W
EB
-B
ASED
M
ANAGEMENT
3-10
• PPPoA LLC. Point to Point Protocol over ATM Logical Link Control
allows multiple protocols running over one virtual circuit (slightly
more overhead).
• 1483 Bridged IP LLC (Logical Link Control) provides indirect access
to the Internet by flooding, forwarding or filtering bridged protocols
through each relevant virtual circuit.
Bridging is a standardized layer 2 technology. It is typically used in
corporate networks to extend the physical reach of a single LAN
segment and increase the number of stations on the common LAN
without compromising performance. Bridged data is encapsulated
using the RFC1483 protocol to enable data transport.
• 1483 Routed IP LLC (Logical Link Control). The barricade looks up
the network address for each packet seen on the LAN port. If the
address is listed in the routing table as local, it is filtered. If the address
is listed under the ADSL port, it is forwarded. Or if the address is not
found, then it is automatically forwarded to the default router (i.e., the
ADSL router at the head end).
Routing is often contrasted with bridging. The primary difference
between the two is that bridging occurs at Layer 2 (the link layer) of the
OSI reference model, whereas routing occurs at Layer 3 (the network
layer).
• 1483 Bridged IP VC-Mux. Bridged IP Virtual Circuit Multiplexer (null
encapsulation) allows only one protocol running per virtual circuit with
less overhead.
• 1483 Routed IP VC-Mux. Routed IP Virtual Circuit Multiplexer (null
encapsulation) allows only one protocol running per virtual circuit with
less overhead.
• Classical IP over ATM provides a direct replacement for IP links
between routers, using IP to ATM address mapping.
• Native ATM. Asynchronous Transfer Mode. International standard
for cell relay in which multiple service types (such as voice, video, or
data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells
allow cell processing to occur in hardware, thereby reducing transit
delays. ATM is designed to take advantage of high-speed transmission
media.