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Chapter 6 Broadband
AMG1312-T Series User’s Guide
84
VC-based Multiplexing
In this case, by prior mutual agreement, each protocol is assigned to a specific virtual circuit; for
example, VC1 carries IP, etc. VC-based multiplexing may be dominant in environments where
dynamic creation of large numbers 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, for example, if
charging heavily depends on the number of simultaneous VCs.
6.5.3 VPI and VCI
Be sure to use the correct Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI) numbers
assigned to you. The valid range for the VPI is 0 to 255 and for the VCI is 32 to 65535 (0 to 31 is
reserved for local management of ATM traffic). Please see the appendix for more information.
6.5.4 IP Address Assignment
A static IP is a fixed IP that your ISP gives you. A dynamic IP is not fixed; the ISP assigns you a
different one each time. The Single User Account feature can be enabled or disabled if you have
either a dynamic or static IP. However the encapsulation method assigned influences your choices
for IP address and ENET ENCAP gateway.
IP Assignment with PPPoA or PPPoE Encapsulation
If you have a dynamic IP, then the IP Address and Gateway IP Address fields are not applicable
(N/A). If you have a Static IP Address assigned by your ISP, then they should also assign you a
Subnet Mask and a Gateway IP Address.
IP Assignment with RFC 1483 Encapsulation
In this case the IP address assignment must be static.
IP Assignment with ENET ENCAP Encapsulation
In this case you can have either a static or dynamic IP. For a static IP you must fill in all the IP
Address and Gateway IP Address fields as supplied by your ISP. However for a dynamic IP, the
AMG1312-T Series acts as a DHCP client on the WAN port and so the IP Address and Gateway IP
Address fields are not applicable (N/A) as the DHCP server assigns them to the AMG1312-T Series.
6.5.5 Nailed-Up Connection (PPP)
A nailed-up connection is a dial-up line where the connection is always up regardless of traffic
demand. The AMG1312-T Series does two things when you specify a nailed-up connection. The first
is that idle timeout is disabled. The second is that the AMG1312-T Series will try to bring up the
connection when turned on and whenever the connection is down. A nailed-up connection can be
very expensive for obvious reasons.