E-Series Proprietary; Pos Framing Modes; Hdlc Framing; Gfp-F Framing - Cisco ONS 15454 SDH Configuration Manual

Chapter 20 POS on ONS Ethernet Cards

E-Series Proprietary

The E-Series uses a proprietary HDLC-like encapsulation that is incompatible with LEX, Cisco HDLC,
or PPP/BCP. This proprietary encapsulation prevents the E-Series from interoperating with other ONS
Ethernet cards.

POS Framing Modes

The framing mode is the type of framing mechanism employed by the ONS Ethernet card to frame and
encapsulate data packets into a POS signal. These data packets were originally encapsulated in Ethernet
frames that entered the standard Fast Ethernet or Gigabit Ethernet interfaces of the ONS Ethernet card.
All ONS Ethernet cards support HDLC framing. ML-Series and CE-Series cards also offer GFP-F
framing mode.

HDLC Framing

HDLC is one of the most popular Layer 2 protocols. The framing mechanism used by the HDLC
protocol, HDLC framing, is employed by a variety of other protocols, including POS on the ONS
Ethernet cards. The HDLC framing mechanism is detailed in the IETF's RFC 1662, "PPP in HDLC-like
Framing."
The HDLC frame uses the zero insertion/deletion process (commonly known as bit stuffing) to ensure
that the bit pattern of the delimiter flag does not occur in the fields between flags. The HDLC frame is
synchronous and therefore relies on the physical layer to provide a method of clocking and
synchronizing the transmission and reception of frames.

GFP-F Framing

GFP defines a standard-based mapping of different types of services onto SONET/SDH. The ML-Series
and CE-Series support frame-mapped GFP (GFP-F), which is the PDU-oriented client signal adaptation
mode for GFP. GFP-F maps one variable length data packet onto one GFP packet.
GFP is composed of common functions and payload specific functions. Common functions are those
shared by all payloads. Payload-specific functions are different depending on the payload type. GFP is
detailed in the ITU recommendation G.7041.

POS Characteristics of Specific ONS Ethernet Cards

The following sections list and illustrate the various framing and encapsulation options supported by
specific ONS Ethernet cards.

ONS 15454 and ONS 15454 SDH E-Series Framing and Encapsulation Options

LEX is not available on the ONS 15454 or ONS 15454 SDH E-Series cards. These cards are limited to
the original proprietary E-Series encapsulation, which does not allow POS interoperability with
non E-Series cards.
encapsulation.
Figure 20-7 illustrates ONS 15454 and ONS 15454 SDH E-Series framing and
Cisco ONS 15454 and Cisco ONS 15454 SDH Ethernet Card Software Feature and Configuration Guide, R8.0
E-Series Proprietary
20-7