chap06 - Cisco Router Handbook Sackett $70.00 0-07-058098-7...

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Cisco Router Handbook Sackett $70.00 0-07-058098-7 Backward Chapter: 1 | 2 | 3 | 4 | 5 | 6 _________________________________________________________________ Chapter Six ATM Internetworking Design Asynchronous Transfer Mode (ATM) is the first networking architecture developed specifically for supporting multiple services. ATM networks are capable of supporting audio (voice), video and data simultaneously. ATM is currently architected to support up to 2.5 Gbps bandwidth. Data networks immediately get a performance enhancement when moving to ATM due to the increased bandwidth over a WAN. Voice networks realize a cost savings due in part to sharing the same network with data and through voice compression, silence compression, repetitive pattern suppression, and dynamic bandwidth allocation. The ATM fixed-size 53-byte cell enables ATM to support the isochronicitiy of a time-division multiplexed (TDM) private network with the efficiencies of public switched data networks (PDSN). Most network designers are first challenged by the integration of ATM with the data network. Data network integration requires legacy network protocols to traverse a cell-based switched network. ATM can accomplish this in several ways. The first of these is LAN emulation. 1. LAN emulation (LANE) ATM employs a standards based specification for enabling the installed base of legacy LANs and the legacy network protocols used on these LANs to communicate over an ATM network. This standard is known as LAN emulation (LANE). LANE uses the Media Access Control (MAC) sublayer of the OSI data link control Layer 2. Using MAC encapsulation techniques enables ATM to address the majority of Layer 2 and Layer 3 networking protocols. ATM LANE logically extends the appearance of a LAN thereby providing legacy protocols with equivalent performance characteristics as are found in traditional LAN environments. Figure 6.1 illustrates a typical ATM topology with LANE support. LANE can use ATM emulated LANs (ELANs). . Using ELANs, a LAN in one location is logically connected to a LAN in another location. This allows a network designer to extend a LAN over an ATM WAN avoiding the need for routing packets between the two locations. LANE services can be employed by ATM attached serves or workstations, edge devices such as switches, and routers when routing between ELANs is required. ATM LANE uses four components to establish end-to-end connectivity for legacy protocols and devices. These are LAN Emulation Client, LAN emulation configuration server (LECS), LAN emulation server (LES), and Broadcast and Unknown Server (BUS). 1. LAN Emulation Client (LEC) Any end system that connects using ATM require a LAN emulation Client (LEC). The LEC performs the emulation necessary in support of the legacy LAN. The functions of the LEC are: * Data forwarding * Address resolution
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* Registering MAC addresses with the LANE server * Communication with other LECs using ATM virtual channel connections (VCCs). End systems that support the LEC functions are:
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chap06 - Cisco Router Handbook Sackett $70.00 0-07-058098-7...

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