Chicago Router Overview

The router configurations for the B.A.N.C. project are as follows (only relevant portions of the configuration files are shown):

hostname Chicago !

voice-card 1

codec complexity high * This command defines which codecs can be used with the Voice Network Module.

High Complexity allows G.711, G.726, G.728, G.729, G.723.1 and Fax-Relay !

ipx routing !

dlsw local-peer peer-id promiscuous

controller T1 1/0

description "1-8:Denver, 9-10:Tokyo" framing esf/ linecoding b8zs clock source line dsO-group 1 timeslots 1-8 type e&m-wink-start dsO-group 2 timeslots 9 type fxo-loop-start dsO-group 3 timeslots 10 type fxo-loop-start

* These commands define the clocking, framing, linecoding and signaling for each DS0

within the T1 controller card. !

voice-port 1/0:1

* A Voice-Port is created for each ds0-group that is created above. !

voice-port 1/0:2 connection trunk 998

* Connection trunk creates a permanent VoIP call between 2 VoIP gateways. It allows features such as hookflash or stuttuer dialtone to be passed over the IP network to the connected telephony devices. The digits with connection trunk as dialed "internally" by the router and are not seen by the user. The digits are matched against a VoIP dial-peer to complete the call. !

voice-port 1/0:3 connection trunk 999

dial-peer voice 1 voip description "trunk/opx connections to Tokyo" destination-pattern 99.

session target ipv4: !

dial-peer voice 2 voip description "calls to Denver office"

destination-pattern 5

session target ipv4: !

dial-peer voice 3 voip description "calls to IP Phones..CallMgr." codec g723r63 destination-pattern 4..

session target ipv4: !

dial-peer voice 4 pots destination-pattern 6.. prefix 6

dial-peer voice 5 pots destination-pattern 6.. prefix 6

dial-peer voice 6 pots destination-pattern 6.. prefix 6 port 1/0:3

interface FastEthernet 1/0/0 ip address

ipx network 100 !

interface FastEthernet 1/0/1

ip address ipx network 101 !

interface serial 2/0/0 encapsulation frame-relay frame-relay traffic-shaping !

interface serial 2/0/0.1

ip address

ipx network 102

frame-relay interface-dlci 102 frame-relay class voip qos 128k

*This command maps the frame-relay traffic-shaping, FRF.12 and QoS features to this

interface serial 2/0/0.2 ip address frame-relay interface-dlci 103 frame-relay class voip qos 128k ipx network 103 !

interface serial 2/0/0.3 ip address frame-relay interface-dlci 104 frame-relay class voip qos 256k ipx network 104 !

map-class frame-relay voip qos 128k no frame-relay adaptive-shaping becn frame-relay ip rtp priority 16384 16383 48

frame-relay cir 128000

frame-relay bc 560

frame-relay fragment 160

frame-relay fair-queue frame-relay ip rtp header compression

* These commands define the rules for Frame-Relay Traffic-Shaping, FRF.12 fragment size and VoIP QoS using IP RTP Priority. !

map-class frame-relay voip qos 256k no frame-relay adaptive-shaping becn frame-relay ip rtp priority 16384 16383 48

frame-relay cir 256000

frame-relay bc 560

frame-relay fragment 320

frame-relay fair-queue frame-relay ip rtp header compression !

router rip network network network network network

B.A.N.C has a five-digit dialing plan so that any employee can call another office by dialing five digits. The numbering is as follows:

Chicago Office: 6xxxx IP Phones: 4xxxx Denver: 5xxxx

Tokyo: Uses 6xxxx Off-Premise Extensions from the PBX

The 3660 router in B.A.N.C.'s Chicago office has VoIP dial-peers that point to all the company's remote offices. The Tokyo office is a special case because it has hookflash functionality, which makes it appear to the PBX as though it is a directly connected station. Hookflash is a method of providing additional services, such as call waiting or conferencing between the PBX and the handset. Hookflash is activated when a user briefly presses the cradle button on his or her phone. Hookflash sends a momentary on-hook/off-hook signal to the PBX, notifying the PBX that the user is requesting additional services.

Hookflash requires a permanent VoIP call between two gateways. A connection trunk provides this capability. A permanent call is created when the IP connectivity between two gateways is established. This differs from a switched call, which is established when a user needs to place a call. Also, a permanent call provides the capability to emulate a "wire" between the two devices so that they appear to be directly connected, and it enables the passing of certain signaling such as hookflash or stutter dial tone. This is often useful when users want to maintain their dial plan on their connected PBXs, or when they want to maintain "directly connected to PBX" functionality for remote stations.

Each Chicago Frame Relay permanent virtual switch (PVC) is traffic-shaped to enable only data and voice traffic up to the guaranteed CIR. This is done to prevent packets from being dropped or excessively delayed (queued in the Frame Relay switch). Each PVC uses Frame Relay Forum 12 (FRF.12) to fragment the data packets at Layer 2, thereby preventing serialization delay. The PVCs also use IP RTP Priority to identify the VoIP packets and to give them highest priority for outbound queuing.

The 3660 in the Tokyo office is configured to use a connection trunk which provides a permanent VoIP call that can pass hookflash calls as well as keep the dial plan on the PBX for digital signal level 0 (DS-0) calls. The 3660 in this office also has a VoIP dial-peer that points to the IP address of the Cisco Call Manager for Cisco IP phones.

Cisco Call Manager is an IP-PBX system. It provides all PBX functionality to IP phones through Call Manager software that runs on a Windows NT server. All communication between CCM, the IP phones, and VoIP gateways is done through IP.

You also can integrate Cisco Call Manager with legacy PBXs or key-systems using VoIP gateways.

Cisco Call Manager can support only G.711 or G.723.1 codecs. In this case, G.723.1 is configured to conserve bandwidth, and all the other connections are made with the G.729 codec. The Frame Relay PVCs are traffic-shaped so that data or voice cannot burst above CIR. This guarantees that the voice packets are not dropped within the Frame Relay cloud or queued so that delay and jitter are created within the cloud. Also, the VoIP traffic is defined to receive the highest QoS on the WAN links.

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