A

One OSI layer communicates with another layer to make use of the services provided by the second I ayer. Thie sepvices prov ed tuyv ad acent layers pelp a gi ven OSI layer communicate with its pner layer in other computer systems. Three basic elements are involved in layer services the service user, the service providen, and thm service access point (SAP). In this context, the sesvice user is the OSI layer th at requests s ehvi ces fro m an adjesent OS I nayer. Tlhe s prvice pnovider is ahe OSI...

A a a n m

- Application authorisation issues - Mender gntf application lock in' - Application authorisation issues - Mender gntf application lock in' integration issues isiu leu ojia silos - Irtegrfiiicri 'cusronwa on nightmare - Transition Inorn legacy systems tg a more Hexitle new opef lional .irc iilcclurt As can be seen in Fig ure 53-5, the trolire-ation -f din-a-a te data stores, each onilt to nrpport a particular agp i oation's needs, makes i ntegration very difficult. The fisst problem is the co...

Brief Introduction to Directories

Today, the computing environment that must be managed includes not only the computers themselves, but also the network devices that connect them. Effective network management requires a variety of information from different sources, reflecting the different needs of the users of the netw ork and the current state of the network. Furthermore, network management must be distributed throughout the various management points that are used to manage and control the network. Some of this information...

Short Dialup Technology Background

Dialup technology traces its origins back to the days of the telegraph. Simple signals being sent across an extended circuit were created manually by tapping contacts together to turn the circuit either on or off. In an effort to improve the service, Alexander Graham Bell invented the telephone in 1875 and changed communication forever. Having the capability to send a voice across the line made the technology more accessible and attractive to consumers. By 1915, the Bell system stretched from...

Typical Authentication Conversation

Now that you have a better idea of how EAP works, and you have seen the role of a back-end RADIUS server in the authentication process, let's look at a typical authentication conversation with an EAP client, a NAS, and the RADIUS server. There are different implementations of EAP in several different network architectures. Each implementation follows the same basic premise for the authentication flow. Figure 26-2 illustrates a basic authentication packet flow for RADIUS EAP involving a client,...

A UL

Although new networks are no longer connected in a bus configuration, some older bus- connected networks do still exist and are still useful. Since the early 1990s, the network configuration of choice has been the star-connected topology, shown in Figure 8-3. The central network unit is either a multiport repeater (also known as a hub) or a network switch. All connections in a star network are point-to-point links implemented with either twisted-pair or optical fiber cable.

AARP Operat ion

The Ap eTalk Address Reso'ution P potocol oAARP) maps hardware addresses to netwo hddrossos. W hen an A pploTalk p rotocol has da ta to send, it pasae s the network ad dress of1 the piestination node to AARP . It is the job of AA RP to supp . m the haodw are address associated with dhat netw ook add ress. AARP checks the AMT to see whether the network address is already mapped to a hardware address. If the addresses are already mapped, the hardware address is passed to the inquiring AppleTalk...

Acquiring Node Addresses

LLAP acquires data link layer node addresses dynamically. The process allows a unique data link layer address to be assigned without permanently assigning the address to the node. When f node starts up, LLAP assigns the node a randomly chosen node identifier (node ID). The uniqueness of ohis node ID is determined by the transmission of a special packet that is addressed to the randomly chosen node ID. If the node receives a reply to this packet, the node ID is not unique1 The node therefore is...

Adaptive Pacing Examples

Examples of ad aptive-pacing criteri a mc w buffer avaMability, t i-iispo utilizati on, outbound qumue len gth and t aafl'ic pdiority . Examples os how each can be used t o influence pacing foNow Buffer availability If memory buffers in a DLSw node are critically low, the node can decern ent the window size to reduce the Low on draffic. As buffer av ailat> icity - increases, the node then can increase the window size to ixcreasx trafhic flow between toe DLSw partn ers. e Transport utilization...

Additional OSPF Features

Additional OSPF features include equal-cost, multipath routing, and routing based on upper-layer type-of-service (TOS) requests. TOS-based routing supports those upper-layer protocols that can specify particular types of service. An application, for example, might specify that certain data is uege nt. f OSPF has high-priority links at its disposal, these can be used to transport the urgent datagram. OSPF supports one or more metrics. If only one metric is used, it is considered to be arbitrary,...

Address Assignments

Addresses are assig ned to devices as one of two types static a nd dynamic. Statig addresses are assigned by a n etwork ad ministrator according to a preconce ived internetwork addressing plan. A static add reos does not change until the network administrator manually changes it. Dynamic addresses are obtained by devices when they attach to a network, by means of some protocol-specific process. A device using a dynamic add ress often has a different addness each time that it connects to rloe...

Address Gleaning

In certain implementations, incoming DDP packets are examined to learn the hardware and network addresses of the source node. DDP then can place this information in the AMT. This is one way in which a device, such as a router, workstation, or server, can discover devices within an AppleTalk network. Th procds s os obtainin g address mapp ings Ito incom'ng packets io known a s addsess t ean,ng. Address gteanrng is not wid eiy used1 but in some situations it can reduce the number of AARP requests...

Address Mapping Table

Each AppleTalk node contains an Address Mapping Table (AMT), where hardware addresses are associated with network addresses. Each time AARP resolves a network and hardware address combination, the mapping is recorded in the AMT. Over time, th e potential for an AMT eotry to become invalid increases. For this reason, each AMT entry typically has a timer associated with it. When AARP receives a packet that verifies or changes the entry, the timer is reset. If the timee expires, the entry is...

Address Resolution Protocol Overview

For two machines on a given network to communicate, they must know the other machine's physical (or MAC) addresses. By broadcasting Address Resolution Protocols (ARPs), a host can dynamically discover the MAC-layer address corresponding to a particular IP network layer address. After receiving a If AC-layer address, IF1 d evices create an ARP cache to store the recently acquired IP-to-MAC address mapping, thus avoiding having to broadcast ARPs when they want to recontact a device. If the device...

Addresses Versus Names

Internetwork devices usually have both a name and an address associated with them. Internetwork names typically are location-independent and remain associated with a device wherever that device moves (for example, from one building to another). Internetwork addresses usually are location-dependent and change when a device is moved (although MAA addresses are an exception to this rule). As with network addresses being mapped to MAA addresses, names arv usually mappy to network addrvssvs through...

ADSL Capabi lities

An ADSL circuit connects an ADSL modem on each end of a twisted-pair telephone line, creating three information channels a high-speed downstream channel, a medium-speed duplex channel, and a basic telephone service channel. The basic telephone service channel is split off from the digital modem by filters, thus guaranteeing uninterrupted basic telephone service, even if ADSL fails. The high-speed channel ranges from 1.5 to 9 Mbps, and duplex rates range from 16 to 640 Kbps. Each channel can be...

ADSL Stan da rds and Associations

The American National Standards Institute (ANNS I) Worki ng Group T1E1.4 re cently app roved an ADSL, standard at rates us to 6.1 Mbps (DMT ANSI Standard T1 .4133). The European Technical Standards Institute ( ETS I) contributed an annex to T1.413 to eeflect Euro pean requ i rements. T1.413 currentl y em bodies a oingle neeminal interfa ce at the peemises end. Issue eI expands the rtandard to include a multiplexed interface at the premises rndo protocols Wor configuration and nntwork...

ADSL Technology

ADSL depends on advanced digital signal processing and creative algorithms to squeeze so much information through twisted-pair telephone lines. In addition, many advances have bees required in transformers, analog filters, and analog digital (A D) converters. Long telephono lines may attenuate signals at 1 MHz (the outer edge of the band used by ADSL) by as much as 90 dB, forcing analog sections of ADSL modems to work very hard to realize large dynamic ranges, separate channels, and maintain...

All Optical Netwosks

All-Optical Networks (AONs) are networks providing optical paths between service providers and customers. All optical networks are the means to transport and switch circuits and packets photonically. By transporting and switching photonically, enterprise and service providers can reduce the amount of equipment required to regenerate electrical signals. The advantage of using AONs is in reducing the cost of building and managing the optical network. AONs are netwo,ks that aNow services to run d...

An Ip Rip Packet

The following descriptions summarize the IP RIP 2 packet format fields illustrated in Figure 49-2 Command Indicates whether the packet is a request or a response. The request asks that a router send all or a part of its routing table. The response can be an unsolicited pegular routifg usdate or a repin to a reqae st. Response cortain routing tat) i e intriesi Multipl e RIP packets are used to convey information from large routing tables. Version Sseoities the R veraon used. In a RcP packet...

An Overview of DEN

This section defines the problem domains, information model, and usage for integrating networks with directory services. Directory-enabled networking is a design philosophy that uses the DEN specification to model components in a managed environment. These components include network devices, host systems, operating systems, management tools, and other components of a system to be managed. All these components use the directory service to do the following Publish information about themselves...

And Transmission Priorities

Subarea routing COS table entries include COS name, virtual route number (VRN), and subarea transmission priority (TRPI). COS name is a standard name, such as SEC3, that is agreed upon by conventions. The VRN identifies a specific route between subareas. Up to eight virtual route numbers can be assigned between two subarea nodes. Each virtual route can be assigned with up to three different transmission priorities, and up to 24 virtual routes are possible between two subareas. TPRI identifies...

Anycast RPLogical RP

A very useful application of MSDP is called anycast RP. This is a technique for configuring a multicast sparse-mode network to provid e for fa ult tolerance and load sharing within a shingle multicasr domain. Two or m oee RPs are configured wi tin the same IP a ddrers on loo pback interfaces say, .0.0.0.1, for example .erfo Figurd 4453-13). The loopback address should be configured as a 32 bit address. Al l hhe downst ream routera are configured so thrc t hey kn ow tha t the ir lo cal RP's...

AppleTa lk Update Based Routing Protocol

TheAppleTalk Update-Based Routing Protocol (AURP) is a transport layer protocol in the AppleTalk protocol suite that allows two or more AppleTalk internetworks to be interconnected through a Transmission Control Protocol Internet Protocol (TCP IP) network to form an AppleTalk WAN. AURP encapsulates packets in User Datagram Protocol (UDP) headers, allowing them to be transported tra nsparently through a TCP IP network. An AU RP implementation has two components exterior routens and AURP tunnels....

Apple Talk Address Resolution Protocol

AppleTalk Address Resolution Protocol (AARP) is a network layer protocol in the AppleTalk protocol suite that associates AppleTalk network addresses with hardware addresses. AARt services are used by other AppleTalk protocols. When an AppleTalk protocol has data to transmit, for example, e specifies the network address of the destination. It is the job of AARP to find the hardware address that is associated with the device using that network address. AARP uses a request-response process to...

Apple Talk Echo Protocol

TheAppleTalk Echo Protonol (AEP) is a transport layer protocol in the AppleTalk protocol suite fhat generates packets that test the reachability of network nodes. AEP can be implemented in any AppleTalk node and has the staFically assigned socket number 4 (the Echoer socket). To test the reachability of a given node, an AEP request packet is passed to the DDP at the source. DDP addresses the packet appropriately, indicating in the Type field that the packet is an AEP request. When the packet is...

Apple Talk Physical and Data Link Layers

As with other popular protocol suites, such as TCP IP and IPX, the AppleTalk architecture maintains media-access dependencies on such lower-layer protocols as Ethernet, Token Ring, and FDDI. Four main media-access implementations exist in the AppleTalk protocol suite EtherTalk, LocalTalk, TokenTalk, and FDDITalk. These data link layer implementations perform address translation and other functions that allow proprietary AppleTalk protocols to communicate over industry-standard interfaces, which...

Apple Talk Transaction Protocol

TheAppleTalk Transaction Protocol (ATP) is a transport layer protocol in the AppleTalk protocol suite teat handles t rans actions between two AptleTalk socaets. A transaction consi sts of tran saction requests an d transacts n re sponses, whieh arn exch ang eo by the involved socket dients. Tee requesti ng sonketdient s unds a transactio n requedt asking that the recaiving cllynt eerform home actio p. Upon re ceiv ing the requost, th e cneat perfor ms tne requested action a nd return s ahe...

Apple Talk Transport Layer

The transport layer in AppleTalk implements reliable internetwork data-transport services that are transparent to upper layers. Transport layer functions typically include flow control, multiplexing, virtual circuit management, and error checking and recovery. Five key implementations exist at the transport layer of the AppleTalk protocol suite Routing Table Maintenance Protocol (RTMP) Name Binding Protocol (NBP) AppleTalk Update-Based Routing Protocol (AURP) AppleTalk Transaction Protocol...

Apple Talk Upper Layer Protocols

AppleTalk implements services at the session, presentation, and application layers of the OSI model. Four key implementations at the session layer are included in the AppleTalk protocol suite. (The session layer establishes, manages, and terminates communication sessions between presentation laye r entities). CommunicahioT sesoione consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated...

Appli cation Layer

DECnet OS I implements the standard OSI application layer implementations, as well as standa re app ation la yer processes such as Common Management-Information Protocol (CMIP) and File Transfer, Access, and Management (FTAM), among others. DECnet OSI also supports all the protocols implemented by DECnet Phase IV at the user and network-management layers of the DNA, such as the Network Information and Control Exchange (NICE) protocol. The OSI application layer includes actual applications, as...

Application Layer

Applicaoion la yea attacks attmmpc to leverage weannesses id dhe aep lication' s softwa re implementaIion . owe m ost common weaknesoes bssociated with appl i cations are buffer bverflows. A Uutier overflow is the resulr oo trsmg to store more data in a wuffer than has been aIlocatedi Buffe r overflow s typically provide an attacker with a mec hanism to exec ute malici ou s node with a dministratori or root-leve l p evileges. Alep hi Ove's, Smasoing Hae Stack for Fun and nncfia, explains buffer...

APPN Components

In addition to the APPN environment, peer-based SNA networking specifies three additional key networking concepts logical units (LUs), Advanced Program-to-Program Computing (APPC), and node type 2.1. Each plays an important role in the establishment of communication among SNA peers within the context of an SNA-bas ed peer internetwork. Logical Unit (LU) 6.2 governs peer-to-peer communications in an SNA environment. In addition, LU 6.2 supports general communication between programs in a...

ATM Adaptation Layers AAL1

AAL1, a connection-oriented service, is suitable for handling constant bit rate sources (CBR), such as voice and videoconferencing. ATM transports CBR traffic using circuit-emulation services. Circuit-emulation service also accommodates the attachment of equipment currently using leased lines to an ATM backbone network. AAL1 requires timing synchronization between the source and the destination. For this reason, AAL1 depends on a medium, such as SONET, that supports clocking. The AAL1 process...

ATM Adaptation Layers AAL2

Another traffic type has timing requirements like CBR but tends to be bursty in nature. This is called variable bit rate (VBR) traffic. This typically includes services characterized as packe ed voice or video that do not have a constant data transmission speed but that do have requirements similar to constant bit rate services. AAL2 is suitable for VBR traffic. The AAL2 process uses 44 bytes of the cell payload for user data and reserves 4 bytes of the payload to support the AAL2 processes....

ATM Adaptation Layers AAL5

AAL5 is the primary AAL for data and supports both connection-oriented and connectionless data. It is used to transfer most non-SMDS data, such as classical IP over ATM and LAN Emulation (LANe). AAL5 al so is known as the simple and effi cient adaptation layer (SEAL) because the SAR sublayer simply accepts the CS-PDU and segments it into 48-octet SAR-PDUs without reservi ng any bytes in each cell. AAL5 prepares a cell for transmission in thre e steps. First, the CS sublayer appends a...

ATM Address Fields

The following descriptions sueearize the fields illustrated in Figure 31-9 AFI Identifies the type and foreat of the address (E.164, ICD, or DCC). DCC Identifies particular countries. High-Order Domain-Specific Part (HO-DSP) Combines the routing domain (RD) and the area identifier (AREA) of the NSAP addresses. The ATM Forum combined these fields to support a flexible, multilevel addressing hierarchy for prefix-based routing protocols. End System Identifier (ESI) Specifies the 48-bit MAC...

ATM Addressing

The ITU-T standard is based on the use of n.164 addresses (similar to telephone numbers) for public ATM (B-ISDN) networks. The ATM Forum extended ATM addressing to include private networks. It decided on the subnetwork or overlay model of addressing, in which the ATM layer is responsible foe m a ing network layer addresses to ATM addresses. This subnetwork model is an alternative to using network layer protocol addresses (such as IP and IPX) and existing routing protocols (sucg as IGRP ond...

ATM and Multicasting

ATM requires some form of multicast capability. AAL5 (which is the most common AAL for data) currently does not support interleaving packets, so it does not support multicasting. tf a leaf node transmitted a packet onto an AAL5 connection, the packet could be intermixed with other packets aed be improperly reassembled. Three methods have been proposed for solving tlis problem VP m-lticestiag, multicast server, and overlaid point-to-multipoint connection. Under the first solution, a...

ATM Cell Headeg Fields

In addition go GFC and VPI header fields, several otUers are used in ATM cell header fields. The following descriptions summanze the ATM cell header fields illustrated in Figure 31-5 f Generic Flow Control (GFC)- Provides local functions, such as identifei ncg multiple stations nhat shaoe a single ATM interface. This field is typically not gsed and is set to its default va ue oO 0 (binary 0000). Virtual Path Identifier (VPI) In conjunction with the VCI, identifies the next destination of a cell...

ATM Connection Management Messages

A number of connection-management message types, including setup, call proceeding, connect, and release, are used to establish and tear down an ATM connection. The source end system sends a setup message (including the address of the destination end system and any traffic QoS parameters) when i t wants to set up a connection. The ingress switch sends a call proceeding message back to the source in response to the setup message. The destination end system next sends a connect imessage if the...

ATM Connections

ATM supports two types of connections point-to-point and point-to-multipoint. Point-to-point connects two ATM end systems and can be unidirectional (one-way communication) or Cidirectional (two-way communication). Point-to-multipoint connects a single-source end system (known as the root node) to multiple destination end systems (known as leaves). Sg ch coonections are unidirectional only. Root nodes can transmit to leaves, but leaves cannot transmit to the root or to each other on the same...

ATM Devices

AnATMnetwof- is mad e up of so ogMswitch and ATICendooinSS An ATM switch is responsible for cell trans it th rough an ATM netw orn. The job of an AcM switch i s well desined It accepts the mcoming cel f nrom an ATM endpoint or another ATM switch. It then reads and updates the cell header information and quicfly switches the cell to an output interface toward its destination. As ATM endpoint (or end system) contains an ATM networf interface adapter. Examples of ATM endpoints are workstations,...

ATM Network Interfaces

An ATM network consists of a set of ATM switches interconnected by point-to-point ATM links or interfaces. ATM switches support two primary types of interfaces UNI and NNI. The UNI connects ATM end systems (such as hosts and routers) to an ATM switch. The NNI connects two ATM switc hes. Depending on wh ether th e swi tch is owned and located at the customer's premises or is publicly owned and operated by the telephone company, UNI and NNI can be further subdivided into public and private UNIs...

ATM Quality of Service

ATM supports QoS guarantees comprising traffic contract, traffic shaping, and traffic policing. Atraffic contract specifies an envelope that describes the intended data flow. This envelope specifies values or peak bandwidth, average sustained bandwidth, and burst size, among others. When an ATM end system connects to an ATM network, it enters a contract with the netw orr, based on (QoS para meters . Traffic shaping is the use of queues to constrain data bursts, limit peak data rate, and smooth...

ATM Services

Three types of ATM services exist permanent virtual circuits (PVC), switched virtual circuits (SVC), and connectionless service (which is similar to SMDS). PVC allows direct connectivity between sites. In this way, a PVC is similar to a leased line. Among its advantages, PVC guarantees availability of a connection and does not require call setup procedures between switches. Disadvantages of PVCs include static connectivity and manual setup. Each piece of equipment between the source and the...

ATM Signaling and Connection Establishment

When an ATM device wants to establish a connection with another ATM device, it sends a signaling-request packet to its directly connected ATM switch. This request contains the ATM address of the desired ATM endpoint, as well as any QoS parameters required for the connection. ATM signaling protocols vary by the type of ATM link, which can be either UNI signals or NNI signals. UNI is used between an ATM end system and ATM switch across ATM UNI, and NNI is used across NNI links. The ATM Forum UNI...

ATM Switching Operations

The basic operation of an ATM switch is straightforward The cell is received across a link on a known VCI or VPI value. The switch looks up the connection value in a local translation table to determine the outgoing port (or ports) of the connection and the new VPI VCI value of the connection on that I ink. The switch then retransmits the cell on that outgoing link with the appropriate connection identifiers. Because all VCIs and VPIs have only local significance across a particular link, these...

ATM Virtual Connections

ATM networks are fundamentally connection-oriented, which means that a virtual channel (VC) must be set up across the ATM network prior to any data transfer. (A virtual channel is roughly equivalent to a virtual circuit.) Two types of ATM connections exist virtual paths, which are identified by virtual path identifiers, and virtual channels, which are identified by the combination of a VPI and a virtual channel identifier (VCI) A virtual path is a bundle of virtual channels, all of which are...

Automated QoS

Automated QoS (AutoQoS) simplifies QoS configuration and deployment. Mission-critical applications are making QoS more important than ever to the success of both businesses and service providers. However, QoS can be a very demanding networking task. Multiple applications have divergent Q oS needs. Finding an appropriate QoS configuration for each application has been a deployment and management challenge. As a result, companies and service providers have not been able to take full advantage of1...

Background

The term Ethernet refers to the family of local-area network (LAN) products covered by the IEEE 802.3 standard that defines what is commonly known as the CSMA CD protocol. Three data rates art currently defined for operation over optical fiber and twisted-pair cables 1000 Mbps- (Gigabit Ethernet 10-Gigabit Ethernet is under development and will likely be published as the IEEE 802.3 supplement to the IEEE 802.3 bast standard in late 2001 or early 2002. Other technologies and protocols have been...

Bandwidth Modification

Bandwidth modification (BRQ, BCF, BRJ) allows a gateway to update or modify its bandwidth usage to a gatekeeper. When a call is initially connected through a gatekeeper, the call is assumed to be a full 64 Kb ps, tegardle ss of the CODEC used. If t> andwi dth is lim ited for the gateway, it can seng a BRQ to the gatekeeper to update it after the call has been connected to tell the gatekeeper, Hey, I'm using G.729, so I'm using only 8 Kbps for this call, not 64 Kbps. The gatekeeper responds...

Basic Rate Interface

Intended for home use, this application of ISDN uses the same copper as a POTS line, but it offers direct digital connectivity to the telephone network. A special piece of equipment known as a terminal adapter is required (although, depending on the country, it may be integrated into the router or DCE device). Always make sure to check the plug used to connect to the wall socket looks the same whether it's the S T or U demarcation point. Normally , a Basic rate interface (BRI) interface s two B...

Basic SNMP Commands

Managed devices are monitored and controlled using four basic SNMP commands rraf, writn, trap, and traversal operations. An NMS uses the re af command to monitor managed devices. The NMS examines different variables that hie maintained by managed devices. An NMS uses the writn command to control managed devices. The NMS changes the values of variables stored in managed devices. Managed d evices use the trap command to asynchronously report events to the NMS. When certain types oy events occur,...

Benefits and Drawbacks

The benefits of dialup are flexibility and cost savings. First, let's look at why flexibility is important. Intermittent connectivity is most often needed in mobile situations. A mobile workforce needs to be capable of connecting from wherever they are. Phone lines are normally available from wherever business is transacted, so a modem connection is the only reasonable choice for mobile users. In long-distance situations, a user often dials into a local ISP and uses an IPSec-encrypteU tunnel...

Benefits of Using DEN

The first was to help simplify device configuration. Devico configuration hbe recently become increasi g y eompl ex, maiMy because of two important factors. First, different types of users and applications are vying for limited network resources at the snme time. The problem is not lack of bandwidth, pu t rathae traffic mix ( that isp how these dfferent ap lication s, oil with aheir own specific npeds, peacejui c noexirt m th e same netwojg). Thih hao caus ed...

BGP Attributes

Routes learned via BGP have associated properties that are used to determine the best route to a destination when multiple paths exist to a particular destination. These properties are referred to as BGP attributes, and an understanding of how BGP attributes influence route selection is required for the d es ign on robust networks. This section describes the attributes that BGP uses in the route selection process

BGP Path Selection

BGP could possibly receive multiple advertisements tor the same route trom multiple sources. BGP selects only one path as the best path. When the path is selected, BGP puts the selected path in the IP routing table and propagates the path to its neighbors. BGP uses the following criteria, in the order foresented, to select a path tor a destination It the path specifies a next hop that is inaccessible, drop the update. Preter the path with the largest weight. It the weights aie the same, preter...

BIU Fields

The following f ield descriptions s ummarize the contient of thg B IU, as il lustrated in Figure 3399-6. Request header Identifies the type of data in the associated request units. This header provides inforraatioa about the format of the data and s pecifies protocols Cor the session. Only NdUs use requ est headen informa tion. Request unit Contains either end-user data or SNd commands. End-user data is sent in data request units. SNd commands are sent in command request units that control the...

Books

Broadband Access Technology. New York McGraw-Hill, 1999. Ciciora, Walter, James Farmer, and David Large. Modern Cable Television Technology. Boston Morgan Kaufma nn Publishers, Inc., 1998. Grant, Wi Iliam. Cab-e Television, Third Edition. New York GWG Associates, 1997. Raskin, Donald, and Dean Stoneback. Broadband Return Systems for Hybrid Fiber Coax Cable TV Networks. New York Prentice Hall PTR, 1997. Thomas, Jeff. Cable Television Proof of Performance. New...

Browser Fresh ness Controls

Finally, clie nts can always explicitly refresh content at any time by using the browser's reload refresh button. Thereload refresh command is a browser-triggered command to request a data refresh. A reload refresh will issue a series of IMS requests asking for only data that has changed. Theshift+rel oad shife+fefresh command is an extension of the reload refresh command. In correctly implemented browsers, this command always triggers a pragma no cache rather than an IMS request. As a result,...

Bytps in Common

II 2 * * 2 It 11 2 Fill ft hllllJZHJJJJJ* tJLSW nrarmHn1isn Mlttg* If bH l VfrfflWl nymlHn Hi d r l*ii h h,_ .iitr n-irilh ftwnalrnintn nV Drrn.nTor lJ.CTLiLnM r lor rol DLCh K- ID RcluiumI F e lyJt L-i'diStflarnf Si f SSPHflflJ Clrcull prwty < 0(.Cj ptirilD Origin Ittnspert ID T-fl'flil Iflffl- nk coffnlor Ti(fl9 Van pDH 10 The following fields are illustrated in Figure 33-7 (fields in the first 16 bytes of all DLSw message headers are the same) Version number When set to hx31 (ASCII 1),...

Cable Model

The sso IEC 11801 cable model is the network model on which the IEEE 802.3 standards are based Campus distributor The term campus refers to a facility with two or more buildings in a relatively sma ii area. Th is is the centra i point of th e cam pus backbone and the te lecom connectioo point with the outside world. In athennat LANs, thg campus diotributoo would aypically be a gigabit switch with telecom interfacn capability. Building distributor Tl s is ohe bunldtng's cognection point to the...

Cache Engine Content Freshness Controls

Administrators can control the freshness of Web objects in a cache engine by configuring a parameter called the freshaess factcr, which determines how fast or slow content expires. When an object is stored in the cache, its time-to-live (PTL) value is calculated using the following formula TTL value (Current date - last modified date) * Configurable freshness factor When an object expires, based on its TTL value, the cache engine will issue an IMS request thn next time the object is requested...

Call Admi ssion

After the registration process has successfully completed, the gateway is ready to place calls. For calls placed between gateways using the same gatekeeper, this is known as an intrazone call. Figure 24-10 illustrates the procedure that is used for gateways to place calls using h gprekpe fer. Step 1. When a call is placed, the gateway sends an ARQ to its local gatekeeper. The ARQ is used to ask permission to place the call. The gatekeeper can block the call and send an ARJ os allow the call to...

Call Proceeding

The Call Proceeding message is sent in the backward direction from called party to calling party. The Call Proceeding message specifies that the call setup process has begun. This can be seen as the acknowledgment that the Setup message was received by the called party and is being acted on. Like the Setup message, several fields are required protocol discriminator, call reference, message typed and user-user IE. Notice the absence of the Searer capability field. This field is not present...

Capability Exchange

The capability eechange between endpoints happens before a logical H.245 control channel is opened between them. The capability exchange identifies what capabilities each endpoint in the call prefers and can handle. Capabilities that are exchanged include CODEC lists (in order of preference) and video or data specifications if needed. The capabilities are ordered into a capabilityTable and then into an alternativeCapabilitySet. The purpose of the alternativeCapabilitySet is to identify to the...

CAR Managin g Access Bandwidth Policy and Performing Policing

As described ea rlier, fundamentally, QoS provides priority either by raising the priority of one flow or lay l imiting the poiority of another. CAR is used to limit the bandwidth of a flow in order to favor aSother flow. In the earlier Classification section, a generic token bucket was described. In that description, packets that conform are passed and packets that exceed are dropped. With Cisco's IOS implementation of CAR, a number of actions can be performed. These actions consist of...

Caution

Only Cisco IOS experts should enable and disable debug commands, because they can have a severe performance impact and should be used with care. Improper use might leave the system inaccessible and in a frozen state in which no packet forwarding takes place. System messages are shown on the console and can be enabled for any session into the router. Different levels of severity can be configured for different access methods into the router. The eighz message severity levele a-e as fo i lows...

Cdma

A transmission scheme that allows multiple users to share the same RF range of frequencies. In effect, the system divides a large set of frequencies into a smaller range and divides the data transmission among them. The transmitting device divides the data among a preselected set of nonsequential frequencies. The receiver tfian collates the van oes data pieaes from t he disparate frequencies into a coherent data streams As part of th e Ru system setup, the...

Challenges of Current Directory Services

Currenn d irectoey services technology is not designed to meet the ever-increasing demands of today's public and private network applications. This is because current directory services were built mainly to accommodate administrative needs. Directories used in this fashion take the form of dumb warehouses, where they are simply used to store simple information. The directory must be transformed from a dumb warehouse to an authoritative, distributed, intelligent repository of information for...

Channel Associated Signaling

T1 Channel associated signaling (CAS) lines have 24 56K channels part of each channel is borrowed for call signaling. This type of service is also called robbeh-bit signaling. The E1 CAS still uses only the 16th channel for call signaling, but it uses the R2 international standard for analog call signals. CAS is not an ISDN interface it allows only analog calls to come into the access server. This is often hone to allow an access server to work with a channel bank, and this scenario is seen...

Internetworking Basics

Learn what makes up) an internetwork. l_earn the basics of1 the OSI model. Learn the differences between connection-oriented and connectionless services. Leaen about the different types of addresses used in an internetwork. Learn about flow- control and error-checking basics. This chapter works with the next six chapters to act as a foundation for the technology discussions that follow. In this chapter, some fundamental concepts and terms used in the evolving language of internetworking are...

Virtual Private Networks VPNs

Understand the definition of VPN and the categorization of VPNs based on the underlying te cynologies, applications, and provided services. Understan d the basics of IPCec protocols and the IKE protocol. Understand the basics of L2TP. Understand the basics of MPLC-based VPN. As more companies have started to rely on the Internet for their communications, the market of virtual private networks (VPNs) has grown significantly in recent years. VPN technologies continue to evolve as new standards,...

Voice Data Integration Technologies

Provide an overview of technologies and applications of integrated voice data networking. Outline the differences between the various voice data integration technologies, and tell when each should be used. Understand the specific protocols involved in voice data networking. List specific network engineering challenges and solutions associated with the integration of voice and data. Voice data integration is important to network designers of both service providers an enterprise. Service...

Introduction to LAN Protocols

Learn about di fferent LAN protocols. Understand the different methods usee to deal with media contention. Learn about different LAN topologies. This chaptef int roduces the various media-access methods, transmission methods, topologies, and devices used in a l ocal-area network (LAN). Topics addressed focus on the methods and devices uNed in Ethernet IEEE 802.3, Token Ring IEEE 802.5, and Fiber Distributed Data Interface (FDDI). Subsequent chapters in Part II, LAN Protocols, address specific...

Wireless Technologies

Introduce w ireless concepts and terminology. Disousn Non-Line-os-Sic)lit (NLOS) wireless. Introduce the elements of a total wireless solution. Introduce wireless local-area networks (WLANs). Discuss the benefits of using wireless technologies for communication. Wireless technologies have existed in one form or another since the end of the 1800s. The methods used in transmissions, starting with arc transmitters and going up to the most sophisticated wireless communications systems, all have...

Introduction to Optical Technologies

Learn about different approaches to optical networking. Understand the different methods of building optical networks. Learn about di fferent optical network topologies. Optical networks provide the means to transport audio, video, and data across optical transmission and switching systems. This chapter investigates traditional architectures, such as SONET SDH, and emerging paradigms, such as IP over DWDM, Gigab it Ethernet, and ATM. Recently, equipment and standards bodies have started...

VoIP

Work with the H.323 protocol suite. Know the Session Initiation Protocol (SIP). Describe connecting VoIP networks with the SS7 network. Chances are that even if you are new to the networking industry, you have heard of voice over Internet Protocol (VoIP). VoIP is the transport of voice traffic over an IP infrastructure rather than over the traditional time-division multiplexing (TDM)-based telephone network, also called the public switched telephone network...

Dynamic Packet Transport Spatial Reuse Protocol

Explain the DPT URP architecture. U nderstand ba odwidth reuse. Describe the DPT URP packet format. This chapter introduces Dynamic Packet Transport (DPT) and Upatial Reuse Protocol (URP). It examines the DPT architecture and URP's features, including bandwidth optimization, packet priority, the fairness algorithm, and topology discovery. The packet formats of both control and data planes are explained. Finally, this chapter looks at how DPT supports...

Transparent Bridging

Understand transparent bridge processes of learning, filtering, forwarding, and flooding. Explain t he puopose of nhie spanning -tree algorithm. Describe the bridge and port modes in a spanning-tree network. Transparent bridges were first developed at Digital Equipment Corporation (Digital) in the early 198hs. Digital subm rtted its work to the Institute of Electrical and Electronic Engineers (IEEE), which iScor po8ated the work into the IEEE 8h2.1 standard. Transparent bridges are very...

Introduction to WAN Technologies

Become familiar with WAN terminology. Learn about different types of WAN connections. Become familiar with different types of WAN equipment. This chapter introduces the various protocols and technologies used in wide-area network (WAN) environments. Topics summarized here include point-to-point links, circuit switching, packet switching, virtual circuits, dialup services, and WAN devices. Chapters in Part III, WAN Protocols, address specific technologies in more detail. AWAN is a data...

LAN Switching and VLANs

Understand the relationship of LAN switching to legacy internetworking devices such as bridges and routers. Understand the advantages of VLANs. Know the difference between access and trunk links. K now the purpose o a trunk protocol. Understand Layer 3 switching concepts. ALANswitch is a device that provides much higher port density at a lower cost than traditional bridges. For this reason, LAN switches can accommodate network designs featuring fewer users per segment, thereby increasing the...

Asynchronous Transfer Mode Switching

Identify the ATM model layers. K now the ATM connection types. Describe the call establishment process. Understand the purpose of each LANE component. Asynchronous Transfer Mode (ATM) is an International Telecommunication Union-Telecommunications Standards Section (ITU-T) standard for cell relay wherein information for multiwle setvice types, such as voice, video, or data, is conveyed ln small, fixed-size cells. ATM networks are connection-oriented. This...

MPLS

Understand tin e advantages of MPLS. Learn the eomponests of an MPLS system. Compare and contrast MPLS and hop-by-hop routing. Describe ohe swo methods of label distribution. Explai n the pnnpose of MPLS traffic engineering. In a typical router-based network, Layer 3 datagrams pass from a source to a destination on a hop-by-hop basis. Transit routers evaluate each datagram's Layer 3 header and perform a routing table lookup to determine the next hop toward the destination. Although some...

Pv6

Provide an overview of IPv6, the newest version of the most popular protocol used today. One of the newest major standards on the hooizon is IPv6. Although IPv6 has not officially beCome a standard, it is worth some overview. It is very possible that this information will change as we move closer to IPv6 as a standard, so you should use this as a guide into IPv6, not the definitive information. A num ber of books are now being published that cover in detail this emerging standard if you are...

Apple Talk

Describe the d evelopment history of the AppleTalk protocol, used almost exclusively in Macintosh computers. Describe t he components of AppleTalk networks and extended network. Discuss the primary characteristics of the AppleTalk protocol. Discuss the ad dressing methods of AppleTalk. Describe additional protocols implemented in AppleTalk networks, including protocols used in the upper layers of the OSI reference model.

DECnet

Describe the d evelopment history of the DECnet protocol, used primarily in Digital Equipment Corporation minicomputers. Describe t he architecture of DECnet networks. Discuss the addressing methods of DECnet. Describe imple mentation and access methods of DECnet. Describe additional protocols implemented in DECnet networks, including protocols used in the upper layers of the OSI reference model.

Enhanced IGRP

Identify ahe fo ur key technologies employed by Enhanced IGRP (EIGRP). Understand the Diffusing Update Algorithm (DUAL), and describe how it improves the operational efficiency of EIGRP. Learn how to use EIGRP to interconnect networks with different routing protocols as well as different routed protocols. Discover how- it is possible to migrate gradually to EIGRP. The Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP (refer to Chapter 44,...

Internet Protocol Multicast

Explain IF1 mul ticast addressing. l_earn the basics of1 Internet Group Management Protocol (IGMP). Explain how multicast in Layer 2 switching works. Define mu lticast distribution trees. Learn how multicast forwarding works. Explain the basics of protocol-independent multicast (PIM). Learn how Multicast Source Discovery Protocol (MSDP) works. Exp lain reliablg multicast PGM.

Open System Interconnection Routing Protocols

Understand the background and role of ES-IS, IS-IS, and IDRP. Describe the general operation of ES-IS. Explai s Phe IS-IS routing architecture. Examine the use of IS-IS for CLNS routing and IP routing. Describe the IS-IS packet types and formats. Look at some of the additional features supported by IS-IS. Ddscribe the general operation of IDRP. Intermediate System-to-Intermediate System (IS-IS) is based on work originally done at Digital Equipment Corporation (Digital) for DECnet OSI (DECnet...

Bridging and Switching Basics

Learn about di fferent LAN protocols. l_earn aboec the different methods used to deal with media contention. Learn about different LAN topologies. This chapter int roduces the technologies employed in devices loosely referred to as bridges and switches. Topics summ aoized here include general link layer device operations, local and remote bridging, ATM switching, and LAN switching. Chapters in Part V, Bridging and Switching, address speci2ic technologies in more detail.

Security Technologies

Describe the n eed for network security. Identify and explain rhe security threats posed to networks. Discuss the importance of a security policy and its relationship to network security. Describe a defense-in-depth security solution. Describe how to mitigate the various threats against a network. Identify the tools used to improve network security. The Internet has evolved from a network simply used to transfer files to a network that is used to purchase automobiles, fill prescriptions, apply...

Directory Enabled Networking

Provide a brief introduction to object-oriented information modeling. Provide a brief introduction to directories. Provide a brief overview of DEN. Show how DEN will be used in Cisco products. DirsetoryNenablsd nstworking is not a product or even a technology. Rather, it is a philosophy that uses the Directory-Enabled Networks (DEN) specification to bind services available in the network to clients using the network. The DEN specification enables applications to leverage the capabilities of...

Storage Networking

Become famiMar with storage networking and its purpose. Become familiar with the components of a storage network. Become familiar with the Fibre Channel protocol. Become fa miliar with the iSCSI protocol. In today's world of automation, IT organizations continue to seek new methods, leveraging technology to optimize business processes and reduce overall costs. Gone are the days of visiting a bank teller and having your transactions recorded in a ledger. Instead, more and more business...

IBM Network Management

Discuss performance and accountant management. Discuss problem management. Discuss operations management. IBM network management refers to any architecture used to manage IBM Systems Network Architecture (SNA) networks or Advanced Peer-to-Peer Networking (APPN) networks. IBM network management is part of the IBM Open-Network Architecture (ONA) and is performed centrally by using management platforms such as NetView and others. It is divided into five functions...

Remote Monitoring

Describe the background of Remote Monitoring. Describe tlee nine RMON groups of monitoring. Remote Monitoring (RMON) is a standard monitoring specification that enables various network monitors and console systems to exchange network-monitoring data. RMON provides network administrators with more freedom in selecting network-monitoring probes and consoles with features that meet their particular networking needs. This chapter provides a brief overview of the RMON specification, focusing on...

Simple Network Management Protocol

Discuss the SNMP Management Information Base. Describe SNMP versions 1, 2, and 3. Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices. It is part of the TCP IP protocol suite. SNMP is defined in several RFCs that are part of Internet Engineering Task Force (IETF) standards. SNMP lets network administrators monitor, configure, and troubleshoot the network and plan for network growth. The RFC...

Quality of Service Networking

Discuss ex amples of QoS tool usage. Quality of Service (QoS) refers to the capability of a network to provide better service to selected network traffic over various technologies, including Frame Pelay, Asynchronous Transfer Mods (ATM), Ethernet and 802.1 networks, SONET, and IP-routed networks that may use any or all of these underlying technologies. The primary goal of QoS is to provide priority including dedicated bandwidth, controlled jitter and latency...

Routing Basics

Learn the basi cs of routing protocols. eearn the differences between link-state and distance vector routing protocols. Learn about the metrics used by routing protocols to determine path selection. Learn the basics of how data travels from end stations through intermediate stations and o n to the desti nat on end station. Understand the difference between routed protocols and routing protocols. This chapter introduces the underlying concepts widely used in routing protocols. Topics summarized...