network management principles and practice mani subramanian 2nd edition ch15

Part IV: Broadband Network Management > Broadband Home Networks

Objectives

Residential and SOHO networks

Transport technologies

Applications and application protocols

Middleware between multiple applications andtransports

Transport technologies

Wired: IEEE 802.3/Ethernet LAN and other options

Wireless: IEEE 802.11/WiFi

Wired home networks

Comprehensive view

Lower-layer protocols

Ethernet-like protocols and management

Power Ethernet

Wireless home network

WiFi (802.11a/b/g) wireless LAN

802.11 standards and amendments

Hierarchical network using access point

Basic service set (BSS)

Ad-hoc networks

Special network management considerations

Security management

QoS management

Centralized management

Network Management: Principles and Practice > Review of Information ... file:///D:/TC Engg/8th Semester/TMN/Book Network Management Princ...

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WLAN MIBs: ieee 802dot11MIB and CAP-WAP-BASE-MIB

In Chapter 1 we introduced the network segment associated with homeand customer premises as one of the three segments of broadbandnetwork. The customer premises equipment (CPE) network in anenterprise environment is either an IEEE 802.3-based Ethernet localarea network (LAN) or an IEEE 802.11-based wireless LAN, also knownas WiFi, or a hybrid of both. Home network provides the opportunity toutilize multiple technologies besides Ethernet LAN and WiFi. HomePNA isimplemented using a twisted-pair telephone cable medium, HomePlugtakes advantage of power line wiring in the house, and cable utilizes thetelevision coaxial cable. FireWire is also a wired medium and is based onIEEE 1394 protocol to transmit high-speed video digital data andUniversal Serial Bus (USB) with its own hub for transmitting digital data.Wireless home network technologies include IEEE 802.15.1 Bluetoothand ultra-wide band (UWB) personal area networks (PANs) for shortdistances. Residential gateway and the home network, which is the CPEnetwork for residences, will be the subject of this chapter.


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Chapter 15. Broadband Home Networks > Home Networking Technologies

Home networking technology, or more appropriately technologies, is stillin its embryonic stage. We will present here only a brief description ofits various components. You are referred to Subramanian [2005a, b]for a detailed presentation.

Figure 15.1 shows higher- and lower-layer protocols in an integratedarchitecture. The protocols used could be classified into application-layerprotocols and transport-layer protocols, with middleware that acts as agateway between the two. Applications have protocol specifications tohandle functions, services, and messages. Transport protocols deal withtransport functions belonging to transport, network, MAC, and physicallayers. We notice at the application layer that there are four protocols—OSGi, JINI, UPnP, and HAVi. Open Service Gateway Initiative (OSGi)and JINI, which are both based on Java Virtual Machine (JVM) and useTransmission Control Protocol (TCP)/Internet Protocol (IP) for transportand network layers. Universal Plug and Play (UPnP) is based on HTTPand hence HTTP is under UPnP. Home Audio–Video Interoperability(HAVi) and UPnP show IEEE 1394 for the MAC and PHY layers. HAVi isplatform and language agnostic, although IEEE 1394 has been adoptedas the lower layers. OSGi and JINI use either 802.3 or modified 802.3with HomePlug and HomePNA or physical layers. X10, Infrared DataAssociation (IrDA) data, and CEBus are also shown as they do interfacewith IP.

Figure 15.1. Home Network Protocol Architecture


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HAVi architecture is a set of APIs, services, and a wired transportprotocol, IEEE 1394. It is intended to interface with multivendorconsumer electronic devices and computing devices. HAVi focuses onhome entertainment and AV devices.

JINI technology was developed by Sun Microsystems in 1998 forintegrating IP-based devices in a computer network, and is based on itsJava technology. It is considered as a middleware technology andcomprises a set of APIs and network protocols. Its infrastructure enablesall devices interoperable irrespective of their operating system andinterface constraints.

UPnP is architecture for pervasive peer-to-peer network connectivity ofsmart home wired and wireless devices. It is Microsoft’s initiative forhome networking and uses Web technologies for device description andcontrol. It also contains a set of APIs, but its strategy is different fromthat of JINI. JINI APIs are a contract between vendors, and UPnP allowsvendors to build the APIs.

OSGi is a residential gateway platform that supports the integration ofdifferent home networking technologies and the delivery of differentservices from service providers. Based on Java technology, differentsoftware components, called bundles, can be downloaded remotely tothe gateway.

Just as most managed applications are managed as part of theEnterprise Management System using Simple Network ManagementProtocol (SNMP) agents, residential applications could also haveSNMP-like agents built in them. As of now, home network applicationsare more in a research stage. Application and middleware technologiesare based on TCP/IP protocol for the transport and network layers used


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for transport protocols.

The medium of transport for the home network could be either a wiredor a wireless medium, or a hybrid of the two. Wired medium could beany one of the following: copper wire such as power line, twisted pairsuch as phone line, Cat 3 or Cat 5 Ethernet cable, coaxial cable such asthe one used for TV distribution, or optical fiber. Modern homes arebeing built wired with optical fiber. Wireless transmission is the radiofrequency (RF) with single or multiple antennas. Cabling could be hybridtransmission with wired distribution in the home and wireless inside therooms.

Figure 15.2 shows a comprehensive view of the home network. Theaccess network is one of three choices, namely DSL, HFC, or wireless.Each feed terminates in the respective modem, whose output isconnected to a residential gateway. Although a personal computerfunctions as a residential gateway, in the future this would be adedicated intelligent device with built-in communication and applicationmodules. In Figure 15.2 the residential gateway has four types ofdistribution networks connected to it. The USB network has low- andhigh-speed digital data devices connected to it. The very high-speeddigital triple play devices comprise IEEE 1394 network, also known asFireWire® branded by Apple. The third type of network is LAN, thepredominant one being wired Ethernet network. Other less populartypes of LANs are HomePNA using telephone cable or HomePlug usingpower line. They could be based on the above-mentioned schemes ofeither. The fourth home distribution network shown in Figure 15.2 isWiFi, wireless LAN network based on IEEE 802.11. We will next addresswired and wireless technologies based on various physical media.

Figure 15.2. Home Networks

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Chapter 15. Broadband Home Networks > Wired Home Distribution Network

Wired transport protocol for transport and network layers is TCP/IP. Thelower-layer protocols address physical and MAC layers and there areseveral choices.

X-10 protocol communicates between the transmitter and the receiverby sending RF bursts–1 millisecond bursts of 120 kHz—over power linewiring. CEBus Standard and Home Plug and Play (HomePnP) devices arecapable of communicating with each other over the power line withoutthe need for new wires.

The USB is an alternative to Ethernet as a computer peripheralinterface. However, it is data-centric as opposed to multimedia andlimited to PC peripheral applications.

USB 1.0 1.5 Mbps Low speed Cable length = 3 m USB 1.1 12 Mbps Full speed Cable length = 3 mUSB 2.0 400 Mbps High speed Cable length = 5 m

IEEE 1394 is more suitable for home networking as it can be applied toaudio and video in addition to IP data transmission. It was originallydeveloped as a high-performance serial bus by Apple, known asFireWire. It can be transmitted over copper, as well as fiber, and has thepotential of carrying up to 3.2 Gbps.

Cable is prevalent in North America and is extensively used to distributeanalog video and data. Digital telephone over cable is being introducedin selected sites by cable service providers. Packet cable beingdeveloped by CableLabs will have the capability of delivering anddistributing VoIP, video (also digital), and data over cable to and inhome.

Home Phoneline Network Alliance (HomePNA) is a technology that candistribute broadband over the phone line in the house. Home PhonelineNetworking Alliance was formed in 1998. It is expected to handle datarate up to 10 Mbps and is applicable to phone and low data-ratetransmission.

HomePlug, also known as power line communication (PLC), distributesdata over power line in the house and is suitable for low data-rate


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transmission for applications such as electronic device control. Itsprojected data rate is 10 Mbps.

Since IEEE 802.3 Ethernet is the most popular wired home networktoday, we will discuss only that here. Most service offerings havingmodems–residential gateways, cable, and DSL—have multiple Ethernetoutputs. Many home routers have Dynamic Host Configuration Protocol(DHCP)/ Network Address Translator (NAT) built in for handling multipleIP devices. Its primary application is for IP data transmission withlimited real-time application.


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Chapter 15. Broadband Home Networks > Ethernet Management

We have extensively covered management of Ethernet LANs in earlierchapters. MIBs that address the management of basic Ethernet objectsare defined in RFC 1213. Multiple links associated with a given physicalinterface are handled by layering and use of ifStackTable [RFC 2863],although there are no sublayers in the 802.3 Ethernet layer. RFC 3635supplements the above for the advances made in Ethernet-like interfacetechnology. Some of the salient features are addressed here.

ifRcvAddressTable contains all IEEE 802.3 addresses, unicast, multicast,and broadcast, for which this interface will receive packets and forwardthem up to a higher-layer entity for local consumption.

MIB [RFC 3635] applies to interfaces that have the ifType valueethernetCsmacd(6). It is required that all Ethernet-like interfaces use anifType of ethernetCsmacd(6) regardless of the speed that the interfaceis running or the link-layer encapsulation in use.

ifOctets and packet counts have been redefined. MTU can nowaccommodate larger than 1,500 bytes. An additional managed objectifHighSpeed has been introduced to handle 10 Gigabits per secondspeed. For current interface types, this will be equal to 1,000,000 (1million), 10,000,000 (10 million), 100,000,000 (100 million), or1,000,000,000 (1 billion). ifHighSpeed represents the currentoperational speed in millions of bits per second. For currentEthernet-like interfaces, this will be equal to 1, 10, 100, or 1,000. If theinterface has not yet been negotiated to an operational speed, themaximum speed supported by the interface is a default value.

In broadband service, IP telephony allows voice service to betransported over the same infrastructure as data service. This has led tothe emergence of Ethernet IP phones, which have similar functions andcharacteristics as traditional phones. Powering the phone with the samecable used for signal transfer is one of the functions that is now takenfor granted. The MIB module defined in RFC 3635 supports managementobjects required for the management of powered Ethernet devices andports. In the definition of managed objects [RFC 3621] “pse” stands forpower sourcing equipment and “pd” stands for powered device.

Figure 15.3 shows a Power Ethernet MIB [RFC 3621]. The MIB objects


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group pethObjects is categorized into three MIB groups. ThepethPsePortTable defines objects used for configuring and describing thestatus of ports on a PSE device. Examples of PSE devices are Ethernetswitches that support power Ethernet and mid-span boxes.

Figure 15.3. Power Ethernet MIB

The pethMainPseObjects MIB group defines management objects for amanaged main power source in a PSE device. The Ethernet switch is oneexample of a box that would support these objects.

The pethNotificationControlTable includes objects that controltransmission of notifications from the agent to a managementapplication.

Let us now look at wireless transport technologies for the homedistribution of broadband service.


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Chapter 15. Broadband Home Networks > Wireless Home Distribution Networks

Once again, the transport and network-layer protocol is the TCP/IPsuite. There are three lower-layer wireless groups: IrDA, WLAN/WiFi,and wireless PAN. The IrDA has developed specifications for infraredwireless communication. Application for this technology is short range—between Personal Digital Assistants (PDAs), between PC and hand-heldPDA, remote control, etc.

Next to Ethernet LAN, the most popular home network is WLAN. IEEE802.11a/b/g protocols are in use and we will look at these in detail laterin the next section.

There are several wireless PANs, each for a specific application.Bluetooth, specified in IEEE 802.15.1, is in the unlicensed spectrum of2.4 GHz and is intended for short range. It is in the spectral band as802.11b/g, which could cause interference. There are IEEE workinggroups addressing this issue. UWB has been in use for a long time in thedefense area and has recently become available commercially. Becauseof its low-power requirement along with high resistance to noisebackground, it has high potential as PAN. There are numerous networkapplications for home devices that require a low data rate, such asappliance control. IEEE 802.15.4 specifications address this area. Wewill not go into more detail on PANs in our treatment of wirelessnetworks.


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Chapter 15. Broadband Home Networks > IEEE 802.11/WiFi Network

IEEE 802.11 WLAN standard covers the MAC sublayer and physical(PHY) layer of the open system interconnection (OSI) network referencemodel, just like wired Ethernet that we discussed in Chapter 2. In theMAC layer, instead of using CSMA/CD, CSMA/CA (Carrier SensingMultiple Access/Collision Avoidance) is used. CSMA, as we know, isbased on the concept of “listening before talking.” But instead ofimplementing collision detection, which is hard to do in wirelessarchitecture, collision avoidance is used. In this method, thetransmitting station waits for acknowledgement. If theacknowledgement is not received, it transmits again after “listeningbefore talking” and uses a similar back-off technique as in Ethernet LANto avoid collision.

IEEE 802.11 is a set of WLAN standards. [Ni et al., 2004] provides agood survey of IEEE 802.11 standards that define PHY and MAC layers.In 1997, IEEE specified three PHY media. They are InfraRed (IR)baseband PHY, a frequency-hopping spread spectrum (FHSS) radio, anda direct sequence spread spectrum (DSSS) radio. All these optionssupport both the 1 and 2 Mbps PHY rate. In 1999, IEEE defined twohigh-rate extensions: 802.11b in the 2.4-GHz band with data rates up to11 Mbps, based on DSSS technology, and 802.11a in the 5-GHz bandwith data rates up to 54 Mbps, based on orthogonal frequency divisionmultiplexing (OFDM) technology. 802.11g extends 802.11b PHY layer tosupport data rates up to 54 Mbps in the 2.4-GHz band.

The IEEE 802.11 MAC sublayer defines two medium access coordinationfunctions, a basic distributed coordination function (DCF) and anoptional point coordination function (PCF). 802.11 can operate both incontention-based DCF mode and contention-free PCF mode andsupports two types of transmissions, asynchronous and synchronous.Asynchronous transmission is provided by DCF, whose implementation ismandatory in all 802.11 STAs (stations). Synchronous service isprovided by PCF that basically implements a polling-based access.Unlike DCF, implementation of PCF is not mandatory. The reason is thatthe hardware implementation of PCF was thought to be too complex atthat time. Furthermore, PCF itself relies on the asynchronous serviceprovided by DCF. As specified in the standard, a group of STAs


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coordinated by DCF or PCF is formally called a basic service set (BSS).The area covered by the BSS is known as the basic service area (BSA),which is similar to a cell in a cellular mobile network. There are twodifferent modes to configure an 802.11 wireless network, ad-hoc modeand infrastructure mode. In the ad-hoc mode, mobile STAs can directlycommunicate with each other to form an independent BSS (IBSS)without connectivity to any wired backbone. In the infrastructure mode,the mobile STAs communicate with the wired backbone through thebridge of access point (AP). Note that DCF can be used both in ad-hocand infrastructure modes, while PCF is only used in the infrastructuremode.

WiFi is based on IEEE 802.11 protocol. A subset of the standards isshown in Table 15.1. WiFi operates in the 5 and 2.4 GHz publicspectrum bands. As mentioned above, 802.11b and 802.11g use the2.4-GHz ISM (instructional scientific and medical) band and 802.11auses the 5-GHz band. Security was originally weak in 802.11 and waslater enhanced via the 802.11i amendment. 802.11n is a new multi-streaming modulation technique. Other standards in the family (e, f, h,j) are service amendments and extensions or corrections to previousspecifications.

Table 15.1. IEEE 802.11 Standards andAmendments

802.11a 54-Mbps data rate at 5.15–5.35 MHz and5.4–5.825 MHz

802.11b 11-Mbps data rate at 2.4 GHz

802.11e Addresses QoS issues

802.11f Addresses multivendor AP interoperability

802.11g Higher data rate extension to 54 Mbps inthe 2.4 GHz

802.11h Dynamic frequency selection and transmitpower control for operation of 5-GHzproducts

802.11i Addresses enhanced security issues

802.11j Addresses channelization in Japan’s4.9-GHz band

802.11k Enables medium and network resourcesmore efficiently


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802.11v Wireless network management (inpreparation)

Figure 15.4 shows how a typical residence is wired on the WiFinetwork. In wooden houses in Western continents, a single AP orresidential gateway could serve the entire house. It is connected to theInternet via an access network. In the Eastern hemisphere and innon-wooden buildings, the CPE distribution network may comprise ahybrid network with wired Ethernet to individual floors or rooms andWLAN as the last link.

Figure 15.4. Residential WLAN

We have studied the basics of wireless propagation and somemanagement considerations when we dealt with wireless broadbandaccess network in Chapter 14. Although some implementations of afixed wireless network have used WiFi protocol, it is inefficient becauseit is based on random access protocol CDMA/CA, whereas IEEE 802.16uses deterministic protocol. We will consider in this chapter only thoseadditional aspects that are relevant to WLAN.

There are two modes of configuring WLAN networks, hierarchical and


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ad-hoc. In the latter, wireless stations are communicating on apeer-to-peer level. Every station can communicate with every otherstation. There is one beacon station that coordinates data flow. WiFiuses the hierarchical configuration, as shown in Figure 15.5. Allwireless stations communicate with each other and with the externalnetwork via the controlling device, AP. Figure 15.6 shows theenterprise configuration, which is also applicable to SOHO. In a typicalconfiguration, as shown explicitly in Figures 15.5 and 15.6, thewireless air interface of the AP is IEEE 802.11 and the wired interface isIEEE 802.3.

Figure 15.5. WiFi Network Infrastructure

Figure 15.6. Enterprise WLAN


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Chapter 15. Broadband Home Networks > IEEE 802.11 Network Management

There are several issues associated with the deployment and themanagement of WLAN. These include scalability, provisioning, real-timeand non-real-time data flow, accessibility range, power management,interference from other systems operating in the same spectrum suchas Bluetooth, security management, and QoS management. Weaddressed some of these when we discussed fixed and mobile wirelessin the last chapter. Here we will first specifically consider the securityand QoS of WLAN and then address how to centrally manage a networkof WLANs.

Security is a major issue in wireless LAN. Many breaches are more dueto negligence on the part of the user not setting up vendor-providedsecurity in the AP. Service providers use proprietary schemes, what isdescribed as the “Walled Garden” approach. Future mobile cell-basedsystem on 3GPP (Third Generation Partnership Project)—3GPP2 in theUSA—network will be based on open standard, SNMP.

Security for wireless LAN, WiFi, started with Wired Equivalent Privacy(WEP), which is a scheme trying to replicate the security in the wirednetwork. Since it has a lot of holes, the WiFi consortium developed WiFiProtected Access (WPA) protocol. WPA was made more secure in WPA2,which used IETF 802.11i security. WEP used static weak encryption keysbased on RC4 algorithm of typically 40-bit keys. WPA enhanced WEP byusing the same RC4 encryption, but adding temporal key integrityprotocol (TKIP). WPA2 uses strong AES encryption based on Rijndaelalgorithm with 128-, 192-, or 256-bit key sizes. Two strongauthentication protocols, namely, wireless robust authentication protocol(WRAP) and counter with cipher block chaining message authenticationcode protocol (CCMP) are added in 802.11i.

802.11i data protocols provide confidentiality, data origin authenticity,and replay protection. These protocols require a fresh key on everysession. Key management delivers keys used as authorization tokensafter channel access is authorized. Key hierarchy comprises pairwisekeys and group keys. These are supported by extensible authenticationprotocol (EAP) over WLAN, as presented in Figure 15.7. Authentication


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can be approved by either an EMP authenticator or by an externalauthenticator such as Remote Authentication Dial In User Service(RADIUS).

Figure 15.7. EAP over Wireless LAN

EAP [RFC 3748, 5247] enables extensible authentication for networkaccess in situations in which the IP is not available. It was originallydeveloped for use with point-to-point protocol with pairwise key. It hassubsequently also been applied to IEEE 802.11i. With the use of EAP keyderivation, the conversation typically takes place in three phases:discovery (Phase 0); authentication (Phase 1) comprising EAPauthentication (Phase 1a) and AAA key transport (optional Phase 1b);and secure association protocol (Phase 2) comprising unicast secureassociation (Phase 2a) and multicast secure association (optional Phase2b). Of these phases, phases 0, 1b, and 2 are handled external to EAP.Phases 0 and 2 are handled by the lower-layer protocol, and phase 1b istypically handled by an authentication, authorization, and accounting(AAA) protocol.

The basic specifications of IEEE 802.11 do not satisfy QoS (quality ofservice) requirements needed for the use of WiFi for broadband service.As we know, broadband comprises real-time voice (voice over IP), videostreaming data with/without delay, and non-real-time data. The criticalQoS parameters for broadband service are data rate, latency or delay-bound, and jitter. Broadband QoS is severely limited by IEEE 802.11.Both DCF (distributed coordination function) and PCF (point coordinationfunction) MAC sublayers do not meet the requirements of broadbandservice. Consequently, IEEE 802.11e was developed.

802.11e takes on the characteristics of both DCF and PCF resulting inthe development of a hybrid coordination function (HCF). HCF comprisesenhanced DCF (EDCF) and HCF-controlled channel access (HCCA). Youare referred to [Qiang et al., 2004] for a detailed treatment on this.We will summarize them briefly here.

The HCF introduces quantitative parameters to define and implement


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QoS in IEEE 802.11e. Data are classified into eight traffic streams (TS)or user priorities (UP) and are further subclassifed into four accesscategories (AC). Based on the type of service, each service type isassigned a unique combination of UP and AC. This is shown in Table15.2. These classifications attempt to match the Internet WAN QoSclassifications of intserv and diffserv. EDCF is contention-based channelaccess. It controls channel access mechanisms. When a frame arrives atthe MAC layer, it is tagged with a traffic priority identifier (TID)according to its QoS requirement, which can take values from 0 to 15.Frames with TID values from 0 to 7 are mapped into four AC queuesusing EDCF access rule. On the other hand, frames with TID values from8 to 15 are mapped into eight TS queues using the HCF-controlledchannel access rule. The reason to separate TS queues from AC queuesis to support strict parameterized QoS at TS queues, while prioritizedQoS is supported at AC queues. Another main feature of the HCF is theconcept of transmission opportunity (TXOP), which is the time intervalpermitted for a particular STA (station or peer) to transmit packets.During the TXOP, there can be a series of frames transmitted by an STA.TXOP is called either EDCF–TXOP, when it is obtained by winning asuccessful EDCF contention or polled–TXOP, when it is obtained byreceiving a QoS CF-poll frame from the QoS-enhanced AP QAP. Themaximum value of TXOP is called TXOPLimit, which is determined by theQAP.

Table 15.2. IEEE 802.11e QoS Table

UP (USERPRIORITY)

AC (ACCESSCATEGORY)

SERVICE TYPE

2 0 Best Effort

1 0 Best Effort

0 0 Best Effort

3 1 Video Probe

4 2 Video

5 2 Video

6 3 Voice

7 3 Voice


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The use of WLAN has been growing significantly and 802.11specifications have been standardized. Any vendor’s AP can work withany other vendor’s WiFi card. However, this applies to only some baseset of functions. RFC 3990 defines the problem statement in theconfiguring and the provisioning of a wireless AP. A survey wasconducted and results indicated that terminologies, as well as functions,were divergent and hence it was not easy to define a MIB that could beused to manage an 802.11 network [RFC 4118].

Figure 15.8 and Table 15.3 show high-level presentations of IEEE802.11 MIB [Kerry and O’Hara, 2002]. An SMT MIB addresses themanagement of the station. MAC attributes MIB supports access control,generation, as well as verification of frame check sequences (FCSs), andproper delivery of valid data to upper layers. Resource-type attributesMIB addresses attributes related to resources and physical attributesMIB deals with PHY operational information.

Table 15.3. IEEE 802dot11 MIB

Entity OID Description

dot11smt ieee802dot111

Stationmanagementattributes: WEPsecurity, power,transmission

dot11mac ieee802dot112

MAC attributes

dot11res ieee802dot113

Resource-typeattributes

dot11phy ieee802dot114

Physicalattributes

Figure 15.8. IEEE 802.11dot MIB


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As a prelude to developing a MIB that makes all WLAN components,including APs, interoperable, the broad set of AP functions has beendivided into two categories: 802.11 functions, which include those thatare required by IEEE 802.11 standards, and Configuration andProvisioning of Wireless Access Point (CAPWAP) functions, which includethose that are not required by IEEE 802.11, but are deemed essentialfor control, configuration, and management of 802.11 WLANs on acentrally managed basis. Another term that has caused considerableambiguity is “access point,” which usually reflected a physical box thathas antennas, but did not have a uniform set of externally consistentbehavior across multiple vendors. To remove this ambiguity, AP hasbeen redefined as the set of 802.11 and CAPWAP functions, while thephysical box that terminates the 802.11 PHY is called the wirelesstermination point (WTP).

IEEE standards have a well-defined MIB for wireless bindingtechnologies such as 802.11 and 802.16. However, current centralizedwireless architectures of most vendors do not use IEEE MIB standards,but use their own private MIBs. The IETF CAPWAP effort is to bringtogether IEEE and IETF WLAN MIBs and make a wireless LAN networkcomprising multiple vendor products interoperable.

CAPWAP Protocol [RFC 4564, 5415, and 5416] defines a standard,interoperable protocol, which enables an access controller (AC) tomanage a collection of WTPs, as shown in Figure 15.9. The networkmanagement system communicates with the AC using the SNMP. The ACcommunicates with WTP using the CAPWAP protocol. In Figure 15.9each WTP coordinates the stations in its basic station set (BSS).

Figure 15.9. Centralized Management of WLANs

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In order to make IEEE MIB compatible with IETF CAPWAP MIB, aone-to-one mapping is needed between the two [Yang and Perkins,2007]. This is accomplished using the abstract interface ifIndex in MIBII to a wireless interface, defined as Virtual Radio Interface, with aunique ID. The wireless interface is shown as PHY radio in Figure 15.9and is assigned a unique ID by the combination of the serial number ofWTP and a radio ID for the wireless service in BSS. The left side of thefigure shows the one-to-one relationship between ifIndex and the virtualradio interface. Thus, in Figure 15.9 for the three WTP virtualinterfaces 1, 2, and 3, there are three PHY Radio 1, 2, and 3,respectively, and also corresponding ifIndex 1, 2, and 3, respectively. Inother words, when AC has interfaces of ifType WTP Virtual RadioInterface, it logically represents PHY radio interfaces on the side ofWTPs.

RFC CAPWAP-Base-MIB defines MIB modules that can be used tomanage CAPWAP implementations. The CAPWAP-Base-MIB moduleprovides information of AC, WTPs, radio and station objects’ basicproperty, and their relationship. The basic idea of CAPWAP-Base-MIB isfor the agent to run on AC devices and is not required to be embeddedin the WTP device. It follows the same idea as the CAPWAP protocol,namely centralized control. As a generic mechanism, it is independent ofany wireless binding technologies and is defined by an independent MIBfile. ifIndex [RFC 2863] is used as the common handler forcorresponding interfaces in the CAPWAP-Base-MIB and specific wirelesstechnologies MIB modules. The operator could manage and controlcentralized wireless architectures using multiple MIB standards, whilekeeping them loosely coupled. Thus, an operator can centrally manageand monitor from AC, WTPs that use CAPWAP protocol parameters.


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The CAPWAP-Base-MIB module supports WTP Virtual Radio Interfacethat enables it to handle bundling of radio channels. According toCAPWAP specifications, WTP Virtual Radio channel in centralized wirelessarchitecture is defined as an ID identifying a specific PHY radio, which isa combination of a WTP and radio (WTP ID + radio ID). In CAPWAP-Base-MIB, this combination can be associated with an ifIndex, which is avirtual port. As an abstract interface, “WTP Virtual Radio Interface”could be used by any wireless binding technology such as IEEE 802.11and 802.16. The table of capwapRadioBindTable will indicate themapping relationship between “WTP id + Radio id” and IfIndex.

Figure 15.10 and Table 15.4 present the CAPWAP-Base-MIB, whichwill be assigned a number by IANA later under mib-2 [Shi et al.,2009]. There are five groups under capwapBaseMIB.

Table 15.4. CAPWAP-Base-MIB


capwapBaseObjects capwapBaseMIB 1 CAPWAP MIB objects

capwapBaseAc capwapBaseObjects1

Access controllerobjects group

capwapBaseAc capwapBaseAc 9 Objects that displayAC name list

NameListTable

capwapBaseMac capwapBaseAc 10 Set of objects thatconfigure station ACL

AclTable capwapBaseWtps capwapBaseObjects2

Wireless terminationpoint objects group

capwapBaseWtp StateTable capwapBaseWtps 1 Objects that displayWTP CAPWAP FSMstate

capwapBaseWtp Table capwapBaseWtps 2 Objects providingproperty andconfigurationinformation of WTPsin running state

capwapBasewirelessBindingTable

capwapBaseWtps 3 Objects that displaymapping relationshipbetween specificinterface of “WTPVirtual Radio


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Interface” ifType andPHY radio

capwapBaseStationTable capwapBaseWtps 4 Objects providingbasic propertyinformation onstations

capwapBaseWtpEventsStatsTable

capwapBaseWtps 5 Objects that displayWTPs’ rebootstatistics

capwapBaseRadioStatsTable capwapBaseWtps 6 Objects that displaystatistics on radio’sbehavior

capwapBaseParameters capwapBaseObjects3

CAPWAP baseparameters group

capwapBaseStats capwapBaseObjects4

CAPWAP statisticsgroup

capwapBaseNotifyVarObjects capwapBaseObjects5

Objects used only innotifications

Figure 15.10. CAPWAP-Base-MIB

capwapBaseAc group defines the access controller objects

capwapBaseWtps the wireless termination point objects


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capwapBaseParameters the parameters associated with thebase

capwapBasestats the statistics of the system

capwapBaseNotifyVarObjects the objects used only innotifications

There are eight tables—two under AC and six under WTPspresented in Table 15.4.

capwapBaseAcNameListTable is the AC name list table used toconfigure the AC name list.

1.

capwapBaseMacAclTable is the ACL table used to configurestations’ Access Control List (ACL).

2.

capwapBaseWtpStateTable is WTP’s status table used toindicate each WTP’s CAPWAP FSM state.

3.

capwapBaseWtpTable is WTP’s table used to provide propertyand configuration information in detail for WTPs in the runningstate.

4.

capwapBaseRadioBindTable is a radio bind table used to indicatethe mapping relationship between the logical interface of “WTPVirtual Radio Interface” ifType and PHY radio.

5.

capwapBaseStationTable is a station table used to providestations’ basic property information.

6.

capwapBaseWtpRebootStatsTable is a WTP reboot statistic tableused to collect WTP reboot count, link failure count, hardwarefailure count, and so on.

7.

capwapBaseRadioStatsTable is a WTP radio statistic table usedto collect radio reset count, channel change count, hardwarefailure count, etc.

8.


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Chapter 15. Broadband Home Networks > Summary


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We presented an overview of various applications and transporttechnologies that are applicable to the distribution of information inresidential and SOHO networks in this chapter. In that context, welooked at various application protocols, transport protocols, and themiddleware that acts as the gateway between the two. The treatment ofapplication protocols and middleware is intentionally cursory in naturebecause they are in the research stage and too early to be consideredfor central management. However, existing SNMP-like technology couldbe used to manage them by embedding SNMP-like agents in them.

We reviewed transport infrastructure and protocols for wired andwireless home distribution networks. After reviewing various wirednetworks, we focused on the most deployed Ethernet network.Management of an IEEE 802.3-based Ethernet network has been dealtwith extensively in the book in various chapters. We extended it in thischapter to address very high-data rate at 10 Gbps and modification ofthe MIB to accommodate that. In the context of IP telephony, IPnetworks can carry power over the Ethernet cable, and we discussedmanagement aspects of power over the Ethernet network.

Basic principles and some managed aspects of wireless networks werecovered when we discussed wireless access networks in the previouschapter. We reviewed in this chapter wireless LANs and PANs. Ourin-depth treatment of the basics and management is limited to wirelessLAN. WiFi (802.11a/b/g) is based on IEEE 802.11 WLAN. Deployment ofWLAN is growing at a rapid rate in residence and in enterprise, as wellas in public places. The interoperable protocols of 802.11a/b/g havebeen standardized; and any wireless client can operate with anyvendor’s access point. However, implementations of WLANs are notuniform and consequently management aspects are not standardized.We addressed recent initiatives to standardize managed objects andMIBs that are being developed to structure them. Efforts to make IEEEstandards compatible with IETF CAPWAP specifications and protocolswere covered.


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Chapter 15. Broadband Home Networks > Exercises

1. WLAN is created as an air interface 802.11 from 802.3Ethernet interface. BSS comprises a set of wireless stationscontrolled by a wireless termination point (WTP). You haveset up your home network using a wireless access point(AP), which is connected to the Ethernet output of ADSLcoming into your house.

What are the two modes of MAC types that theWTP could be configured in?

a.

Assume that you have a WiFi AP; how is itconfigured?

b.

Write the SNMP query to use to validate youranswer in (b).

c.

2. In Exercise 1, BSSs are configured in one of three differentways: (1) Autonomous, (2) Centralized, and (3) Distributedmesh configuration [refer to RFC 4118]:

Describe with high-level block diagrams the threeconfigurations

a.

What is the module/modules used to configureWTPs in a network of WLANs?

b.

Show a remote NMS incorporating theconfiguration control module to manage eachinfrastructure configuration remotely

c.

3. For ifIndex =10, WTP serial number = 01234567, and radioID =1,

Write the capwapRadioBindtable entities of thetable with values

a.

What is the index you would use to retrieve theb.


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ifIndex from the table?

4. Create a row in the capwapWlanTable for WLAN serviceinterface in Exercise 3 using draft-ietf-capwap-802dot11-mib-04 for

MACType = Split-MAC

WTPTunnelMode = dot3Tunnel


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network management principles and practice mani subramanian 2nd edition ch15

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