • This IP is set in TCP/IP settings • Router port that your host connects to- same local network – If the host knows the IP, it will use ARP to find out the MAC address on router port – Example on next slide Default Gateway Default Gateway Lab • Complete 3.5.3-2 Routing Tables • Networks & best path to reach them • Knows this info by: – Dynamically learned from other routers – Manually entered by admin • No route in table? – Drop it OR – Default Route is set by admin Routing Tables Where does data go? • Directly to the network destined for • To another router • When router forwards the frame, it MUST include a destination MAC – If it is connected, it will use the dest MAC from its ARP table – If not, it will sub MAC address of connected router’s port • ARP table for each port/local network Look at… • 3.5.4.2 • 3.5.4.3 activity LAN • Network over a small area – Under one administration – Router will separate How many local networks? Adding hosts to a LAN • Advantages/Disadvantages? Adding hosts to a LAN • Advantages/Disadvantages? Planning a Network • Ethernet is most popular • Planning is key! • First, gather this info: – The number & type of hosts to be connected – The applications to be used – Sharing & Internet connectivity requirements – Security & privacy considerations – Reliability & uptime expectations – Connectivity requirements including, wired and wireless Plan & Document • Maps of topology • Physical environment – Temperature – Power • Physical configuration – Location of network devices – Length of cables – Hardware config • Logical Configuration – Broadcast & collision domains – IP & Naming Scheme Physical Topology • How many broadcast, collision & networks? Review 1. Describe a default gateway. 2. Each router port has an _______ table that hold the MAC addresses of devices connected to each port. – ARP 3. Which one device will separate or segment a network? – Router 4. Describe a routing table. Multifunction Devices • Integrated Routers – Usually for SOHO – Switch/router/access point in one – Single point of failure • Cisco ISR – Separate components to add/replace Linksys Linksys Connecting the Linksys • All connected to switch ports MUST be in same IP network to communicate • Display IP configuration settings – Ipconfig – Ipconfig /all Lab • 3.6.4 Sharing Resources • XP has simple file sharing – You can set more specific – Full Control – Modify – Read & Execute – List Folder Contents – Read – Write • Look at 3.6.5 3: Connecting to the Network Networking for Home & Small Business