
Efficient Networks
®
Router family
Technical Reference Guide
Chapter 2: Product Overview
Efficient Networks
®
Page 2-11
Encapsulation Options
This section describes the packet format for each encapsulation option supported by
the router.
The same encapsulation method must be used by both ends of the connection (the
router and the DSLAM).
PPP
This protocol uses VC multiplexing, as defined in RFC 2364; it dedicates a virtual
circuit to PPP traffic only. (The other encapsulation method defined in RFC 2364, LLC
multiplexing, is described in the next section, PPPLLC.)
Each packet begins with a one- or two-byte protocol ID. Typical IDs are:
With PPP over ATM, the address and control fields (i.e., FF03) are never present; this
also is the case for LCP packets.
PPPLLC
This protocol (LLC-multiplexed) allows PPP traffic to be carried simultaneously with
other traffic on a single virtual circuit (as opposed to the PPP method of encapsulation
- VC multiplexing - which dedicates a virtual circuit to PPP traffic only).
Each PPP packet is prepended with the sequence 0xFEFE03CF. Thus, an LLC
packet has the format: 0xFEFE03CF 0xC021.
0xc021 LCP
0x8021 IPCP
0x0021 IP
0x002d Van Jacobson compressed TCP/IP
0x002f Van Jacobson uncompressed TCP/IP
0x8031 Bridge NCP
0x0031 Bridge Frame
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