Nortel Remote Gateway 9110 Reference Manual
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Nortel Remote Gateway 9110 Reference Manual

Remote gateway 9100 series
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555-8421-103
Remote Gateway 9100 Series Network Engineering Guidelines
Product Release 1.6
Standard 1.6
June 2005
Copyright © 2000–2005 Nortel. All Rights Reserved.
Printed in Canada.
All information contained in this document is subject to change without notice. Nortel reserves the
right to make changes to equipment design or program components, as progress in engineering,
manufacturing methods, or other circumstances may warrant.
*Nortel, the Nortel logo, the Globemark, Unified Networks, Meridian 1 PBX, Communication Server
1000 (CS 1000), and Communication Server 2100 (CS 2100) are trademarks of Nortel.

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  • Page 1 Copyright © 2000–2005 Nortel. All Rights Reserved. Printed in Canada. All information contained in this document is subject to change without notice. Nortel reserves the right to make changes to equipment design or program components, as progress in engineering, manufacturing methods, or other circumstances may warrant.
  • Page 2 Standard 1.6 June 2005 Remote Gateway 9100 Series Network Engineering Guidelines...

  • Page 3: Table Of Contents

    Contents In this document About this document Introduction to packetized voice The E-model to measure audio quality and user satisfaction Compressed audio quality under ideal conditions Compressed audio quality under packet loss conditions Evaluating your network Bandwidth usage table Quality of service issues Ordering ISDN lines Remote Gateway 9100 Series Network Engineering Guidelines...

  • Page 4: In This Document

    Nortel's patented QoS Transitioning Technology instructions on how to order ISDN lines Terminology Throughout this document, the term “host PBX” refers to the following Nortel PBXs: Meridian 1 PBX Communication Server 1000 (CS 1000) Communication Server 2100 (CS 2100) Unless otherwise specified, the term “Remote Gateway 9100 Series units”...

  • Page 5: Introduction To Packetized Voice

    (Codec) chosen. A Codec compresses audio, reducing the amount of bandwidth required to have a conversation. — G.711 (64 Kbps data rate - equivalent to a wired telephone [no compression]) — G.726 (32 Kbps data rate - reduces the required bandwidth by one half in trade for a slightly lower audio fidelity) —...
  • Page 6 International Telephony Union G.107 Recommendations (ITU-G.107). This document and the subsequent G.108 and G.113 documents have been developed by industry leaders, including Nortel. Many of the ITU recommendations have been “rolled” into the TIA TSB116 document that clearly outlines the methods of engineering an excellent packetized voice system.

  • Page 7: The E-Model To Measure Audio Quality And User Satisfaction

    The E-model to measure audio quality and user satisfaction The ITU developed what is called the E-model. The E-model uses the factors described in “Introduction to packetized voice” on page 5 to derive a quality value corresponding to the quality experienced by the VoIP system users. The following graph shows the E-model rating, R value, versus the traditional Mean Opinion Score (MOS) values.

  • Page 8: Compressed Audio Quality Under Ideal Conditions

    Compressed audio quality under ideal conditions The following graph shows the Remote Gateway 9100 Series Codecs graphed against the R value and conversational delay. Remote Gateway 9100 Series Codecs - No Impairments Note: T is one-way delay in milliseconds (ms). To fully use this graph, you must know the Remote Gateway 9100 Series inherent delay values.
  • Page 9 There are additional delays experienced that are a function of the customer network: end-to-end delay The time it takes to pass an Internet Protocol (IP) packet from the RLC to the Remote Gateway 9150 unit (or the opposite direction) jitter buffer depth If the network has low jitter, the jitter buffer can be reduced.
  • Page 10 Remote Gateway 9150 unit to Remote Gateway 9150 unit When a customer environment uses multiple Remote Gateway 9150 units, the audio must be treated by each individual Remote Gateway 9150 unit. Therefore, the delay each Remote Gateway 9150 unit experiences is added together. For example, assuming one Remote Gateway 9150 unit over IP (G.711) communicating to another Remote Gateway 9150 unit over BRI (G.729A): 30 ms (G.711 encoding/decoding) + 20 ms (one-way network delay) + 60 ms...

  • Page 11: Compressed Audio Quality Under Packet Loss Conditions

    Compressed audio quality under packet loss conditions The following graph shows the effect of random packet loss on the Remote Gateway 9100 Series G.711 Codecs. Note: T is one-way delay in ms. Remote Gateway 9100 Series Network Engineering Guidelines G.711 w ith Random Packet Loss User Satisfaction Very satisfactory...
  • Page 12 The following graph shows the effect of random packet loss on the Remote Gateway 9100 Series G.729A Codecs. Note: T is one-way delay in ms. G.729A w ith Random Packet Loss Remote Gateway 9100 Series Network Engineering Guidelines User Satisfaction Very satisfactory G.711...

  • Page 13: Evaluating Your Network

    To ensure success, network evaluation is a critical step in engineering a VoIP solution. Do not skip this critical step, as it is the foundation for the projects success. Nortel can provide network evaluation services, either directly or through our business partners. Network engineering for real time traffic Packetized voice, or VoIP, is a form of real time traffic where delays and retransmission cannot be tolerated.
  • Page 14 Remote Gateway 9150 unit Remote Gateway 911x series units and Digital Telephone IP Adapter units It is common that the Remote Gateway 9100 Series product is directly plugged into a hub or a switch as shown in the following illustration:...
  • Page 15 A switch manages the traffic so only packets addressed for the Remote Gateway 9100 Series product are transmitted to the Remote Gateway 9100 Series product. Nortel recommends that you connect the Remote Gateway 9100 Series product to a data switch as shown in the following illustration:...
  • Page 16 9100 Series traffic. UDP port 0x5000 (20480) is used for voice traffic. UPD port 0x5002 (20482) is used to test during QoS Transition. TCP port 0x3200 (12800) is used for the Remote Gateway 9100 Series product and telephone signaling. Note: All packets are tagged with the DiffServ CodePoint you configure in Remote Gateway 9100 Series Configuration Manager on the IP Configuration property sheet for your specific unit.
  • Page 17 Queuing techniques help to provide the most efficient method for guaranteeing VoIP delivery while sharing the bandwidth with other data traffic. Recommendation 4 For WAN serial links 768 Kbps or less, Nortel recommends that you use the following packet fragmentation and queuing techniques: Remote Gateway 9100 Series Network Engineering Guidelines...
  • Page 18 2. High-Level Data Link Control (HDLC) links, however, can only be fragmented at the IP layer, layer 3 by setting a maximum Maximum Transmission Unit (MTU) size. Nortel does not recommend this method due to the added processing requirements, and unreliable results.
  • Page 19 queuing techniques Priority Queuing (PQ) Customer Queuing (CQ) Developed to solve the PQ problems of bandwidth Weighted Fair Queuing (WFQ) Remote Gateway 9100 Series Network Engineering Guidelines Queuing techniques help to isolate priority traffic, such as VoIP, from the normal data traffic. By placing the priority voice traffic into a separate queue, or holding bucket, this type of traffic can be given special treatment.
  • Page 20 Class Based Weighted Fair Queuing (CBWFQ) Low Latency Queuing (LLQ) The following illustration shows high speed to low speed aggregation: Consideration 5 The real time traffic is now in the appropriate queue waiting to be passed onto the next segment. The timeliness of the delivery is important. Therefore, you must review multiple considerations.
  • Page 21 Recommendation 5 Maximum Transmission Unit (MTU) is the maximum packet size that is placed on the segment. Since the link speed is low, a large packet takes a larger amount of time to transmit across the link. The following table shows the fragmentation size versus the link speed, which is called the transmission time, or serialization delay (shown in ms).
  • Page 22 Note: A small MTU (less than 768 bytes) can cause performance degradation on certain PC applications. Therefore, Nortel recommends that you use fragmentation techniques such as FRF.12 or PPP fragmentation/interleaving, rather than physically changing the MTU size. The following illustration shows...
  • Page 23 This is similar to rt-VBR, but the amount of delay is not specified. Therefore, jitter can be a problem. Nortel does not recommend this for real time traffic such as voice. A guaranteed minimum amount of bandwidth is defined, but the delay and loss parameters are not specified when a defined peak is reached.
  • Page 24 Discard Eligible (DE) bit set, so that during periods of congestion, it is dropped before real time traffic. For Frame Relay VoIP, Nortel recommends the following: Do not exceed the CIR of the PVC: — Queuing of voice packets must be minimized.
  • Page 25 For ATM to Frame Relay links, Nortel recommends the following: Be sure to properly map Frame Relay parameters (CIR, Bc, and Be) into equivalent ATM values. — Use FRF.8 (RFC 1490), Section 5.1. FRF.8 details the method of interworking between a Frame Relay end-point and an ATM end-point...

  • Page 26: Bandwidth Usage Table

    1. compression algorithm 2. 9600 bps (14400 bps not supported) 3. The Remote Gateway 911x series and Digital Telephone IP Adapter units transmit packets that are based on 64 byte boundaries. In other words, G.729A equals 128 bytes and G.711 equals 320 bytes.
  • Page 27 When using the Remote Gateway 9100 Series products with PSTN bandwidth, the requirements are as follows: G.711 = 64 Kbps G.726 = 32 Kbps G.729A = 8 Kbps If VAD is disabled, the PSTN bandwidth requirements increase by 20% due to inefficiencies in the HDLC protocol used.

  • Page 28: Quality Of Service Issues

    QoS Transitioning Technology When voice quality degrades on your Remote Gateway 9100 Series network, the RLC provides improved QoS. Nortel’s patented QoS Transitioning Technology enables the RLC to move Remote Gateway 9100 Series calls from the IP network to the PSTN. The more stable PSTN provides improved QoS until IP network QoS improves.
  • Page 29 The RLC and the remote units constantly monitor the QoS level on the data paths between the host PBX and the individual remote sites. Each node calculates the prevailing QoS level based upon the following factors: jitter delay packet loss compression algorithm The RLC calculates the QoS level based upon ANSI TR56 and the E-model found in ITU-T Reg.
  • Page 30 PSTN and the IP network. This can occur when QoS hovers around configured degrade and recover thresholds producing higher than normal PSTN charges. In the telephone call represented by the chart on page 30, signal quality begins in the acceptable range; that is, signal quality is above the X threshold. While signal quality remains in the acceptable range, the RLC routes calls through the IP network.
  • Page 31 The setting represents signal quality on the IP network is unacceptable below this point. signal quality on the IP network is acceptable above this point. the amount of time that signal quality must be lower than the X threshold before the RLC transitions calls to the PSTN. the amount of time that signal quality must be higher than the Y threshold before the RLC recovers calls to the IP network.
  • Page 32 QoS traffic measurements As voice packets travel across the IP network, the RLC monitors the following QoS parameters: average packet delay The RLC calculates this delay using the following statistics gathered from its voice jitter attenuation buffer: — minimum packet holding time in the jitter buffer —...
  • Page 33 Reach Line Card Installation and Administration Guide (NTP 555-8421-210). Telephone display messages Meridian digital telephone sets with display capability can display the following Resource Limit messages: Bandwidth Limit indicates that there is insufficient BRI bandwidth available to complete the requested action.
  • Page 34 Relationship between users and services In the context of a host PBX and Remote Gateway 9150 unit, there are two interfaces that you must consider in the relationship between users and services: The Remote Gateway 9100 Series node (that is, the RLC on the host PBX and the Remote Gateway 9100 Series unit at the remote site) provides an interface to the Remote Gateway 9100 Series system for end users.

  • Page 35: Ordering Isdn Lines

    Note: Both B-channels must be PSTN voice and data. Also, although Nortel requires 56 or 64 Kbps clear, 64 Kbps clear is preferred. Caller Line Identification (CLID, known in the United Kingdom as Calling Line Identity Presentation–CLIP)
  • Page 36 For European installations, the Remote Gateway 9150 unit supports country- specific EuroISDN installations, but does not support pre-EuroISDN installations. Using supplementary services Nortel does not recommend the following supplementary data services for use with Remote Gateway 9150 and 911x units: call waiting bearer-channel bonding...
  • Page 37 If you need to order Hunt services, order Multiline hunting rather than Overflow (EKTS) forward. The following must be true when you order these services on the BRI circuits: — The B-channel requested during call set-up must be the B-channel that the call presents to —...
  • Page 40 Copyright © Copyright © 2000–2005 Nortel. All Rights Reserved. Printed in Canada. All information contained in this document is subject to change without notice. Nortel reserves the right to make changes to equipment design or program components, as progress in engineering, manufacturing methods, or other circumstances may warrant.

This manual is also suitable for:

Remote gateway 9115Remote gateway 9150

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