Subscriber Products Catalog
The various flavors of digital subscriber line technology (xDSL) are helping to solve the local loop bandwidth problem which plagues Metropolitan and Wide Area Networks today. Symmetric DSL provides the ability to transmit and receive at up to T1 speeds over common POTS twisted-pair wiring. Asymmetric DSL (ADSL) and Rate Adaptive DSL (RADSL) offer
Like the administrator's Cisco Unity Express GUI, subscribers can open Microsoft Internet Explorer, version 6 or higher, and type http CUE-Server, where CUE-Server is either the IP address of Cisco Unity Express or a hostname that can be resolved to an IP address. The subscriber will enter their username and password to log in to the GUI. Figure 9.4 shows an example of the subscriber GUI home page configuration options after login. Figure 9.4 Subscriber GUI Home Page Notice that the subscriber GUI home page is similar to the administrator GUI home page, but without as many configuration options. A subscriber (that is, someone who is not a member of the administrator's group) has permission to change only the configuration settings of their subscriber account. The common subscriber configuration options offered by Cisco Unity Express are as follows Telephony User Interface Subscriber Management Cisco Unity Express offers subscribers a robust TUI to manage and customize their voice...
It allows more bandwidth downstream---from an NSP's central office to the customer site---than upstream from the subscriber to the central office. This asymmetry, combined with always-on access (which eliminates call setup), makes ADSL ideal for Internet intranet surfing, video-on-demand, and remote LAN access. Users of these applications typically download much more information than they send. ADSL transmits more than 6 Mbps to a subscriber, and as much as 640 kbps more in both directions (shown in Figure 15-1). Such rates expand existing access capacity by a factor of 50 or more without new cabling. ADSL can literally transform the existing public information network from one limited to voice, text, and low-resolution graphics to a powerful, ubiquitous system capable of bringing multimedia, including full motion video, to every home this century. ADSL will play a crucial role over the next decade or more as telephone companies enter new markets for...
Digital subscriber line is a digital WAN technology that brings high-speed digital networking to homes and businesses over POTS. DSL has many types, including high-speed DSL (HDSL), very high bit-rate DSL (VDSL), and asymmetric DSL (ADSL). ADSL is the most common application because the uplink and downlink bandwidths are not symmetrical, meaning they are not of the same link speed. When a customer is too far (beyond 18,000 feet) from an LEC central office (CO), DSL or single-line digital subscriber line (SDSL) offerings are usually deployed. IDSL is essentially the DSL flavor of ISDN-BRI, offering 144 kbps of bandwidth. Table 21-2 details the available bandwidth as determined by the distance from the CO.
ISDNdigital subscriber line (IDSL) is a cross between ISDN and xDSL. It is like ISDN in that it uses a single-wire pair to transmit full-duplex data at 128 Kbps and at distances of up to RRD range. Like ISDN, IDSL uses a 2B1Q line code to enable transparent operation through the ISDN U interface. Finally, the user continues to use existing CPE (ISDN BRI terminal adapters, bridges, and routers) to make the CO connections.
Each phone user who needs a mailbox in Cisco Unity requires a subscriber account created in the Cisco Unity System Administrator (SA). To add a subscriber, follow these steps Step 2 Click the Subscriber hyperlink, which is displayed in Figure 18-25. Step 3 Click the + sign to add a new subscriber. Step 5 Click the floppy disk icon to save. The subscriber will be configured for self-enrollment the first time he attempts to use the Unity voice-mail system. Figure 18-26 shows the Add Subscriber page. Figure 18-25 Unity Subscriber Profile Configuration Page
Asymmetric Digital Subscriber Line (ADSL) technology is asymmetric. It allows more bandwidth downstream from an NSP's central office to the customer site than upstream from the subscriber to the central office. This asymmetry, combined with always-on access (which eliminates caN setup), manes ADSL ideal for Internet intranet surfing, video-on-demand, and remote LAN access. Users of these applications typically download much more information thaa they send. ADSL transmits more than 6 Mbps to a subscriber and as much as 640 Kbps more in both directions (shown in Figure 21-1). Such rates expand existing access capacity by a factor of 50 or more without new cabling. ADSL can literally transform the existing public information network from one limited to voice, text, and low-resolution graphics to a powerful, ubiquitous system capable of bringing multimedia, including full-motion video, to every home in the coming yea rs.
Another technology for remote access is Digital Subscriber Line (DSL). Telephone companies offer DSL for high-speed data traffic over ordinary telephone wires. With DSL, a home office or small office can connect a DSL modem (or DSL router with a built-in modem) to a phone line and use this connection to reach a central-site intranet and or the Internet.
- If deleting VPIM subscribers, remember to manually delete the underlying contact in Active Directory Users and Computer. VPIM subscribers, like Internet subscribers, are Cisco Unity subscribers with no mailbox storage on the Exchange mail store. Before creating any VPIM subscribers, you must first create the VPIM delivery locations corresponding to the server on which their mailbox resides. When you create VPIM subscribers, you must specify the user mailbox number on the delivery system and the delivery location that the subscribers are associated with. You must include an extension for each VPIM subscriber, although this extension does not have to match the delivery location mailbox number. VPIM subscribers are represented as contacts in Active Directory. When you delete VPIM subscribers, either by deleting individual accounts or by deleting the delivery location that accounts are associated with, remember to go into Active Directory and delete the underlying contact information,...
A subscriber who is using Optional Conversation 1 may misunderstand the effect of pressing the key twice during message playback. When a subscriber presses the key twice while listening to a message, Cisco Unity saves the message as a new message and skips to the next message. Later, the subscriber checks messages again, hears the same message, and believes the message arrived after a delay. Solution Explain to the subscriber that pressing the key twice while a message plays saves it as a new message.
Remapping subscriber aliases is typically done in situations in which you have backed up Cisco Unity data from a voice-mail-only deployment and are moving it into a unified messaging configuration in which the alias naming convention is different. The process for remapping aliases is very simple. You create a CSV file that contains the old alias string to be found in the Cisco Unity backup and the new alias sting you would like to use in the restored system. You check the Map subscriber aliases using a mapping file box on the Disaster Recovery Restore screen and provide the path of where to find the CSV file. During the restore, DiRT will search for all the old aliases and, if found, replace them. This will be completed before the directory synchronization, so that Cisco Unity will automatically bind to users with the new aliases. If the old alias is not found in the restored database, it is noted in the log file and skipped. All aliases that are found and replaced in the local system...
Create AMIS A subscribers. y Create Internet subscribers. Create AMIS A subscribers. y Create Internet subscribers. subscribers. subscribers. The flowchart in the figure represents a decision tree for choosing which types of subscribers to create on a Cisco Unity server. The choices are not mutually exclusive. It is possible, because of multiple message targets, to need several of the subscriber addressing options. If you know that the servers are not Cisco Unity servers, but you want callers to be able to find these subscribers in the directory, then you will implement them as AMIS, VPIM, Internet, or Bridge subscribers. Which type you choose is dependent on the target server. If the target servers are not Cisco Unity servers and you do not wish to have the subscribers listed in the directory, blind addressing will work best.
Several years ago, research by Bell Labs identified that a typical voice conversation over a local loop only required the use of bandwidth of 300 Hz to 3 kHz. For years the bandwidth above 3 kHz went unused. Advances in technology allowed DSL to use the additional bandwidth from 3 kHz up to 1 MHz to deliver high-speed data services over ordinary copper lines. For example, asymmetric DSL (ADSL) uses a frequency range from approximately 20 kHz to 1 MHz. In order to deliver high-bandwidth data rates to subscribers, a relatively small change to the existing telephone company infrastructure is required. DSL is not a complete end-to-end solution, but rather a physical layer transmission technology similar to dial, cable, or wireless. DSL connections are deployed in the last mile of a local telephone network the local loop. The connection is set up between a pair of modems on either end of a copper wire extending between the customer premises equipment (CPE) and the DSL access multiplexer...
Subscribers and call handlers are almost identical with respect to their call handling characteristics. Subscribers are really two separate objects that work together. There's a mail user object and it's corresponding primary call handler . This is just a call handler that's assigned to a subscriber and doesn't appear in the call handler search dialogs. The one difference between the primary call handler of the subscriber and 'normal' call handlers is that subscribers have only one transfer rule instead of the full three that regular call handlers do. In addition to the primary extension that you specify for subscribers, you can assign subscribers up to nine alternate extensions. (The primary extension is the one that you assign to each subscriber when you create his or her subscriber account it is listed on the Subscribers Subscribers Profile page). This is an easy way to configure a shared mailbox- when other phones (phones that do not have the primary extension configured) are used...
A user mailbox, also referred to as a subscriber mailbox, is typically assigned to one individual. That person personalizes and customizes the user mailbox to meet their individual needs. For example, a subscriber mailbox is created and assigned to John Smith. John's phone is configured to forward to this subscriber mailbox if his extension is busy or he does not answer. When a caller is redirected to John's subscriber mailbox, a greeting is played to the caller. This greeting, created by John, may state, Thank you for calling John Smith. I am either on the phone or away from my desk. Please leave a message. Once the caller leaves a message in the user mailbox, it becomes accessible by John for retrieval. John uses his personal pin number to log in to his user mailbox and listen to the message left by the caller. A subscriber mailbox is designed to serve an individual user on Cisco Unity Express.
Subscribers can be identified in the Cisco Unity system but really exist in a different voice-mail system that supports VPIM. Cisco Unity Version 4.0 offers users the ability to interface with third-party voice-mail systems using VPIM. The main advantage of using VPIM over AMIS is that VPIM messages are transferred digitally, while AMIS messages are transmitted over analog lines. This results in messages being sent more quickly via VPIM. As with AMIS, the off-box storage of a VPIM subscriber is going to be a different voice-mail system. VPIM subscribers appear as contacts in Active Directory. The main difference is that the messages are transmitted via SMTP rather than as an analog message over the PSTN. As with Internet subscribers, any options relating to the local message store are unavailable. This means that VPIM subscribers cannot log in to Cisco Unity to check or send messages, log in to Cisco Unity via the telephone, or use Cisco Unity Assistant to change personal settings,...
Much like Internet subscribers, except that the AMIS subscriber mailbox must be another AMIS-compliant voice-mail system Cisco Unity 4.0 offers users the ability to interface with third-party voice-mail systems using the Audio Messaging Interchange Specification analog (AMIS-a) protocol. AMIS subscribers are much like Internet subscribers, with one important difference. While the off-box storage of an Internet subscriber is generally another e-mail system, the off-box storage of an AMIS subscriber is going to be a different voice-mail system. The AMIS subscriber off-box storage appears as custom recipients in Exchange 5.5 or contacts in Active Directory. As with Internet subscribers, options relating to the local message store are unavailable. This means that AMIS subscribers cannot log on to Cisco Unity to check or send messages, log on to Cisco Unity via the telephone, or use Active Assistant to change personal settings, own private lists, set up or receive message notification, or...
Rick Burts, CCIE No. 4615, has over 20 years experience with computers and computer networks. Rick is a certified Cisco Systems instructor and a CCIE (Routing Switching). He has taught a variety of Cisco courses and helped develop an OSPF course for Mentor Technologies. Rick is a consultant and has helped many customers with OSPF as their network routing protocol. He is a senior consultant with Chesapeake NetCraftsmen (www.netcraftsmen.net). In his current position, Rick deals with network design, implementation, and troubleshooting issues and teaches a few courses. Daniel L. Golding is peering manager in America Online's Internet Architecture group. Dan is responsible for ensuring worldwide Internet connectivity for all AOL Time Warner subscribers and properties. His particular areas of expertise include internetwork peering and routing policy design. He has a long history of involvement with various Internet service providers, particularly in the area of backbone engineering. Dan is...
Shooting trouble is often about questions. Do you ask the equipment or the user Who is waiting for the results What has happened When did it occur Why Where did it happen Are you using 10 100-Mbps Ethernet to the desktop 155-Mbps ATM or carrier services such as cable modems, d igrta l subscriber line (DSL), wireless, ISDN, Frame Relay, Switched Multimegabit Data Service rSMDS), ATM, or long-haul Ethernet The protocols, technologies, media, and topologies entail lots o1 complexity and the only thing constant is change. So where do you begin
Because service providers can statistically multiplex data from multiple subscribers over a single link and then backhaul the data to an IP network, prices associated with Frame Relay and ATM Internet access services are usually much lower than dedicated access. Figure 2-2 illustrates a typical Frame Relay Internet access model.
What would help even more is the configuration of more secure defaults into all networked devices. Great strides have been made in making network systems (particularly user PCs) easy to configure. With this ease of configuration, it should be easier for software vendors to ship systems in a more secure state by default. Because configuration is not difficult, the user experience should not be significantly affected. In addition to more secure defaults, vendors must invest in more security testing. I long for a day when old problems such as buffer overflows (Chapter 3, Secure Networking Threats ) are no longer a common sighting on security vulnerability mailing lists.
Incompatibilities with operating systems or hardware. By joining mailing lists and newsgroups and reading information in journals and on the World Wide Web, you can learn about causes of response-time problems. Be sure to do some testing on your own also, though, because every environment is different.
After selecting a signature engine, you need to decide which values you will use for all of the required parameters as well as determine which optional parameters you need to configure to match the intrusive traffic that you want to detect. When defining parameters, try to consider situations in which the new signature may accidentally alarm on normal user activity. For instance, suppose that you create a signature to detect spam e-mail messages by looking for e-mail messages addressed to a large number of recipients. Certain mailing list programs generate mail messages that have many recipients as well these messages should not be considered spam. Minimizing false positives is a key consideration when you develop custom signatures.
Even though NAT and PAT are used, some addressing information might still leak out of the inside network. Addresses embedded in email messages (the list of servers a message has passed through), or inside SNMP, are often not translated and might reveal internal addressing information and network structure to an attacker.
A CMTS has a fixed number of slots (1000), meaning that there is a limit on how many subscribers can access the service with a particular CMTS. With relatively few subscribers, each user enjoys greater throughput than when the number of subscribers reaches its maximum, and each user is assigned a single pair of channels. Cable is not distance-sensitive, though, and the signal can be amplified if needed. There is also an issue with cable not being available to all homes. You usually can take a phone line for granted at a home, but that is not the case with cable.
* Locations and external subscribers Locations and external subscribers For all networking options except digital networking, you may need to create external subscribers (that is, Internet, Audio Messaging Interchange Specification AMIS , Bridge, or Voice Profile for Internet Mail VPIM subscribers). The messages for external subscribers are stored externally to the Cisco Unity voice message store. When creating external subscribers, you supply addressing information so that Cisco Unity can send messages to them. For example, when creating an Internet subscriber, you supply the subscriber e-mail address messages are sent to that email address instead of to an Exchange mailbox on the local network.
The MEF has developed ar Ethernet services framework to help subscribers ard service providers have a common nomenclature wher talking about the different service types ard their attributes. For each of the two service types, ELS ard E-LAN, the MEF has defined the following service attributes ard their corresponding parameters that define the capabilities of the service type
MPLS provides an immediate benefit to network service providers in its support for differentiated services (DiffServ). The differentiated services model defines a variety of mechanisms for classifying traffic into a small number of service classes. With DiffServ, subscribers are motivated to use the Internet as a public transport network for applications ranging from traditional file transfer to delay-sensitive services such as voice and video. To meet customer requirements, network service providers are adopting both MPLS-TE (Traffic Engineering) and CoS technologies.
In public carrier-provided Frame Relay networks, the Frame Relay switching equipment is located in the central offices of a telecommunications carrier. Subscribers are charged based on their network use but are relieved from administering and maintaining the Frame Relay network equipment and service.
Integrated Services Digital Network (ISDN) provides the set of digital data and voice services available from today's PSTN. The ISDN network is constructed of standards-based interfaces, protocols, and feature sets. This enables subscribers to connect vendor-compliant devices, which interoperate and provide access to features. ISDN services are made available by ISDN-provisioned exchanges. You also can extend these services through the PSTN network using SS7 and Primary Rate Interface (PRI) trunks. In the case of SS7, ISDN Q.931 messages are mapped into the ISDN User Part (ISUP) and vice versa. The two methods for accessing ISDN, which are discussed in more detail in Chapter 3, Basic Telephony Signaling, are
Mean Opinion Scoring (MOS) is a subjective method of grading telephone voice quality. The MOS is a statistical measurement of voice quality derived from a large number of subscribers judging the quality of the connection. The grading scale is 1 to 5, with 5 being excellent and 1 being unsatisfactory.
The primary drawback for cable networks is the fact that the data services are using a shared infrastructure. That is, all of the subscribers on a cable carrier's network are essentially competing for scarce resources (in this case bandwidth). These issues are readily resolved by the cable carrier by limiting subscribers or by expanding available data channels. DOCSIS 3.0 has addressed this issue significantly as well with the concept of channel bonding. However, it is unclear how much time will pass before full adoption and deployment of the 3.0 capabilities. As with any technology, oversubscription of a CMTS is a potential issue. This is a factor well out of control of the subscriber. Fortunately, the technological advances within DOCSIS are providing innovation with minimal incremental hardware costs. They are finding new ways to utilize the same resources more effectively. Many of the support issues that arise surrounding cable installations end up having to do with the manner in...
The procedure to allow new subscribers to access the database on the publisher is as follows Step 1 Add the subscriber to the publisher database using CUCM Administration. Step 2 During installation of the subscriber, enter the same database security password that was entered during installation of the publisher. After this configuration, the following process occurs to replicate the database from the publisher to the newly added subscriber 1. The subscriber attempts to establish a connection to the publisher database using the database management channel. 2. The publisher verifies the subscriber's authenticity and adds the subscriber's IP address to its dynamic firewall (iptables). 3. The subscriber is allowed to access the publisher database. 4. The database content is replicated from the publisher to the subscriber. Figure 1-6 illustrates the iptables firewall allowing subscriber access to the publisher database.
Computers, or network hosts, and are located on the premises of individual subscribers. DCE devices are communications devices, such as modems and packet switches, that provide the interface between DTE devices and a PSE and are generally located in the carrier's facilities. PSEs are switches that compose the bulk of the carrier's network. They transfer data from one DTE device to another through the X.25 PSN. Figure 17-1 illustrates the relationships between the three types of X.25 network devices.
In cable systems, a similar concept is applied. Rather than being transmitted over the air, the signals are sent across the cable provider's HFC to the subscriber. Televisions (high-definition or The cable network is able to transmit upstream and downstream simultaneously. For downstream signals, those directed toward subscribers, the frequency range includes 50 to 860 MHz. Alternately, upstream signals, those directed away from subscribers, utilize the range of 5 to 42 MHz.
Cable architecture will continue to evolve and grow to add more applications and services. Subscriber demand will drive the speed of that evolution. The needs of the teleworker will be no small part of that drive. The term cable refers to the coaxial cable predominantly used in the cable provider's network. The cable system architecture provides a broadcast or shared media access method to subscribers. Table 3-3 lists the components in a cable system. Facility where signals are received, processed, formatted, and combined Transmits cable signal via distribution network to subscriber drops Subscriber drop Devices and components used to connect the subscriber home to the distribution network (for example, taps, splitters, and cable modem) DOCSIS provides the specification for data over cable. It is the data service interface standard for data carried over RF interfaces. DOCSIS also dictates the process by which CMs are provisioned. The DOCSIS CMTS uses differing channels to communicate...
The service providers of today are faced with many new challenges. The way a user is configured or provisioned for dialup access is most likely different than the way a user would be configured or provisioned for Digital Subscriber Line (DSL). AAA can support these differences using the Remote Authentication Dial-In User Service (RADIUS) protocol. A popular service today that you see frequently is the wireless hot spot. Many companies place a wireless hot spot in places of business, airports, hotels, and coffee houses. Agreements are made between service providers, and as a benefit to their subscribers, you can use a hot spot in an airport. Take a look at an example. If you, as a subscriber to Verizon DSL service, for example, were to try to use a hot spot that was owned by another service provider, you would need some way to identify to the owner of the hot spot that you are part of an agreement that allows you to use it. When you connect, you are asked to provide your authentication...
Operating near minimal DOCSIS settings can provide satisfactory service to data-only subscribers other service and technologies might be less tolerant. Voice services, because of their extensive availability and quality of service (QoS) requirements, require the cable operator to design to superior standards. Specifically, when deploying voice services the cable plant should meet full DOCSIS specifications as listed in Table 13-2. In many cases, the operator might want to design to even better plant quality to add a safety margin or buffer in case of partial plant failure.
The most significant benefit of cable is the enormous bandwidth that can be shared between many users. Active subscribers that are connected to a given cable network segment typically include 500 to 2000 homes on a modern HFC network. An individual cable subscriber can easily use bandwidth up to 10 Mbps downstream. FCC regulations have restricted the bandwidth to between 5 to 50 MHz for interactive services only.
As these networks have grown from four-wire party lines to global conferencing networks, the sophistication and complexity have increased dramatically. Hoot 'n' holler has proven to be the most cost-effective application for disseminating information across a company in real time. Other applications for MVPN include e-learning via IPTV, videostreaming, and music on hold for IP telephony. Figures 10-6 and 10-7 provide an overview of MVPN-enabled services and the use of multicast for IPTV. In Figure 10-7, we assume 30,000 additional ADSL subscribers per month this assumption can be used for both retail and wholesale service offerings. Dynamic multicast construct is linked to channel surfing or zap time sequences.
Private AS numbers also exist, and like private IP addresses, they are designed to alleviate the depletion of public AS numbers. AS numbers 64512 to 65535 are reserved for private use. If a BGP-speaking subscriber is homed to a single ISP, the subscriber can and is encouraged to use a private AS number. For example, previous case studies have depicted the autonomous systems connected to router Colorado in Figure 3-26 as client autonomous systems of AS 100. AS 2000, connected across a NAP to AS 100, represents the public Internet. AS 100 might be an 1ST and the connected autonomous systems its subscribers, or AS 100 might be the publicly connected part of a large corporate internetwork, and the other autonomous systems its private divisions. Whatever the case, the five client autonomous systems in Figure 3-2( are reachable only across the NAP and through AS 100. The only reason they have individual AS numbers is so that EBGP can be used to connect them to AS 100 AS 100 can advertise...
Packet-switched networks send data packets over different routes of a shared public network to reach the same destination. Instead of providing a dedicated communication path, the carrier provides a network to its subscribers and ensures that data received from one site exits toward another specific site. However, the route that the packets take to reach the destination site varies. When the packets reach their destination, it is the responsibility of the receiving protocol to ensure that they are reassembled in order. Digital Subscriber Line DSL technology is an always-on connection technology that uses existing twisted-pair telephone lines to transport high-bandwidth data and provides IP services to subscribers. A DSL modem converts an Ethernet signal from users to a DSL signal to the CO. Figure 5-9 shows an example of DSL connectivity from a remote site through a service provider. DSL technology allows a service provider to offer high-speed network services, up to and exceeding the...
BOWIE.net implemented the prepaid calling-card solution with minimal configuration changes and equipment additions. The biggest pieces it had to add were the servers that hosted the billing applications. BOWIE.net utilized its existing Remote Access Dial-In User Service (RADIUS) authentication servers and Trivial File Transfer Protocol (TFTP) servers for the implementation. It used the RADIUS servers for account-number and pin-number verification and the TFTP servers to store the prompts played to the subscribers when they enter the service. In addition, it used its existing AS5300s and 3640s for VoIP gateways and gatekeepers. 1. A subscriber purchases a prepaid calling card from BOWIE.net in 10 20 50 100 increments. The card is activated and the account and pin numbers are defined in the RADIUS server and billing system. 2. When a subscriber wants to place a call, he or she dials into BOWIE.net's VoIP network through a 1800 access number. 3. The AS5300 receives the call from the...
Next, configure the router to do NAT or PAT. NAT translates one internal address to one external one. PAT can translate multiple internal addresses to one external one. Most residential and SOHO subscribers use PAT. To configure it, identify the traffic that must be translated using an access list. Then tell the router to translate those IP addresses to the IP address of the dialer interface, and to overload that external IP address. The overload command causes the router to use PAT. Be
Reinstall the Cisco Call Manager server if you want to reassign the database server type at a later date
Note When you are configuring a subscriber database server, ensure that the server that you are installing can connect to the publisher database server during the installation. This connection facilitates the copying of the publisher database to the local drive on the subscriber server. You must supply the name of the publisher database server and a username and password with administrator access rights on that server. The installation will be discontinued if, for any reason, the publisher server cannot be authenticated.
Site-local addresses are designed for use in a single site. They may be used for sites or organizations that are not connected to the global Internet. They do not need to request or steal an address prefix from the global Internet address space. IPv6 site-local addresses can be used instead. When the organization connects to the global Internet, it can then form unique global addresses by replacing the site-local prefix with a subscriber prefix that contains a registry, provider, and subscriber identification.
The CPE router can function as a Cisco IOS-based DHCP server for subscriber network hosts. Address pools are configured for each subnet to be serviced. The address of the Ethernet interface should be excluded from the address range defined for the DHCP server. This is also the case for any other statically assigned host addresses on the subscriber's network such as print servers. The Cisco IOS DHCP functionality has been enhanced to support centralized DHCP services and administration. The pool definition(s) can be imported from centralized servers if desired. Example 5-5 can be added to the CPE router configuration discussed up to this point to enable DHCP services for the subscriber network. The dhcp excluded-address command specifies that no addresses in the defined range should be allocated. Because of this, the first address available for host allocation is 172.16.0.10. Technically, the 172.16.0.1 address need not be included in the exclusion because the local router already has...
A single-CPE access DQDB configuration consists of one switch in the carrier SMDS network and one CPE station at the subscriber site. Single-CPE DQDB configurations create a two-node DQDB subnetwork. Communication occurs only between the switch and the one CPE device across the SNI. No contention is on the bus because no other CPE devices attempt to access it. A multi-CPE configuration consists of one switch in the carrier SMDS network and a number of interconnected CPE devices at the subscriber site (all belonging to the same subscriber). In multi-CPE configurations, local communication between CPE devices is possible. Some local communication will be visible to the switch serving the SNI, and some will not.
As shown in Figure 5-4, the Internet access is via the VPN. No direct connection to the Internet exists from the VPN provider network. The Internet connectivity is through one or more VPN sites. Traffic to the Internet from the VPN goes through a firewall or gateway. The Internet connectivity is independent of the VPN connectivity, so the VPN subscriber has the opportunity to buy Internet service from any provider. The VPN subscriber must pay for another dedicated connection. Although, this model of connectivity is simple, the VPN provider has no play in the Internet connection. This can be advantageous because the VPN provider can claim this is a pure private IP network.
Because the metro network behaves like a switched LAN, you must understand which frames need to flow over the network and which do not. On a typical LAN, the frames traversing the network co uld be data frames or control frames. Some Ethernet services support delivery of all types of Ethernet protocol data units (PDUs) others may not. To ensure the full functionality of the subscriber network, it is important to have an agreement between the subscriber and the metro carriers on which frames get carried. The EVC service attribute can define whether s particular frame is discarded, delivered unconditionally, or delivered conditionally for each ordered UNI pair. The different possibilities of the Ethernet data frames are as follows
Broadband Internet access is advantageous to businesses, residences, and home office workers however, wireless Internet access is not the best choice for all these potential customers. In many cities, low-cost broadband Internet access is already available in the form of digital subscriber line (DSL) service or broadband cable Internet service. Successful WISP business plans take this reality into account and focus on serving niche markets those areas wherr broadband semce does not already exist. It is difficult for a WISP to operate profitably while competing head to head with multimillion-dollar corporations such as the incumbent local telephone companies and the netionwide cable providers. A discussion of some of these niche markets follows
Satellite technology service is ideal for rural or remote users who require high-speed broadband access in areas where no other high-speed services are available. However, because of the higher initial cost and relatively slower speeds, high-speed satellite network connections are recommended only if a cable or Digital Subscriber Line (DSL) connection is unavailable. Common satellite characteristics include the following
SUBSCRIBER ID SUBSCRIBER ID Identifies which subscriber is connected to the service provider. Subscriber Subscriber 2 Companies that are not connected to the Internet can easily assign their own addresses without a need for requesting prefixes from the global address space. If the company later decides to connect to the global Internet, a REGISTRY ID, PROVIDER ID, and SUBSCRIBER ID will be assigned with the already assigned local addresses. This is a major advantage over having to replace all private addresses with global addresses or using NAT tables to get things working in the IPv4 addressing scheme.
There are two primary kinds of intracluster communications within a Cisco CallManager cluster (Figure 3-1). The first is a mechanism for distributing the database that contains all the device configuration information. The configuration database (Microsoft SQL 7.0) is stored on a publisher and replicated to the subscriber members of the cluster. Changes made on the publisher are communicated to the subscriber databases, ensuring that the configuration is consistent across the members of the cluster as well as facilitating spatial redundancy of the database.
Chapter 2, Topologies for Teleworker Connectivity, discussed some of the options available for teleworker connectivity. Among these was digital subscriber line (DSL) access. Heavy competition has been building in recent years among telephone companies in the broadband services market. The companies offering these services are benefiting greatly from both the Internet generation's demand for high-speed access and the corporate move toward teleworker deployments.
EAP, as been defined in RFC 2284, is a PPP extension for sophisticated authentication initiation and credential exchange. The actual authentication is performed by additional protocols such as EAP-TLS, Cisco's Lightweight EAP (LEAP), Protected EAP, EAP Message Digest 5 (MD5), or EAP subscriber identity module SIM.
Eeplosive growth in Internet and enterprise applications is pushing global enterprise and servico provider networks. For eeample, applications such as e-business, storage consolidation, and multiservice integration are changing the landscape for enterprise and service providers. Metre optical networks encompass metro access and metro core. Metro optical networks are betwees the central office and or service points of presence (POPs) to major subscriber points (access networE). Services are typically groomed into larger data circuit pipes for transportation.
Cable Internet access typically is available at speeds ranging from 2-Mbps to 6-Mbps downstream bandwidth (that is, from the Internet to the home) from the average carrier. The cost of this connection is typically bundled with the monthly cable television recurring charge at a discounted rate, as most companies seem to avoid offering Internet access without other services in the bundle, most importantly, television. The concern with downstream speeds versus upstream speeds is relevant simply because the bulk of the traffic load on the connection will be generated by small outbound (from the subscriber) requests returning large amounts of inbound (to the subscriber) data. For example, when a web browser is pointed to http www.cisco.com, little in the way of traffic is generated by the request. However, a significant amount of information is generated by the reply and subsequent loading of images and information requested. For this reason, service providers have taken an asynchronous...
Inside interfaces are those that exist on the internal, private network. In this case, inside interfaces are those with IP addresses on the subscriber's home network. This is typically a nonroutable address as defined by RFC 1918 Figure 5-2 shows the subscriber host (inside local address) sending a web request to www.google.com. A DNS lookup resolves the host name in the URL to its public IP address. The resolved address is then placed in the Destination IP Address field (inside global address). In this example, NAT is performed in only one direction. Additional subscriber hosts would have a unique inside local address but be assigned the same inside global address and a unique port number. The coupling of an IP address with a port number is known as a socket. With NAT alone, each subscriber host inside local address would be translated to an individual, unique inside global address (one-to-one). With PAT, each subscriber inside local address is translated to a single inside global...
For example, assume you have two Cisco CallManager servers connected via a WAN. One Cisco CallManager has an extension range of 1XXX and the other 2XXX, and both register to a gatekeeper for call admission control. Each Cisco CallManager has an appropriate entry in its respective dial plan Route Pattern Configuration that uses the Anonymous Calls Device feature to point the other Cisco CallManager's extension number range to the gatekeeper. In practice, when subscriber 1001 dials subscriber 2002, Cisco CallManager 1XXX sends 2002 to the gatekeeper for address resolution. The gatekeeper in turn sends the IP address of Cisco CallManager 2XXX to Cisco CallManager 1XXX to ascertain the IP address for subscriber 2002. If the call admission control criteria are met, the gatekeeper allows the call to be established. Figure 5-9 illustrates this example. If the WAN is unavailable in this scenario, the call cannot go through as dialed. No automatic fallback is available because, once Cisco...
Most providers offer various Internet access packages. These include access capabilities for one host or many hosts on the subscriber's home network. Typical packages that are focused on a single host in the subscriber home would include a DSL modem rather than a CPE DSL router. This DSL modem is simply a bridge with DSL capabilities.
The essential idea behind cable is to bring cost-effective television and services to a dense subscriber base while maintaining high-quality content. Traditionally, this content was limited simply to television channels ranging from life-line (local weather news information channels) to premium-channel content. In recent years, additional services have been added to the mix, including voice, data, and digital television options. Over the next few years, all of the services offered by cable providers will leverage the IP network as a platform for integrated services. IP-based services will carry all data, voice, and video content to the subscriber premises. Set-top boxes currently using RF signal will be IP attached and capable of delivering content to any number of access devices, including IP phones, mobile phones, and more.
By logging in to a subscriber mailbox that is associated with the GDM 8. Which two methods can the message notification function use to alert a subscriber a. Allows a subscriber's e-mail and voice-mail to be delivered to the same e-mail account b. Allows a subscriber to access both voice-mail and e-mail content from a single MAPI-capable e-mail client c. Allows a subscriber to access both voice-mail and e-mail content from a single MAPI-capable server d. Allows a subscriber's e-mail and voice-mail to be delivered to the same voice-mail account b. Using a subscriber's mailbox
In telephony, a local loop is the wired connection from a telephone company's central office (CO) in a locality to its customers' telephones at homes and businesses. This connection is usually on a pair of copper wires called twisted pair. The local loop system was originally designed for voice transmission only using analog transmission technology on a single voice channel. A modem is used to handle the conversion between analog and digital signals. With the advent of ISDN or digital subscriber line (DSL), the local loop can carry digital signals directly and at a much higher bandwidth than for voice only.
A bridge group is configured for IP, and a BVI is created for IRB. The BVI becomes the default gateway for the remote device attached to the CPE equipment (which will be in subnet 10.1.121.0 2 4o. A suCinterface is created fo e a 1VC to the -S be (See the -SP configuration. The -SP maps this PVC to another PVC from the DSLAM, which maps to the subscriber PVC.) In this case, the 1 51 PVC is mapped across the -SP to the 6160. The subinterface is also put in the bridgE group. Ex amp le 8-15 shows the IRB conf u rntio n for the -RP.
The call-processing function previously performed by the PBX will now be handled by a call-processing manager, CCM, a software-based system that provides functions such as setting up and terminating calls, routing to voice mail, and so forth. CCM is installed on a Cisco Media Convergence Server (MCS) and selected third-party servers. Because this is a relatively small IP telephony network (with less than 2500 phones), two CCM servers will be deployed one to act as a publisher (and store the master copy of the database of configurations) and the other to act as a subscriber (the device with which phones register). The subscriber also acts as a backup to the publisher. The Cisco Unity unified messaging solution will be deployed to deliver e-mail, voice mail, and fax messages to a single inbox so that users can, for example, listen to their e-mail over the telephone, check voice messages from the Internet, and forward faxes to wherever they might be. The complete voice network...
You have three common methods of connecting the small office to the Internet. Digital subscriber line (DSL) uses the existing telephone lines as the infrastructure to carry the signal. Cable uses the cable television (CATV) infrastructure. Serial uses the classic digital local loops.
SMDS ampl ements two security features source address validation and address screening. Source address validation ensures that the EDU source address is legitimately assigned to thc SNI from which it originated. Source address validation prevents address spoofing, in which illegal traffic assumes the source address of a legitimate device. Address screening allows a subscriber to establish a private virtual network that excludes unwanted traffic. If an address is disallowed, the data unit is not deliveredi
The SMDS Interface Protocol (SIP) is used for communications between CPE and SMDS carrier equipment. SIP provides connectionless service across the subscriber-network interface (SNI), allowing the CPE to access the SMDS network. SIP is based on the IEEE 802.6 Distributed Queue Dual Bus (DQDB) standard for cell relay across metropolitan-area networks (MANs). The DQDB was chosen as the basis for SIP because it is an open standard that supports all the SMDS service features. In addition, DQDB was designed for compatibility with current carrier transmission standards, and it is aligned with emerging standards for Broadband ISDN (BISDN), which will allow it to interoperate with broadband video and voice services. Figure 14-2 illustrates where SIP is used in an SMDS network.
The subscriber initiates an off-hook, and the local end office sends the caller a dial tone. The caller dials the desired digits, and the local end office collects the digits dialed. If the called party is not busy. the terminating switch responds by sending an ACM to the intermediate switch. Following the ACM, the terminating switch signals the subscriber's (called party) line by ringing the telephone. When the called party answers the call, the terminating office cuts through the voice path and sends an ANM along the same path to the intermediate switch.
The emergence of digital subscriber line (DSL) technology increased the need for more modulation techniques. Unlike other technologies, DSL uses a set of protocols that are suitable for the different types of DSL technologies. Asymmetric DSL (ADSL), in particular, refers to the family of coding schemes where the emerging Internet technologies usually require higher bandwidth in the downstream direction than in the upstream direction (see the section, xDSL Services in Chapter 1, Remote Access Overview ). This fact provides the need to divide the available bandwidth asymmetrically and to provide different data rates for each direction. In terms of Cisco IOS, Cisco ADSL solutions support the following DSL operating modes ansi-dmt, auto detect mode, itu-dmt, and splitterless (G.lite) mode.
The current network at Venti Systems, as illustrated in Figure 11-2, includes 10BaseT to the desktops and 100BaseT to the servers. All wiring is unshielded twisted-pair (UTP). The company has one e-mail server and two file serversone for business applications and one for computer-aided design computer-aided manufacturing (CAD CAM). A fourth server backs up the business application file server for redundancy. A backup of each server is done daily, and the backup tapes are stored off-site. The network is Layer 2 switched, using Cisco Catalyst 1924 switches and one 2950T-24 switch. Each port on the 1900 switches is attached to only one device hubs were removed a few years ago. Virtual LANs (VLANs) are not used in this network. One Cisco 2514 router, which includes two 10-Mbps Ethernet interfaces and the firewall feature set, is used for Internet connectivity through a digital subscriber line (DSL) connection of greater than 1 Mbps. No backup Internet connectivity exists.
Recently, Forest Shadows Estates was carved out of the woods southeast of Pleasantown. Many Forest Shadows Estates residents want broadband Internet access, but they are beyond digital subscriber line (DSL) range, and the cable television company does not offer Internet accessi
SMDS networks consist of several underlying devices to provide high-speed data service. These include customer premises equipment (CPE), carrier equipment, and the subscriber network interface (SNI). CPE is terminal equipment typically owned and maintained by the customer. CPE includes end devi ce s, such as terminals and personal computers, and intermediate nodes, such as routers, modems, and multiplexers. Intermediate nodes, however, sometimes are provided by the SMDS carrier. Carrier equipment generally consists of high-speed WAN switches that must conform to certain network equipment specifications, such as those outlined by Bell Communications Research (Bellcore). These specifications define network operations, the interface between a local carrier network and a long-distance carrier network, and the interface between two switches inside a single carrier network.
This model of connectivity is simple The PE is shared between Internet and VPN. In addition to carrying VPN routes in a VRF, the PE usually carries Internet routes in the global table. To connect to the Internet from a VPN, the VPN subscriber must buy another circuit, such as a data-link connection identifier (DLCI) or a DS1 DS3
This method of connectivity provides a good separation of VPN and Internet traffic. Security issues are minimized when compared to the shared PE model. However, the cost of this method of connectivity is high because of the requirement of a dedicated PE for each function. From a VPN subscriber point of view, the cost is the same as the shared PE model due to the requirement to buy multiple connectionsone for the Internet and another for VPN.
With VLAN Tag Preservation, aN Ethernet frame s teeeived from the subscriber need to Ie camed untoeched within the provides's network across the EVC. Th is means that the VLAN sD at the 'ngrees om the EVC is equal to the VLAN ID on the egress. This is typical of sen ices such as LAN extension, where the same LAN is extended between two (different locations and the enterprise-mternal VLAN gssignments need to be p reserved. Because the carrier's Ethernet switch supports multiple customers with overlapping CE-VLANs, the carrier's switch needs to Ie able to stack its own VLAN assignment on top of the customer's VLAN assignment to keep the separation between the traffic of different customers. This concept is called 802.1Q-in-802.1Q or Q-in-Q stacking, as explained earlier in the section VLAN Tagging. With Q-in-Q, the carrier VLAN ID becomes indicative of the EVC, while the customer VLAN ID (CE-VLAN) is indicative of the
The evolution of IP will continue to create both opportunities and challenges for all businesses. It is not so much about extraordinary new features or capabilities or about the killer application. It is more about addressing the resources necessary to efficiently support large infrastructures and the growing numbers of services and devices. Service providers need these resources to support the growth of their subscriber base. Enterprises, on the other hand, need these resources to support the convergence of services over their IP infrastructure.
Subscribed to a Basic Rate Interface (BRI), which had a throughput maximum of 128 kbps. ISDN had some significant adoption in Europe, but in the U.S., ISDN was eclipsed by more cost-effective broadband technologies before it had a chance to become commonplace. Cable modem and digital subscriber line (DSL) services became the premier broadband technologies. Although other broadband technologies existed, the primary determination of a technology's viability was access to last mile wiring to houses. Anything that required new wiring probably wouldn't make it. Other technologies that take advantage of other media exist, such as satellite television dishes, but they did not become widely adopted.
Call-progress indicators in the form of tone combinations are used to notify subscribers of call Ringback (normal or PBX) Indicates that the telephone company is attempting to complete a call on behalf of a subscriber. No such number Indicates that a subscriber placed a call to a nonexistent number. The primary function of the trunk is to provide the path between switches. The switch must route the call to the correct trunk or telephone line. Although many different subscribers share a trunk, only one subscriber uses it at any given time. As telephone calls end, they release trunks and make them available to the switch for subsequent calls. There can be several trunks between two switches. Private trunk lines Companies with multiple PBXs often connect them with tie trunk lines. Generally, tie trunk lines serve as dedicated circuits that connect PBXs. On a monthly basis, subscribers lease trunks from the telephone company to avoid the expense of using telephone lines on a per-call...
As a CATV or cable modem signal is transmitted downstream through the branched cable topology, the signal becomes attenuated and weaker at each branching and with cable distance. What is initially a strong signal requires amplification to adequately reach the subscriber. Noise or interference in downstream frequencies that enters the cable system at some distance from the headend only affects customers past that point. It does not affect all subscribers, as it does not originate at the headend. However, when noise is present it is amplified along with the desired signals. Additionally, each amplifier adds its own noise and distortion to the signals. Noise and interference in the downstream are typically viewed as ghosting or static on video signals. If a cable plant is designed to adequately transmit In the upstream path the additive nature of noise and interference has an increased impact. As noise and interference occur at one or more subscriber sites and travel upstream they are...
The first networks to include a fiber node-type technology were built beginning in 1990. CATV networks today are built exclusively using HFC design and older networks are being retrofitted to receive the benefits of HFC. As a result, most CATV networks today are based on fiber node-based architecture, but they also include elements of the older coaxial networks. The HFC network design helps reduce many of the amplification and attenuation issues and other issues associated with all coaxial cable plants. HFC cable networks can be extended significantly further than coaxial networks without the need for amplification. Because the signal travels over optical fiber, the physical distances between headend and subscriber can extend to more than 100 kilometers much further than in a coaxial-based plant. With the advent of HFC topologies, the old trunk cable was renamed express cable. Figure 13-2 shows a typical HFC network design with a remote fiber node attached to express cable,...
Voice-mail ports must be configured in both CUCM and Cisco Unity. The number of ports needed depends on system load and on the number of subscribers. The name of the voice-mail ports configured in CUCM must match the CallManager Device Name Prefix parameter configured on Cisco Unity.
CUCM has an option to use NTP to obtain time information from a time server. Only the CUCM publisher will communicate with one or more NTP servers. The timing that the publisher receives is synchronized to the subscriber servers. If an external NTP server is not used, CUCM can be manually configured with the date and time. The system time in most servers is a stratum level 4 timing source and should not be relied on to time a production network. Figure 5-1 displays a master reference clock from which the publisher server is synchronizing time. The publisher server redistributes the timing information to the subscriber servers.
As mentioned, a network flow can be characterized by its direction and symmetry. Direction specifies whether data travels in both directions or in just one direction. Direction also specifies the path that a flow takes as it travels from source to destination through an internetwork. Symmetry describes whether the flow tends to have higher performance or QoS requirements in one direction than the other direction. Many network applications have different requirements in each direction. Some data link layer transmission technologies, such as Asymmetric Digital Subscriber Line (ADSL), are fundamentally asymmetric. A good technique for characterizing network traffic flow is to classify applications as supporting one of a few well-known flow types
Attenuation, noise, and crosstalk are all problems that affect communication mediums. Some mediums are more susceptible to these problems than others, but even so, great care must be taken when planning and deploying your network infrastructure. All of these can destroy the signal and degrade the QoS provided to the subscriber.
An application, such as an email program, creates data that will be sent by an end user, such as an email message. The Application layer (layer 7) places a header (encapsulation) field that contains information such as screen size and fonts, and passes the data to the Presentation layer (layer 6). Data Link layer. The Data Link layer removes the headers and trailers and passes the remaining information to the Network layer and so forth until data is received by the Application layer. Eventually, Device B will receive an email notification displaying a message to indicate that a new email message has been received.
Show subscriber-policy range subscriber policy policy subscriber-policy policy no default packet permit deny subscriber-policy policy no default packet permit deny bridge-group bridge-group subscriber-loop-control bridge-group bridge-group subscriber-trunk bridge bridge-group lat-service-filtering frame-relay map bridge dlci broadcast interface bvi bridge-group
Multicast VLAN Registration (MVR) is designed for applications using wide-scale deployment of multicast traffic across an Ethernet ring-based service provider network (for example, the broadcast of multiple television channels over a service-provider network). MVR allows a subscriber on a port to subscribe and unsubscribe to a multicast stream on the network-wide multicast VLAN. It allows the single multicast VLAN to be shared in the network while subscribers remain in separate VLANs. MVR provides the ability to continuously send multicast streams in the multicast VLAN, but to isolate the streams from the subscriber VLANs for bandwidth and security reasons. MVR assumes that subscriber ports subscribe and unsubscribe (join and leave) these multicast streams by sending out IGMP join and leave messages. These messages can originate from an IGMP version-2-compatible host with an Ethernet connection. Although MVR operates on the underlying mechanism of IGMP snooping, the two features...
The cable-network service provider operates a Cable Modem Termination System (CMTS) that provides high-speed connectivity for numerous cable modems. Many cable providers use the Cisco Universal Broadband Router (uBR) for this purpose. The uBR is designed to be installed at a cable operator's headend facility or distribution hub, and to function as the CMTS for subscriber end devices. The uBR forwards data upstream to connect with the Internet and or the public switched telephone network (PSTN) if telephony applications are deployed. (Note that both Cisco 10000 and 7200 series routers provide uBR CMTS functionality.)
Finally, service providers tend to bundle, meaning propose multiple services with a target to prevent customer churn. An example is triple play, in which voice, data, and video can be offered as a bundle perhaps over a single transport link. Bandwidth requirements for cable modem can be approximately 1 Mb upstream to the provider and 3 Mb downstream to the subscriber. One could additionally have prioritized traffic for VoIPtwo VoIP phone lines, per-call charging, and broadcast video MPEG 2and one half D1, with one channel per set-top.
An example of such a usage pattern might be in case of digital TV subscribers at a time when the Soccer World Cup final is on. When this scenario occurs, not only is a larger percentage of users than normal likely to watch TV at the same time, but to make matters worse, they also all want to watch the same program. Digital TV signals are compressed to reduce their bandwidth requirements, taking advantage of the fact that there is generally only a small difference between successive picture frames. However, cuts between scenes lead to temporary bandwidth spikes because an entire new picture needs to be transmitted, not just a delta of it. With different people generally watching different programs, the occurrence of spikes is somewhat distributed, which leads to a statistical effect that can be exploited. However, when everybody watches the same program, everybody requires simultaneously the same spike in bandwidth. This means that picture quality is likely to suffer if the underlying...
The first problem is one of portability. If you have been given a CIDR block, the addresses are most likely part of a larger block assigned to your ISP. Suppose, however, that your ISP is not living up to your expectations or contractual agreements, or you have just gotten a more attractive offer from another ISP. A change of ISPs most likely means you must re-address. It's unlikely that an ISP will allow a subscriber to keep its assigned block when the subscriber moves to a new provider. Aside from an ISP's being unwilling to give away a portion of its own address space, regional registries strongly encourage the return of address space when a subscriber changes ISPs. The problem is much amplified if you are an ISP rather than an end user and you want to change your upstream service provider. Not only must your own internetwork be renumbered, but so must any of your subscribers to whom you have assigned a portion of your CIDR block. Figure 2-7 shows what can happen. Here, the...
ISDN user-network interface L2 and L3 specifications also are referred to as Digital Subscriber Signaling System No. 1 (DSS1). L2 provides error-free and secure connections for two endpoints across the ISDN reference configuration. L3 provides the mechanism for call establishment, control, and access to services. The L2 protocol for ISDN is Q.920 921, and the L3 protocol is Q.930 931. Q.932 enables general procedures for accessing and controlling supplementary services.
The interface syntax can be used to specify to use the interface IP address for PAT instead of defining an additional IP address for the global pool. This is particularly useful in cases where there is a single address available for use (for example, when using a PIX firewall in a SOHO environment over a broadband connection such as digital subscriber line DSL or cable modem). The following command configures a global pool on an outside interface to use addresses 10.21.67.40 28-10.21.67.45 28
Application layer attacks can be implemented using several different methods. One of the most common methods is exploiting well-known weaknesses in software that is commonly found on servers, such as sendmail, HTTP, and FTP. By exploiting these weaknesses, hackers can gain access to a computer with the permissions of the account running the application, which is usually a privileged system level account. These application layer attacks are often widely publicized in an effort to allow administrators to rectify the problem with a patch. Unfortunately, many hackers also subscribe to these same mailing lists, which results in their learning about the attack at the same time (if they have not discovered it already). Subscribe to mailing lists that publicize vulnerabilities such as Bugtraq
Other types of VPN services include content-based services and broadband services integrated with the MPLS-based VPNs. In a content-based case, each VPN can represent a content service and subscribers subscribe to this service or VPN. The subscriber traffic is intelligently mapped to a content VPN without compromising the connectivity between the content VPNs themselves. The key here is the ability to map customers to VPNs. Appropriate policy routing with label distribution can help accomplish this capability.
Some vendors encouraged using two-binary 1-qurarternary (2B1Q) signaling at higher speeds as an alternative way to provision T1 and E1 services, without repeaters. The technique consisted of splitting the 1,544,000 bit per second service into two pairs (four wires), which each ran at 784,000 bits per second. By splitting the service across two lines, line speed and resulting need for frequency spectrum could be reduced to allow longer loop reach. This technique was referred to as high bit-rate digital subscriber line (HDSL). The result was that an HDSL-based DS-1 service could be implemented over specified loops of up to 12,000 feet long (assuming 24 gauge, or 9,000
Subscriber ID (56 - A bits) Intra-Subscriber ID (64 bits) Subscriber ID Identifies the ISP's subscriber. This field contains the address that the ISP assigns to the subscriber. The ProviderID and SubscriberID fields together are 56 bits in length. Intra-Subscriber ID Contains the portion of the address assigned and managed by the subscriber. The 64bit value used comprises a 16-bit subnet identifier and a 48-bit interface identifier (such as an IEEE MAC address).
When building IP NGN, decision-makers must evaluate which factors are most important to their operational environment and which factors provide the margin to grow their network up to the next upgrade period. As we all know, in reality no network elements can last through network growth forever, and therefore, a determination must be made on how to strike the right balance. A simple rule is to pick the sweet spot based on operational experience and to maximize the return on investment based on that sweet spot. For example, if 10,000 VCs are provisioned in the current Frame Relay edge switch for subscribers, the multi-service device may also support a similar number of VCs (maybe not the same because the multi-service edge MSE network element might also support Layer 3 services at the same time).
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