Product specifications

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.
NOTE:
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:
NOTE:
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