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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet-Draft Daniele Giordano 3 Expires: 5 May 2008 2 November 2007 5 Ethernet preamble variation - Use Ethernet preamble to perform 6 frame's classification and a switching optimization 8 draft-giordano-ethpre-class-opt-01 10 Status of this Memo 12 By submitting this Internet-Draft, each author represents that any 13 applicable patent or other IPR claims of which he or she is aware 14 have been or will be disclosed, and any of which he or she becomes 15 aware will be disclosed, in accordance with Section 6 of BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 Copyright Notice 35 Copyright (C) The IETF Trust (2007). 37 Abstract 39 Ethernet, standardized as IEEE802.3, is a family of frame-based 40 networking technologies for local area networks. It's the most 41 widespread wired LAN technology. 42 This document proposes a variation of the original frame's structure 43 to perform a frame's classification and a switching optimization 44 (fundamental steps for QoS mechanism). 46 Table of Contents 48 1. Conventions Used In This Document . . . . . . . . . . . . . . . 3 49 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 50 3. Implementation and Operations . . . . . . . . . . . . . . . . . 5 51 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 52 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 53 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 54 6.1. Normative References . . . . . . . . . . . . . . . . . . . 6 55 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 56 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 57 Intellectual Property and Copyright Statements . . . . . . . . . . 7 59 1. Conventions Used In This Document 61 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 62 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 63 document are to be interpreted as described in [RFC2119]. 65 2. Introduction 67 Ethernet, standardized as [IEEE] [802.3], (now Ethernet or 802.3) is 68 a family of frame-based networking technologies for local area 69 networks (LAN). It's the most widespread wired LAN technology. 70 This document proposes a variation of the frame's structure to 71 perform a frame's classification and a switching optimization 72 (fundamental steps for QoS mechanism). 74 Actual 802.3 frame 76 ----------------------------------------- 77 field |PRE |SFD |DA |SA |LT |Payload |FCS | 78 ----------------------------------------- 79 byte |7 |1 |6 |6 |2 |46 - 1500|4 | 80 ----------------------------------------- 82 Acronyms: 83 PRE - The preamble field consists of seven bytes of alternating ones 84 and zeros and It's used for synchronization. 85 SFD - Start Frame Delimiter is the 8-bit sequence 10101011 and It's 86 the same as the eighth byte of the Ethernet preamble. 87 DA - The destination address specifies the station or stations to 88 which a frame should be sent. 89 SA - The source address field contains the unique address of the 90 transmitter station. 91 LT - The length field. 92 FCS - Frame check sequence is an error checking field. It's generated 93 using the Cyclic Redundancy Check (CRC) on the destination address, 94 source address, length, and payload fields. 96 In this frame there isn't information about the type or the 97 priority of data carried. 98 Now a days IEEE [802.1q] standard (the evolution of 802.3) has a 99 classification mechanism implemented with [802.1p] or CoS but this 100 type of frame is not large supported from all LAN devices. 102 Actual 802.1q frame 104 ---------------------------------------------- 105 field |PRE |SFD |DA |SA |TAG |LT |Payload |FCS | 106 ---------------------------------------------- 107 | \ 108 | \ 109 -------------------- 110 |TPID|PRI |CFI |VID| 111 -------------------- 112 bit |16 |3 |1 |12 | 113 -------------------- 115 Acronyms: 116 PRE, SFD, DA, SA, LT and FCS fields are similar to corresponding 117 fields in the 802.3 frame. 118 TPID - The Tag Protocol Identifier identifies the frame as an 119 IEEE 802.1q tagged frame. 120 PRI - Priority, this field refers to the IEEE 802.1p 8 levels 121 priority (CoS). 122 CFI - The Canonical Format Indicator specifies if the MAC address is 123 in canonical or non canonical format. 124 VID - The VLAN Identifier identifies the VLAN to which the frame 125 belongs. 127 This type of classification can also be defined as best-effort 128 Layer 2 QoS. It is implemented in network adapters and switches. 129 The traffic is simply classified and sent to the destination. 130 No type of resources reservation are established. 132 e.g. 1) A switch which supports both types of protocols (802.3 and 133 802.1q) receives traffic in a 802.3 frame from a PC; 134 2) It converts the original frame in a 802.1q frame; 135 3) the switch performs an IP packet inspection to read [DSCP] 136 value writing from the PC in the IP header; 137 4) It writes this value in the PRI field of the 802.1q frame; 138 5) the frame is sent in a specific output queue in function of 139 CoS value; 140 6) when the queue is served the switch converts the frame in a 141 802.3 format and It sends that in a UART output interface. 142 THE NEW FRAME DOESN'T HAVE ANY INFORMATION OF PRIORITY. 143 7) The process restarts for any switch encountered. 145 3. Implementation and Operations 147 New Ethernet preamble format 149 ---------------------------------------------- 150 field |PRE |SFD+PRI |DA |SA |LT |Payload |FCS | 151 ---------------------------------------------- 152 byte |7 |1 |6 |6 |2 |46 - 1500|4 | 153 ---------------------------------------------- 154 | \ 155 | \ 156 ----------- 157 |SFD |PRI | 158 ----------- 159 bit |5 |3 | 160 ----------- 162 Acronyms: 163 PRE - The preamble field consists of seven bytes of alternating ones 164 and zeros and It's used for synchronization. 165 SFD - Start Frame Delimiter is the 5-bit sequence 10111 and it 166 identifies the start of the frame. 167 PRI - Priority, It is a 3-bit field similar to the IEEE 802.1p 168 levels priority. 169 DA, SA, LT and FCS are similar to corresponding fields in the 802.3 170 frame. 172 Using preamble's bits a switch can know the frame's priority before 173 of the switching process. It doesn't use resources to perform IP 174 packet inspection to read the IP DSCP. It doesn't convert 802.3 frame 175 in other format. The frame maintains its information of priority. 177 Another advantage is represented by the fact that the switch MUST 178 change its switching modality (if supported) according to priority 179 value: 181 preamble priority < 5 ---> switch engine: store & forward 182 preamble priority >= 5 ---> switch engine: cut through 184 In cut through modality the switch starts forwarding a frame before 185 the whole frame has been received. This technique reduces latency 186 through the switch and delay of critical applications. 188 4. IANA Considerations 190 None. 192 5. Security Considerations 194 This document is not directly concerned with security. 196 6. References 198 6.1. Normative References 200 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 201 Requirement Levels", BCP 14, RFC 2119, March 1997. 203 6.2. Informative References 205 [802.3] "IEEE Standard for Information technology Telecommunications 206 and information exchange between systems Local and metropolitan 207 area networks", IEEE 802.3-2005/Cor 1-2006 209 [802.1q] "IEEE Standard for Local and metropolitan area networks / 210 Virtual Bridged Local Area Networks", IEEE 802.1Q-2005, 19 May 211 2006. 213 [802.1p] "Traffic Class Expediting and Dynamic Multicast Filtering", 214 IEEE 802.1d-1998 216 [IEEE] Institute of Electrical and Electronics Engineers 217 . 219 [DSCP] K. Nichols, S. Blake, F. Baker, D. Black, "Definition of the 220 Differentiated Services Field (DS Field) in the IPv4 and IPv6 221 Headers", RFC 2474,December 1998. 223 Author's Address 225 Daniele Giordano 226 Email: d.giordano@fastpiu.it 228 Full Copyright Statement 230 Copyright (C) The IETF Trust (2007). 232 This document is subject to the rights, licenses and restrictions 233 contained in BCP 78, and except as set forth therein, the authors 234 retain all their rights. 236 This document and the information contained herein are provided on an 237 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 238 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 239 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 240 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 241 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 242 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 244 Intellectual Property 246 The IETF takes no position regarding the validity or scope of any 247 Intellectual Property Rights or other rights that might be claimed to 248 pertain to the implementation or use of the technology described in 249 this document or the extent to which any license under such rights 250 might or might not be available; nor does it represent that it has 251 made any independent effort to identify any such rights. Information 252 on the procedures with respect to rights in RFC documents can be 253 found in BCP 78 and BCP 79. 255 Copies of IPR disclosures made to the IETF Secretariat and any 256 assurances of licenses to be made available, or the result of an 257 attempt made to obtain a general license or permission for the use of 258 such proprietary rights by implementers or users of this 259 specification can be obtained from the IETF on-line IPR repository at 260 http://www.ietf.org/ipr. 262 The IETF invites any interested party to bring to its attention any 263 copyrights, patents or patent applications, or other proprietary 264 rights that may cover technology that may be required to implement 265 this standard. Please address the information to the IETF at 266 ietf-ipr@ietf.org. 268 Acknowledgment 270 Funding for the RFC Editor function is provided by the IETF 271 Administrative Support Activity (IASA).