Study up: A look at architecture from a CompTIA Network+ perspective
A new version, (N10-006), of the popular CompTIA Network+ certification exam will be released soon. Last month, we looked at the security domain of the new exam. This month we will look at the topic of network architecture as it relates to that exam: It is the second-most heavily weighted domain of five (constituting 22 percent of the total exam).
General N10-006 Observations
When creating objectives for the new exam, CompTIA took the existing topics and added to them (subtracting some outdated technologies), but they also did a crazy thing. They moved a lot of the topics that were on the N10-005 exam around into unexpected places. As a result of this, Network Architecture, which is the very first domain on the exam, became a kind of catch-all. Yes, it covers topologies, the cloud, network devices and other topics you would expect to find here, but it also covers specific technologies like DHCP and DNS, has all the wiring possibilities here, and throws in IP addressing (4 and 6) as well.
In short, don’t get fooled by the 22 percent weighting. You really need to know everything under this domain and will see much of it appear over and over in other domains as you study for this exam. In other words, you need to shift your Network+ perspective. If you don’t know the topics here, you will find it very difficult (next to impossible) to pass the exam.
What You Need To Know
The following discussion is intended to represent a study guide for this domain. It does not include every topic (space will not allow for that), but it covers most of the main topics. In coming months, we will look at some of the other domains and a few of those not touched upon here will be covered down the road in an attempt to reduce redundancy as much as possible.
Most of the bullets and tables are very straightforward but if you don’t understand any of the subjects, you would be well-advised to research them further. You should also keep in mind that CompTIA recommends candidates for this certification have CompTIA A+ certification (or equivalent knowledge) and 9 to 12 months of work experience in IT networking.
● A LAN is a data network that is restricted to a single geographic location and typically encompasses a relatively small area, such as an office building or school. The function of the LAN is to interconnect workstation computers for the purpose of sharing files and resources.
● A WAN is a network that spans more than one geographic location, often connecting separated LANs. WANs are slower than LANs and often require additional and costly hardware such as routers, dedicated leased lines, and complicated implementation procedures.
● Cisco has created architecture that can look at the different types of media available and the application types and make a choice about what the best combination to use is. Known as a Medianet, this can be useful with video teleconferencing (VTC) and is often used with SIP (Session Initiation Protocol), which runs over IP, and associated with ISDN.
● The role of the client computer in the client/server model is to request the data from the server and present that data to the users.
● A topology refers to a network’s physical and logical layout. A network’s physical topology refers to the actual layout of the computer cables and other network devices. A network’s logical topology refers to the way in which the network appears to the devices that use it.
● Wireless networks typically are implemented using one of two wireless topologies: infrastructure (managed, wireless topology), or ad hoc (unmanaged, wireless topology).
● The term hybrid topology also can refer to the combination of wireless and wired networks, but often just refers to the combination of physical networks.
Table 1: Network Devices Summary
|Hub||Connects devices on an Ethernet twisted-pair network||A hub does not perform any tasks besides signal regeneration.|
|Switch||Connects devices on a twisted-pair network||A switch forwards data to its destination by using the MAC address embedded in each packet.|
|Router||Connects networks||A router uses the software-configured network address to make forwarding decisions.|
|Modem||Provides serial communication capabilities across phone lines||Modems modulate the digital signal into analog at the sending end and perform the reverse function at the receiving end.|
|Firewall||Provides controlled data access between networks||Firewalls can be hardware- or software-based. They are an essential part of a network’s security strategy.|
|Multilayer switch||Functions as a switch or router||Operates on Layers 2 and 3 of the OSI model as a switch and can perform router functionality.|
|Content switch||Forwards data by application||Content switches can identify and forward data by its port and application.|
|Load balancer||Distributes network load||Load balancing increases redundancy and performance by distributing the load to multiple servers.|
|Packet shaper||Manages network bandwidth||The shaper monitors and controls bandwidth usage.|
|VPN concentrator||Increases remote-access security||Establishes a secure connection (tunnel) between the sending and receiving network devices.|
|Access Point||Used to create a wireless LAN and to extend a wired network||Use the wireless infrastructure network mode to provide a connection point between WLANs and a wired Ethernet LAN.|
|HIDS||Host-based intrusion detection||Monitors the host, analyzes data and identifies intrusion attempts|
|IDS/IPS||Detects and prevents intrusions||Monitors the network and attempts to detect and/or prevent intrusion attempts|
● An IDS can detect malware or other dangerous traffic that may pass undetected by the firewall. Most IDSs can detect potentially dangerous content by its signature.
● An IPS is a network device that continually scans the network, looking for inappropriate activity. It can shut down any potential threats.
● A VPN extends a LAN by establishing a remote connection, a connection tunnel, using a public network such as the Internet.
● PPTP creates a secure tunnel between two points on a network, over which other connectivity protocols, such as PPP, can be used. This tunneling functionality is the basis for VPNs.
● VPNs are created and managed by using protocols such as PPTP and L2TP, which build on the functionality of PPP. This makes it possible to create dedicated point-to-point tunnels through a public network such as the Internet. Currently, the two most common techniques for creating VPNs.
● Terminal Access Controller Access Control System+ (TACACS+) is a security protocol designed to provide centralized validation of users who are attempting to gain access to a router or Network Access Server (NAS).
● In a network that does not use DHCP, you need to watch for duplicate IP addresses that prevent a user from logging on to the network.
Table 2: Comparing WAN Technologies
|WAN Technology||Speed||Supported Media||Switching Method Used||Key Characteristics|
|ISDN||BRI: 64kbps to 128kbpsPRI: 64kbps to 1.5Mbps||Copper/fiber-optic||Can be used for circuit- switching or packet-switching connections||ISDN can be used to transmit all types of traffic, including voice, video, and data. BRI uses 2B+D channels; PRI uses 23B+D channels. B channels are 64kbps. ISDN uses the public network and requires dial-in access.|
|T-carrier (T1, T3)||T1: 1.544MbpsT3: 44.736Mbps||Copper/fiber-optic||Circuit switching||T-carrier is used to create point-to-point network connections for private networks.|
|ATM||1.544Mbps to 622Mbps||Copper/fiber-optic||Cell switching||ATM uses fixed cells that are 53 bytes long.|
|Frame Relay||56kbps to 1.544Mbps||Copper/fiber-optic||PVCs and SVCs||Frame Relay is a packet-oriented protocol, and it uses variable-length packets.|
|SONET/OCx||51.8Mbps to 2.4Gbps||Fiber-optic||N/A||SONET defines synchronous data transfer over optical cable.|
● Punchdown tools are used to attach twisted-pair network cable to connectors within a patch panel. Specifically, they connect twisted-pair wires to the insulation displacement connector (IDC).
● UTP cabling is classified by category. Categories 5/5e and 6/6a offer transmission distances of 100 meters.
● F-type connectors are used with coaxial cable, most commonly to connect cable modems and TVs. F-type connectors are a screw-type connector.
● SC, ST, LC, and MT-RJ connectors are associated with fiber cabling. ST connectors offer a twist-type attachment, and SC, LC, and MT-RJ connectors are push-on.
● RJ-45 connectors are used with UTP cable and are associated with networking applications. RJ-11 connectors are used with telephone cables.
● Plenum-rated cables are used to run cabling through walls or ceilings.
● The horizontal cabling extends from the telecommunications outlet, or network outlet with RJ-45 connectors, at the client end. It includes all cable from that outlet to the telecommunication room to the horizontal cross-connect.
● Vertical cable, or backbone cable, refers to the media used to connect telecommunication rooms, server rooms, and remote locations and offices.
Table 3: Selected DSL Speeds
|DSL Variation||Upload Speed*||Download Speed*|
*Speeds may vary greatly, depending on the technologies used and the quality of the connection.
● The bus network topology is also known as a linear bus because the computers in such a network are linked using a single cable called a trunk or backbone. If a terminator on a bus network is loose, data communications might be disrupted. Any other break in the cable will cause the entire network segment to fail.
● In a star configuration, all devices on the network connect to a central device, and this central device creates a single point of failure on the network.
● The wired mesh topology requires each computer on the network to be individually connected to every other device. This configuration provides maximum reliability and redundancy for the network.
● A wireless infrastructure network uses a centralized device known as a wireless access point (AP). Ad hoc wireless topologies are a peer-to-peer configuration and do not use a wireless access point.
Table 4: Twisted-Pair Cable Categories
|6||10/100/1000Mbps plus 10Gbps|
|6a||10Gbps and beyond networking|
● 568A and 568B are telecommunications standards from TIA and EIA that specify the pin arrangements for the RJ-45 connectors on UTP or STP cables. The number 568 refers to the order in which the wires within the cable are terminated and attached to the connector. Often referred to as T568A and T568B (for termination standard), they are quite similar; the difference is the order in which the pins are terminated. The signal is the same for both. Both are used for patch cords in an Ethernet network.
● A wire crimper is a tool that you use to attach media connectors to the ends of cables.
● Wire strippers come in a variety of shapes and sizes. Some are specifically designed to strip the outer sheathing from coaxial cable, and others are designed to work with UTP cable.
● Voltage event recorders are used to monitor the quality of power used on the network or by network hardware.
● Toner probes are used to locate cables hidden in floors, ceilings, or walls and to track cables from the patch panel to their destination.
● Protocol analyzers can be hardware- or software-based. Their primary function is to analyze network protocols such as TCP, UDP, HTTP, FTP, and more.
● A TDR is a device used to send a signal through a particular medium to check the cable’s continuity.
● An OTDR performs the same basic function as a wire media tester, but on optical media.
● Packet sniffers are either a hardware device or software that eavesdrop on transmissions that are traveling throughout the network.
● Throughput testers identify the rate of data delivery over a communication channel.
● Port scanners are a software-based utility. They are a security tool designed to search a network host for open ports on a TCP/IP-based network.
Table 5: IPv4Private Address Ranges
|Class||Address Range||Default Subnet Mask|
|A||10.0.0.0 to 10.255.255.255||255.0.0.0|
|B||172.16.0.0 to 172.31.255.255||255.255.0.0|
|C||192.168.0.0 to 192.168.255.255||255.255.255.0|
● A MAC address is a 6-byte hexadecimal address that allows a device to be uniquely identified on the network. A MAC address combines numbers and the letters A to F. An example of a MAC address is 00:D0:59:09:07:51.
● A Class A TCP/IP address uses only the first octet to represent the network portion, a Class B address uses two octets, and a Class C address uses three octets.
● Class A addresses span from 1 to 126, with a default subnet mask of 255.0.0.0.
● Class B addresses span from 128 to 191, with a default subnet mask of 255.255.0.0.
● Class C addresses span from 192 to 223, with a default subnet mask of 255.255.255.0.
● The 127 network ID is reserved for the IPv4 local loopback.
● NAT translates private network addresses into public network addresses.
● Subnetting is a process in which parts of the host ID portion of an IP address are used to create more network IDs.
● APIPA is a system used on Windows to automatically self-assign an IP address in the 169.x.x.x range in the absence of a DHCP server.
● DNS resolves hostnames to IP addresses.
● Port Address Translation (PAT) is a variation on NAT in which all systems on the LAN are translated into the same IP address but with different port number assignment.
● 6to4 is a tunneling technology, allowing IPv6 packets to be transmitted over an IPv4 network without having to create a complex tunnel. It is often used during the transition period when a network is being updated and is not intended to be a permanent solution. Its counterpart is 4to6.
● Teredo gives full IPv6 connectivity for IPv6-capable hosts, which are on the IPv4 Internet but lack direct native connection to an IPv6 network. Teredo can do this from behind network address translation (NAT) devices (such as home routers). One of the most popular Teredo implementations is Miredo; it is a client designed allow full IPv6 connectivity to systems that are strictly IPv4-based.
Table 6: Comparing IPv4 and IPv6
|Address Feature||IPv4 Address||IPv6 Address|
|Loopback address||127.0.0.1||0:0:0:0:0:0:0:1 (::1)|
|Network-wide addresses||IPv4 public address ranges||Global unicast IPv6 addresses|
|Private network addresses||10.0.0.0172.16.0.01922.214.171.124||Site-local address ranges (FEC0::)|
|Autoconfigured addresses||IPv4 automatic private IP addressing (169.254.0.0)||Link-local addresses of FE80:: prefix|
● Quality of Service (QoS) allows administrators to predict bandwidth use, monitor that use, and control it to ensure that bandwidth is available to applications that need it.
● A router that uses a link-state protocol differs from a router that uses a distance-vector protocol because it builds a map of the entire network and then holds that map in memory. Link-state protocols include Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS).
● Hops are the means by which distance-vector routing protocols determine the shortest way to reach a given destination. Each router constitutes one hop, so if a router is four hops away from another router, there are three routers, or hops, between itself and the destination.
● Routing Information Protocol version 2 (RIPv2) is a distance-vector routing protocol used for TCP/IP.
● The route add command adds a static route to the routing table. The route add command with the -p switch makes the static route persistent.
● Distance-vector routing protocols operate by having each router send updates about all the other routers it knows about to the routers directly connected to it.
● When you want the best of both worlds, distance vector and link state, you can turn to a hybrid protocol. A popular hybrid protocol is the Border Gateway Protocol (BGP).
● Default gateways are the means by which a device can access hosts on other networks for which it does not have a specifically configured route.
● The NIST (National Institute of Standards and Technology) defines three cloud computing service models: Software as a Service (SaaS); Platform as a Service (PaaS); and Infrastructure as a Service (IaaS).
● The NIST defines four possible cloud delivery models: private, public, community, and hybrid.
● Virtualization makes it possible to take a single physical device and make it appear as if it is a number of stand-alone entities.
● There two methods of virtualization implementation: Type I (known as bare metal) and Type II (known as hosted). Type I is independent of the operating system and boots before the OS while Type II is dependent on the operating system and cannot boot until the OS is up and it needs the OS to stay up so it can operate.
● The machine on which virtualization software is running is known as a host while the virtual machines are known as guests.
● A virtual switch works the same as a physical switch but allows multiple switches to exist on the same host, saving the implementation of additional hardware.
● A virtual firewall (VF) is either a network firewall service or an appliance running entirely within the virtualized environment. Regardless of which implementation, a virtual firewall serves the same purpose as a physical one: packet filtering and monitoring. The firewall can also run in a guest OS VM.
● In a virtual environment, shared storage can be done on SAN, NAS, etc., the virtual machine sees only a “physical disk”. With clustered storage, you can use multiple devices to increase performance.
● Switches introduce microsegmentation, by which each connected system effectively operates on its own dedicated network connection.
Table 7: Comparison of Switching Methods
|Switching Method||Pros||Cons||Key Features|
|Packet switching||Packets can be routed around network congestion. Packet switching makes efficient use of network bandwidth.||Packets can become lost while taking alternative routes to the destination. Messages are divided into packets that contain source and destination information.||The two types of packet switching are datagram and virtual circuit. Datagram packets are independently sent and can take different paths throughout the network. Virtual circuit uses a logical connection between the source and destination device.|
|Circuit switching||Offers a dedicated transmission channel that is reserved until it is disconnected.||Dedicated channels can cause delays because a channel is unavailable until one side disconnects. Uses a dedicated physical link between the sending and receiving devices.||Offers the capability of storing messages temporarily to reduce network congestion.|