1.1 Networking Overview PDF

1.1.1 Networking Concepts A network is two or more computer systems that are linked by a transmissio medium and share one or more protocols that enable them to exchange dat can think of any network in terms of nodes and links. The nodes are devices send, receive, and forward data, and the links are...

1.1.1 Networking Concepts A network is two or more computer systems that are linked by a transmissio medium and share one or more protocols that enable them to exchange dat can think of any network in terms of nodes and links. The nodes are devices send, receive, and forward data, and the links are the communications pathw between them. There are two general kinds of nodes: intermediate nodes and end systems Intermediate nodes perform a forwarding function, while end system nodes those that send and receive data traffic. End systems are often also referred hosts. Client-Server vs. Peer-to-Peer Networks End system nodes can be classified as either clients or servers: A server makes network applications and resources available to other A client consumes the services provided by servers. A client-server network is one where some nodes, such as PCs, laptops, and smartphones, act mostly as clients. The servers are more powerful compute Application services and resources are centrally provisioned, managed, and A peer-to-peer network is one where each host acts as both client and serve a decentralized model where provision, management, and security of servic data are distributed around the network. A small peer-to-peer network can a referred to as a workgroup. Business and enterprise networks are typically client-server, while residentia networks are more often peer-to-peer. However, note that in a client-server often, hosts will function as both clients and servers at the same time. For ex computer hosting a web application acts as a server to browser clients but is client of database services running on other server computers. It is the cent administered nature of the network that really defines it as client-server. Appliances, Applications, and Functions You can also think of a network as having appliances, applications, and func Appliances—Networks make use of many types of specialized platfor Unlike general-purpose Windows or macOS computers and servers, a appliance is a computer with an operating system and software desig perform a particular network role. Examples of these roles include the switches, routers, and wireless access points that forward data, the fir and intrusion detection systems that enforce security rules, and the lo balancers and proxies that improve network performance. An appliance can be deployed as physical hardware, meaning that the app OS/software runs on its own CPU, memory, storage, and network interfaces possible to deploy virtual appliances. This means that the appliance OS is d as a virtual machine running on a hypervisor computing platform. The same hypervisor computer could run multiple virtual appliances. Applications—The nodes and links of networking infrastructure are d to run services. Services are shared applications that allow the networ useful work, such as sharing files or allowing employees to send ema Functions—Networks can be configured with additional properties to different functions. For example, the security properties of a virtual pr network allow devices to join a local network from across the Internet another example, quality of service functionality allows optimization o network to suit a particularly time-sensitive application, such as voice Copyright © The Computing Technology Industry Association, Inc. All rights reserved. 1.1.2 Network Types A network type refers primarily to its size and scope. The size of a network c measured as the number of nodes, while the scope refers to the area over w nodes sharing the same network address are distributed. Local Area Networks A local area network (LAN) is confined to a single geographical location. In all nodes and segments are directly connected with cables or short-range w technologies. Most of the network infrastructure in a LAN would be directly and managed by a single organization. Some examples of LANs include the following: Home/residential network—With an Internet router and a few comp plus mobile devices, gaming consoles, and printers. Small office/home office (SOHO) network—A business-oriented net possibly using a centralized server in addition to client devices and pr but often still using a single Internet router/switch/access point to pro connectivity. Small and medium-sized enterprise (SME) Network—A network su dozens of users. Such networks would use structured cabling and mu switches and routers to provide connectivity. Enterprise LAN—A larger network with hundreds or thousands of se clients. Such networks would require multiple enterprise-class switch router appliances to maintain performance levels. Datacenter—A network that hosts only servers and storage, not end client devices. Wide Area Networks  A wide area network (WAN) is a network of networks, connected by long-d links. A typical enterprise WAN would connect a main office site with multipl office sites, possibly in different countries. A WAN could link two or more lar or could be used for remote workers connecting to an enterprise network v public network such as the Internet. WAN links are also used to connect data to one another. WANs are likely to use leased network devices and links, ope and managed by a service provider. Copyright © The Computing Technology Industry Association, Inc. All rights reserved. 1.1.3 Network Topology Where the type defines the network scope, the topology describes the phys logical structure of the network in terms of nodes and links. A network's physical topology describes the placement of nodes and how th connected by the transmission media. For example, in one network, nodes m directly connected via a single cable; in another network, each node might c to a switching appliance via separate cables. These two networks have differ physical topologies. The logical topology describes the flow of data through the network. For exa given the different physical network topologies described previously, if in ea the nodes can send messages to one another, the logical topology is the sam different physical implementations—directly connected via a cable versus co to the same switch—achieve the same logical layout. In the simplest type of topology, a single link is established between two no is called a point to point link. Because only two devices share the connectio are guaranteed a level of bandwidth.  Description The steps are as follows. 1. In a point-to-point (or duplex) network, only two nodes are connected the network media. 2. When the network media is half-duplex, a node cannot transmit and receive at the same time. 3. When the network media is full-duplex, nodes can transmit and receiv simultaneously. Physical point to point topologies using different media types for half-duplex duplex communications. A point to point link can be a physical or logical topology. For example, on a two router appliances might be physically linked via multiple intermediate n and physical devices but still share a logical point to point link, where each c address only the other router. With either a physical or logical topology, it is relationship that defines a point to point link. Copyright © The Computing Technology Industry Association, Inc. All rights reserved. 1.1.4 Star Topology In a star topology each endpoint node is connected to a central forwarding appliance, such as a switch or router. The central node mediates communica between the endpoints. The star topology is the most widely used physical t For example, a typical SOHO network is based around a single Internet rout appliance that clients can connect to with a cable or wirelessly. The star topo easy to reconfigure and easy to troubleshoot because all data goes through point, which can be used to monitor and manage the network. Faults are automatically isolated to the media, node (network card), or the switch, rout wireless access point at the center of the star. Description The steps are as follows. 1.In a star topology, each node is connected to a concentrator over dedicated network media. 2.When a node transmits, the signal is sent over the network media to t concentrator.  3.The concentrator forwards signals to other nodes. It may do this by repeating the signal to all nodes, working as logical bus topology (implemented as an Ethernet hub). 4.More commonly, the concentrator tracks node addresses and selectiv switches communication paths to establish point-to-point links. 5.The concentrator is a single point of failure. Also each node must be w the media’s maximum transmission distance of the concentrator or mus use a repeater to overcome the distance limitation. Star topologies using different types of concentrators. You may also encounter the hub-and-spoke topology, which has the same p layout as a star topology but is primarily used in a different context. While th topology is often seen in local area networks (LANs), the hub-and-spoke top more commonly applied to wide area networks (WANs) with remote sites. Copyright © The Computing Technology Industry Association, Inc. All rights reserved. 1.1.5 Mesh Topology A mesh topology is commonly used in WANs, especially public networks su Internet. A full mesh network requires that each device has a point to point every other device on the network. This approach is normally impractical, ho The number of links required by a full mesh is expressed as n(n–1)/2, where number of nodes. For example, a network of just four nodes would require s while a network of 40 nodes would need 780 links! Consequently, a hybrid a is often used, with only the most important devices interconnected in the m perhaps with extra links for fault tolerance and redundancy. This type of top referred to as a partial mesh. Description The steps are as follows. 1.In a fully connected mesh network, each node has a point-to-point lin with every other node. This requires exponentially more link as nodes a added: n times (n minus 1) over 2.  2.Provisioning so many interface and link is difficult, so partial mesh networks are often preferred, in a partial mesh, nodes can forward pack to a destination by learning the network topology. 3.Packets can take multiple routes through the network, providing resili if some nodes or links fail. Fully connected and partial mesh topology examples. Mesh networks provide excellent redundancy, because other routes, via inte devices, are available between locations if a link failure occurs. Copyright © The Computing Technology Industry Association, Inc. All rights reserved. 1.1.6 Legacy Topologies Most modern networks use the star topology due to its reliability and scalab However, there are two legacy topologies that you should still be familiar wi bus topology and the ring topology. Although these topologies may no long widespread use, you will still often find them in legacy systems or in specific situations. Bus Topology A bus topology consists of a trunk cable with nodes either inserted directly i trunk or tapped into the trunk using offshoot cables called drop cables. A de called a terminator is placed at both ends of the trunk cable. Their purpose is absorb signals, preventing them from reflecting repeatedly back and forth o cable. Signals travel from one node to all other nodes. The major downside bus topology is that a broken cable anywhere on the bus breaks the termina prevents communications between all devices on the network. This can mak difficult to isolate cabling problems. Bus Topology Ring Topology A ring topology connects neighboring nodes until they form a ring or a circle travel in one direction around the ring, with each device on the network acti repeater to send the signal to the next device. Because a continuous ring is the installation of this topology requires careful planning. A node malfunctio cable break can prevent signals from reaching nodes beyond the malfunctio  interconnectedness can cause difficulties with problem isolation, requiring t troubleshooter to check several physical locations along the ring. Ring Topology Copyright © The Computing Technology Industry Association, Inc. All rights reserved.