158 ITG engineering guidelinesTLAN subnet designThe IP Trunk 3.01 (and later) nodes must connect to the intranet to minimizethe number of router hops between the systems if there is adequatebandwidth on the WAN links for the shorter route. This reduces the fixedand variable IP packet delay, and improves the voice QoS.If a mixed-codec IP Trunk 3.01 (and later) network, or a non-default payloadsize or fax settings is used, then use the LAN bandwidth consumptionin Table 17 "Silence Suppression disabled TLAN Ethernet and WAN IPbandwidth usage per IP Trunk 3.01 (and later) " (page 113) to estimate theamount of LAN bandwidth used by each card.The TLAN network interface must connect to a 10/100BaseT switch. Theuplink from the TLAN network interface to the router should be at least 100Mbps. If the uplink is 100 Mbps, then the maximum number of IP trunkcards allowed on the switch is subject to the limits described in "CalculateEthernet and WAN bandwidth usage" (page 111).Consider implementing LAN resiliency. This can involve installing redundantup-links, backup routers and an Uninterruptible Power Source (UPS).ATTENTIONIMPORTANT!Shared media hubs are not supported. Use Layer 2 switches.Place the IP Trunk 3.01 (and later) node and the TLAN subnet router asclose to the WAN backbone as possible. This enables the following:• minimizes the number of router hops• segregates constant bit-rate voice traffic from bursty LAN traffic• simplifies the end-to-end QoS engineering for packet delay, jitter, andpacket lossIf an access router separates the IP Trunk 3.01 (and later) node from theWAN router, there should be a high-speed link, such as Fast Ethernet,FDDI, SONET, OC-3c, ATM STS-3c, between the access router and theWAN backbone router.Configure the TLAN subnet IP routerThe IP Trunk 3.01 (and later) node must be placed on its own TLAN subnet.The router should have a separate 10/100BaseT interface for the TLANsubnet and should not contain any other traffic. Other IP devices shouldnot be placed on the TLAN subnet.Nortel Communication Server 1000IP Trunk FundamentalsNN43001-563 02.01 StandardRelease 5.5 21 December 2007Copyright © 2007, Nortel Networks.
