CompTIA Network+ Certification Study Guide part 38 ppt

CHAPTER 7: TCP/IP and Routing 356 14. You have a main corporate location and several branch locations. All locations access the Internet through their own dedicated con- nections. What type of routing would you enable for this approach? A. None B. Dynamic C. Static D. Classless 15. You have been asked to set up a routed network within your com- pany. Your company routers are homogenous having standardized on Cisco. You want to set up the best routing solution within your company for this equipment. What routing protocol would you use? A. RIP B. OSPF C. IS-IS D. EIGRP 16. You have a DHCP server that is configured to have only 10 addresses available in the pool of addresses to be handed out. When a colleague tries to lease an IP address, he is unable to do so. In viewing the log, you see the following packets relating to his attempt to get an address. DHCPDiscover, DHCPOffer, DHCPRequest, DHCPNack. What might be the potential cause of the issue? A. The DHCP server is not running. B. The DHCP server handed out an IP address to your colleague. C. The DHCP server was unable to hand out an IP address to his system. D. The DHCP server is really a BootP server. SELF TEST QUICK ANSWER KEY A1. D2. C3. D4. A and D5. D6. B7. A8. B9. C10. B11. C12. C13. B14. D15. C16. 357 CHAPTER 8 EXAM OBJECTIVES IN THIS CHAPTER SWITCHING METHODS 358 WAN PROTOCOLS AND PROPERTIES 360 INTERNET ACCESS METHODS 368 INTRODUCTION In this chapter, we categorize wide area network (WAN) technology types and properties that you will see not only on the CompTIA Network+ (2009 edition) exam objectives but also in a large production environment. Most of these technologies and protocols are used often and you will need to know about them for the Network+ exam. Be familiar with the speeds, capacities, and the types of media used for each WAN technology covered. In this chapter, we discuss the specifics of several WAN protocols, including Frame Relay, E1/T1, digital subscriber line (DSL), cable modem, wireless, and satellite. After reading this chapter, you will also understand the basic charac- teristics of specific WAN technologies, such as how packet switching and circuit switching differ. What is a WAN? A WAN is a computer network covering a wide geographical area, includ- ing more than one remote location and typically a core network where all resources are kept. A WAN is common to any company doing business with remote sites that are connected via a network topology. The remote sites build on the core site and a WAN is born. Chapter 1 discussed the basics of WANs, and in this chapter, we discuss in a little deeper into how WANs Wide Area Networking 358 CHAPTER 8: Wide Area Networking operate and which types are the most commonly used. WANs may be created in different configurations, with the most common being some combination of public and private networks. When working within the realm of a public network, you are working with networks that are publicly accessed and most likely connected to the Internet. Internet Protocol Security (IPSec) and vir- tual private network (VPN) technologies allow you to build a WAN over the Internet. When working in the realm of private networks, you are working with networks that are accessed only by designated individuals. This means that you are most likely running a private access network using Frame Relay or Multiprotocol Label Switching (MPLS), or a similar technology, and not allowing access to anybody except the company paying for it. This means that the network users aren’t at the mercy of the public Internet, where you do not get a guarantee of delivery. SWITCHING METHODS When working with WANs, the operations you do are transparent to you, so you may be unaware of the underlying technology that gets data from one location to another. There are a number of methods by which data are processed through the network to get from point A to point B. WANs oper- ate within two types of switching methods: circuit switching and packet switching. Although almost all WAN protocols in use today are packet-switched, there are still some old networks out there using circuit-switching technol- ogies. Technologies such as X.25 and Frame Relay are always available – their connections are constant, so they do not have to be set up every time they are used. Packet-switching technologies are always available but circuit switching is not. Circuit switching requires a separate setup for each con- nection session – this is the biggest difference between these two types of switching methods. Test Day Tip A WAN is a data communication network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as tele- phone companies. WAN technologies generally function at the lower three layers of the Open Systems Interconnection (OSI) reference model: the physical layer, the data link layer, and the network layer. X.25 is a good example of a WAN technology that operates at all three layers, whereas Frame Relay only operates up to Layer 2. Switching Methods 359 Circuit Switching Circuit-switched networks are not always available, since connections have to be initiated before transmission can take place. This means that when you use technologies such as Integrated Services Digital Network (ISDN), you will find that the call must first be initiated (to set up the circuit) and then data can traverse it. Once completed, the circuit can be taken down. If a router at a site has to send data to another router at a remote site, the circuit is initiated (brought up and online for use). The switched circuit is initiated with the circuit number of the remote network. In the case of ISDN, the setup will use a service profile identifier (SPID) number, which is essentially a phone number that the router dials to initiate the circuit with the WAN switch. An example of a sample carrier network is shown in Figure 8.1. The cloud represents the carrier’s telecommunications network. Packet Switching Packet switching is the method of sending data from location to location on a WAN that is always available. There is no need to initiate a call to a WAN switch, as the connection is already up and running from the start. When you set the carrier’s link up (let’s use Frame Relay for this example), it stays up. The only time this link should drop is during scheduled outages, problems, and FIGURE 8.1 Viewing a Carrier Network. 360 CHAPTER 8: Wide Area Networking emergencies. Other than that, consider packet-switched networks to always be available. Some examples of packet-switching networks include Asynchronous Transfer Mode (ATM), Switched Multimegabit Data Service (SMDS), and X.25, to name a few. Packet-switched networks will also divide the transmitting data into packets, and each packet is sent individually from the source to the desti- nation. All packets are given sequence numbers so that they can all be put back together again in the right order at the destination. The benefit of this is that each packet can take a different route to get to its destination. Once there, the message will be recompiled and take its original form. Packet- switched networks are often shared. This doesn’t open you up to security issues, but it does open you up to bandwidth challenges. Just be aware that packet-switched networks are not the same as point-to-point private lines that provide dedicated bandwidth to the purchaser. Exam Warning The telephone service provided by your carrier is most likely based on a circuit-switching technology. Circuit switching is ideal when data must be transmitted quickly and must arrive in the same order in which it’s sent. Packet switching is the opposite of circuit switching. Packet switching is more efficient and robust, and it is commonly used for data that can withstand some delays in transmission. WAN PROTOCOLS AND PROPERTIES Now that you have reviewed the underlying concepts of the WAN and cov- ered some of the methods in which they transmit data, let’s take a good look at some of the technologies that make up the WAN. In this section, we dis- cuss the CompTIA Network+ (2009 edition) exam objectives based on WAN protocols and standards such as T carriers, ISDN, and Fiber Distributed Data Interface (FDDI). You must be able to understand and respond to ques- tions about the speeds, capacity, transmission media, and distance for the 2009 Network+ exam. T/E Carrier T1 lines have been around for a long time and are still very much in use today. The name T (Terrestrial) and the number following it denotes the type of line. If it is a T1, then it is a dedicated media connection supporting data rates of 1.544 Mbps. This speed is derived from 24 individual channels of 64 Kbps (only 23 are available for data transfer and network use). If it is a T3, the line can support data rates of approximately 43 Mbps, which is WAN Protocols and Properties 361 created with 672 channels of 64 Kbps. E1 and E3 lines are similar, but they are European-based, and J lines are used within Japanese carrier systems. For any Network+ technician in the field, it’s common to work with T1 and E1 lines very often. Users can also access just a fraction of the whole bandwidth, which would mean that you have leased lines with specific data rates. A T1 line, with its 24 individual channels, can be configured to carry voice or data traffic. Most telephone companies allow you to buy just some of these individual channels, known as fractional T1 access. T3 lines are used mainly by Internet service providers (ISPs) connecting to the Internet backbone, although many private companies have implemented T3 lines in some of their core networks and data centers. As stated earlier, an E1 line is similar to the North American T1 line. E1 is the European format for digital transmission and is similar to a T1 line, but has higher data transmission rates. E1 carries signals at 2 Mbps (32 channels at 64 Kbps, with two channels reserved for signaling and controlling). An E3 is the European equivalent to the T3, but the T3 has a higher data rate (E3 lines carry data at a rate of approximately 34.368 Mbps, usually rounded up to 35 Mbps). T1 channels are sometimes known as digital signal zeros (DS0s). In T-carrier systems, DS0 is a basic digital signaling rate of 64 Kbps, corresponding to the capacity of one voice or data channel. Twenty-four DS0s (24 × 64 Kbps) equal one DS1. A full T1 is equal to a DS1; a full T3 is equal to a DS3. Exam Warning Make sure you are familiar with the speeds of the T- and E-carrier links, as well as the number of channels that make up a T1. T3 lines are faster than T1 lines because they have more bandwidth. Use common sense on the exam when determining which has a higher capacity. A T3 has a higher capacity than an E3 and a T3 has a higher capacity than an E1, and so on. You may be asked to determine which line you would recommend based on the needs of the client, so be able to respond by knowing which technologies offer which benefits. ISDN ISDN is a WAN protocol based on an international communications stan- dard for sending voice, video, and data over digital telephone lines or nor- mal telephone wires. ISDN is commonly seen in the corporate offices of companies worldwide. Mostly used for WAN links from one company to another, ISDN is unique in that it is call-initiated and call-terminated, so you only pay for what you use. ISDN uses telephone number-like entities called SPIDs to dial from peer to peer in order to bring up the line when 362 CHAPTER 8: Wide Area Networking traffic has to be sent across it. Once the connection is no longer required, usually due to inactivity, the call is ended and so is the billing for that usage. ISDN supports data transfer rates of 64,000 bits per second (64 Kbps) per channel, and most ISDN circuits used today are configured as two channels to provide 128 Kbps of throughput. There are two types of ISDN: Basic Rate Interface (BRI) and Primary Rate Interface (PRI). BRI consists of two 64 Kbps B channels and one D channel for transmitting control information. BRI ISDN has a maximum speed of 128 Kbps. PRI consists of 23 B channels and one D channel (in North America) or 30 B channels and one D channel (in Europe). The B channel is used for control. BRI The BRI ISDN service uses two B channels and one D channel (2B+D). Now that you understand what a T1 is, it should be pretty simple to under- stand that a channel represents a DS0.You would use two channels at 64 Kbps to total 128 Kbps, which is the rate of a BRI ISDN service. If you want to get more than that basic rate, you can move to a PRI. The B channels are used to send and receive data; the D channel is used for signaling. BRI B-channel service operates at 64 Kbps and is meant to carry user data; BRI D-channel service operates at 16 Kbps and is meant to carry control and signaling information, although it can support user data transmissions under certain circumstances. The D-channel signaling protocol comprises Layers 1 through 3 of the OSI reference model. BRI also provides for framing control and other overhead, bringing its total bit rate to 192 Kbps. Test Day Tip Remember the following: the ISDN BRI service offers two B channels and one D channel (2B+D). BRI B-channel service operates at 64 Kbps and is meant to carry user data; BRI D-channel service operates at 16 Kbps and can also carry user data but is normally used for management purposes such as signaling. PRI PRI offers 23 B channels and 1 D channel in North America and Japan, yielding a total bit rate of 1.544 Mbps (the PRI D channel runs at 64 Kbps). In Europe, Australia, and other parts of the world, PRI provides 30 B chan- nels plus one 64 Kbps D channel and a total interface rate of 2.048 Mbps. The PRI physical layer specification is ITU-T I.431. This is essentially the same as getting a full T1, except you are getting the ISDN service benefits. WAN Protocols and Properties 363 Test Day Tip Remember that PRI service offers 23 B channels and 1 D channel in North America and Japan, yielding a total bit rate of 1.544 Mbps (the PRI D channel runs at 64 Kbps). In Europe (and other parts of the world), PRI provides 30 B channels plus one 64 kbps D channel and a total interface rate of 2.048 Mbps. FIGURE 8.2 Circuit- and Packet- Switching Technologies Used Together. It is important to remember that ISDN is comprised of digital telephony and data transport services offered by regional telephone carriers using pre- existing telephone wiring. ISDN is also used very often as backup links since they are circuit-switched. They can be brought up when needed, as in the case of an emergency where the main link to a site is down. In these cases, ISDN can be used to fix the problem. Figure 8.2 shows an example of both circuit-switched and packet-switched networks in use simultaneously. You can save money using a hybrid network as well. Because you pay for Frame Relay service to be up at all times, it becomes your primary network and is where your data mainly travels. At the same time, each router is conveniently configured with another technology (in this example, ISDN), which provides a failsafe or backup network in case of failure of the frame circuit, thereby providing high availability to the network users. 364 CHAPTER 8: Wide Area Networking FDDI Although considered more of a local area network (LAN) technology, and debated to be a LAN technology, FDDI (whether based on the LAN or WAN) is a technology that is used to provide very high-speed, redundant backbone service to your network. Listed in the Network+ objectives, it’s imperative that you understand the underlying technology used with FDDI. FDDI, which is based on fiber, is the standard for a 100 Mbps dual-ring token- passing technology. Also based on copper cable, Copper Distributed Data Interface (CDDI) provides high-speed, redundant transmission of data. The FDDI is generally used as a backbone technology due to its redundant design and high speed. Figure 8.3 shows FDDI’s overall design. Note If you would like to research this technology and design more thoroughly, visit the Cisco ISDN DDR page at www.cisco.com/en/US/tech/tk801/tk379/technologies_ configuration_ example09186a00800b1147.shtml. FIGURE 8.3 Fiber Distributed Data Interface. WAN Protocols and Properties 365 FDDI works by using a dial ring token-passing architecture that allows for bidirectional traffic – traffic traveling opposite directions – which is also called counter rotation. FDDI and its primary and secondary rings are based on providing high-speed service reliably. The dual rings offer redundancy in case of failure, since if one link becomes unavailable the traffic can traverse the other link. Frame Relay Frame Relay is a packet-switching protocol for connecting devices on a WAN. Frame Relay networks in the United States support data transfer rates at T1 (1.544 Mbps) and T3 (45 Mbps) speeds and can be purchased as DS0s. This allows you flexibility, so you could have a Frame Relay link from one site to another and need 128 Kbps of available circuit bandwidth. You could then purchase two channels at 64 Kbps each and that would be your circuit speed for your Frame Relay link. Frame Relay, when used in the WAN, is often used between a company’s core and remote sites and sized very perfectly to whatever bandwidth is needed between the sites. The sizing is done so that you can take advantage of bursting, which is when the carrier allows you to use some of the additional bandwidth on the line (up to 1.544 Mbps on a T1, for example), if available. Frame Relay has a high transmission speed, very low network delay if configured properly and sized correctly, and is fairly reliable. Because of how the system is maintained in the carrier’s internal network, it’s easy to make mistakes, as there is a lot to configure when you use Frame Relay. This is especially true if you are an engineer working on routers or WAN switches inside a carrier’s network. Because the service is not highly reliable at all times, it’s common to back up a Frame Relay network with another network such as ISDN. Frame Relay is based on the older X.25 packet-switching technology, which was designed for transmitting analog data such as voice conversa- tions, and is the skeleton for the MPLS solutions now being used in most enterprises today. See the section later in this chapter for more information on MPLS. Although it is losing ground to other technologies that operate using purely Layer 3 communications (Frame Relay primarily operates at Layer 2 of the OSI model), Frame Relay is one of the most prevalent technologies used in wide area networking today. Because carriers quickly move to update (and upgrade) their infrastructures to stay competitive, Frame Relay and ATM technologies are quickly losing ground in favor of pure IP-based Layer 3 WAN infrastructure, as this is more compatible with today’s voice and video applications. Frame Relay networks are still used in many enterprises . wide area network (WAN) technology types and properties that you will see not only on the CompTIA Network+ (2009 edition) exam objectives but also in a large production environment. Most of. good look at some of the technologies that make up the WAN. In this section, we dis- cuss the CompTIA Network+ (2009 edition) exam objectives based on WAN protocols and standards such as T carriers,. of these technologies and protocols are used often and you will need to know about them for the Network+ exam. Be familiar with the speeds, capacities, and the types of media used for each WAN