architectural concepts for voip over b-max

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Architectural Concepts forVoIP over BreezeMAX

BreezeMAX

September 2005DN0873


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Architectural Concepts for VoIP over BreezeMAX Legal Rights

Copyright 2005 Alvarion Ltd. All rights reserved.

The material contained herein is proprietary, privileged, and confidential and owned by Alvarion or itsthird party licensors. No disclosure thereof shall be made to third parties without the express writtenpermission of Alvarion Ltd.

Alvarion Ltd. reserves the right to alter the equipment specifications and descriptions in this publicationwithout prior notice. No part of this publication shall be deemed to be part of any contract or warranty

unless specifically incorporated by reference into such contract or warranty.

Alvarion, BreezeCOM

, WALKair

, WALKnet

, BreezeNET

, BreezeACCESS

, BreezeMANAGE

,

BreezeLINK, BreezeCONFIG

, BreezeMAX

, AlvariSTAR

, MGW

, eMGW

, WAVEXpress

,

MicroXpress

, WAVEXchange

, WAVEView

, GSM Network in a Box and TurboWAVE

and/or otherproducts and/or services referenced here in are either registered trademarks, trademarks or servicemarks of Alvarion Ltd.

All other names are or may be the trademarks of their respective owners.

Limitation of Liability:

(a) Alvarion shall not be liable to the purchaser or to any third party, for any loss of profits, loss of use,interruption of business or for any indirect, special, incidental, punitive or consequential damages of anykind, whether arising under breach of contract, tort (including negligence), strict liability or otherwise andwhether based on this agreement or otherwise, even if advised of the possibility of such damages.

(b) To the extent permitted by applicable law, in no event shall the liability for damages hereunder ofalvarion or its employees or agents exceed the purchase price paid for the product by purchaser, norshall the aggregate liability for damages to all parties regarding any product exceed the purchase pricepaid for that product by that party (except in the case of a breach of a partys confidentiality obligations).

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Architectural Concepts for VoIP over BreezeMAX Contents

Contents

1 Scope ........................................................................................................1

2 General VoIP Architecture.......................................................................2

3

Configuration Guidelines ........................................................................3

3.1 Example 1 Using DRAP and No VLANs ............................................................... 3

3.1.1 VG Configuration ................................................................................................. 3

3.1.2 BreezeMAX Configuration ................................................................................... 4

3.1.3 Other Network Elements...................................................................................... 5

3.2 Example 2 Using DRAP and Separate VLANs for Voice and Data Traffic ........ 6


3.2.2 BreezeMAX Configuration ................................................................................... 6


3.3 Example 3 No DRAP Used..................................................................................... 8


3.3.2

BreezeMAX Configuration ................................................................................... 8


4 Summary ................................................................................................11

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Architectural Concepts for VoIP over BreezeMAX Contents

Figures

Figure 1: General VoIP Architecture ........................................................................ 2

Figure 2: L2 Service Profile With DRAP Enabled ...................................................... 5

Figure 3: L2 Service Profile & Voice Service Profile................................................... 7

References(1) DN0846 Dynamic Resource Allocation Protocol (DRAP) March 2005

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Architectural Concepts for VoIP over BreezeMAX Abbreviations

Abbreviations

AAA Authentication, Authorization and Accounting

CIR Committed Information Rate

CG Continuous Grant

DHCP Dynamic Host Configuration Protocol

DRAP Dynamic Resource Allocation Protocol

DSCP Differentiated Services Code Point

GW GateWay

NPU Network processing Unit

POTS Plain Old Telephony Service

PPPoE Point to Point Protocol over Ethernet

PSTN Public Switching Telephony Network

QoS Quality of Service

RT Real Time

RTP Real Time Protocol

SIP Session Initiation Protocol

ToS Type of Service

UDP User Datagram Protocol

VG Voice Gateway

VLAN Virtual Local Area Network

VoIP Voice over Internet Protocol

VPL Virtual Path Link

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Architectural Concepts for VoIP over BreezeMAX Scope

1 Scope

The purpose of this document is to describe different concepts for using

VoIP over the BreezeMAX system. The document provides a general

description of the architecture required for enabling voice services over the

BreezeMAX platform. It includes several examples of using the BreezeMAX

with the Alvarion Voice Gateway (VG) and the Dynamic Resource Allocation

Protocol (DRAP) as well as guidelines for providing a voice solution without

the DRAP.

The document focuses on the required configuration for the BreezeMAX

system as well as the Voice Gateway. It does not provide a detailed SIP

server/H.323 gatekeeper configuration or a detailed network design, but

rather provides guidelines for them.

IMPORTANT

All DRAP related configurations and examples should be used only with BreezeMAXequipment running version 1.5 and up, on all components, i.e., NPU, AU and SU.

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Architectural Concepts for VoIP over BreezeMAX General VoIP Architecture

2 General VoIP Architecture

A basic VoIP architecture includes the following components:

1. Voice GW A device with 1, 2 or more POTS interfaces located at thecustomers premises providing a gateway between the regular telephone

device and the SIP/H.323 network.

2. BreezeMAX platform The wireless access system providing the

connectivity between the operators transport network and the

customers premises.

3. SIP server/H.323 Gatekeeper A component serving as the registrar for

the SIP VoIP GWs (or the registry for the H.323 GWs). This device

registers all the GWs as well as provides AAA features and switching

information for the SIP/H.323 network.

4. SIP/H.323 GW An optional device used to connect the SIP/H.323

network to other telephony networks such as mobile networks or PSTN.

The following diagram provides a general view of a VoIP architecture.

NetworkNetworkNetwork

SIP Voice

GW

Subscriber UnitBreezeMAX base station

SIP GW

SIP Server

Figure 1: General VoIP Arch itectu re

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Architectural Concepts for VoIP over BreezeMAX Configuration Guidelines

3 Configuration Guidelines

This section describes three different configuration scenarios for the

architecture described above. Two scenarios are based on the use of the

DRAP and the Alvarion VG and one is based on a non-DRAP solution. These

scenarios are commonly used scenarios, but do not reflect the only possible

configurations for the system.

Each example will include the general guidelines for the configuration of the

VG, the BreezeMAX system and any special notes regarding other network

elements.

For more specific and detailed information on how to configure VG

parameters or BreezeMAX parameters (such as service profiles and

services), please refer to the relevant VG and BreezeMAX system manuals.

IMPORTANT

The information provided in this section provides general guidelines and does not reflect a fullvoice network design or a full configuration example.

3.1 Example 1 Using DRAP and No VLANs

NOTE

The same guidelines refer when using the same VLAN for the Voice and Data traffic. In suchcases, the VPL and the VLAN listed in the service profile and in the service should be setaccording to the VLAN used and also VG configuration should enable VLANs.

3.1.1 VG Configuration

To enable the DRAP mechanism, the DRAP must be enabled in the BW

Reservation configuration tab. It is also recommended to have the Pre-

allocation enabled; this allows the DRAP functionality to start when the

user picks up the phone. Hence, if no bandwidth is available a busy tone

will be heard. When this is not enabled, the DRAP functionality will startonly after the user has finished dialing.

All the relevant SIP/H.323 information should be configured in the VG

according to the specific network parameters used.

The VG IP address should be provided by a DHCP server or using a fixed IP.

If a fixed IP is used, the IP address has to be an address in the voice

network, which is unique and can be routed between the different voice

components. Also a default GW address must be configured in the VG. This

address should be of a router installed on the network side of the

BreezeMAX NPU.

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The ToS settings for the voice traffic in the VG should be set to a higher

priority than the regular data traffic, allowing the backbone network to

prioritize the traffic accordingly.

If a VLAN is used for the voice and data traffic, the VG should have the

VLAN configured in it. Make sure the VLAN list includes the required VLAN

ID and the LAN and WAN tagging options are configured correctly. In this

case, the VLAN priority field can be used for prioritization of the voice traffic

in the backbone network instead of the ToS bits.

3.1.2 BreezeMAX Configuration

On the BreezeMAX system, a service for the voice and data traffic should be

configured. As the DRAP is used, all voice configurations will be done

automatically. The operator should only configure an L2 service with the

required QoS for the data traffic and the appropriate VLAN and VPLconfigurations. Following the initial DRAP discovery message from the VG

(automatically sent by the VG after DRAP is enabled) the BreezeMAX will

automatically allocate a RT connection for all VG management, SIP/H.323

signaling and DRAP messages from or to the VG IP address. All traffic with

source IP or destination IP equal to the VG IP address will be transmitted

on this automatically generated connection.

When a call is initiated, another automatic connection will be set by the

BreezeMAX system. This is a CG connection for the RTP traffic. This

connection will have priority over the RT service and all traffic with the

source or destination IP of the VG and the UDP port of the specific call will

be transmitted over this connection (the UDP port for each specific call is

exchanged between the VG and the BreezeMAX system using the DRAP

messages).

IMPORTANT

The QoS configured for the L2 service is applicable for the data traffic only. All signaling, VGmanagement and voice traffic will be transmitted over the automatically generatedconnections as mentioned above.

Contrary to the above, the forwarding rule used will be applied to the voice traffic. Hence, toallow voice traffic between two SUs in the same Base Station, the forwarding rule must allowrelaying.

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SIP Voice

GW


Configured L2 service with QoS for Data traffic

Automatically Generated RT QoS for signaling & DRAP

Automatically generated CG QoS for each voice call

Figure 2: L2 Service Profi le With DRAP Enabled

NOTE

To activate DRAP on a network without DRAP when there is one L2 service configured for thevoice and data traffic similarly to the above mentioned, the operator needs only to activate theDRAP functionality in the VG and the voice connections will automatically be configured asdescribed.

3.1.3 Other Network Elements

It is important to make sure the network supports prioritization according

to the ToS bits in the IP header. This will allow higher priority for voice

traffic in the network (and not just over the air in the BreezeMAX system).

If a VLAN is used, the appropriate configuration throughout the network

should be in place to allow the tagged traffic. In this case, the VLAN priority

can also be used instead of the ToS bits.

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3.2 Example 2 Using DRAP and Separate VLANs

for Voice and Data Traffic

In most networks the voice and data traffic is split on two or more differentVLANs to differentiate between them. In these cases, the voice traffic may

be tagged with one VLAN ID, and the data traffic may be tagged with several

different VLANs according to the data type.

NOTE

The VLAN tag for VG management traffic in these cases should be the same as the voiceVLAN tag on the access network, as both have the same IP address.


The same guidelines mentioned in Example 1 apply, except for the following

ToS and VLAN issues:

The ToS setting for the voice traffic is not needed, as most likely the

prioritization of the voice traffic will be done according to the VLAN tag.

The VLAN configuration tab should include all the VLANs used (voice VLAN

and data VLANs). The VG can act as a tagging switch for the data traffic if

needed.


On the BreezeMAX system two separate services should be configured: one

for voice and one for data traffic.

The data service should be a regular L2 service (in this case a PPPoE service

can be used for the data traffic if PPPoE is used in the network) with the

appropriate VPL and VLAN list configured according to the data VLAN ID.

The Voice service should use a VOICEtype service profile with the

appropriate VPL and VLAN list configured according to the voice VLAN ID.

This special service profile type does not require a QoS setting as it is

automatically configured with a RT connection. This service will create a

connection, which allows only DHCP, ARP and DRAP traffic on it. Hence,

when a DRAP enabled VG is connected, it first sends a DHCP message (if it

is not configured for a fixed IP), then it will send an ARP message searching

for its default GW and immediately after, it will send a DRAP discovery

message. All these messages will go over the VOICE type service. As

mentioned in example 1, following the DRAP discovery message the

BreezeMAX system will setup appropriate connections automatically for all

the voice related traffic. The original service configured will not be used

again until the system is rebooted. As it does not allow any traffic other

than the three protocols mentioned above this service cannot be used for

any malicious act.

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IMPORTANT

The voice service and the L2 service must be configured on two separate and different VPLs.

SIP VoiceGW


Configured L2 service with QoS for Data traffic VLAN Data

Automatically Generated RT QoS for signaling & DRAP

Automatically generated CG QoS for each voice call

Configured Voice service (Automatically RT QoS) VLAN Voice

Only DHCP, ARP and DRAP packets

Figure 3: L2 Service Profile & Voice Service Profile

NOTE

To activate DRAP on a network without DRAP when there are two L2 service configured onefor the voice and one for data traffic similarly to the above mentioned, the operator needs onlyto activate the DRAP functionality in the VG and the voice connection s will automatically beconfigured as described.

As in this case the voice traffic will be running over an L2 service profile and not a Voicetypeservice profile, other traffic with the same VLAN as the voice can be transmitted on thisservice. This might be an opening for malicious acts. Therefore, it is recommended in thesecases to delete the old services and the old service profile dedicated for the voice traffic andthen create a new service profile of type Voiceand new services.


As the network uses multiple VLANs all network elements must be

configured correctly to pass the relevant VLAN tagged packets.

IMPORTANT

All voice traffic mentioned above as well as all call limitations configured in the BreezeMAXsystem apply to DRAP based voice calls only. Any voice traffic from other non alvarion voicegateways does not follow these rules and is handled as regular data traffic.

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3.3 Example 3 No DRAP Used

NOTE

When working with VoIP in the BreezeMAX system it is always recommended to work withDRAP, as this provides better air efficiency as well as additional voice features, such asautomatic voice connection configuration, call limitation per sector and call limitation perservice profile.

When DRAP is not used all voice service configuration have to be done

manually by the operator.

The following VG configuration guidelines are based on the Alvarion VG

capabilities but can be used with any Voice GW with similar features.


The DRAP must be disabled in the BW Reservation configuration tab.

All the relevant SIP/H.323 information should be configured in the VG

according to the specific network parameters used.

The VG IP address should be provided by a DHCP server or using a fixed IP.

The traffic coming out from the VG should be marked with different DSCP

marking according to its priority:

1. Voice (RTP packets) - should be marked with a high DSCP mark, for

example 60.

2. SIP/H.323 signaling traffic should be marked with a different mark for

example 40.

3. Data and other traffic should not be marked, i.e., 0.

If a VLAN tag is used, the differentiation between the traffic types can be

done using the VLAN priority in a similar manner.


On the BreezeMAX system a service for the voice and data traffic should be

configured. As the DRAP is not used, the operator should configure an L2

service with the needed QoS for the data as well as the voice traffic. For

this, the priority classification should be used in the service profile in the

following way. If DSCP is used (as in the example above):

1. Classification 0-30 should use the QoS designated for the data traffic.

2. Classification 31-50 should use a RT QoS for the SIP/H.323 signaling

traffic. Typically a RT with 256 kbps CIR QoS should be enough.

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3. Classification 51-63 should use a CG QoS for the actual voice traffic.

Typically, the CG service should be configured according to the Codec

used, for example for 20ms G729 packets a packet size of 78 bytes and

a sample rate of 20 ms should be used. If more than one simultaneous

call is expected, the sample rate should be divided by the number of

simultaneous calls expected (up to sample rate of 5 ms). For example,

for 2 calls use sample rate of 10 ms; for 4 calls use 5 ms.

NOTE

The CG connection will always be configured (unlike the situation with the DRAP mode). Thecapacity of the system can therefore be affected.

A CG connection with no traffic running for more than 2 seconds will stop allocating airresources until the next packet is received, at which time the CG connection will again beallocated resources every sample rate.

If VLANs are used, the same guidelines apply, but the VLAN priority can be

used to differentiate between the different QoS required.

IMPORTANT

The packet size should take into account the entire RTP packet size including all headers(RTP, UDP, IP, Ethernet). For example, if VLANs are used, 4 additional bytes should beadded to the packet size.

It is important that the packet size be greater or equal to the actual packets expected, neversmaller, to assure the best voice quality.

If the Voice Gateway does not support different marking for the RTP and the

signaling traffic, all voice traffic will be marked with the same DSCP or

VLAN priority. As this will include signaling messages and not just the voice

RTP packets, the operator may use a RT service for the voice traffic. In this

case, the RT QoS should be allocated with a CIR of 250 kbps plus 50 to 150

kbps per each expected simultaneous call. For example, a service for 2

simultaneous calls using G729 20 ms should have a RT QoS of 350 kbps

CIR.

NOTE

In these cases the operator might still consider using a CG connection in order to achievebetter voice quality at the expense of a possible degradation of the sector capacity.


It is important to make sure the network supports prioritization according

to the DSCP bits in the IP header or the VLAN priority. This will allow

higher priority for voice traffic in the network (and not just over the air in

the BreezeMAX system).

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Architectural Concepts for VoIP over BreezeMAX Summary

4 Summary

This document provides general guidelines for the overall system

configuration of a combined VoIP and BreezeMAX system. The document

provides several examples of common architectures and the relevantguidelines for them.

As mentioned in the document it is always recommended to use the DRAP

when working with VoIP as this allows for improved air efficiency as well as

additional voice features such as call limitation per sector and automatic

voice service configuration.

It is always important to properly design the specific network according to

the operators needs, as well as perform a detailed capacity plan and a

detailed network design. This document should not replace any of these,

but rather assist the operator with general architectural guidelines.

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