Implementing Avaya™ IP Office Server Frame Relay FRF.12 with a Cisco MC3810 Router and an Avaya™ S8300 Media Server and Avaya™ IP Telephones – Version 1.0
Abstract
These Application Notes document how to implement Avaya™ IP Office Server queuing for frame relay FRF.12 and the Cisco MC3810 router. Additionally, this document illustrates IP Office’s priority queuing mechanism and its ability to interoperate with Cisco’s Low Latency Queuing (LLQ). Lastly, these notes show how to optimize the Avaya™ S8300 Media Server and the Avaya™ IP Office for most efficient bandwidth utilization over the frame relay infrastructure.
1. Introduction Due to the cost benefits of Voice over IP (VoIP), many companies are converting their data Frame Relay networks to VoIP converged networks. These Application Notes document how to implement Avaya™ IP Office Server queuing for frame relay FRF.12 and the Cisco MC3810 router. Additionally, this document illustrates IP Office’s priority queuing mechanism and its ability to interoperate with Cisco’s Low Latency Queuing (LLQ). Lastly, these notes show how to optimize the Avaya™ S8300 Media Server and the Avaya™ IP Office for most efficient bandwidth utilization over the frame relay infrastructure.
The FRF.12 standard is an implementation of frame relay that supports frame fragmentation and interleaving, as well as IP RTP header compression. The manipulation of these packets in such a matter reduces latency and jitter characteristics of voice phone calls, while optimizing bandwidth for frame relay links. In conjunction with FRF.12, Layer 3 QoS queuing methods can be used to further increase voice quality during congested links. The Avaya IP Office uses a strict priority queuing strategy, which consists of three hardware queues for voice and data prioritization whereas Cisco commonly uses LLQ, a software queuing strategy that combines Priority Queuing with Class Based Weighted Fair Queuing for different types of data traffic. Both of these queuing strategies can be used together to enhance the benefits of Frame Relay to include support for voice traffic as well as data traffic. This document was verified with the Avaya IP 403 Office and the Cisco MC3810, but can be used as a model for all Avaya IP Office Server products and most Cisco series products that support IOS 12.2, LLQ, and Frame Relay FRF.12.
Figure 1: Network Diagram of an IP Office and a Cisco Router in Frame Relay network and Avaya’s S8300 IP Telephony solutions
In Figure 1, the Avaya IP Office and MC3810 router are configured to operate with an Avaya S8300 Media Server and G700 Media Gateway and an Avaya IP Telephone through an Avaya P333T Stackable Switch. The configuration consists of a Cisco router connected to an IP Office via a Frame Relay network. The service provider is offering a PVC that has a 512Kbps port speed and 256Kbps Committed Information Rate (CIR) for the IP Office, and a 256Kbps port speed and a 256Kbps Committed Information Rate (CIR) for the Cisco router. In turn, the Cisco router connects to the Layer 2 switch via an Ethernet connection, whereas the IP Office contains its own FastEthernet hub.
2. Equipment and Software Validated The following equipment and software were used for the sample configuration provided:
Equipment Software Avaya™ S8300 Media Server R011X.02.0.110.1 Avaya™ G700 Media Gateway 8 (B) Avaya™ 4624 IP telephone R1.71 Avaya™ IP 403 Office Server with T-1 PRI module 2.0.3 Avaya™ P333T Layer 2 Stackable Switch 3.12.1 Cisco MC3810 IOS 12.2-11
3. Configuration Overview Items of Note:
• Throughout the example, all IP endpoints are standardized on the DSCP value of 46 for RTP packets. In addition, Avaya transmits voice-signaling information to support VoIP applications. To make sure voice signaling is transmitted successfully through the network, the DSCP value of 34 is used. Since voice signaling is not latency sensitive, a unique queue can be assigned to it, but it is not necessary to share voice signaling priority with the voice queue.
• Although codec selection information is shown in this document, H.323 trunking, extension setup and route pattern examples are not shown. Please consult other Application Notes and the Administrators Guides for information on administering these procedures.
• The IP Office codec selection box is on the same form where the H.323 trunk is defined. Since no attempt is offered here in showing how to define H.323 trunks, assume that the default value of “automatic” is selected for codec selection on this form. However, the codec selection on the S8300 is shown in this document, and is set as a G.729 codec. This will force a G.729 H.323 connection between the IP Office and the S8300.
• In order for FRF.12 RTP header compression to work correctly, the destination port range for RTP traffic should be between 16384-32767 or between 49152-65535. This range must be manually configured in the S8300. This procedure is shown in this document. Note: Some non-GA versions of Cisco IOS do not support all of the port ranges. This is known to be true of some of the “T” trains of the IOS. Only use GA versions of the Cisco IOS. The version of IOS in this document is known to work correctly.
• IP Office automatically allows for 100 percent of the bandwidth to be prioritized for voice, whereas the Cisco value for the priority queue is manually configured. This document sets aside 100Kbps of bandwidth for voice calls on the Cisco side. Do not
allocate more channels than what is set aside for the Cisco priority queue. Channel setup is part of H.323 trunk configuration and is not shown in this document.
• The P333T Layer 2 Switch is set for factory defaults; no additional configuration is necessary and no additional setup information is given in this document.
Some things to note about frame relay topology architecture:
• Frame relay services can become complex and must be designed by an experienced engineer or architect in advance of installation. The installer must make sure that he or she has all frame relay parameters before installation. The engineer or architect that is assigned to the project provides these parameters.
• Frame relay is a multipoint topology with asymmetrical bandwidth capabilities. This means that port speeds on one part of the network do not have to match speeds from other parts of the network. In this example, the network consists of two parts, the IP Office side and the Cisco side. The IP Office side has a 512Kbps port speed, and the Cisco side has a 256Kbps port speed.
• In this example, it is assumed that the carrier is supplying ANSI LMI, however both IP Office and Cisco support multiple LMI types (ANSI ANNEX D, Q933, Cisco, and AutoLearn).
3.1. Avaya IP Office Queuing and FRF.12 Avaya’s IP Office uses a strict priority queuing strategy and consists of three hardware queues. The first queue is the strict priority queue, where packets with the DSCP values specified in IP Office are sent. The next queue is where voice signaling packets are sent. Finally, the last queue is where all other traffic is sent. The Avaya IP Office implementation of frame relay, as with all WAN protocols, uses unnumbered IP interfaces and “borrows” the LAN1 interface for the WAN IP address.
The frame relay parameters form on the IP Office Manager assigns frame relay traffic shaping features to the frame relay interface. The most popular features that the user should be aware of are Committed Information Rate (CIR), Committed Rate Measure Interval (Tc), Committed Burst Size (Bc—Computed and not shown on form), and Excess Burst Size (Be). The CIR is measured in bits per second where the Bc and the Be are simply measured in bits.
The Avaya IP Office implementation of FRF.12 automatically supports Cisco’s frame relay encapsulation types. In addition, frame fragmentation is automatically computed based upon CIR and Tc values. Therefore, manual fragmentation values are not entered. Lastly, fragmentation occurs only in the presence of voice packets thus minimizing any potential CPU latency on low priority data streams.
Avaya does not recommend Be for frame relay traffic that carries VoIP. This value is set to 0.
For best voice quality, Avaya recommends a Tc of 10ms. Tc is defined as a time interval over which Bc (or more accurately, Bc+ Be) bits are transmitted. The Tc value is directly configured on IP Office where Bc is calculated and is not entered.
3.2. Configure the Avaya IP Office
1. Configure basic system information. Using IP Office Manager, select the System menu. Under the System tab, enter the IP addresses of the TFTP, License and Time Servers as shown in Figure 2. This would be the server that is running IP Office Manager. In these Application Notes, the IP Office Manager PC is also the DHCP server.
3. Configure the Gatekeeper QoS parameters. Configure the Gatekeeper QoS parameters as shown in Figure 4. The fields called “DSCP(Hex)” and “DSCP Mask (Hex)” determines which packets are placed in the priority queue.
4. Configure the T1 channels. Click on Line and select Line 5. Put the appropriate amount of timeslots into service. In this example, eight 64K timeslots have been placed into service.
5. Configure T1 circuit options. Click on the Advanced tab and set the clocking, framing and linecoding to that of the carrier specifications. The example here shows the most common selections.
7. Create a WAN Port. Create a WAN Port called “LINE5.0”. Make sure that it is in upper case. The port name and number maps directly into the line 5 starting at the first timeslot (timeslot assignments are one less then the actual slot number, hence “0”). Under the WANPort tab, set the port speed and mode as in Figure 8.
8. Set frame relay information. Click on the Frame Relay tab and enter the information as shown in Figure 9. (Note: it is assumed that the carrier is supplying ANSI LMI. Contact the carrier for appropriate LMI configurations.)
9. Add DLCIs. Click on the DLCIs tab and double click on the blank list area. Fill out the form as in Figure 10. DLCIs and CIR are assigned by the carrier. Note: Avaya does not recommend an excessive burst size (Be) for voice packets. Enable IP header compression. Set TCP header compression to 0.
When configuring Cisco LLQ, a class map is defined for a particular traffic type. In this case, the class maps voip-fr and vosig-fr are defined to match traffic that is marked as DSCP 46 and DSCP 34, respectively.
In turn, the policy-map defines what to do with the traffic that meets the class map parameters. In this case, policy map llq reserves 100 Kbps of priority bandwidth for the voip-fr class map, 8 Kbps of non-priority bandwidth for vosig-fr class map, and all other traffic, the weighted-fair queue for class-default class map.
The class-default class map is a special case. Class-default is automatically defined by IOS. Therefore, it is not necessary to create a class map for this traffic type. Any traffic that does not conform to the parameters of the user-defined class maps is automatically assigned to the class-default class map. Any queuing strategy can be defined by class-default. However, in this example, class-default is defined by a weighted fair-queue that is reserved for the remainder of the bandwidth.
The llq policy map is applied to the interface by using the service-policy command. It is normally applied outbound to the interface; in this case the serial interface, but if the serial interfaces on the routers are frame relay interfaces and have frame relay class maps associated with them, then the policy map is applied in the frame relay class map definition. In this example, Frame_Class_1 is defined as the frame relay class map.
The frame relay class map assigns frame relay traffic shaping features to the frame relay interface. The most popular features are Committed Information Rate (CIR), Committed Burst Size (Bc), and Excess Burst Size (Be). The CIR is measured in bits per second where the Bc and the Be are simply measured in bits.
For voice, Cisco recommends a Committed Rate Measure Interval (Tc) of 10ms. Tc is defined as Time interval over which Bc or (Bc+ Be) bits are transmitted. Tc is calculated as Tc = Bc / CIR. The Tc value is not directly configured on Cisco routers. It is calculated after the Bc and CIR values are configured.
For example, in order to guarantee a Tc of 10ms, the CIR of 256 Kbps, a Bc of 2560 bits and a Be of 0 bits are used. The router will send 2560 bits every 2560 / 256,000 (or 10 ms) and queue any excess bursts. The default frame relay Be value of 0 is used to prevent any bursting over CIR. Cisco does not recommend bursting for frame relay traffic that carries VoIP.
Cisco recommends fragmentation for low speed links (less than 768kbps). Fragmentation size is calculated so that voice packets are not fragmented and do not experience a serialization delay greater than 20 ms. The fragmentation size is based on the lowest port speed between the routers. For example, in a hub and spoke Frame Relay topology where the hub is a 1.544Mbps CIR and the remote routers are 64 Kbps CIRs, the fragmentation size should be set for the 64 Kbps CIR on all routers. Any other PVCs that share the same physical interface should configure the fragmentation to the size used by the voice PVC.
3.5. Configure the Avaya IP Telephone Manual IP telephone configuration is not necessary. To verify that the IP telephones have the correct DSCP code points, perform the following task.
Press HOLD (or MUTE) 767 # Press # five times until L3 audio appears. Verify 46 appears. If so, then press # For L3 signaling, verify that 34 appears. Press # to save
Figure 13: Avaya IP Telephone verification
3.6. Configure the Avaya S8300/G700 Server
After logging into the S8300/G700 Server, enter change ip-network-region X where X refers to a number. In this example, X is 1. Enter 34 for the both the “Call Control PHB Value” and the “BBE PHB Value”. Enter 46 for the “VOIP Media PHB Value”. Enter the “UDP Port Range” values from 16384 to 32767. Set “Direct IP-IP Audio Connections” to no. (See Figure 14.)
change ip-network-region 1 Page 1 of 2IP Network Region
Region: 1Name: C-HAWK
Audio Parameters Direct IP-IP Audio Connections? nCodec Set: 1 IP Audio Hairpinning? yLocation:
UDP Port Range RTCP Enabled? yMin: 16384 RTCP Monitor Server ParametersMax: 32767 Use Default Server Parameters? y
DiffServ/TOS ParametersCall Control PHB Value: 34
VoIP Media PHB Value: 46BBE PHB Value: 34
802.1p/Q Enabled? n
Figure 14: S8300/G700 Communications Server Configuration
Choose G.729 Codec. Enter change IP-codec-set X where X is the IP Codec set ID, in this case 1. Tab down to field ID of “1” and enter G.729
change ip-codec-set 1 Page 1 of 1
IP Codec Set
Codec Set: 1
Audio Silence Frames PacketCodec Suppression Per Pkt Size(ms)
1: G.729 n 2 202:3:4:5:6:7:
Figure 15: S8300/G700 Communications Server Configuration
4. Verification Steps The network administrator may validate network reachability by pinging all router LAN interfaces. Because IP Unnumbered is used, The Avaya IP Office WAN interfaces will not be pingable. From the IP Office Manager PC, launch the monitor program. Disable all tracing except frame relay. Ping a device across the frame relay cloud. The user should see the following results in the monitor screen:
On the Cisco router, execute the “show frame-relay pvc” and “show frame-relay fragment” commands to verify queuing and fragmentation information. 7206vxr#show frame-relay pvc 101
PVC Statistics for interface Serial1/0:0 (Frame Relay DTE)
input pkts 1885352 output pkts 2066296 in bytes 349097036out bytes 378106450 dropped pkts 0 in FECN pkts 0in BECN pkts 0 out FECN pkts 0 out BECN pkts 0in DE pkts 0 out DE pkts 0out bcast pkts 151145 out bcast bytes 15933026pvc create time 1w6d, last time pvc status changed 1w5dservice policy llq
Service-policy output: llq
Class-map: voip-fr (match-all)102506 packets, 11894192 bytes5 minute offered rate 0 bps, drop rate 0 bpsMatch: ip dscp 46
5. Conclusion In summary, IP Office queuing can work well with Cisco’s LLQ mechanism in order to optimize voice traffic over IP networks. By using this method with IP over Frame Relay, the enterprise has a robust choice of transports, speeds and convergence types.
