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Prestige 782R G.SHDSL Router
3-10 Internet Access
3.4.1 VPI and VCI
Be sure to use the correct VPI (Virtual Path Identifier) and VCI (Virtual Channel Identifier) numbers
supplied by the telephone company. Valid range for VPI is 0 to 255 and for the VCI is 32 to 65535 (1 to 31
is reserved for local management of ATM traffic).
3.4.2 Multiplexing
Two conventions are used in identifying what protocols the virtual circuit (VC) is carrying. Be sure to use
the multiplexing method required by your ISP.
VC-based Multiplexing
In this case, by prior mutual agreement, each protocol is assigned to a specific virtual circuit, e.g., VC1
carries IP, VC2 carries IPX, etc. VC-based multiplexing may be dominant in environments where dynamic
creation of large number of ATM VCs is fast and economical.
LLC-based Multiplexing
In this case, one VC carries multiple protocols with protocol identifying information being contained in
each packet header. Despite the extra bandwidth and processing overhead, this method may be
advantageous if it is not practical to have a separate VC for each carried protocol, e.g., if charging heavily
depends on the number of simultaneous VCs.
3.4.3 Encapsulation
Be sure to use the encapsulation method required by your ISP. The Prestige supports the following
methods:
PPP
Select this option when the peer is using a “PPP over ATM” networking model. Please refer to RFC-2364
for more information on PPP over ATM Adaptation Layer 5 (AAL5). Refer to RFC-1661 for more
information on PPP.
RFC-1483
Select this option when the peer is using a “Multi-protocol over ATM” networking model. RFC-1483
describes two methods for Multi-protocol Encapsulation over ATM Adaptation Layer 5 (AAL5). The first
method allows multiplexing of multiple protocols over a single ATM virtual circuit (LLC-based
multiplexing) and the second method assumes that each protocol is carried over a separate ATM virtual
circuit (VC-based multiplexing). Please refer to the RFC for more detailed information.