ROUTING

We now take up the question of finding the host that datagrams go to based on the IP address. Different parts of the address are handled in different ways; it is your job to set up the files that indicate how to treat each part.

IP Network

When you write a letter to someone, you usually put a complete address on the envelope specifying the country, state, and Zip Code. After you put it in the mailbox, the post office will deliver it to its destination: it will be sent to the country indicated, where the national service will dispatch it to the proper state and region. The advantage of this hierarchical scheme is obvious: wherever you post the letter, the local postmaster knows roughly which direction to forward the letter, but the postmaster doesn't care which way the letter will travel once it reaches its country of destination.
IP networks are structured similarly. The whole Internet consists of a number of proper networks, called autonomous systems. Each system performs routing between its member hosts internally so that the task of delivering a datagram is reduced to finding a path to the destination host's network. As soon as the datagram is handed to any host on that particular network, further processing is done exclusively by the network it self


Subnetwork

This structure is reflected by splitting IP addresses into a host and network part, as explained previously. By default, the destination network is derived from the network part of the IP address. Thus, hosts with identical IP network numbers should be found within the same network.[1]

It makes sense to offer a similar scheme inside the network, too, since it may consist of a collection of hundreds of smaller networks, with the smallest units being physical networks like Ethernets. Therefore, IP allows you to subdivide an IP network into several subnets.
A subnet takes responsibility for delivering datagrams to a certain range of IP addresses. It is an extension of the concept of splitting bit fields, as in the A, B, and C classes. However, the network part is now extended to include some bits from the host part. The number of bits that are interpreted as the subnet number is given by the so-called subnet mask, or netmask. This is a 32-bit number too, which specifies the bit mask for the network part of the IP address.
The campus network of Groucho Marx University is an example of such a network. It has a class B network number of 149.76.0.0, and its netmask is therefore 255.255.0.0.
Internally, GMU's campus network consists of several smaller networks, such various departments' LANs. So the range of IP addresses is broken up into 254 subnets, 149.76.1.0 through 149.76.254.0. For example, the department of Theoretical Physics has been assigned 149.76.12.0. The campus backbone is a network in its own right, and is given 149.76.1.0. These subnets share the same IP network number, while the third octet is used to distinguish between them. They will thus use a subnet mask of 255.255.255.0.
Figure 2-1 shows how 149.76.12.4, the address of quark, is interpreted differently when the address is taken as an ordinary class B network and when used with subnetting.

Figure 2-1. Subnetting a class B network

It is worth noting that subnetting (the technique of generating subnets) is only an internal division of the network. Subnets are generated by the network owner (or the administrators). Frequently, subnets are created to reflect existing boundaries, be they physical (between two Ethernets), administrative (between two departments), or geographical (between two locations), and authority over each subnet is delegated to some contact person. However, this structure affects only the network's internal behavior, and is completely invisible to the outside world.
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Data Link Control (DLC)

DLC

Generally, the services that the data-link layer of the Open Systems Interconnection (OSI) reference model provides to adjacent layers of the OSI protocol stack. Specifically, a Data Link Control (DLC) is a specialized network protocol that is used primarily for two purposes:

* To provide connectivity with IBM mainframe or AS/400 environments, such as Systems Network Architecture (SNA), which are configured to run DLC. DLC complements SNA because SNA operates only at higher levels of the OSI model.
* To provide connectivity for network print devices (such as certain Hewlett Packard printers that have their own network cards and are connected directly to the network).

DLC is not used as a network protocol in the usual sense of enabling communication among computers on the network. It is not used by the redirector in the Microsoft Windows NT and Windows 2000 operating systems and so cannot be used for session-level communication over a network. DLC is not routable; it is designed only to give devices direct access to the data-link layer. DLC is supported by most Windows operating systems, including Windows 95, Windows 98, Windows NT, and Windows 2000. Windows 95 OSR2 includes both a 16-bit and a 32-bit version of DLC.
TIP

To use DLC on Windows NT or Windows 2000 to connect to a Hewlett-Packard network print device, perform the following steps:

1. Connect the printer to the network, and run the self-test routine to obtain the MAC address of the printer. Also think of a friendly name for the printer.
2. Install the DLC protocol on the Windows NT or Windows 2000 server that will be used as a print server for the network print device. (Use the Network utility or the Windows 2000 Network and Dial-up Connections utility in Control Panel.)
3. Run the Add Printer Wizard on the print server, choosing My Computer, Add Port, Hewlett Packard Network Port, and New Port. Enter the friendly name for the printer and select its MAC address from the list (or type it if the print device is offline). In Windows 2000, run the Add Printer Wizard, then right-click on the printer in the Printers folder and choose Properties. In the Property sheet for the printer, click the Ports tab, click Add Port, select Hewlett Packard Network Port, and then click New Port. Enter the friendly name for the printer and select its MAC address from the list (or type it if the print device is offline).

Generic Data Link Control Environment

Generic data link control (GDLC) is a generic interface definition that allows application and kernel users a common set of commands to control data link control (DLC) device managers within the operating system.

For problem determination, see GDLC Problem Determination in AIX 5L™ Version 5.3 Communications Programming Concepts.

Generic data link control (GDLC) is a generic interface definition that provides application and kernel users a common set of commands to control DLC device managers within the operating system.

The GDLC interface specifies requirements for entry point definitions, functions provided, and data structures for all DLC device managers. DLCs that conform to the GDLC interface include:

• 8023 (IEEE 802.3 for Ethernet)
• ETHER (Standard Ethernet)
• SDLC (Synchronous Data Link Control)
• TOKEN (Token-Ring)
• FDDI (Fiber Distributed Data Interface)

DLC device managers perform higher-layer protocols and functions beyond the scope of a kernel device driver. However, the managers reside within the kernel for maximum performance and use a kernel device driver for their I/O requests to the adapter. A DLC user is located above or within the kernel.

Synchronous data link control (SDLC) and IEEE 802.2 Data Link Control are examples of DLC device managers. Each DLC device manager operates with a specific device driver or set of device drivers. SDLC, for example, operates with the multiprotocol device driver for the system's product and its associated adapter.

The basic structure of a DLC environment is shown in the "DLC Device Manager Environment" figure. Users within the kernel have access to the communications memory buffers (mbufs) and call the add entry points through the fp kernel services. Users above the kernel access the standard interface-to-kernel device drivers, and the file system calls the dd entry points. Data transfers require a move of data between user and kernel space.

Figure 1. DLC device manager environment

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RFID

Radio frequency identification (RFID) is a generic term that is used to describe a system that transmits the identity (in the form of a unique serial number) of an object or person wirelessly, using radio waves. It's grouped under the broad category of automatic identification technologies.
RFID is in use all around us. If you have ever chipped your pet with an ID tag, used EZPass through a toll booth, or paid for gas using SpeedPass, you've used RFID. In addition, RFID is increasingly used with biometric technologies for security.

Unlike ubiquitous UPC bar-code technology, RFID technology does not require contact or line of sight for communication. RFID data can be read through the human body, clothing and non-metallic materials.



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ATM: Asynchronous Transfer Mode Protocol

Asynchronous Transfer Mode ( ATM )

The Asynchronous Transfer Mode (ATM) composes a protocol suite which establishes a mechanism to carry all traffic on a stream of fixed 53-byte packets (cells). A fixed-size packet can ensure that the switching and multiplexing function could be carried out quickly and easily. ATM is a connection-oriented technology, i.e.; two systems on the network should inform all intermediate switches about their service requirements and traffic parameters in order to establish communication.
The ATM reference model, which has two forms - one for the user-to-network interface (UNI) and the other for the network-to-node interface (NNI), is divided into three layers: the ATM adaptation layer (AAL), the ATM layer, and the physical layer. The AAL interfaces the higher layer protocols to the ATM Layer, which relays ATM cells both from the upper layers to the ATM Layer and vice versa. When relaying information received from the higher layers, the AAL segments the data into ATM cells. When relaying information received from the ATM Layer, the AAL must reassemble the payloads into a format the higher layers can understand. This is called Segmentation and Reassembly (SAR). Different AALs are defined in supporting different types of traffic or service expected to be used on ATM networks.
The ATM layer is responsible for relaying cells from the AAL to the physical layer for transmission and from the physical layer to the AAL for use at the end systems, it determines where the incoming cells should be forwarded to, resets the corresponding connection identifiers and forwards the cells to the next link, as well as buffers cells, and handles various traffic management functions such as cell loss priority marking, congestion indication, and generic flow control access. It also monitors the transmission rate and conformance to the service contract (traffic policing).
The physical layer of ATM defines the bit timing and other characteristics for encoding and decoding the data into suitable electrical/optical waveforms for transmission and reception on the specific physical media used. In addition, it also provides frame adaptation function, which includes cell delineation, header error check (HEC) generation and processing, performance monitoring, and payload rate matching of the different transport formats used at this layer. SONET, DS3, Fiber, twisted-pair are few media often used at the physical layer.
Protocol Structure
ATM Cell Format:

HEADER	GFC or VPI	VPI
	VPI	VCI
	VCI
	VCI	PT(3 bit)	CLP
	HEC
IE	Cell Payload (48 Bytes)

• Header - (5 Bytes) Generic flow control, VPI/VCI, and other control header.
• IE - (48 Bytes) Cell Payload.

Physical Layer Specification - Private UNI:

Frame Format	Bit Rate/Line Rate	Media
Cell Stream	25.6 Mbps/ 32 Mbaud	UTP-3
STS-1	51.84 Mbps	UTP-3
FDDI	100 Mbps/ 125 Mbaud	Multimode Fiber
STS-3c, STM-1	155.52 Mbps	UTP-5
STS-3c, STM-1	155.52 Mbps	Single-Mode Fiber, Multimode Fiber, Coax pair
Cell Stream	155.52 Mbps/ 194.4Mbaud	Multimode Fiber, STP
STS-3c, STM-1	155.52 Mbps	UTP-3
STS-12, STM-4	622.08 Mbps	SMF, MMF

Physical Layer Specification - Public UNI:

Frame Format	Bit Rate/Line Rate	Media
DS1	1.544 Mbps	Twisted pair
DS2	44.736 Mbps	Coax pair
STS-3c, STM-1	155.520 Mbps	Single-mode Fiber
E1	2.048 Mbps	Twisted pair, Coax pair
E3	34.368 Mbps	Coax pair
J2	6.312 Mbps	Coax pair
T1	1.544 Mbps	Twisted pair

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WIMAX

What is WiMAX?

WiMAX is an IP based, wireless broadband access technology that provides performance similar to 802.11/Wi-Fi networks with the coverage and QOS (quality of service) of cellular networks. WiMAX is also an acronym meaning "Worldwide Interoperability for Microwave Access (WiMAX).

WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet (30 - 100m).

With WiMAX, WiFi-like data rates are easily supported, but the issue of interference is lessened. WiMAX operates on both licensed and non-licensed frequencies, providing a regulated environment and viable economic model for wireless carriers.

At its heart, however, WiMAX is a standards initiative. Its purpose is to ensure that the broadband wireless radios manufactured for customer use interoperate from vendor to vendor. The primary advantages of the WiMAX standard are to enable the adoption of advanced radio features in a uniform fashion and reduce costs for all of the radios made by companies, who are part of the WiMAX Forum™ - a standards body formed to ensure interoperability via testing. The more recent Long Term Evolution (LTE) standard is a similar term describing a parallel technology to WiMAX that is being developed by vendors and carriers as a counterpoint to WiMAX.



What is the Range of WiMAX?

The answer to this question probably generates more confusion than any other single aspect of WiMAX. In the early days of WiMAX it was common to see statements in the media describing WiMAX multipoint coverage extending 30 miles. In a strict technical sense (in some spectrum ranges) this is correct, with even greater ranges being possible in point to point links. In practice (and especially in the license-free bands) this is wildly overstated especially where non line of sight (NLOS) reception is concerned.

Due to a variety of factors explained in more detail in other FAQ answers, the average cell ranges for most WiMAX networks will likely boast 4-5 mile range (in NLOS capable frequencies) even through tree cover and building walls. Service ranges up to 10 miles (16 Kilometers) are very likely in line of sight (LOS) applications (once again depending upon frequency). Ranges beyond 10 miles are certainly possible, but for scalability purposes may not be desirable for heavily loaded networks. In most cases, additional cells are indicated to sustain high quality of service (QOS) capability. For the carrier class approach, especially in regards to mobility, cells larger than this seem unlikely in the near future. The primary WiMAX focused US carrier Clearwire has stated that its cell sites are planned at about 1.5 miles apart for mobile purposes. This choice is clearly one intended to meet NLOS requirements. In licensed frequencies, expect similar performance or better for WiMAX than in traditional cellular systems.
What RF Frequencies does WiMAX work in?

The most recent versions of both WiMAX standards in 802.16 cover spectrum ranges from at least the 2 GHz range through the 66 GHz range. This is an enormous spectrum range. However, the practical market considerations of the Forum members dictated that the first product profiles focus on spectrum ranges that offered Forum vendors the most utility and sales potential.

The International standard of 3.5 GHz spectrum was the first to enjoy WiMAX products. The US license free spectrum at 5.8 GHz has a few WiMAX vendors building products. Licensed spectrum at 2.5 GHz used both domestically in the US and fairly widely abroad is the largest block in the US. Also, in the US and in Korea products are shipping for the 2.3 GHz spectrum range. Also in the US the 3.65 GHz band of frequencies now has WiMAX gear shipping to carriers.

The technology appears easily extensible to lower frequencies including the valuable 700 MHz spectrum range at which the nation's largest auction (in terms of money spent) concluded in 2008. More likely near term frequencies likely to be supported include the new 4.9 GHz public safety band (sometimes described as a Homeland security band).

The second largest block of frequencies ever auctioned (in terms of money spent) occurred in the summer of 2006 with the AWS auction from the FCC. This spectrum was split with the bulk being at 1.7 GHz and the rest at 2.1 GHz. At this point, the Forum is not expected to develop a product profile for this range as most licensees have announced support for LTE systems or plan to use it for existing GSM/UMTS networks.

The physics of radio signals typically place two primary constrictions on spectrum. To generalize, the higher the spectrum frequency the greater the amount of bandwidth that can be transported---lower frequencies transport less bandwidth. Secondly, the lower the frequency the greater the carry range and penetration of a signal. For example: A 900 MHz license free radio will travel farther and penetrate some tree cover fairly easily at ranges up to one to two miles. But it can carry much less bandwidth than a 2.4 GHz signal which cannot penetrate any tree cover whatsoever, but can deliver a lot more data. The caveat that can somewhat alter this equation is power. Licensed band spectrum such as 2.5 GHz by virtue of being dedicated to one user is allotted significantly higher power levels which aids in tree and building wall penetration.
Where did the idea of WiMAX come from?
Much of the credit for the formation of the WiMAX Forum™ and to the founding members of the WiMAX Forum, which committed themselves early to the process of creating a collaborative standards body. As a founding member of the WiMAX Forum, Intel recognized that a well developed ecosystem was necessary to drive adoption and thereby drive lower hardware costs. Intel was also instrumental in getting other silicon chip manufacturers involved whose products would form the core of WiMAX technology.
What factors will most greatly affect range for WiMAX products?

Many factors affect range for any broadband wireless product. Some factors include the terrain and density/height of tree cover. Hills and valleys can block or partially reflect signals. Bodies of water such as rivers and lakes are highly reflective of RF transmissions. Fortunately OFDM can often turn this to an advantage---but not always. The RF shadow of large buildings can create dead spots directly behind them, particularly if license-free spectrums are being used (with their attendant lower power allotments). How busy the RF environment of a city or town is can greatly degrade signals---meaning that properly designed and well thought out networks are always desired.

The physics of radio transmission dictate that the greater the range between the base station and customer radio, the lower the amount of bandwidth that can be delivered, even in an extremely well-designed network. The climate can affect radio performance---despite this there are ubiquitous wireless networks deployed today with great success in frozen Alaskan oil fields as well as lush South American and Asian climates. And increasingly WiMAX radio antenna technology coupled with the inherent advantages of OFDM/OFDMA based radios can be a major factor in range and bandwidth capability. The new multiple input multiple output (MIMO) and adaptive antenna systems (AAS) based antenna systems promise to maintain and even link connection and link budgets with much higher bandwidth than older technology.

No two cities are exactly alike in terms of the challenges and opportunities presented. In many respects, broadband wireless remains very much an art form. However, this is also true for the cellular carriers most of us use daily. It can be done quite well. Mobile broadband wireless will be more difficult. Achieving high quality of service (QOS) will be easier with fixed broadband wireless. Despite all of these challenges, current broadband wireless is very effectively serving customers even in the most challenging environments.


Business Planning 

The WiROI™ Business Case Analysis Tool offers network operators and equipment manufacturers a comprehensive analysis of the capital and operational expenses required for deploying a broadband wireless network. Developed through extensive industry experience with actual network deployments, the WiROI™ Tool has the flexibility to model a variety of deployment plans and service models.

The WiROI™ Tool has been designed to allow operators to customize a business case analysis for any target market. The tool accepts a wide range of market data, technical parameters, and financial and service planning inputs that an operator can tailor for their particular deployment plan. It simulates a wireless network deployment and operations using a variety of service plans and produces a detailed 10 year income statement, financial output graphs, and key financial metrics.

As an added feature, the WiROI™ Tool has an easy-to-use, interactive, dashboard-style Graphical User Interface (GUI). It enables the user to perform Sensitivity Analysis in real-time and to view the results in an animated graphical format instantly.

Visible Results

The WiROI™ Tool provides a dashboard of graphs that outline the financial performance of an operators deployment plan. In addition, the WiROI™ Tool produces a complete income statement up to a full 10 year business case including CapEx and OpEx as well as cash flow, cumulative cash flow, NPV and IRR outputs. A wide compliment of system and financial metrics is calculated for an Operator to visualize the network’s future financial performance.

Sample Business Case Results Charts

 
The WiROI™ Tool GUI

The WiROI™ Tool GUI incorporates animated selectors, sliders and buttons, which allow the user to vary key input parameters and visualize the output immediately. Answers can be seen instantly to questions like:

- What would the effect of a link budget be on my overall WiMAX™ business plan?
- How will the cost of backhaul affect my OpEx?
- How would the core network affect my CapEx and what might the impact be on my 10 year business plan?
- How would using a 2.5 GHz spectrum vs. a 3.5 GHz spectrum impact my business plan?
- How do the costs of base stations and CPE’s affect my business plan?
- How can the service agreements be optimized for my business plan?
- These and many other critical questions can be answered instantly, interactively and easily by using WiROI.


Sensitivity Analysis

Because of the dashboard-style GUI, the WiROI™ Tool can produce sensitivity analyses based on certain input parameters for a particular deployment. Now, Operators can quickly and easily visualize and understand the critical issues that affect their deployment plan. In addition to estimating the number of cell sites, the tool includes various options for selecting the wireless network infrastructure required to support specific coverage and capacity requirements. The user can select from a variety of core networks, access networks, base stations, as well as backhaul options. WiROI™ provides answers to a variety of “what if” scenarios to help identify the most important variables influencing the specific wireless business plan.

Developing a broadband wireless network business plan could be a very complex and time-consuming process. Quickly choosing among over 280 different input variables and assumptions, the ability to instantly modify these variables, test key assumptions and instantly visualize their impact on your wireless business plan, are invaluable capabilities.






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