Unit A - Connecting to the Network 1 What is a network? The ability to connect people and equipment no matter where they are in the world. telephone computers television How does your body work as a network? 2
Networking and Its Benefits A CONVERGED NETWORK!!! 3 Networking and Its Benefits SOHO Network Small Office/Home Office sharing of resources Internet Printer 4
Networking and Its Benefits Schools, Corporations Internet 5 Networking and Its Benefits Define the components of an Information network Hosts PCs send and receive information across the network connected to a network device Peripherals not directly connected to the network, but connected to hosts Network devices hub, switch, router Network media used to connect hosts/devices 6
Networking and Its Benefits Clients and servers software installed determines the role of a client or a server Server software enables the server to provide information to other hosts Client software enables the client to request and display information from the server Example: Internet Explorer 7 Networking and Its Benefits Build computer peer-to-peer network and verify The ability to act as both a client and server 8
Network Topologies Physical topology created to record where each host is on the network shows how each host is connected (media, devices, etc) 9 Network Topologies Logical topology how the host uses the network host names, addresses, groups, applications 10
Communication Protocols Primary purpose of a network to communicate Elements of communication Sender (source) has a need to communicate Receiver (destination) receives message and interprets it Channel pathway for information to travel 11 Successful delivery of the message Rules (protocols) must be followed: Identification of the sender and/or receiver Channel in which to communicate (face-to-face) Mode of communication (written or spoken) Language Grammar Speed or timing 12
Communication Protocols Encoding vs. Decoding Encoding Humans converting thoughts into language, symbols, or sounds Computers Decoding messages converted into bits by the sending host each bit encoded into sound, light, or electrical impulses destination host then decodes the signal reverse of encoding 13 Communication Protocols Message formatting and encapsulation Message needs a specific format Compare to parts of a letter Identifier (recipient) Salutation Message Closing Identifier (sender) Encapsulation placing the letter into the envelope De encapsulation letter removed from the envelope 14
Communication Protocols Messages have size restrictions depending on the channel used If the message is broken into smaller pieces, it is easier to understand If the message is too long or too short, will be considered undeliverable. 15 Communication Protocols Timing when to speak; how fast or how slow how long to wait for a response Access Method determines when someone is able to send a message can speak when no one else is talking, otherwise a COLLISON occurs Flow Control timing for negotiations sender might transmit messages faster than the user can handle Response Timeout how long should you wait for a response and what action to take Acknowledgment may be required to ensure message was delivered 16
Communication Protocols Message Patterns Unicast single destination Multicast same message to a group Broadcast all hosts need to receive the message 17 Communication Protocols PROTOCOLS = RULES TO FOLLOW 18
Communication Across a Local Ethernet Network Computers must speak the same language in order to communicate!! 19 Standards in technology Standards rules by which equipment from different vendors operate Benefits of standards: Facilitate design Simplify product development Promote competition Provide consistency Facilitate training More vendor choices for customers 20
Communication Across a Local Ethernet Network IEEE (Institute of Electrical and Electronic Engineers) maintains networking standards 802.3 Ethernet standard A breakdown of terminology 100 Base-T 100 = Speed in Mbps Base = Baseband transmission T = Twisted Pair 21 Communication Across a Local Ethernet Network Physical addressing MAC address (Media Access Control) Ethernet communication each interface has a MAC address each device may look at the data that has been transmitted, but only the interface that matches the destination MAC will respond 22
MAC Addresses by another Name Other names for a MAC address include: physical address hardware address Ethernet address burned-in address data-link layer address (7-layer model) Layer 2 address (of 7-layer model) 23 The Ethernet Frame Preamble beginning of the timing SFD (Start Frame Delimiter) marks the end of the timing, but beginning of the frame Destination MAC Source MAC Length/Type Length tells which protocol receives the data Type number of bytes of data Encapsulation packet of information FCS (Frame Check Sequence) used to check for damaged frames 46-1500 24
Example Ethernet Type Values EtherType value of 0x0800 signals that the frame contains an IPv4 frame. EtherType of 0x0806 indicates an ARP frame EtherType of 0x8100 indicates an IEEE 802.1Q frame -Used with Virtual Lans (vlans) EtherType of 0x86DD indicates an IPv6 frame. 25 Cisco 3-layer Networking Model Cisco has defined a hierarchical model known as the hierarchical internetworking model. This model simplifies the task of building a reliable, scalable, and less expensive hierarchical internetwork because rather than focusing on packet construction, it focuses on the three functional areas, or layers, of your network: Access Distribution Core 26
3-layer Networking Model Core layer: This layer is considered the backbone of the network and includes the high-end switches and high-speed cables such as fiber cables. This layer of the network does not route traffic at the LAN. In addition, no packet manipulation is done by devices in this layer. Rather, this layer is concerned with speed and ensures reliable delivery of packets. Distribution layer: This layer includes LAN-based routers and layer 3 switches. This layer ensures that packets are properly routed between subnets and VLANs in your enterprise. This layer is also called the Workgroup layer. Access layer: This layer includes hubs and switches. This layer is also called the desktop layer because it focuses on connecting client nodes, such as workstations to the network. This layer ensures that packets are delivered to end user computers. 27 The Hierarchical Design Structure (3-layer model) Smaller, more manageable groups allow traffic to remain local on the networks Divided into three layers Access Layer connection to the hosts Distribution Layer interconnects smaller networks Core Layer high speed connection between distribution devices (high-speed backbone > internet) 28
29 Logical Addressing MAC vs. IP IP Address (Logical Address) assigned based on where the host is located assigned by the administrator Parts of an IP address (Network and Host parts) Network same for all hosts connected to the LAN Host unique to each host on the network 30
Access Layer Devices Most basic level Made up of: host devices first line of networking devices hub, switch, workstations Hub or switch 31 Access Layer Device A HUB Accepts data signal from one port and sends it (regenerates) out all other ports multiport repeater Collisions results in message being garbled and unreadable occur when two or more hosts send a message at the same time (undesirable in a network) NOT VERY SMART a hub will not recognize there is a collision and sends it to all ports 32
Hubs And Collision Domains Collision domain area where the collision has occurred. More collision domains = better performance How many collision domains exist in the graphic shown? 33 Access Layer Device A SWITCH SMARTER THAN A HUB dedicated bandwidth out each port no need to share with other ports (unlike a hub) Can forward messages to a specific host by looking in its MAC table If destination MAC is not in its MAC table, floods the network out all ports looking for a response Only the host with the correct MAC address will respond 34
More Stuff on Switches How does the MAC table get built? keeps track of frames being sent between hosts records the information when there is a response -records the source MAC address of frames received Collision Domains each port on a switch is its own collision domain 8 port switch = 8 collision domains 35 Broadcasts If there is only one destination MAC in a message, how can you contact everyone else? send a broadcast MAC hexidecimal digits FFFF.FFFF.FFFF (FF:FF:FF:FF:FF:FF) Useful when hosts need to send information but doesn't know what hosts are to receive it Switches and hubs send the broadcast out to everyone on their network. (Broadcast Domain) 36
ARP Request Sent when the sending host knows the destination IP, but not the MAC Will discover the MAC address of any local host on the network 37 Distribution Layer Devices and Communication Methods Responsible for making sure local traffic stays local on the network Traffic destined for other networks will be passed on. 38
Distribution Layer Devices The Router Routers directs traffic based on the destination IP address Routers build routing tables; switches build MAC tables Routers decode packets; switches decode frames Routers look at only the network portion of the IP address finds the best path to take to get to the destination Routers do not forward broadcasts!!! 39 Default Gateway Used when a host wants to send data to a host on a different network. Must be set on the workstation connected to the routing device the router interface connected to the PC 40
Routing Tables and ARP tables Used by routers to store information The diagram to the right shows two networks connected together via a router. The router maintains an ARP table and ROUTING table with information similar to the tables shown above. 41 Types of Routing Dynamic information is obtained from neighboring routers Static manually entered by the network administrator What happens to a message that contains an IP destination address that does not exist in the routing table? It is dropped unless... A default route is set last resort type of router will send it to the router it thinks may have the destination IP 42
Distribution Layer Devices and Communication Methods LAN Local Area Network Under the same administrative control 43 Plan, Implement and Verify a Local Network Consider the following before beginning: Number and type of hosts Applications to be run on the network Data and devices to be shared Speed requirements (bandwidth) Level of security Reliability of the network Connectivity requirements 44
Building the Network Physical environment temperature control availability/placement of outlets Physical configuration location of devices how are devices connected location/length of cable runs hardware configurations (hosts, servers) Logical configuration size of broadcast & collision domains IP addressing scheme Naming Permissions Sharing 45 Multifunction Devices Integrated routers Linksys wireless router problem = single point of failure Cisco Integrated Services Router (ISR) performs services of three different devices router switch wireless access point 46
Implement and Document the Network Develop a prototype tests network design 47 Sharing Resources Main reason for networking sharing resources File sharing Print sharing Consider this before sharing: security issues permissions granted Windows XP and Windows 7 users use Simple File Sharing (default) 48
Simple file sharing in Windows 7 It is pretty easy and common It is to be used to share file/folder with other users that use Windows XP, Vista or 7 in the same workgroup. Other users are allowed to access the shared file/folder without doing authentication with username and password, and so we call it simple file sharing. However, please don t enable this simple file sharing when your computer is connected to public network (at library, airport, restaurant, etc), because the other public users can also access the shared file/folder without authentication after you have enabled it. It s not safe! 49 Summary Information networks carry data using hosts as clients, servers, or both. All computer communication involves a source, destination, and channel. Rules called protocols govern computer communications. Larger networks are divided into smaller, more manageable ones using a layered hierarchical design. Each network host needs both a physical MAC address and a logical IP address. Good network design requires a network plan. 50