Networking Basics CCNA 1 Chapter 2. Networking Fundamentals

Networking Basics and Terminology A Brief History of Networking Universe Earliest commercial computers were large mainframes, run by computer scientists Terminals were invented, allowing users to interact with the computers Eventually (1960s), some terminals were located to allow remote access

Networking Basics and Terminology A Brief History of Networking Universe By late 1960s minicomputers entered marketplace “Mini’s” were smaller, less powerful and less expensive than mainframes Mid 1970s – First personal computers (PCs) built by researchers

Networking Basics and Terminology A Brief History of Networking Universe 1977 – Apple introduces the Apple-II 1981 – IBM introduces its first PC Mid 1980s – Computer users with standalone computers start sharing data through the use of modems connecting to another computer (dialup, point-to-point)

Networking Basics and Terminology The Need for Networking Protocols and Standards 1960s to 1980s – Each vendor set its own protocols and standards Equipment from different vendors would not interoperate Eventually, open standards were agreed upon Open standards allow more competition, which increases speed of development

Networking Basics and Terminology Popular Network Standards Organizations

Networking Basics and Terminology Ethernet LANs and LAN Devices The networking protocol used in most modern computer networks is Ethernet. Ethernet LANs originally used coaxial cable (similar to Cable TV cable) Network Interface Cards (NICs) would attach to a length of cable called a segment. A segment is also a section of a network separated by bridges, switches, and routers.

Networking Basics and Terminology Ethernet LANs and LAN Devices In early Ethernet LANs, all devices sent their data on one wire All other devices on the segment received the signal These types of Ethernet are said to be “broadcast” media, because any signal sent by one device is received by all other devices

Networking Basics and Terminology Characteristics of Early Ethernet LANs Limited to a relatively small geographic area Allows multiple devices access to high-speed media Administrative control rests within a single company Provides full-time connectivity Typically connects devices that are close together

Networking Basics and Terminology Cisco Networking Device Icons

Networking Basics and Terminology Ethernet Repeaters When a signal is sent over a wire, it degrades 10BASE5 limited a single segment to 500 meters; 10BASE2 to a little less than 200 meters (185 meters) – hence their names (the 5 and the 2; the 10 is for 10Mbps) To extend the distance of LANs, repeaters were developed

Networking Basics and Terminology Features of Ethernet Repeaters Typically had two ports connecting two different Ethernet segments Interpreted the incoming signal on one port as 1’s and 0’s Sent a regenerated clean signal out the other port

Networking Basics and Terminology Repeated Ethernet Signal

Networking Basics and Terminology Ethernet Hubs and 10BASE-T Coax cables were expensive and difficult to work with – led to the creation of 10BASE-T If the cable broke, everyone on the LAN had problems – led to the creation of hubs

Networking Basics and Terminology 10BASE-T with a Hub – Star Topology

Networking Basics and Terminology Functions of a Hub Connects multiple twisted pair Ethernet devices together to form a single network segment Provides RJ-45 jacks so cables with RJ-45 connectors can be attached Repeats any incoming signal out all other ports Was originally called a “multiport repeater”

Networking Basics and Terminology Ethernet Bridges Examine incoming signal, interpret signal as 0’s and 1’s, find the destination MAC address listed in the frame If destination MAC address is reachable via a different interface than the one on which it was received, then clean, regenerate and forward the frame out that interface Otherwise, discard the frame (this is called “filtering”). Bridges interconnect two segments together and isolate broadcast within each of them.

Networking Basics and Terminology A Bridge Making a Filtering Decision 0 2 1

Networking Basics and Terminology A Bridge Making a Forwarding Decision

Networking Basics and Terminology Bridging Table – Expiration Counter The source MAC address is stored into the bridge table as soon as a host talks (transmits a data packet) on the LAN. The MAC address entries stored in a bridge table are temporary. Each MAC address entry to the bridge table remains active as long as there is periodic data traffic activity from that host on its port.

Networking Basics and Terminology Bridging Table – Expiration Counter (cont.) An entry into the table is deleted if the port becomes inactive. In other words, the entries stored into the table will have a limited lifetime. An expiration timer will commence once the MAC address is entered into the bridge table. The lifetime for the entry is renewed by new data traffic by the computer and the MAC address is re-entered.

Networking Basics and Terminology Broadcast & Ethernet Bridge Excessive amounts of broadcasts being forwarded by the bridge can lead to a broadcast storm resulting in degraded network performance in terms of a network slowdown. For example, the broadcast associated with an ARP will appear on all hosts connected within the bridged LANs. All networking devices (e.g., computers) contain an ARP cache (arp –a), temporary storage of MAC addresses recently contacted.

Networking Basics and Terminology Ethernet Frames An Ethernet frame is the data sent by an Ethernet NIC or interface The first bits sent are the header; contains info such as the destination and source MAC addresses Includes headers from other protocols, such as IP

Networking Basics and Terminology Conceptual View of an Ethernet Frame

Networking Basics and Terminology LAN Switches Like a hub, a switch provides a large number of ports/jacks to plug in cables When forwarding a frame, the switch regenerates a clean signal Like bridges, switches use the same filtering/forwarding logic on a per-port basis

Networking Basics and Terminology The switching table of a switch is known as the Content Addressable Memory. The MAC address and port information remain in CAM as long as the device connected to the switch port remains active. Switches limit the amount of time address and port information are stored in CAM. This is called aging time.

Networking Basics and Terminology A switch = a multiport bridge The use of the switch enables simultaneous direct data connections for multiple pairs of hosts connected to the network. Each switch connection provides a link with minimal collisions and therefore maximum use of the LAN’s bandwidth.

Hub-Switch Comparison – a lab exercise The objective of this experiment was to show that data traffic is isolated with a switch but not with a hub. The objective of this experiment was to show that data traffic is isolated with a switch but not with a hub. For this experiment, a LAN using a hub and a LAN using a switch were assembled. For this experiment, a LAN using a hub and a LAN using a switch were assembled. Each LAN contains four computers connected in a star topology. Each LAN contains four computers connected in a star topology.

Computer 1 pinged computer 3. Computer 1 pinged computer 3. Computer 1 was used to capture the LAN data traffic using the Surveyor Demo protocol analyzer software. Computer 1 was used to capture the LAN data traffic using the Surveyor Demo protocol analyzer software. What are the expected results? What are the expected results?

Again, computer 1 pinged computer 3. Again, computer 1 pinged computer 3. Computer 2 was used to capture the LAN data traffic using the Surveyor Demo protocol analyzer software. Computer 2 was used to capture the LAN data traffic using the Surveyor Demo protocol analyzer software. What are the expected results? Remember, a hub is a multiport repeater and all data traffic input to the hub is passed on to all hosts connected to its ports. What are the expected results? Remember, a hub is a multiport repeater and all data traffic input to the hub is passed on to all hosts connected to its ports.

This time using a switch to interconnect the computers instead of a hub. This time using a switch to interconnect the computers instead of a hub. The same experiment was repeated: computer 1 pinged computer 3 and computer 2 was used to capture the LAN data traffic. The same experiment was repeated: computer 1 pinged computer 3 and computer 2 was used to capture the LAN data traffic.

Hub – Switch Comparison The results of this experiment show that the use of the switch reduces unnecessary data traffic in the LAN. The results of this experiment show that the use of the switch reduces unnecessary data traffic in the LAN. The experiment shows that the broadcast associated with an ARP request is seen by all computers but not the ARP replies in a LAN using a switch. This is because a direct data connection is established between the two hosts. The experiment shows that the broadcast associated with an ARP request is seen by all computers but not the ARP replies in a LAN using a switch. This is because a direct data connection is established between the two hosts. The advantage of using switches is true for all data transfers e.g. file transfers, image downloads, file printing, and so on). The data traffic is isolated from other computers on the LAN. The advantage of using switches is true for all data transfers e.g. file transfers, image downloads, file printing, and so on). The data traffic is isolated from other computers on the LAN.

Networking Basics and Terminology Wide-Area Networks (WANs) Cover a large geographic area WAN Technologies: –Modems –Integrated Services Digital Network (ISDN) –Digital Subscribe Line (DSL) –Frame Relay –T1 or E1 leased lines – T1, E1, T3, E3, etc. –Synchronous Optical Network (SONET) – synchronous transport Level 1(STS-1) optical carrier [OC]-1, STS-3 (OC-3), etc.

Networking Basics and Terminology Point-to-Point Leased Lines (Private Circuits) A point-to-point leased line extends between two locations (LANs) The line is not owned by the user; it is leased from a service provider The service provider is often a telephone company Often, the term link is used to describe a point-to- point leased line Increasingly being used by companies instead of the Internet because they afford faster data transfer rates and are cost-effective for heavy users of the Internet.

Networking Basics and Terminology Leased lines are drawn like lightning bolts

Networking Basics and Terminology Routers and Their Use with LANs Routers are the perfect device to connect a LAN to a WAN Routers perform a basic but very important forwarding process in which they receive data packets and then forward the packets toward the destination Routers can send and receive traffic on most any kind of physical networking media

Networking Basics and Terminology Metropolitan Area Networks (MANs) A medium-sized network, perhaps city- wide Usually very high speed Optical media used between routers can move data at 10 Gbps or even 40 Gbps

Networking Basics and Terminology High-Speed City-Wide MAN

Networking Basics and Terminology Storage-Area Networks (SANs) A SAN is a dedicated, high-performance network that moves data between servers and storage resources. Because it is dedicated, a SAN avoids any traffic conflict between clients and servers and relieves any problems associated with existing network connectivity.

Networking Basics and Terminology Typical SAN Used by a Server Farm

Networking Basics and Terminology Storage-Area Networks (SANs) Features of SANs: –Performance: SANs enable concurrent access to disk or tape arrays by two or more servers at high speed, providing enhanced system performance. –Availability: SANs have disaster tolerance built in, which can back up data to offsite locations up to 10 km away. –Scalability: Like a LAN/WAN, a SAN can use a variety of technologies. This allows easy relocation of backup data, operations, file migration, and data replication between systems

Networking Basics and Terminology Virtual Private Networks (VPNs) A VPN is a private network that is constructed within a public network infrastructure such as the global Internet. Companies can use the Internet to send data between sites, instead of using leased lines –For example, a telecommuter can access the company’s headquater’s network through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the headquater.

Networking Basics and Terminology Virtual Private Networks (VPNs) Packets are encrypted before they leave for the Internet Often less expensive than leased lines VPNs are the most cost-effective method of establishing a point-to-point connection between remote users and an enterprise network. Can be less secure than leased lines

Networking Basics and Terminology Virtual Private Networks (VPNs)

Networking Basics and Terminology Physical Network Topologies

Networking Basics and Terminology Physical Bus Topology 10BASE2 and 10BASE5 use a bus topology Looks like a city street where each of the computers is a bus stop A frame sent by one device is received by all other devices – broadcast

Networking Basics and Terminology Physical Star Topology 10BASE-T Ethernet connects with a hub The hub is the device at the center, so it resembles a start The actual physical layout of the cable may not be in a star pattern

Networking Basics and Terminology Logical Bus Topology “Logical” refers to how the network operates, not where the cables run 10BASE-T is a logical bus, because all devices see any signal sent by other devices on the network – broadcast

Networking Basics and Terminology Physical versus Logical Topology Physical Topology – The topology is determined by the physical layout of the cabling and transmission media Logical Topology – The topology is determined by the media access control logic and how the devices collectively send traffic over the network

Networking Basics and Terminology Typical Modern LAN and Its Similarities to a Star Topology