idnits 2.17.1 draft-delregno-pwe3-mandatory-control-word-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 15, 2010) is 4936 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'CBIT' -- Possible downref: Non-RFC (?) normative reference: ref. 'DEL' ** Obsolete normative reference: RFC 4447 (Obsoleted by RFC 8077) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group N. Del Regno, Ed. 3 Internet-Draft Verizon Communications 4 Intended status: Standards Track T. Nadeau 5 Expires: April 18, 2011 Huawei 6 V. Manral 7 IP Infusion 8 D. Ward 9 Juniper Networks 10 October 15, 2010 12 Mandatory Use of Control Word for PWE3 Encapsulations 13 draft-delregno-pwe3-mandatory-control-word-00 15 Abstract 17 Of the many variations of PWE3 Encapsulations and Modes (e.g. 18 Ethernet, Port Mode, VLAN Mode, etc), only five have the Control Word 19 (CW) as being optional. As a result, this causes an issue with VCCV 20 Control Channel selection. This draft endeavors to resolve the issue 21 going forward by making the Control Word, and subsequently the CW- 22 based VCCV Control Channel, mandatory for all PWE3 Encapsulations. 24 Requirements Language 26 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 27 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 28 document are to be interpreted as described in RFC 2119 [RFC2119]. 30 Status of this Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on April 18, 2011. 47 Copyright Notice 48 Copyright (c) 2010 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Mandatory Control Word . . . . . . . . . . . . . . . . . . . . 4 65 3. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 4 66 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 67 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 68 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 69 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 72 1. Introduction 74 The PWE3 working group has defined many encapsulations of various 75 Layer 1 and Layer 2 links. Within these encapsulations, there are 76 often several modes of encapsulation which have differing 77 requirements in order to fully emulate the service. As such, the use 78 of the PWE3 Control Word is mandated in many of the encapsulations, 79 but not all. This can present interoperability issues related to A) 80 Control Word use and B) VCCV Control Channel negotiation in mixed 81 implementation environments. 83 In the various encapsulations where the Control Word is optional, the 84 language from [RFC4385] is consistently referenced: "The features 85 that the control word provides may not be needed for a given PW. For 86 example, ECMP may not be present or active on a given MPLS network, 87 strict frame sequencing may not be required, etc. If this is the 88 case, the control word provides little value and is therefore 89 optional." As such, early implementations may not have supported the 90 Control Word for those encapsulations which didn't require it. 91 However, as recent discussions have shown [CBIT], the lack of the 92 Control Word opens up other issues related to control-word 93 negotiation (e.g. preferred vs. not- preferred) and VCCV Contol 94 Channel negotiation and selection [DEL]. 96 The encapsulations and modes for which the Control Word is currently 97 optional are: 99 o Ethernet Tagged Mode 101 o Ethernet Raw Mode 103 o PPP 105 o HDLC 107 o Frame Relay Port Mode 109 o ATM (N:1 Cell Mode) 111 While the encapsulation for PPP, HDLC and Frame Relay Port Mode are 112 the same encap, the services which they emulate may have different 113 requirements, and are therefore listed separately. 115 Unfortunately, some early implementations of PWE3 standard (and/or 116 prestandard) encapsulations are limited in their support for Control 117 Word for the above encapsulations due to A) hardware deficiencies, B) 118 software deficiencies or C) a combination of the two. In other 119 cases, deployed implementations support control word, but the service 120 provider has had no impetus to suffer the minor loss of overhead 121 efficiency. However, this document asserts based on operational 122 feedback of the PWE3 protocols in actual deployments, that the 123 benefits of requiring a mandatory control word in the PWE3 standards 124 outweigh the minor efficiencies gained when not using it. 126 One of the major benefits of consistent use of the Control Word 127 pertains to the choice of the VCCV Control Channel. As identified in 128 [DEL], Control Channel Type 1 is the only "in-band" PWE3 control 129 channel. This provides the advantage of proper VCCV forwarding 130 behavior in the presence of ECMP. Further, while the sequencing 131 supported by the Control Word is not mandatory, the use of the 132 Control Word enables the use of sequencing without forcing the 133 renegotiation of the PW. 135 All increases in the amount of overhead used to provide service 136 should be weighed versus their perceived gain, especially when that 137 overhead is large in comparison to the data being carried. This is a 138 common concern with the ATM N:1 encapsulation. In theory, if only a 139 single cell is encapsulated per PSN packet, not only is the inherent 140 overhead inacceptably large, the additon of 4 bytes only compounds 141 the problem. However, in practice, the PDUs, or groups of PDUs, 142 carried in encapsulations above, including ATM (N:1 Cell Mode), are 143 sufficiently large that the additional 4-bytes of CW overhead 144 represent a relatively minor increase in the total overhead 146 2. Mandatory Control Word 148 The Control Word SHALL be mandatory for all PWE3 encapsulations. The 149 use of the sequence number remains OPTIONAL. 151 As a result of the Control Word being Mandatory, all implementations 152 of the PWE3 encapsulations SHALL follow Section 6.1 of [RFC4447] 153 wherein the "PWs MUST have c=1". This requirement SHALL remain until 154 such time, if ever, RFC4447 is superceded and the support for Control 155 Word negotiation is removed as a result of this mandate. 157 3. Backward Compatibility 159 This Control Word mandate will not support backward compatibility 160 with implementations which cannot support Control Word. For those 161 implementations, CW negotiation identified in [RFC4447] will result 162 in the PW negotiation never completing since the end which cannot 163 support CW will ignore the Label Mapping message with c=1. However, 164 for those implementations which currently support Control Word, the 165 Control Word mandate will be supported as long as CW is set to 166 PREFERRED and the subsequent c=1 is negotiated. 168 4. IANA Considerations 170 This document makes no request of IANA. 172 Note to RFC Editor: this section may be removed on publication as an 173 RFC. 175 5. Security Considerations 177 This document specifies the mandatory behavior which must be 178 supported by implementations of PWE3 encapsulations. As the Control 179 Word is either already mandated by various encapsulations or is 180 optional, this mandate does not introduce any security issues not 181 already addressed by the encapsulation definitions, if any. Further, 182 the mandate of Control Word use may improve the security of related 183 protocol behaviors, such as VCCV Control Word (e.g. no need for 184 Router Alert Label support). 186 6. Acknowledgements 188 7. Normative References 190 [CBIT] Jin, L., Key, R., Delord, S., Nadeau, T., and V. Manral, 191 "Pseudowire Control Word Negotiation Mechanism Analysis 192 and Update", October 2010. 194 [DEL] Del Regno, N., Manral, V., Kunze, R., Paul, M., and T. 195 Nadeau, "Mandatory Features of Virtual Circuit 196 Connectivity Verification Implementations", October 2010. 198 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 199 Requirement Levels", BCP 14, RFC 2119, March 1997. 201 [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, 202 "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for 203 Use over an MPLS PSN", February 2006. 205 [RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. 206 Heron, "Pseudowire Setup and Maintenance Using the Label 207 Distribution Protocol (LDP)", April 2006. 209 Authors' Addresses 211 Nick Del Regno (editor) 212 Verizon Communications 214 Phone: 215 Fax: 216 Email: nick.delregno@verizon.com 217 URI: 219 Thomas Nadeau 220 Huawei 222 Phone: 223 Fax: 224 Email: t.nadeau@lucidvision.com 225 URI: 227 Vishwas Manral 228 IP Infusion 230 Phone: 231 Fax: 232 Email: vishwas@ipinfusion.com 233 URI: 235 David Ward 236 Juniper Networks 238 Phone: 239 Fax: 240 Email: dward@juniper.net 241 URI: