CXO

Taking the Network+ plunge!

Getting ready to take the Network+ exam plunge? Don't go in unprepared. Instead, let TechProGuild and Tige Chastain help you to understand the fundamentals necessary for the exam.


So you want to get a certification that will demonstrate an understanding of basic networking concepts, practices, and operations? Network+ from CompTIA might be just the certification you have been searching for. I'll cover what the certification is, who supports it (always important), and what is covered on the exam.

The Network+ exam from CompTIA is a vendor-neutral certification that covers the basics of networking, general installation, and troubleshooting issues. An industry-recognized certification, Network+ is acknowledged by companies such as 3Com, Cisco, Intel, HP, Novell, and Lotus, who give credit towards their certifications. In general, if you have a formal education background in networking with some field experience, the Network+ certification exam will be a quick hit. Those wanting to go for CCNA or other network vendor certification could view it as a good review before attempting to achieve a higher level of knowledge.

The questions for the exam range from designing and documenting a new networking implementation to troubleshooting network problems. A broad range of networking hardware and software is required, focusing generally on theory with some applied theory to follow it up.

Networking
As traditionally found in formal education, the aspiring student should start with the basics of computer networking: the OSI model (listed below).
  • Application layer
  • Presentation layer
  • Session layer
  • Transport layer
  • Network layer
  • Data Link layer
  • Physical layer

By mapping the theoretical model to specific hardware and protocol implementations, one will find it much easier to understand how everything fits together.

The Network+ exam requires a sound understanding of the OSI model, listed above, and the general theory of how data is passed from one host to another. When a host needs to send data, each layer passes its data down to the next layer. The receiving layer encapsulates the previous layer’s data into its own and passes its data down to the next layer.

Physical layer
The Physical layer of the OSI model deals with the media connection and electrical signal specifications that are required for any computer system to connect to a network. Specifically, cable types, pin-outs, electrical signal standards, and voltage requirements are found in this layer. The Network+ exam requires that the student be familiar with the function of each piece of hardware at this layer. The hardware areas specifically covered on the exam are hubs, media converters, multistation access units (MAU), network interface cards (NIC), repeaters, and transceivers. Basically, all of these devices provide the same function—passing electrical signals along the physical media in the correct format. At this point, things don't get too interesting until data encounters the second layer, the data link layer.

As media is directly related to the physical layer of the OSI model, it makes sense to discuss it here. CompTIA believes it is vitally important that you understand and know the common cable types used in networking. Not only is it important to be familiar with the types of cable and connectors that will no doubt be found in installations, it is equally beneficial to know the limitations for each media type. Table 1 summarizes the common cable types found and their distance ratings.

Table 1
Cable rating Media type Rated distance Throughput
RG-58 - 5mm Coaxial 285 meters 10 Mbps
RG8 - 10mm Coaxial 500 meters 10 Mbps
Category 3 UTP 100 meters 10-Mbps Ethernet
4- and 16-Mbps Token Ring
Category 5 UTP 100 meters 100-Mbps Fast Ethernet
Single-Mode Fiber (SMF) Fiber 5 kilometers Up to 1 Gbps
Multi-Mode Fiber (MMF) Fiber 2 kilometers
550 meters
10 and 100 Mbps
1 Gbps
Common cable classifications, types, distance, and throughput

In addition to the names and ranges of cables, the exam covers what implementations utilize a specific type of cable. Table 2 shows the matching of cable to implementation standard.

Table 2
Specification Cable type
10Base2 (ThinNet) RG-58, 5 mm Coaxial
10Base5 (ThickNet) RG8 Coaxial
10BaseT Category 3 or 5 unshielded twisted pair
100BaseT4 Category 3, 4, or 5 unshielded twisted pair
100BaseTX Category 5 unshielded twisted pair
100BaseFX Fiber
100BaseVG Any LAN Category 5 unshielded twisted pair
Ethernet implementations and associated cable types

Finally, you have the types of connectors common in networking installations. Generally, there are three types: RJ-45, BNC, and AUI. The RJ-45 connector is similar to the RJ-11 connector commonly found in residential wiring for telephone usage. The difference is that RJ-45 is slightly wider to accommodate for four pairs of wire versus RJ-11's two. The bayonet-Niell-Concelman (BNC) connector is commonly found in ThinNet (10Base2) implementations. It consists of a round, extended connector with a female center wire. Finally, attachment unit interface (AUI) is a 15-pin, D-style connector used to connect ThickNet (10Base5) networks. Recently, almost all AUI implementations have been replaced with RJ-45 due to the ease of use and lower cost. Now that I have covered the physical layer, as well as the physical media and connectors, let’s get back to the OSI model.

Data-link layer
Before the discussion on media types and connectors, I described an electrical signal on the wire. It was within specifications and ready to be passed to the next layer of the OSI model. This is where the Data-link layer comes in. This layer provides error-free flow control as well as node-to-node connections. Additionally, the Data-link layer provides a mapping from Network layer addresses to its own addresses. The Data-link layer is broken down into two sublayers: the Logical Link Control (LLC) and the Media Access Control (MAC).

The LLC sublayer deals with flow control—specifically how much data can be passed without overflow of the network. Basically, the LLC is responsible for communicating how much data it can take from one or more hosts at one time without losing data. Although the concept of flow control is out of the scope of this article, it is an important part of the LLC sublayer and certainly an area for more study.

The MAC sublayer is equally important to the Data-link layer in terms of identification for each host on the network. The Institute of Electrical and Electronics Engineers (IEEE) proposed this standard (in order to uniquely identify all traffic passed to a host) and recommended that all network card manufacturers follow it. This standard requires that the address consist of a six-octet number into the electronics of the network interface card (NIC). The first three octets are designed to a specific vendor, commonly known as the Organizationally Unique Identifier (OUI). The last three octets are assigned by the manufacturers and are used to uniquely identify the card itself. A valid OUI and unique three-digit octet make up the Universal LAN MAC address.

Additionally, the LLC sublayer carries a framing type that identifies the particular protocol scheme the data is encoded with so that the NIC can correctly identify what is being transmitted. Once the frame type is determined, the flow control established, and the address of the host sending the data has been identified, the data can be passed to the next layer, the Network layer.

The MAC address is a key concept that network engineers need to understand. On the hardware side of things, bridges, gateways, and switches (switching hubs) all utilize the MAC address to set up routing tables that keep track of data sent and received from other hosts. It’s important to understand the concept of bridging and when to utilize a bridge in a network. Remember that bridges forward all broadcast traffic across the network to build their MAC address tables. These tables are built similar to any switch on the network and optimize data traffic so that data passes only to hosts for which the data is intended. Additional coverage on bridges and switching can be found in Cisco Multicast Routing & Switching from the TechProGuild Tech Books library.

The Network+ exam requires the student to understand and recognize the IEEE standards associated with NICs and media. Table 3 lists the standards, along with a brief description of each.

Standard name Description
802.1 802 project description
802.2 Logical Link Control (LLC)
802.3 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) on bus networks
802.4 Token bus
802.5 Token ring
802.6 Metropolitan Area Networks (MAN)
802.7 Broadband Technology Advisory Group
802.8 Fiber Optic Technology Advisory Group
802.9 Voice and data integration on LANs
802.10 Interoperable LAN Security
802.11 Wireless networks
802.12 Demand priority access LAN (100Base-VG-AnyLAN)
IEEE 802 standards and descriptions

Network layer
The Network layer handles unique logical address, routing, and fragmentation/defragmentation of packets for hosts and network segments. This is the layer that the IP, IPX, ICMP, DHCP, BOOTP, and all routing protocols fall into. Although each protocol is different, in general, the Network layer protocol will provide the necessary routing information for the data to the Data-link layer and defragment data packets to be passed to the upper Transport layer.

Now that I’ve explained the theory, what happens on the hardware side? Routers, intelligent hubs and switches, and bridge routers (Brouters ) fall into this layer. Intelligent hubs and switches are the basic Layer 1 and 2 equipment with added "intelligence," which allows for remote management and performance of basic-level routing functions. Brouters can handle both routing data to logical addresses and mapping Data-link layer MAC addresses for efficient traffic routing.

Then, there is the router: the Holy Grail of the internetwork. The router functions as a basic traffic cop, determining which path the data will take based upon several factors, such as number of hops, cost, time, etc. The Network+ exam requires that the student understand the general theory of how routers operate, the basic types of routing (static and dynamic), link-state and distance-vector protocols, the concept of subnetting, and classful subnetting. For a more in-depth look at routing see Advanced IP Routing In Cisco Networks from TechProGuild’s Tech Books library.

Transport layer
The last layer covered in the Network+ exam is the Transport layer, which is responsible for error-free, host-to-host communication and the fragmentation/defragmentation of messages. This layer implements reliable and unreliable internetwork data transport services, such as flow control, virtual circuit management, and error checking and recovery, to the upper layers of the OSI model. Protocols that are typically found in the Transport layer include TCP, UDP, NetBIOS, and SPX. A key area covered on the Network+ exam is that TCP provides reliable transport (versus the unreliable transport provided by UDP). This layer is where most of the data sent across a network resides. When the Transport layer receives data from the Network layer, the data payload is reassembled into larger messages and then transferred either reliably or unreliably to the upper layers. When passing data to the Network layer, the Transport layer breaks down its messages into smaller chunks to accommodate the payload of the Network layer. Additionally, in both sending and receiving data, the Transport protocol handles any errors found in messages and asks for retransmission should errors occur.

As the upper three layers of the OSI model deal with the end-user interface and have no bearing on how the data is passed, they are not covered on the Network+ exam. It is only important to remember that security-specific and application-specific encoding/decoding is accomplished at these layers.

System administration
Although the Network+ exam is primarily geared towards networking, there are some system administration topics covered, as well. The general idea is that, although you may be a network engineer, you should be familiar with the systems that are commonly found on networks, how to do basic levels of administration, and how they operate to enable you to better troubleshoot any problem that may arise.

Hardware
In large production networks, it is common to find a wide range of hardware devices. The Network+ exam expects the student to be familiar with RAID arrays, UPSs, line conditioners, surge protectors, and tape devices. Although an in-depth description of these is outside the scope of this article, I'll cover the basics of the information needed on redundant array of independent disks (RAID), power sources, and tape devices.

RAID
RAID is commonly found in enterprise-level networks, generally in high volumes of storage space. The general concept of RAID is to provide a method to store data across multiple disks to increase disk performance and read/write time, as well as to add a level of redundancy and fault tolerance. Several vendors have their own proprietary solutions for this method of storage; however, the general implementations are what the Network+ exam focuses on.

Specifically, the Network+ exam requires the student to have a basic understanding of the most common levels of RAID and what the cost and benefits are for each level. Although possible to emulate in software, the exam focuses on RAID hardware. Table 4 presents the different levels of RAID, a brief description, and the associated costs and benefits

Table 4
Level Name Description Cost Benefit
RAID 0 Disk striping without parity Data is spread across two or more physical drives without parity. No redundancy Faster, read/write access
RAID 1 Disk mirroring/duplexing An exact copy of data is written to two separate drivers. In duplexing, independent controls are utilized to increase redundancy. Monetary cost Increased read/write performance and redundancy
RAID 2 Disk Striping with error correction Data is written across two or more disks with an Error Checking and Correction scheme (ECC). This method is rarely used, as RAID 5 provides better performance. ECC algorithm is inefficient and requires longer write times. Redundancy with increased read/write performance
RAID 3 Disk striping with single-disk parity Data is written across two or more drivers in blocks, with one drive containing all parity information to rebuild data in the event of a failure. Fault tolerance risk due to single drive parity, low read/write performance due to single parity drive Fault tolerance  
RAID 4 Disk striping with single-disk parity Same as RAID 3, but the data is written in larger areas, in bits versus blocks. This method is rarely used. Penalty in write performance due to parity chunk size change Faster read access, increased fault tolerance due to multiple drives containing parity
RAID 5 Disk striping with distributed parity Similar to RAID 4, with data and parity distributed across multiple drives at the block level. Parity for each data block is not found on the same drive to increase fault tolerance. A minimum of three disk is required with a maximum of 32. Write performance suffers as more disks are added to due parity distribution Only one drive lost to parity, increased fault tolerance  
RAID level descriptions

Power sources and protectors
Following RAID's idea of fault tolerance, the Network+ exam requires you to be familiar with the different types of power protectors and sources that increase the availability and safety of the network equipment and servers. From simple surge protectors to integrated uninterruptible power supplies (UPSs) with line conditioners, it is important to know what each device provides and its benefits. Table 5 provides a brief breakdown of each type of power protector and its benefits.

Table 5
Name Description
Benefit
Surge protector A simple device to turn one outlet into multiple outlets. Generally it has a fuse or switch that will trip in the event of a power surge. It provides the most basic type of protection. Protection from power surges and spikes, low in cost
Line conditioner A device used to filter and stabilize power flow to connected equipment. Utilizes wire coils to provide small amount of power in the event of a brownout. Constant conditioning of power to prevent equipment damage from spikes, surges, and brownouts
UPS A device to provide constant, filtered, regulated power to all connected devices. This device utilizes a battery to supply the actual power and takes the unfiltered power source to constantly recharge the battery. Additionally it can automatically shutdown servers connected to it in the event of a sustained power outage. Same as line conditioner, but also provides power during a sustained blackout and has the capability to initiate remote shutdown of servers to protect data integrity
Electrical power conditioners and supplies

Tape devices
Tape drives are still common in most enterprise networks as the main source of data backup. Although the dropping price in CD-ROM media and drives is changing this, it is expected that you will encounter magnetic tape devices in your future career as a network engineer. There are two basic types of tape drives covered on the Network+ exam: digital audio tape (DAT) and Integrated Device Electronics (IDE).

Due to their high speed and reliability, DATs have become the basic standard for companies utilizing magnetic tape storage. These devices utilize the same technology found in video tapes and VCRs. They use a helical scan recording method, which allows ultra high-density recording on a slow-motion tape. DAT technology has two distinct types of drives: the Digital Data Storage (DDS) and the digital linear tape (DLT).

The DDS type utilizes the helical scan method with a read-after-write and error-correction technology. This provides an efficient storage method while adding some data integrity. DDS-1 class devices can store 1.3 GB on 60-mm tape and 4 GB on 90-mm tape. The DDS-2 class, a later implementation, can store 8 GB of data per 120-mm tape. This was accomplished by increasing the density of information by one half and increasing the tape length by one-third. This solution is commonly found in older or smaller environments where massive data storage is not on top of the list of needs.

DLT is perhaps the highest performance solution in tape drives because it provides a storage capacity of 40 GB or more and a transfer speed of up to 10 Mbps by utilizing multiple read/write channels. Like the DDS type, DLT also uses a read-after-write and error-correction code feature, but does so in a more efficient manner. With its high storage capacity and increased data checking, the DLT is the current leader in high-performance tape backup environments.

IDE is mainly a PC-based technology that has come of age in the last decade. Due to its direct integration on the motherboard of a PC, fast data access and performance is possible. Although not quite at the speeds of SCSI devices, IDE tape devices are becoming more popular in the low cost arena of backup and recovery. Typically these devices are limited to less than 1 GB of storage. However, IDE devices are less costly than SCSI devices and do not require an additional controller or cable connection, as they connect to the same cable as the internal hard drives. Cost, flexibility, and accessibility are the key reasons IDE tape drives should be utilized as backup storage.

Operating systems and methods
Following the hardware line of requirements, the Network+ exam covers different OSs and their associated administration requirements—specifically Microsoft Windows NT, Novell NetWare, and UNIX. Those studying for the exam should be familiar with the Windows Domain model, the Novell Directory Services (NDS) model, and the UNIX user/group file security systems. The key requirements for these systems include: dealing with the creating of user accounts and groups, assigning multilevel administration privileges, the associated administrator accounts, and multiple server communication and placement throughout the network.

Taking the test
As with most certifications, the Network+ exam is administrated by Prometric. The exam is computer-based and currently costs $195.00 (U.S.). A list of sites for testing can be found at the Prometric Online Registration site. Before taking the exam, I highly recommend that you purchase a self-preparation guide or take a formal training class to help you through all of the material. Due to the cost of the exam, many people find it beneficial to purchase practice tests to increase their exposure to the material and to find problem areas to further aid their studies.

Conclusion
The Network+ certification covers several areas of networking including the OSI model, networking hardware, enterprise hardware for fault tolerance and recovery, and basic system administration on multiple OSs. This broad coverage of topics with the support from multiple vendors is what gives Network+ its creditability. A Certified Network+ Professional is primed for more advanced levels of networking concepts and experiences and will be prepared to handle basic networking administration and troubleshooting.

Although I did not cover everything required for the Network+ exam, I hope I have provided enough insight to the Network+ topics for you to determine if this certification is right for you. Being Network+ certified assures employers and coworkers you have demonstrated your knowledge of the basics of networking and system administration. Good luck in your quest for certification, be it Network+ or something else!
The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.

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