configuring cisco avvid phần 8 doc

Design Considerations in a WAN/Campus Environment • Chapter 7 249 UplinkFast This feature is most useful on wiring closet or work- group switches where endstations connect into the network. The UplinkFast feature would be implemented on redundant uplinks between workgroup/access layer switches and the core/back- bone switches by creating an uplink group of multiple ports, only one of which is forwarding. Within two seconds of a link failure, UplinkFast will restore connectivity to the network backbone. UplinkFast can also provide load balancing between redundant uplinks. UplinkFast is not intended for backbone or distribution layer switches. BackboneFast Connectivity to a backbone switch can be restored rapidly with the BackboneFast feature. BackboneFast can detect a link failure on a link that is not directly connected to the switch by listening for certain types of STP messages. When a failure is detected, the switch can immediately transition a port from blocking to forwarding mode in order to provide an alternate path around the failed link. This capability allows a switch connected to the backbone to react much faster to indi- rect failures. In order for BackboneFast to work correctly, it must be enabled on all switches within the network. Per VLAN Spanning Tree (PVST) Redundancy and load balancing can be implemented on connections between access layer and core network switches using the PVST fea- ture. PVST can also help to reduce STP convergence times since the PVST topologies should be smaller than if a single spanning tree topology was used in the network. EtherChannel Fast EtherChannel (FEC) and Gigabit EtherChannel (GEC) enable multiple physical connections between devices to be aggregated or bundled into a single logical channel. The primary benefits of using FEC and GEC are increased bandwidth and redundancy between switches, and the ability to load balance traffic on uplinks between www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 249 250 Chapter 7 • Design Considerations in a WAN/Campus Environment switches. FEC and GEC can be implemented on connections between LAN switches, routers, servers, and workstations using standards unshielded twisted pair (UTP) or fiber optic cabling. Some LAN switch platforms allow up to four physical connections per EtherChannel and others allow up to eight physical connections per EtherChannel. Security Some basic security mechanisms are available in LAN switches to prevent unauthorized users from gaining access to the network or attempting to capture data or voice traffic. These basic tools com- bined with normal physical security measures, such as placing equipment in locked rooms or closets, can increase the security of the LAN infrastructure. Port security is a feature that can be used to prevent potential intruders from gaining access to the network for purposes of cap- turing traffic. This feature works by mapping a specific layer 2 MAC address to a specific switch port. If the switch detects a different MAC address on a given port, or detects that a MAC address has moved to a different port, the switch automatically can disable the ports in question. Protecting the actual network devices themselves can be achieved with the Terminal Access Controller Access Control System (TACACS) protocol. TACACS provides an authentication mechanism that can prevent unauthorized users from gaining Telnet access or direct console access to a switch or router to make configuration changes that would disrupt the network. Deploying TACACS will require the protocol to be enabled on the LAN switches as well as a separate TACACS authentication server. Another benefit of using TACACS is that userid/password administration can be centralized on the TACACS server instead of maintaining userids on each indi- vidual device. Private VLAN edge is another security feature that can be enabled on workgroup Catalyst LAN switches such as the 2900XL and 3500XL. This feature essentially prevents forwarding of unicast, www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 250 Design Considerations in a WAN/Campus Environment • Chapter 7 251 broadcast, or multicast traffic directly between switch ports. Instead, the traffic must be forwarded through a router or layer 3 switch, which would allow ACLs to be used to filter the traffic before being forwarded. Using private VLAN edge ensures that voice traffic will travel directly to its destination without the potential to be redi- rected to another port. This feature can be enabled or disabled on individual switch ports. Designing Enterprise Dial Plans Just as an IP data network needs an IP address plan, a voice net- work needs a dial plan. Constructing a dial plan involves assigning unique addresses (phone numbers) to each handset or terminal, and determining how calls will be routed between all possible desti- nations. A dial plan must support routing of external calls to the PSTN or a separate CallManager cluster. Calls to internal destina- tions must also be supported, which is typically accomplished with abbreviated dialing. Although the IP network will be the preferred path for WAN calls, the dial plan should also support dynamic rerouting of calls in the event of a failure of the IP network. A dial plan not only provides the addresses required for each device, but also implements the logic that is used to route calls to both internal and external destinations. Call routing logic is imple- mented in a CallManager dial plan with a combination of routing decision points and the capability to modify dialed numbers. A dial plan can also incorporate restrictions on calling. Before constructing a dial plan, it is important to understand the terminology that is used by the Cisco CallManager. Dialed Numbers and Number Modification One of the functions of call processing in a voice network is to inter- pret the digits that are dialed by the telephone user and set up a call to the requested destination. Although we generally don’t think of this as we dial the phone, the dialed digits are actually a form of www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 251 252 Chapter 7 • Design Considerations in a WAN/Campus Environment signaling to the network about the destination we are requesting. Once the network receives the dialed digits from the user, the may modify the number before completing the call processing. The fol- lowing is an explanation of the terminology that is associated with this phase of call processing. Dial String Dial string is the set of digits that a user dials to initiate a call. For example, this may include a local extension, a full E.164 number, or some prefix digits followed by a full E.164 phone number. The length of the dial string used for internal calls must be determined when creating a dial plan. In general, the number of digits used should minimize the number of digits that users must dial for internal calls while allowing enough flex- ibility to support growth of the organization. Dial strings can be manipulated by the system, transparent to users, with digit manipulation and digit translations. Digit Manipulation Digit manipulation entails adding or stripping a prefix or suffix to a dial string. Digit manipulation can be applied to outbound external calls only, and may be applied at within route patterns or route groups. This may be necessary when alternate routes to a given destination exist. For example, when calling to a branch office location with a five-digit internal extension, the preferred route for the call would be on-net over the IP WAN. If the IP WAN is congested or unavailable, the call can be routed over the PSTN. If a user dialed only five digits and the call must go over the PSTN, digit manipulation can be performed to add the required prefix back on to route the call over the PSTN. Digit manipulation is performed transparently to the user. Digit Translation Digit translation is applied to outbound or inbound external and internal calls, as well as both the calling and called party numbers. The three types of digit translation that can be applied, in order of processing, are discarding digits, transformations, and adding prefixes. A common application of digit translation for incoming calls is to transform calls to unas- signed direct inward dialing (DID) numbers to roll to an atten- dant automatically. www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 252 Design Considerations in a WAN/Campus Environment • Chapter 7 253 Call Routing Decision Points Receiving a string of dialed digits from a user is only the beginning of the call processing function. There are many potential destina- tions that can be reached by callers using a voice network. The call processing device (the CallManager in an AVVID network) must be programmed to deliver calls to the proper destination and in the most efficient manner. A series of decisions must be made during call processing in order to accomplish this part of the call setup. For example, should a call be handed off to a local PSTN trunk, or will the call be completed over the IP WAN using a voice gateway? The CallManager has several levels of decision logic that can be used to control these decisions. The following section describes the call routing decision points that must be configured in the CallManager. Route pattern Defined in the CallManager to identify or match a dial string that was dialed by a user for external calls only. Route patterns can consist of a single explicit number or can contain wildcards to define a range of numbers to minimize the required entries and simplify the dial plan. When a dial string matches a route pattern, the call is handed off to a route list to determine how the call will be routed. Before handing the call off to the route list, digit manipulation can be performed to add or strip dialed digits as required to process the call. Route patterns are not used to process local calls between two IP phones on the same CallManager or cluster of CallManagers. Typically, a single route pattern is used for external calls to the PSTN. Route list An ordered list of potential routes that a call may take to reach the required destination. A route list determines how a call will be routed according to the listed order of prefer- ence. In the simplest case, a route list may point to a preferred route group to reach the IP WAN, or may secondarily point to a route group to reach the PSTN for fail-over purposes. Multiple route patterns can point to a single route list. Previous to CallManager version 3.x, route lists were referred to as route points. www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 253 254 Chapter 7 • Design Considerations in a WAN/Campus Environment Route group One or more devices that can be used to handle a given call. Devices can be listed within the route group in order of preference. Digit manipulation can also be performed within a route group, and can override the manipulation performed by a route pattern. If a route group contains multiple devices, all devices will have the same characteristics, such as digit manipu- lation. In legacy telephony lingo, a route group can essentially be viewed as a trunk group. Devices Includes IP telephony gateway endpoints such as H.323 gateways, MGCP gateways, and Skinny Gateway Protocol gate- ways. Figure 7.4 shows a sample dial plan that may be implemented on the San Jose CallManager. www.syngress.com Figure 7.4 A Sample Dial Plan for San Jose CallManager IP WAN PSTN CallManager Gateway IP Phone CallManager Gateway IP Phone CallManager Gateway IP Phone San Jose 408-XXX-XXXX Herndon 703-XXX-XXXX Research Triangle Park (RTP) 919-XXX-XXXX Route Group Herndon-PSTN Route Group RTP-PSTN Route Group Herndon-WAN Route Group RTP-WAN Route List Herndon Route List RTP Route Pattern 703XXXXXXX Route Pattern 919XXXXXXX preferred route preferred route alternate route alternate route 94_AVVID_07 1/16/01 1:33 PM Page 254 Design Considerations in a WAN/Campus Environment • Chapter 7 255 Dial Plan Groups and Calling Restrictions Calling restrictions and class of service can also be incorporated into the CallManager dial plan for IP phone users. These features of the dial plan will require configuration of partitions and calling search spaces. Partitions A collection of devices and associated route patterns with similar call processing characteristics. A partition contains directory numbers, route patterns, and IP telephones. Calling Search Space A list of partitions that is searched in a specified order before allowing a call to be completed. Any device that can initiate a call may be subject to the restrictions of calling search spaces, including IP phones, SoftPhones, and VoIP gateways. Users can only dial DNs within a partition in the calling search space that they are assigned; this is how calling restrictions can be implemented. Restricting calls in this fashion is also commonly referred to as class of service in a telephony system. For those familiar with the data routing capabilities of Cisco routers, calling search spaces are somewhat analogous to using access control lists to restrict reachability to certain parts of the network. Summary An AVVID voice network will only be as good as the infrastructure upon which it is built. Designing a solid foundation begins with pro- viding sufficient network capacity to handle voice traffic on a con- verged network. Once sufficient capacity has been provisioned, the proper QoS tools must be deployed in the WAN and LAN in order to guarantee voice quality end-to-end through the network. Lastly, a scalable dial plan must be implemented that supports required user services. www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 255 256 Chapter 7 • Design Considerations in a WAN/Campus Environment FAQs Q: Which is the preferred method of implementing traffic shaping in a Frame Relay network, generic traffic shaping (GTS) or Frame Relay traffic shaping (FRTS)? A: FRTS and GTS are similar in the way that they are imple- mented. However, since FRTS works in conjunction with FRF.12 for fragmentation and GTS does not, FRTS is the better solution. Q: Are new LAN switches required in order to support inline power to IP telephones? A: No, Cisco provides an inline power patch panel that can be used to supply inline power when existing LAN switches do not have inline power capabilities. Q: Can the new 7900 series phones be used if inline power is not available? A: Yes, the 7900 series phones support both inline power and external power from AC wall outlets. Q: Must I acquire additional IP addresses from my ISP in order to support new IP telephones within the network? A: No. Private IP addresses (RFC 1918) can be used internally within the organization for IP telephones. www.syngress.com 94_AVVID_07 1/16/01 1:33 PM Page 256 The Cisco AVVID Fast Track Solutions in this chapter: ■ A Hardware Overview ■ A Software Overview ■ AVVID Design Considerations Chapter 8 257 94_AVVID_08 1/16/01 12:12 PM Page 257 258 Chapter 8 • The Cisco AVVID Fast Track Introduction As with any new technology, there are going to be shortfalls. Some of the products will not have all of the features or functions that are currently offered by some of the legacy systems. Some of the prod- ucts may not scale to all expectations or needs, and information may sometimes be hard to come by. With Cisco’s AVVID model, we are seeing some of these expected problems, However, by carefully considering your options and putting together a solid design, an AVVID infrastructure will give you a 100 percent reliable solution with many benefits that are not offered by your current legacy sys- tems. As we reviewed, Cisco has introduced a line of software appli- cations that will help make your call center and employee productivity increase. Cisco has also developed a sound hardware product offering with product enhancements that are being deliv- ered every day. Cisco Systems, Inc. is definitely on their way to changing the way the world does business. A Hardware Overview As a review of the AVVID architecture, let’s take a look at some of the current hardware offerings and their main features and func- tionality. IP Phones One of the main benefits of an AVVID infrastructure is the flexibility of the solution set. Even down to the handset, Cisco has multiple offerings that the end user can choose from ranging from a low-end “lobby” handset to an executive level handset with multiple lines and a larger display. 7910 IP Telephony Handset The entry line to Cisco’s IP telephones are the 7910 and 7910+SW which provide a low-price unit for areas where phone usage and www.syngress.com 94_AVVID_08 1/16/01 12:12 PM Page 258 [...]... support eight– 48 port blades, totaling 384 ports in a single unit MCS The Cisco Media Convergence servers are PC-based systems that operate on Windows 2000 operating systems to supply call management control and unified messaging services to AVVID clients Cisco currently offers two MCS platforms to choose from, the MCS 782 2 and the MCS 783 5 Table 8. 1 outlines the details on the two products Table 8. 1 A Comparison... the routing of the 6000 series functions similar to a Cisco 4500 router The 6000 series offers complete AVVID support by providing inline power at 48 ports per blade directly to second-generation IP phones In many environments, where a cleaner solution is www.syngress.com 94 _AVVID_ 08 1/16/01 12:12 PM Page 263 The Cisco AVVID Fast Track • Chapter 8 263 required, it is not desirable to use the Catalyst... redundant Windows 2000 1.44MB Standard PC Floppy Drive High Speed IDE Fixed Windows 2000 www.syngress.com 94 _AVVID_ 08 1/16/01 264 12:12 PM Page 264 Chapter 8 • The Cisco AVVID Fast Track IPVC Cisco s IP/VC 3500 series defines the AVVID solution for video conferencing Essentially a hardware-based solution, Cisco s video conferencing offers H.323 and H.320 compatibility for interaction with applications such... Because www.syngress.com 94 _AVVID_ 08 2 68 1/16/01 12:12 PM Page 2 68 Chapter 8 • The Cisco AVVID Fast Track clocking for each channel of the digital line is handled out of band, one channel per T1 or E1 line is removed As such, a T1 link that is composed of 24 channels will effectively allow for utilization of 23 for communication while an E1 permits 30 VG200 Voice Gateway Cisco s VG200 is an advanced... WebAttendant www.syngress.com 94 _AVVID_ 08 1/16/01 12:12 PM Page 271 The Cisco AVVID Fast Track • Chapter 8 271 allows portability to various platforms including Windows 98, Windows NT, and Windows 2000 Working with the Cisco IP Phone, WebAttendant is able to monitor the state of every line in the system, while promptly and efficiently dispatching and accepting calls AVVID Design Considerations Migration... the rest of the world where E1 lines are used, a-law encoding is employed All Cisco digital voice gateways support these standards www.syngress.com 94 _AVVID_ 08 1/16/01 12:12 PM Page 267 The Cisco AVVID Fast Track • Chapter 8 267 as common functionality including the mapping of IP addresses to phone numbers and vice versa Cisco provides a number of products for gateway services Some of these devices... provide interoperability to additional Cisco devices via fiber or copper connection The 3500 series switches provide the ability to interlink to one another through gigabit uplinks Each www.syngress.com 94 _AVVID_ 08 262 1/16/01 12:12 PM Page 262 Chapter 8 • The Cisco AVVID Fast Track 3500 series switch utilizes 4MB of memory, used to buffer between all ports beyond the 8MB used for IOS and its 4MB flash With... can support up to 10,000 IP Phones (2000 phones on each of five servers) Active Voice Active Voice is Cisco s answer to voice mail One of the key items and major benefits of Active Voice and Cisco s IP Telephony solution www.syngress.com 94 _AVVID_ 08 270 1/16/01 12:12 PM Page 270 Chapter 8 • The Cisco AVVID Fast Track is the unified messaging direction With Unified Messaging, Active Voice (Voice Mail) can... technologies together Cisco offers highly flexible solutions for which a modular router can support any number of interface types, software functionality, and protocols Cisco 1750, 2600, and 3600 series routers share common boards that any of these routers can use MCS 381 0 The MCS 381 0 is Cisco s all-encompassing flexible solution for media convergence This router was Cisco s first unit to provide AVVID support,... above described functions www.syngress.com 94 _AVVID_ 08 260 1/16/01 12:12 PM Page 260 Chapter 8 • The Cisco AVVID Fast Track 7960 IP Telephony Handset The 7960 IP telephone is essentially the same as the 7940 with the exception that it includes six lines or speed dial buttons rather than two 7935 IP Telephony Conference Station The 7935 IP conference station is Cisco s answer to corporate needs for an all-encompassing . Hardware Overview ■ A Software Overview ■ AVVID Design Considerations Chapter 8 257 94 _AVVID_ 08 1/16/01 12:12 PM Page 257 2 58 Chapter 8 • The Cisco AVVID Fast Track Introduction As with any new. with any of the above described functions The Cisco AVVID Fast Track • Chapter 8 259 94 _AVVID_ 08 1/16/01 12:12 PM Page 259 260 Chapter 8 • The Cisco AVVID Fast Track 7960 IP Telephony Handset The. to AVVID clients. Cisco currently offers two MCS platforms to choose from, the MCS 782 2 and the MCS 783 5. Table 8. 1 outlines the details on the two products. Table 8. 1 A Comparison of the MCS 782 2