Determining Network Connectivity Strategies
Determining Network Connectivity Strategies |
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The new features of Windows 2000 allow for a more extensible, scalable framework in which to build diverse network structures such as ATM. The following sections describe the new features that are included in Windows 2000 ATM.
Windows 2000 now includes a Call Manager that supports and manages calls on an ATM network. It conforms to the ATM Forum UNI Version 3.1 signaling specifications and supports the creation of switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).
NDIS version 5 now supports ATM network adapters directly. This permits ATM adapter vendors to more effectively use their hardware by writing ATM miniport device drivers that interface with Windows 2000. Drivers for most vendors of ATM network adapters are now included with Windows 2000.
ATM LAN Emulation (LANE) services are needed to provide interoperability between ATM and traditional LAN environments. LANE allows easier migration and integration with traditional networking LAN technologies such as Ethernet or Token Ring by emulating these LANs on ATM networks. Windows 2000 includes support for ATM LAN Emulation, and can participate in an Emulated LAN (ELAN) as a LAN Emulation Client (LEC). The Windows 2000 LAN Emulation Client can use the LAN Emulation Services that ATM vendors supply with their network switches. By default, Windows 2000 will install the LAN Emulation Client if it detects that an ATM network adapter has been installed. The LEC will also, by default, attempt to participate in a default unspecified ELAN. Your LAN emulation services must be configured for this default ELAN.
Figure 7.9 illustrates a LANE network.
Figure 7.9 LANE Network
IP/ATM enables TCP/IP to use the features of ATM networks directly. Windows 2000 now includes IP/ATM support. With this support, applications written to use TCP/IP can make direct use of ATM networks. Also, applications written to use Generic Quality of Service (QoS) under Windows Sockets will benefit directly from the inherent QoS capabilities provided by the ATM network.
IP/ATM is a group of services for communicating over an ATM network that can be used as an alternative to ATM LAN emulation. IP/ATM is handled by two main components: the IP/ATM client and the IP/ATM server. The IP/ATM server includes an ATM ARP server and a multicast address resolution server (MARS). IP/ATM server components can reside on a Windows 2000 server or an ATM switch.
The main advantage of using IP/ATM is that it is faster than LANE, because with IP/ATM, no additional header information is added to packets as they move through the protocol stack. Once an IP/ATM client has established a connection, data can be transferred without modification.
With IP/ATM, you can either use a static IP address or configure the TCP/IP profile to use a DHCP server. Figure 7.10 depicts an IP-over-ATM network.
Figure 7.10 IP/ATM
Windows 2000 includes a Multicast and Address Resolution Service to support the use of IP/ATM. This service supports the IP/ATM Address Resolution Protocol and enables the efficient use of multicasting with ATM networks.
With the coming of digital subscriber line (xDSL) technologies, high-speed network access from the home and small office environment is becoming more common. Several standards exist in these areas, including Asymmetric DSL (ADSL) and Universal ADSL (UADSL or DSL Lite). These technologies operate over the local loop (the last run of copper wire between the telephone network and the home). In most areas in the U.S., this local loop then connects to an ATM core network.
ATM over the xDSL service preserves high-speed characteristics, and QoS guarantees availability in the core networking layer, without changing protocols. This creates the potential for an end-to-end ATM network to the residence or small office. This network model provides several advantages, including:
Adding Point-to-Point Protocol (PPP) over this end-to-end architecture adds functionality and usefulness. PPP provides the following additional advantages:
If each virtual circuit (VC) carries only one Point-to-Point Protocol (PPP) session, each destination will have its own authenticated PPP session, providing authentication for each VC. This provides an extra measure of security and guaranteed bandwidth as if you had a dedicated line. Using Null Encapsulation over AAL5 (because PPP provides the protocol multiplexing) can further reduce overhead.
