



Network Working Group                                           A. Spera
Internet-Draft                                              P. Broccardi
Intended status: Informational                             Cisco Systems
Expires: 20 January 2026                                    19 July 2025


                Bitstream Transport over Ethernet (BToE)
                          draft-spera-btoe-00

Abstract

   This document defines Bitstream Transport over Ethernet (BToE), a
   method for capturing and transporting raw Layer 1 bitstream data
   across Ethernet Layer 2 networks.  Unlike traditional frame-based
   transport mechanisms, BToE enables fully transparent transmission of
   physical layer signals, allowing for cable fault isolation, ASIC/FPGA
   debugging, and transceiver validation by preserving the integrity of
   all bits, including those outside valid Ethernet frames.

Status of This Memo

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   This Internet-Draft will expire on 20 January 2026.

Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
     3.1.  Frame-Centric Limitations . . . . . . . . . . . . . . . .   2
     3.2.  Lack of Bit-Level Visibility  . . . . . . . . . . . . . .   3
     3.3.  ASIC/FPGA and Cable Diagnostics . . . . . . . . . . . . .   3
   4.  BToE Architecture . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Buffering and Transport . . . . . . . . . . . . . . . . .   3
     4.3.  Frame Format  . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Encapsulation and VLAN Tagging  . . . . . . . . . . . . . . .   4
   6.  Conceptual Implementation Considerations  . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Traditional Layer 2 tunneling and encapsulation mechanisms rely on
   the presence of syntactically valid Ethernet frames.  Technologies
   such as SPAN, RSPAN, ERSPAN, and L2VPN XConnect are valuable for
   forwarding frame-aligned data but fail to address scenarios that
   require examination of physical-layer signals or invalid bit-level
   sequences.  BToE (Bitstream Transport over Ethernet) addresses this
   gap by defining a method to transport raw bitstreams, prior to frame
   recognition or protocol validation.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 RFC 2119 [RFC2119] and RFC 8174 [RFC8174].

3.  Problem Statement

3.1.  Frame-Centric Limitations

   Existing frame-based mechanisms for traffic capture and transport
   require valid Ethernet framing.  Protocols that are not supported or
   frames that are malformed cannot be reliably captured, resulting in
   diagnostic blind spots.  Even Layer 2 protocol tunneling mechanisms
   cannot address physical-layer abnormalities that prevent frame
   construction.




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3.2.  Lack of Bit-Level Visibility

   Faults at the physical layer — including bit-level corruption,
   alignment errors, clock mismatches, and FCS violations — often occur
   prior to or during frame construction.  These are undetectable by
   tools that rely on frame interpretation.

3.3.  ASIC/FPGA and Cable Diagnostics

   In ASIC, FPGA, and transceiver validation workflows, engineers
   require access to the raw serialized line signal, including symbols
   and bits that never result in valid Ethernet frames.  No standard
   mechanism exists today to extract and transport this data for remote
   analysis.

4.  BToE Architecture

4.1.  Overview

   BToE defines a mechanism for capturing raw bitstreams on an ingress
   interface at the physical layer and encapsulating those bits into
   Ethernet payloads that can be delivered across a Layer 2
   infrastructure.  This allows transparent inspection and transport of
   all data on a link, including error sequences, idle characters, and
   malformed transmissions.

4.2.  Buffering and Transport

   A buffer is allocated per ingress port to collect bitstream data.
   The size of this buffer is configurable and defines how many bits
   should be collected prior to encapsulation.  Optionally, a timeout
   may be defined to ensure data is not delayed indefinitely in the
   absence of new input.

   Once the buffer threshold or timeout condition is met, the bits are
   encapsulated into a BToE frame and forwarded to a designated
   receiver.

4.3.  Frame Format

   The encapsulating Ethernet frame is structured as follows:










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   +------------------------+
   | Ethernet Header        |
   +------------------------+
   | 802.1Q VLAN Tag        |
   +------------------------+
   | Raw Bitstream Payload  |
   +------------------------+
   | Frame Check Sequence   |
   +------------------------+

   The payload carries the raw bitstream exactly as captured at the
   ingress PHY interface, without any framing, alignment, or protocol-
   awareness applied.  There is no protocol-specific BToE header within
   the payload.

5.  Encapsulation and VLAN Tagging

   The BToE payload is transported inside a VLAN-tagged Ethernet frame
   using 802.1Q.  VLAN IDs may be pre-negotiated between sender and
   receiver to define dedicated transport paths for BToE traffic.  No
   new EtherType is introduced; instead, existing encapsulation
   practices are reused with reserved VLANs or destination MAC addresses
   to identify BToE frames.

6.  Conceptual Implementation Considerations

   BToE-capable ingress interfaces must be able to extract the
   serialized bitstream from the physical layer and feed it into a
   buffer.

   The buffer should support configurable size (in bits) and flush
   timeout.

   At the transmission boundary, the system encapsulates buffered bits
   directly into Ethernet frames with VLAN tagging.

   On the receiving side, the payload is decapsulated, and bitstream
   data is reconstructed for analysis, replay, or validation.

   Transport domains should logically isolate BToE traffic to prevent
   interference with operational data.

7.  Security Considerations

   Transporting raw bitstreams introduces new privacy and integrity
   risks.  BToE bypasses higher-layer protocol parsing and may transmit
   sensitive or malformed data without inspection.  Deployments should
   ensure:



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   - Logical and physical isolation of BToE VLANs - Transport-layer
   encryption when traversing untrusted domains - Rate limiting or
   filtering to prevent replay or injection of invalid BToE frames

8.  IANA Considerations

   This document makes no request of IANA.

9.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, May 2017,
              <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses

   Adam Spera
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA 95134
   United States of America
   Email: adamspera@hotmail.com


   Paul Broccardi
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA 95134
   United States of America
   Email: paulbroccardi@gmail.com

















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