Internet-Draft Daniele Giordano Expires: 5 May 2008 2 November 2007 Ethernet preamble variation - Use Ethernet preamble to perform frame's classification and a switching optimization draft-giordano-ethpre-class-opt-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract Ethernet, standardized as IEEE802.3, is a family of frame-based networking technologies for local area networks. It's the most widespread wired LAN technology. This document proposes a variation of the original frame's structure to perform a frame's classification and a switching optimization (fundamental steps for QoS mechanism). Daniele Giordano [Page 1] Internet-Draft Ethernet preamble variation Oct 2007 Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Implementation and Operations . . . . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Daniele Giordano [Page 2] Internet-Draft Ethernet preamble variation Oct 2007 1. Conventions Used In This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Introduction Ethernet, standardized as [IEEE] [802.3], (now Ethernet or 802.3) is a family of frame-based networking technologies for local area networks (LAN). It's the most widespread wired LAN technology. This document proposes a variation of the frame's structure to perform a frame's classification and a switching optimization (fundamental steps for QoS mechanism). Actual 802.3 frame ----------------------------------------- field |PRE |SFD |DA |SA |LT |Payload |FCS | ----------------------------------------- byte |7 |1 |6 |6 |2 |46 - 1500|4 | ----------------------------------------- Acronyms: PRE - The preamble field consists of seven bytes of alternating ones and zeros and It's used for synchronization. SFD - Start Frame Delimiter is the 8-bit sequence 10101011 and It's the same as the eighth byte of the Ethernet preamble. DA - The destination address specifies the station or stations to which a frame should be sent. SA - The source address field contains the unique address of the transmitter station. LT - The length field. FCS - Frame check sequence is an error checking field. It's generated using the Cyclic Redundancy Check (CRC) on the destination address, source address, length, and payload fields. In this frame there isn't information about the type or the priority of data carried. Now a days IEEE [802.1q] standard (the evolution of 802.3) has a classification mechanism implemented with [802.1p] or CoS but this type of frame is not large supported from all LAN devices. Daniele Giordano [Page 3] Internet-Draft Ethernet preamble variation Oct 2007 Actual 802.1q frame ---------------------------------------------- field |PRE |SFD |DA |SA |TAG |LT |Payload |FCS | ---------------------------------------------- | \ | \ -------------------- |TPID|PRI |CFI |VID| -------------------- bit |16 |3 |1 |12 | -------------------- Acronyms: PRE, SFD, DA, SA, LT and FCS fields are similar to corresponding fields in the 802.3 frame. TPID - The Tag Protocol Identifier identifies the frame as an IEEE 802.1q tagged frame. PRI - Priority, this field refers to the IEEE 802.1p 8 levels priority (CoS). CFI - The Canonical Format Indicator specifies if the MAC address is in canonical or non canonical format. VID - The VLAN Identifier identifies the VLAN to which the frame belongs. This type of classification can also be defined as best-effort Layer 2 QoS. It is implemented in network adapters and switches. The traffic is simply classified and sent to the destination. No type of resources reservation are established. e.g. 1) A switch which supports both types of protocols (802.3 and 802.1q) receives traffic in a 802.3 frame from a PC; 2) It converts the original frame in a 802.1q frame; 3) the switch performs an IP packet inspection to read [DSCP] value writing from the PC in the IP header; 4) It writes this value in the PRI field of the 802.1q frame; 5) the frame is sent in a specific output queue in function of CoS value; 6) when the queue is served the switch converts the frame in a 802.3 format and It sends that in a UART output interface. THE NEW FRAME DOESN'T HAVE ANY INFORMATION OF PRIORITY. 7) The process restarts for any switch encountered. Daniele Giordano [Page 4] Internet-Draft Ethernet preamble variation Oct 2007 3. Implementation and Operations New Ethernet preamble format ---------------------------------------------- field |PRE |SFD+PRI |DA |SA |LT |Payload |FCS | ---------------------------------------------- byte |7 |1 |6 |6 |2 |46 - 1500|4 | ---------------------------------------------- | \ | \ ----------- |SFD |PRI | ----------- bit |5 |3 | ----------- Acronyms: PRE - The preamble field consists of seven bytes of alternating ones and zeros and It's used for synchronization. SFD - Start Frame Delimiter is the 5-bit sequence 10111 and it identifies the start of the frame. PRI - Priority, It is a 3-bit field similar to the IEEE 802.1p levels priority. DA, SA, LT and FCS are similar to corresponding fields in the 802.3 frame. Using preamble's bits a switch can know the frame's priority before of the switching process. It doesn't use resources to perform IP packet inspection to read the IP DSCP. It doesn't convert 802.3 frame in other format. The frame maintains its information of priority. Another advantage is represented by the fact that the switch MUST change its switching modality (if supported) according to priority value: preamble priority < 5 ---> switch engine: store & forward preamble priority >= 5 ---> switch engine: cut through In cut through modality the switch starts forwarding a frame before the whole frame has been received. This technique reduces latency through the switch and delay of critical applications. Daniele Giordano [Page 5] Internet-Draft Ethernet preamble variation Oct 2007 4. IANA Considerations None. 5. Security Considerations This document is not directly concerned with security. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 6.2. Informative References [802.3] "IEEE Standard for Information technology Telecommunications and information exchange between systems Local and metropolitan area networks", IEEE 802.3-2005/Cor 1-2006 [802.1q] "IEEE Standard for Local and metropolitan area networks / Virtual Bridged Local Area Networks", IEEE 802.1Q-2005, 19 May 2006. [802.1p] "Traffic Class Expediting and Dynamic Multicast Filtering", IEEE 802.1d-1998 [IEEE] Institute of Electrical and Electronics Engineers . [DSCP] K. Nichols, S. Blake, F. Baker, D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474,December 1998. Daniele Giordano [Page 6] Internet-Draft Ethernet preamble variation Oct 2007 Author's Address Daniele Giordano Email: d.giordano@fastpiu.it Full Copyright Statement Copyright (C) The IETF Trust (2007). 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Daniele Giordano Expires: 5 May 2008 [Page 7]