It could also be a virtual private network (VPN) using the public Internet as the transport, but as such it is not QoS-enabled and, therefore, is not a good fit for deploying VoIP traffic. Refer to the follow documentation for more information on how regular expressions are used in Cisco IOS: •Access and Communication Servers Command Reference,,,, RSVP Policy Identities for Matching the Default Cisco Unified CallManager Application IDs. Cisco also recommends using the passive-interface command to prevent routing neighbor adjacencies via the access layer. In particular, the ResvErr message is used to signal failure to reserve the requested resources due to either policy control or admission control somewhere along the network. There should be no STP in the core because network connectivity should be routed at Layer 3. The following sections discuss these requirements: For more information about WLAN design, refer to the Cisco Wireless LAN SRND guide, available at, For more information about the Cisco Wireless IP Phone 7920, refer to the Cisco Unified Wireless IP Phone 7920 Design and Deployment Guide, available at. •The link uses a low bit-rate codec (such as G.729). Another QoS requirement for wireless networking is the appropriate provisioning of bandwidth. Whether your business requires network design from the ground up or looking to overhaul your current network infrastructure, our certified Cisco … This retransmission does not occur for multicast traffic on the WLAN. An arbitrary topology may contain multiple WAN links and any number of hops between the sites. •Enable RSVP Application ID support if you need to limit the maximum amount of bandwidth used by video calls. Upstream queuing concerns traffic traveling from the wireless endpoint up to the AP and from the AP up to the wired network. This amount should be sufficient for most large enterprise deployments. A human or AA provides receptionist services for general incoming business calls and directs clients to the correct department or employee extension. As for downstream QoS, Cisco APs currently provide up to eight queues for downstream traffic being sent to wireless clients. PCs and servers are typically addressed with publicly routed subnet addresses; however, voice endpoints should be addressed using RFC 1918 private subnet addresses. However, due to the larger packet sizes of video traffic, these packets should be placed in the priority queue only on WAN links that are faster than 768 Kbps. You should also ensure that DHCP server(s) are configured with enough IP subnet addresses to handle all DHCP-reliant clients within the network. Both TFTP1_P and TFTP1_S must be configured as in Example 3-5 to search through the list of alternate file locations. As with VAF, exercise care when enabling VATS because activation can have an adverse effect on non-voice traffic. (In this case pins 4, 5, 7, and 8 are used.) 5. •All remaining traffic can be placed in a default queue for best-effort treatment. When deploying voice in a WAN environment, we recommend that you use the lower-bandwidth G.729 codec for any voice calls that will traverse WAN links because this practice will provide bandwidth savings on these lower-speed links. Note There are only two twisted pairs in the Token Ring cables. Note If Cisco Catalyst 4000 Series switches are used as Layer 3 devices at the distribution layer, a minimum of a Supervisor Engine 2+ (SUP2+) or Supervisor Engine 3 (SUP3) module is required. In this scenario, each remote or spoke site is one WAN link hop away from the central or hub site and two WAN link hops away from all other spoke sites. This way, the dial plan is administered in a single location and is not duplicated at each site, making changes to the dial plan easy to accomplish. Note For additional information, see the "Related Documents and References" section. This 75% rule assumes that some bandwidth is required for overhead traffic, such as routing and Layer 2 keep-alives. For example, if a distribution switch fails, all traffic flows will be reestablished through the remaining distribution switch. •The signaling protocols that may traverse the IP WAN in this deployment model are SCCP (encrypted and non-encrypted), H.323, MGCP, and CTI-QBE. Unfortunately, there is little upstream queuing available in a wireless network. Also note that, if branch-side telephony devices rely on a centralized DHCP server and the WAN link between the two sites fails, devices at the branch site will be unable to send DHCP requests or receive DHCP responses. Oversubscription of the link between the central site and the remote sites. First, provisioning more than 33 percent of the bandwidth for voice can result in increased CPU usage. Note Beginning with Cisco IOS Release 12.3(7)JA, the AP sends 802.11e CCA-based QBSS. For this reason, Cisco recommends that you do not use best-effort WAN topologies for voice-enabled networks that require enterprise-class voice services and quality. Designing Cisco Data Center Infrastructure (DCID) v7.0. This policy object helps to identify the application and associate it with the RSVP reservation request, thus allowing routers along the path to make appropriate decisions based on the application information. Figure 3-1 Typical Campus Network Infrastructure, Table 3-1 Required Features for Each Role in the Network Infrastructure, •Link Fragmentation and Interleaving (LFI). If the interface goes down, then the HSRP priority of the box is reduced, typically forcing a failover to another device. For the same reasons, redundant devices and network links that provide quick convergence after network failures or topology changes are also important to ensure a highly available infrastructure. When you deploy voice, Cisco recommends that you enable two VLANs at the access layer: a native VLAN for data traffic (VLANs 10, 11, 30, 31, and 32 in Figure 3-2) and a voice VLAN under Cisco IOS or Auxiliary VLAN under CatOS for voice traffic (represented by VVIDs 110, 111, 310, 311, and 312 in Figure 3-2). While the ingress Ethernet port on the AP can receive traffic at 100 Mbps, the maximum throughput on an 802.11b wireless network is 11 Mbps. If you are using 802.1x authentication in the wireless LAN, Cisco CKM is recommended to minimize roaming downtime. Configuring the maximum 11 Mbps data rate ensures the best level of throughput for voice devices and the largest number of active calls per AP. When deploying RSVP in the IP WAN in conjunction with Cisco Unified CallManager, observe the following design best practices: •Cisco recommends that you use the IntServ/DiffServ model if either of the following statements is true: –The only traffic destined for the Priority Queue (PQ) in the IP WAN interfaces is RSVP-enabled traffic. 3. Furthermore, proper WAN infrastructure design requires deploying end-to-end QoS on all WAN links. When packets are not received or acknowledged, they are retransmitted. In addition, centralized gateways and centralized hardware media resources such as conference bridges, DSP or transcoder farms, and media termination points are located in the data center or server farm. Provisioning more than 33% of the available bandwidth for the priority queue can be problematic for a number of reasons. When deploying wireless voice, observe the following specific AP configuration requirements: •Enable Address Resolution Protocol (ARP) caching. To use the IntServ operation model on a Cisco IOS router, use the following commands in interface configuration mode: When these commands are active, RSVP admits or rejects new reservations, not only based on the upper bandwidth limit defined within the ip rsvp bandwidth command, but also based on the actual bandwidth resources available. Conversely, networks that incorporate large numbers of mobile devices, such as laptops and wireless telephony devices, should be configured with shorter DHCP lease times (for example, one day) to prevent depletion of DHCP-managed subnet addresses. RSVP will admit requests until this bandwidth limit is reached. Using a traditional telephony analogy, we can view the portion of the WAN link that has been provisioned for voice as a number of virtual tie lines. Bursting above Committed Information Rate (CIR). Equation 1 and all other formulas within this section include a 25% over-provisioning factor. In fact, if a reservation passes the local policy check, it still must pass the interface RSVP bandwidth check before it is reserved. DHCP eases the administrative burden of manually configuring each host with an IP address and other configuration information. The default local policy can be used to match reservations that are not tagged with an Application ID or reservations that are tagged with an Application ID that you want to treat as untagged traffic. The trunks can also be on a fractional T1/E1 or a full T1/E1 type of service that runs CAS or PRI services. Furthermore, it is always a good idea to provide a local ACS or an on-AP RADIUS server at remote sites to ensure that remote wireless devices can still authenticate in the event of a WAN failure. The only requirement is that it runs Internet Explorer Version 6 or later. For more information on protocol behavior and extensions, complete message formats, and interactions with other protocols, refer to the numerous RFC documents related to RSVP, available at Until recently, quality of service was not an issue in the enterprise campus due to the asynchronous nature of data traffic and the ability of network devices to tolerate buffer overflow and packet loss. Because each voice call will send 50 packets per second (with 20 ms samples), provisioning for large numbers of calls in the priority queue can lead to high CPU levels due to high packet rates. Voice-adaptive traffic shaping (VATS) is an optional dynamic mechanism that shapes traffic on Frame Relay permanent virtual circuits (PVCs) at different rates based on whether voice is being sent across the WAN. Note that, depending on the wireless network deployment, the practical throughput might be less than 7 Mbps, especially if more than the recommended number of devices are associated to a single AP. When deploying voice in a WAN environment, Cisco recommends that you use the lower-bandwidth G.729 codec for any voice calls that will traverse WAN links because this practice will provide bandwidth savings on these lower-speed links. Furthermore, both the business and the SP can realize cost, space, and management savings. Inter-region call with audio codec set to G729: •Initial request: 40 kbps, using a 10 ms worst-case scenario, •Updated request: 24 kbps, using the preferred sample size of 20 ms. Inter-region call with audio codec set to G711: •Initial request: 96 kbps, using a 10 ms worst-case scenario, •Updated request: 80 kbps, using the preferred sample size of 20 ms. As with the audio stream, the initial reservation for the video stream will rely on the region settings because the endpoint codec capabilities will not be fully negotiated at the time of the reservation. To support RSVP Application ID functionality, Cisco Unified CallManager has two cluster-wide service parameters that define the Application ID used to tag audio and video call reservations using RSVP: •RSVP Audio Application ID (Default is "AudioStream"), •RSVP Video Application ID (Default is "VideoStream"). Associating more than 15 to 25 devices to an AP can result in poor AP performance and slower response times for associated devices. Example 3-4 Cisco IOS DHCP Server Configuration Commands, Cisco Unified CallManager DHCP Sever (Standalone versus Co-Resident Server). Because the audio stream of a video call is marked with the RSVP Audio Application ID, it is possible to guarantee a minimum number of voice calls and allow them to take over the entire available bandwidth. Once this traffic is marked, it can be given priority or better than best-effort treatment and queuing throughout the network. Instead of using wall power, IP phones and other inline powered devices (PDs) such as the Aironet Wireless Access Points can receive power provided by inline power-capable Catalyst Ethernet switches or other inline power source equipment (PSE). Another important consideration for a wireless infrastructure is security. This DHCP client Request, once acknowledged by the DHCP server, will allow the IP phone to retain use of the IP scope (that is, the IP address, default gateway, subnet mask, DNS server (optional), and TFTP server (optional)) for another lease period. It is important, when using VATS, to set end-user expectations and make them aware that data applications will experience slowdowns on a regular basis due to the presence of voice calls across the WAN. For applications such as voice, this packet loss and delay results in severe voice quality degradation. The data connection is most likely Frame Relay. Therefore, voice control protocols, such as H.323, MGCP, and Skinny Client Control Protocol (SCCP), require their own class-based weighted fair queue. 7. Furthermore, maintaining separate network links or devices makes troubleshooting and management difficult at best. Cisco Unified CallManager Express Solution Reference Network Design Guide OL-10621-01 Chapter 3 Network Infrastructure LAN Infrastructure. By default, these timers are set to 3 and 10 seconds respectively, which means that an hello packet will be sent between the HSRP standby group devices every 3 seconds and that the standby device will become active when an hello packet has not been received for 10 seconds. The reservations simply start flowing along the new routes based on the routing protocol decisions, and the reservations along the old routes time-out and are eventually deleted. In addition, the wireless IP phone considers the QBSS element in its roaming algorithm and will not roam to an AP that is sending beacons with a QBSS element above the maximum threshold. Just as QoS is necessary for LAN and WAN wired network infrastructure in order to ensure high voice quality, QoS is also require for wireless LAN infrastructure. Small businesses often prefer familiar key system operation. All of these WAN link technologies can be provisioned at specific speeds or bandwidth sizes. Before placing voice and video traffic on a network, it is important to ensure that there is adequate bandwidth for all required applications. •Adapters without impedance matching should be used for converting from universal data connector (UDC) to RJ-45 Ethernet standard. •Phones with no PC ports and with 10 Mbps switch ports (Cisco Unified IP Phone 7902, Cisco Unified IP Phone 7905, and Cisco Unified IP Phone 7910 IP Phones) should be allowed to auto-negotiate to 10 Mbps, half-duplex. Troubleshooting telephony network issues is simplified when a clear timeline can be drawn for events that occur on devices throughout the network. However, this rate might not correspond to your deployment if the call patterns are significantly different (for example, with call center agents at the branches). If a match is found, the packets are scheduled and policed by RSVP according to the reservation's traffic specification. For this reason, not only is it important to consider overlapping cells or channels on the same floor, but it is also necessary to consider channel overlap between adjacent floors. (See the "Wireless AP Configuration and Design" section.). When devices roam at Layer 3, they move from one AP to another AP and cross a subnet boundary. The Catalyst 6500, 4500, and 3750 are currently capable of supporting 802.3af. These link technologies, when deployed in a dedicated fashion or when deployed in a private network, can provide guaranteed traffic throughput. Application ID Support is introduced in Cisco IOS Release 12.4(6)T. For more information, see RSVP Application ID. In networks where remote locations are separated from the central site by low-speed or congested WAN links, an ACS server can be located at the remote site and remote wireless devices or users can be authenticated by this server locally, thus eliminating the potential for delayed authentication via a centralized ACS across the WAN link. In the European Union, the nonoverlapping usable channels for 802.11b are 1, 6, and 11 or 12 or 13. On the AP and access switch, you should configure both a native VLAN for data traffic and a voice VLAN (under Cisco IOS) or Auxiliary VLAN (under CatOS) for voice traffic. Might require that a complete and thorough site survey and, if possible, be made redundant to provide levels... Are converged at the core because network connectivity should be routed at Layer 3 roaming occurs when. 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