configuration note

ConfigNote_PBX_QSIG_Networking.doc 1/10

Configuration Note

PBX Q-SIG Networking, Point-to-Point Leased Line

System Overview This configuration note describes PBX networking with SmartNode devices. It defines SmartNode template configurations, which can be adapted with little effort to the network you want to configure.

With the SmartNode products PBX's can be connected with Q-SIG over a data network. Hence an already existing Q-SIG network over dedicated telecom lines can be migrated easily to the data link between the sites and the expensive telecom lines can be saved.

The two sites are connected directly through a point-to-point leased line. The SmartNode supports the widely available X.21/V.35 standards for private leased lines.


Figure 2: Detailed schematics of the complete network


SmartNodes

Figure 3: Schematic of SmartNode configurations


Session Router Configuration It is assumed that there was a conventional Q-SIG network over dedicated telecom lines between the two sites, which is now migrated to the data link between the sites. An internal numbering plan between both sites exists. E.g. Extension 417 at site A calls extension 605 at site B by simply dialling 605.

Assumption: If an extension at one site calls an internal number of an extension at the other site (e.g. 403 calls 655) the PBX routes these calls to its Q-SIG port.

Routing (see also figure 3):

• Calls coming from the Q-SIG port of the PBX (interface QSIG) are directly routed to the link between the sites (interface isoip BackBone).

• Calls coming from the link between the sites (interface isoip BackBone) are directly routed to the Q-SIG port of the PBX (interface pstn QSIG).

Port Configuration The PRI card in slot 1 (port isdn 1 0) is connected to the Q-SIG port of the PBX. Therefore the layer 3 protocol must be set to Q-SIG (l3proto pss1). The UNI type it must be set to 'user' (uni-side usr).

The hardware port type for the serial port is set to X.21, the layer 2 protocol is set to Frame-Relay: port serial 0 0 hardware-port x21 encapsulation framerelay

Framerelay Fragmentation Fragmentation has been enabled for the PVC to the remote site. Fragmentation breaks up every packet larger than the configured fragment size. The purpose is to support real-time and non-real-time packets without causing excessive delays for the real-time data.

The fragmentation size depends on the available bandwidth the chosen codec and its packet length:

The less bandwidth available per call the smaller the fragment size has to be configured.

The shorter the voice packets the smaller the fragment size can be configured.

The smaller the fragment size the bigger the overhead for long data packets.

The following table shows the minimum fragmentation size depending on the configured codec and its packet length without fragmenting the voice packets:

Codec Packet Period [ms] Fragment Size at least [byte] G.729 10 52 G.729 20 62 G.729 30 72 G.723 30 66 G.723 60 90 G.723 90 114 G.711 10 122 G.711 20 202 G.711 30 282

Table 1: Fragmentation Table


QoS Features To guarantee voice quality under all load conditions QoS features of the SmartWare are configured.

For the prioritisation of the voice traffic and call signalling a service-policy profile (VoicePrio), which sets priority to service class local-voice and local-default, is added to the to the PVC between the sites (context IP router interface Link). All other traffic i.e. the routed traffic (class default) may use the remaining bandwidth.

To avoid an overloading of the link a rate limit is set according to the link bandwidth (we assume 2048 Kbits/s).

IP Routing The default route of SN_Site_A is set to the router at site A: route 0.0.0.0 0.0.0.0 192.168.1.11 The default route of SN_Site_B is set to the PVC to the remote site: route 0.0.0.0 0.0.0.0 Link The route to the remote LAN for SN_Site_A is set to the PVC to the remote site: route 192.168.5.0 255.255.255.0 Link

Fax Fax pass-through method using G.711 is used for fax transmission

Synchronisation The packaging of the ISDN voice frames needs a reference clock to avoid clock slips and related voice quality degradations. This reference clock source can be generated internally or derived from one of the ISDN ports. In this example the SmartNodes can be synchronized through the PBX, which is directly connected to the public ISDN.

system ..clock-source 1 0

port isdn 1 0

clock-mode slave

3rd Party Equipment

Router Site A Default Route: Provider's Backbone

Furthermore it is necessary to add the route to the site B LAN:

Destination 192.168.5.0/24 Next hop 192.168.1.1 (LAN Address of SN_Site_A)

PC's Site A: Default Route 192.168.1.11 (LAN address of Router Site A)

Site B: Default Route 192.168.5.1 (LAN address of SN_Site_B)


How To Adapt To Your Network

IP Addresses LAN:

IP addresses of the SmartNode interfaces towards the LAN within this configuration example: Site A: 192.168.1.1/24, Site B: 192.168.5.1/24

Changing them, affects the routing table and the following sections of the configuration files of both SmartNodes: interface LAN ipaddress <ip address towards the LAN> <mask>

interface isoip BackBone remoteip <ip address towards the LAN of the remote SmartNode)

Do not forget to modify the default routes of the PC's at the site A and B and the static route of the site A router.

Link Bandwidth Within this configuration example we assumed a link bandwidth of 2048 Kbps. For a bandwidth of 768 Kbps the relevant sections within the configuration files of both SmartNodes look as follows: profile service-policy VoicePrio rate-limit 768

Codecs The chosen codec within this example is G.711 (best voice quality but uncompressed): gateway isoip codec g711alaw64k

Using G.729 (best ratio between voice quality and used bandwidth) instead the relevant section within the configuration files of both SmartNodes looks as follows: gateway isoip codec g729

Leased Line Interface If your leased line interface is V.35 instead of X.21 you can change that within the serial port configuration: port serial 0 0 .. hardware-port v35


Complete Configurations

SN Site A #----------------------------------------------------------------#

#

# Project: Configuration Note PBX Q-SIG Networking, Point-To-Point Leased Line

# Element: SmartNode Site A, SN2300 1 x IC-E1V

# Author: KK

# Date: 20.09.2002

#

#----------------------------------------------------------------#

cli version 2.00

system hostname SN_Site_A

system

clock-source 1 0

profile service-policy VoicePrio

rate-limit 2048

mode wfq

source class local-voice

priority

source class local-default

priority

source class default

context ip router

interface Link

ipaddress unnumbered

mtu 1500

use profile service-policy VoicePrio out

point-to-point

interface LAN

ipaddress 192.168.1.1 255.255.255.0

mtu 1500

context ip router

route 0.0.0.0 0.0.0.0 192.168.1.11

route 192.168.5.0 255.255.255.0 Link

multicast-send default-interface Link

context cs switch

no number-prefix national

no number-prefix international

use tone-set-profile default


interface pstn QSIG

routing dest-interface BackBone

bind port 1 0

interface isoip BackBone

routing dest-interface QSIG

remoteip 192.168.5.1

bind gateway isoip

context cs switch

no shutdown

gateway isoip

codec g711alaw64k 10

no shutdown

use voip-profile default

port ethernet 0 1

medium 10 half

encapsulation ip

bind interface LAN router

no shutdown

port isdn 1 0

down

channel-range 0 31

channel-hunting up

l2proto pp

l3proto pss1

channel-numbering etsi

max-channels 30

uni-side usr

clock-mode slave

up

port serial 0 0

shutdown

encapsulation framerelay

hardware-port x21

no shutdown

framerelay

no keepalive

pvc 16

encapsulation rfc1490

bind interface Link router

fragment 300

no shutdown


SN Site B #----------------------------------------------------------------#

#

# Project: Configuration Note PBX Q-SIG Networking, Point-To-Point Leased Line

# Element: SmartNode Site B, SN2300 1 x IC-E1V

# Author: KK

# Date: 20.09.2002

#

#----------------------------------------------------------------#

cli version 2.00

system hostname SN_Site_B

system

clock-source 1 0

profile service-policy VoicePrio

rate-limit 2048

mode wfq

source class local-voice

priority

source class local-default

priority

source class default

context ip router

interface Link

ipaddress unnumbered

mtu 1500

use profile service-policy VoicePrio out

point-to-point

interface LAN

ipaddress 192.168.5.1 255.255.255.0

mtu 1500

context ip router

route 0.0.0.0 0.0.0.0 Link

multicast-send default-interface Link

context cs switch

no number-prefix national

no number-prefix international

use tone-set-profile default

interface pstn QSIG

routing dest-interface BackBone

bind port 1 0


interface isoip BackBone

routing dest-interface QSIG

remoteip 192.168.1.1

bind gateway isoip

context cs switch

no shutdown

gateway isoip

codec g711alaw64k 10

no shutdown

use voip-profile default

port ethernet 0 1

medium 10 half

encapsulation ip

bind interface LAN router

no shutdown

port isdn 1 0

down

channel-range 0 31

channel-hunting up

l2proto pp

l3proto pss1

channel-numbering etsi

max-channels 30

uni-side usr

clock-mode slave

up

port serial 0 0

shutdown

encapsulation framerelay

hardware-port x21

no shutdown

framerelay

no keepalive

pvc 16

encapsulation rfc1490

bind interface Link router

fragment 300

no shutdown

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