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Symington 3 Internet-Draft The MITRE Corporation 4 Intended status: Experimental February 17, 2010 5 Expires: August 21, 2010 7 Delay-Tolerant Networking Previous Hop Insertion Block 8 draft-irtf-dtnrg-bundle-previous-hop-block-11 10 Abstract 12 This document defines an extension block for use with the DTN Bundle 13 Protocol. This Previous Hop Insertion Block (PHIB) extension block 14 is designed to be inserted by a forwarding node to provide the 15 endpoint identifier (EID) of an endpoint of which the forwarding node 16 is a member so that this EID may be conveyed to the next-hop 17 receiving node. Knowledge of an EID of an endpoint of which a 18 previous-hop node is a member may be required in some circumstances 19 to support certain routing protocols (e.g., flood routing). If this 20 EID cannot be provided by the convergence layer or other means, the 21 PHIB defines the mechanism whereby the EID can be provided with the 22 bundle. Each PHIB is always removed from the bundle by the receiving 23 node so that its presence within the bundle is limited to exactly one 24 hop. This document defines the format and processing of this PHIB. 25 This document is a product of the Delay Tolerant Networking Research 26 Group and has been reviewed by that group. No objections to its 27 publication as an RFC were raised." 29 Status of this Memo 31 This Internet-Draft is submitted to IETF in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF), its areas, and its working groups. Note that 36 other groups may also distribute working documents as Internet- 37 Drafts. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 The list of current Internet-Drafts can be accessed at 45 http://www.ietf.org/ietf/1id-abstracts.txt. 47 The list of Internet-Draft Shadow Directories can be accessed at 48 http://www.ietf.org/shadow.html. 50 This Internet-Draft will expire on August 21, 2010. 52 Copyright Notice 54 Copyright (c) 2010 IETF Trust and the persons identified as the 55 document authors. All rights reserved. 57 This document is subject to BCP 78 and the IETF Trust's Legal 58 Provisions Relating to IETF Documents 59 (http://trustee.ietf.org/license-info) in effect on the date of 60 publication of this document. Please review these documents 61 carefully, as they describe your rights and restrictions with respect 62 to this document. Code Components extracted from this document must 63 include Simplified BSD License text as described in Section 4.e of 64 the Trust Legal Provisions and are provided without warranty as 65 described in the Simplified BSD License. 67 Table of Contents 69 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 2. Previous Hop Insertion Block Format . . . . . . . . . . . . . 6 71 3. Previous Hop Insertion Block Processing . . . . . . . . . . . 8 72 3.1. Bundle Transmission . . . . . . . . . . . . . . . . . . . 8 73 3.2. Bundle Forwarding . . . . . . . . . . . . . . . . . . . . 8 74 3.3. Bundle Reception . . . . . . . . . . . . . . . . . . . . . 9 75 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 76 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 77 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 78 6.1. Normative References . . . . . . . . . . . . . . . . . . . 12 79 6.2. Informative References . . . . . . . . . . . . . . . . . . 12 80 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 82 1. Introduction 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 86 document are to be interpreted as described in RFC 2119 [RFC 2119]. 88 This document defines an extension block for use with the Bundle 89 Protocol [RFC 5050] within the context of a Delay-Tolerant Network 90 architecture [RFC 4838]. The DTN Bundle Protocol defines the bundle 91 as its protocol data unit and defines "bundle blocks" to carry data 92 of different types. This document defines an optional bundle block 93 called a Previous Hop Insertion Block (PHIB). 95 The PHIB is inserted into a bundle by a forwarding node to provide 96 the endpoint ID (EID) of an endpoint of which the forwarding node is 97 a member so that this EID may be conveyed to the next-hop receiving 98 node. (Hereafter, an EID of an endpoint of which a node is a member 99 will be referred to as an "M-EID" of that node. A node may have one 100 or more M-EIDs, depending on the number of endpoints to which it 101 belongs. An EID of a singleton endpoint of which a node is a member 102 will be referred to as a "singleton M-EID" of that node.) In 103 situations where there is a requirement that the receiving node be 104 able to determine an M-EID of a forwarding node, but the M-EID of the 105 forwarding node cannot be inferred by the receiving node through 106 existing mechanisms, the forwarding node must explicitly provide this 107 M-EID in the bundle. This specification defines the mechanism 108 whereby a node can insert such an M-EID into a bundle before 109 forwarding it to the bundle's next hop. 111 This previous-hop M-EID information may be used in some circumstances 112 to support various routing protocols. For example, the PHIB could be 113 helpful when implementing flood routing because each receiving node 114 could use the PHIB to determine which EID to exclude from the list of 115 adjacent nodes to which it forwards received bundles as it does its 116 part in flooding the bundle. A node will flood the bundle to all 117 neighboring nodes except for the node from which it received the 118 bundle, as identified in the PHIB. 120 The PHIB could also be used in conjunction with the Bundle 121 Authentication Block (BAB) of the DTN Bundle Security Protocol 122 [DTNBSP] to provide the security source EID for the BAB. The PHIB 123 can be used to carry the BAB's security source EID instead of 124 conveying this EID using a reference in the BAB's EID reference field 125 or including the EID as part of the BAB's key information parameters. 127 In many situations, a node that receives a bundle may be able to 128 infer an M-EID of the node that forwarded the bundle. In some 129 situations, however, no M-EID will be able to be inferred by the 130 receiving node. For example, if tunneling DTN bundles across some 131 portion of the DTN network, it is not possible for the node at the 132 receiving end of the tunnel to determine from the convergence layer 133 the M-EID of the node at the sending end of the tunnel. The node at 134 the receiving end of the tunnel will receive an encapsulating bundle 135 from one of its adjacent nodes and it may be able to tell the M-EID 136 of this adjacent node using the convergence layer protocol. However, 137 the node at the sending end of the tunnel is most likely not adjacent 138 to the node at the receiving end of the tunnel, so in order for the 139 node at the receiving end of the tunnel to be able to learn the M-EID 140 of the node at the sending end of the tunnel, which is the previous 141 hop node of the tunneled bundle, the M-EID must be provided within 142 the tunneled bundle. In this case, the PHIB is the vehicle for 143 enabling the node at the sending end of the tunnel to provide its 144 M-EID to the node at the receiving end of the tunnel. 146 EIDs may be presented in two ways within the PHIB. If the M-EID of 147 the forwarding node is already in the dictionary field of the 148 bundle's Primary Bundle Block, the PHIB MAY identify this EID using 149 its Block EID reference count and EID references field. Otherwise, 150 the PHIB MUST identify this EID by providing the EID in its block- 151 type-specific data field. These two alternative ways of presenting 152 EIDs in the PHIB are further discussed in Section 3. 154 The lifetime of the PHIB is always exactly one hop in the DTN. If a 155 bundle containing a PHIB is received, the receiving node is assured 156 that this PHIB was inserted by the previous node, assuming all nodes 157 are operating correctly; likewise, this PHIB is not retained with the 158 bundle when the bundle is forwarded. If the bundle is forwarded with 159 a PHIB, this PHIB MUST identify an M-EID of the forwarding node. 161 This document defines the format and processing of the PHIB. The 162 capabilities described in this document are OPTIONAL for deployment 163 with the Bundle Protocol. Bundle Protocol implementations claiming 164 to support the PHIB MUST be capable of: 166 -Generating a PHIB and inserting it into a bundle, 168 -Receiving bundles containing a PHIB and making the information 169 contained in this PHIB available for use, e.g., in forwarding 170 decisions. 172 -Deleting a PHIB from a bundle 174 as defined in this document. 176 2. Previous Hop Insertion Block Format 178 The PHIB uses the Canonical Bundle Block Format as defined in the 179 Bundle Protocol [RFC 5050]. That is, the PHIB is comprised of the 180 following elements, which are defined as in all bundle protocol 181 blocks except the primary bundle block. Note that SDNV encoding is 182 also described in the Bundle Protocol: 184 -Block-type code (one byte) - The block type code for the PHIB is 185 0x05. 187 -Block processing control flags (SDNV) - The following block 188 processing control flag MUST be set: 190 -Discard block if it can't be processed. 192 -Block EID reference count and EID references (optional) - 193 composite field defined in [RFC 5050] containing a count of EID 194 references (expressed as an SDNV) followed by an EID reference 195 (expressed as a pair of SDNVs). 197 Whether or not this field is allowed in the PHIB is determined by 198 whether or not an M-EID of the node inserting the PHIB is already 199 in the Dictionary Field of the Primary Bundle Block (e.g., whether 200 an M-EID of the inserting node is also an M-EID of the bundle's 201 source, current custodian, or report-to endpoint, or is the same 202 as some other endpoint in the dictionary that is referenced by 203 another block in the bundle). 205 If an M-EID of the inserting node is already in the dictionary, 206 this field MAY be present in the PHIB. If this field is present 207 in the PHIB, the value of the EID reference count MUST be one, 208 meaning that the field contains exactly one EID reference, which 209 MUST be a reference to an M-EID of the inserting node. Presence 210 of this field MUST be indicated by a set "block contains an EID 211 reference field" flag in the block processing control flags. 213 If no M-EID of the inserting node is in the dictionary, this field 214 MUST NOT be present in the PHIB, which MUST be indicated by an 215 unset "block contains an EID reference field" flag in the block 216 processing control flags 218 -Block data length (SDNV) - If this value is zero, there are no 219 block-type-specific data fields. In this case, the M-EID of the 220 inserting node must be in the dictionary and it MUST be referenced 221 in the Block EID reference count and EID references field as 222 described above. 224 -Block-type-specific data fields (optional) as follows: 226 -Inserting Node's EID Scheme Name - A null-terminated array of 227 bytes that comprises the scheme name of an M-EID of the node 228 inserting this PHIB. 230 -Inserting Node's EID SSP - A null-terminated array of bytes 231 that comprises the scheme-specific part (SSP) of an M-EID of 232 the node inserting this PHIB. 234 If the Block EID reference count and EID references field is not 235 present in the PHIB, the above two EID scheme name and SSP block- 236 type-specific data fields MUST be present. If the Block EID 237 reference count and EID references field is present in the PHIB, 238 the above two EID scheme name and SSP block-type-specific data 239 fields MUST NOT be present. 241 The Structure of a PHIB is as follows: 243 PHIB Format: 244 +----+------------+--------------------------------- -+-------------+ 245 |type|flags (SDNV)|EID ref count and list (comp) (opt)|length (SDNV)| 246 +----+------------+-----------------------------------+-------------+ 247 | Inserting Node EID Scheme Name (opt)| Inserting Node EID SSP (opt)| 248 +-------------------------------------------------------------------+ 250 Figure 1 252 3. Previous Hop Insertion Block Processing 254 The following are the processing steps that a bundle node must take 255 relative to generation, reception, and processing of a PHIB. 257 3.1. Bundle Transmission 259 When an outbound bundle is created per the parameters of the bundle 260 transmission request, this bundle MAY include one or more PHIBs. 261 Whether or not PHIBs are included is a local bundle agent 262 configuration option and may be influenced by other factors, such as 263 the routing protocol in use. 265 3.2. Bundle Forwarding 267 Before forwarding a bundle, the node SHALL delete all PHIBs that were 268 in the bundle when it was received (if any). As described in the 269 Bundle Protocol, the node MAY delete all strings (scheme names and 270 SSPs) in the bundle's dictionary to which no endpoint ID references 271 in the bundle currently refer (if any). 273 The node MAY insert one or more PHIBs into the bundle before 274 forwarding it, as dictated by local policy. If there are already 275 strings (scheme names and SSPs) in the bundle's dictionary that 276 denote the M-EID of the inserting node, the PHIB MAY reference these 277 strings and, if it does, it MUST NOT include any block-type-specific 278 data fields. The inserting node MUST NOT insert strings into the 279 bundle's dictionary in order that they may be referenced by only the 280 PHIB. If the PHIB is constructed such that it does not reference any 281 strings from the dictionary, the inserting node MUST include the 282 scheme name and SSP of one of its M-EIDs as the PHIB's block-type- 283 specific data fields. 285 The node that is inserting a PHIB into the bundle may have more than 286 one endpoint in which it is a member. The choice of which M-EID to 287 insert into the PIB SHALL be made as follows: 289 - If the inserting node is a member of exactly one singleton 290 endpoint, the node may insert at most one PHIB into the bundle and 291 the EID of this singleton endpoint is what MUST be inserted into 292 the PHIB. 294 - If the inserting node is a member of more than one singleton 295 endpoint, then: 297 If the inserting node has a priori knowledge of the URI schemes 298 supported by the next hop node and if the inserting node has 299 one or more singleton M-EIDs that are expressible in one or 300 more of those URI schemes, then the inserting node MAY insert 301 one or more PHIBs into the bundle being forwarded. The EIDs in 302 the inserted PHIBs MUST be unique, they MUST be singleton 303 M-EIDs of the inserting node, and they MUST be expressed in URI 304 schemes supported by the next hop node. Mechanisms for 305 determining what URI schemes are supported by particular next 306 hop neighbors are not defined here. 308 If the inserting node has one or more singleton M-EIDs that are 309 expressible in the same URI scheme as the destination of the 310 bundle that is being forwarded, then the inserting node MAY 311 insert one or more PHIBs into the bundle being forwarded. The 312 EIDs in the inserted PHIBs MUST be unique, they MUST be 313 singleton M-EIDs of the inserting node, and they MUST be 314 expressed in the destination URI scheme of the bundle. 316 Else if the inserting node has neither a singleton M-EID that 317 is expressible in a URI scheme known to be supported by the 318 next hop node nor a singleton M-EID that is expressible in the 319 same URI scheme as the destination of the bundle that is being 320 forwarded, then the inserting node MAY insert one or more PHIBs 321 into the bundle being forwarded. The EIDs in the inserted 322 PHIBs MUST be unique, and they MUST be singleton M-EIDs of the 323 inserting node. 325 3.3. Bundle Reception 327 If the bundle includes a PHIB, the EID identified in the PHIB SHALL 328 be made available for use at the receiving node (e.g., in forwarding 329 decisions or, if the receiving node is the bundle destination, the 330 EID may be made available to the receiving application; whether or 331 not it is made available to the receiving application is an 332 implementation matter). If the EID is identified both by a reference 333 in the PHIB's Block EID reference count and EID references field and 334 by a scheme name and SSP in the block-type-specific fields, the PHIB 335 is not considered to be well-formed. In the case of reception of 336 such an ill-formed PHIB, if the identified EIDs are the same, the 337 receiving node MAY process the PHIB as if it were well-formed. 338 However, if the identified EIDs differ, the receiving node MUST NOT 339 process the PHIB and must take action on the PHIB as specified by the 340 PHIB's Block Processing Control Flags. 342 4. Security Considerations 344 The DTN Bundle Security Protocol [DTNBSP] defines security-related 345 blocks to provide hop-by-hop bundle authentication and integrity, 346 end-to-end integrity, and end-to-end confidentiality of bundles or 347 parts of bundles, as well as a set of ciphersuites that may be used 348 to calculate security results carried in these security blocks. The 349 PHIB will not be encrypted when using the PCB-RSA-AES128-PAYLOAD-PIB- 350 PCB ciphersuite with the Payload Confidentiality Block (PCB) to 351 provide end-to-end confidentiality. This ciphersuite only allows for 352 payload and Payload Integrity Block (PIB) encryption. If encryption 353 of the PHIB block is desired, the Extension Security Block (ESB) 354 could be used for this purpose. 356 All ciphersuites that use the strict canonicalisation algorithm 357 [DTNBSP] to calculate and verify security results (e.g., many hop-by- 358 hop authentication ciphersuites) apply to all blocks in the bundle, 359 and so would apply to bundles that include an optional PHIB and would 360 include that block in the calculation of their security result. In 361 particular, bundles including the optional PHIB would have their 362 integrity protected in their entirety for the extent of a single hop, 363 from a forwarding node to an adjacent receiving node, using the 364 Bundle Authentication Block (BAB) with the BAB-HMAC ciphersuite 365 defined in the Bundle Security Protocol. 367 Ciphersuites that use the mutable canonicalisation algorithm to 368 calculate and verify security results (e.g., the PIB-RSA-SHA256 369 ciphersuite and most end-to-end authentication ciphersuites used with 370 the PIB) will (correctly) omit the PHIB from their calculation. The 371 fact that several different instantiations of this PHIB block may be 372 added to and deleted from the bundle as the bundle transits the 373 network will not interfere with end-to-end security protection when 374 using ciphersuites that use mutable canonicalisation. 376 As stated above, the BAB can be used to ensure the integrity of the 377 PHIB. Nodes receiving bundles with PHIBs should be aware, however, 378 that forwarding nodes that insert PHIBs might lie about the EIDs of 379 endpoints of which they are members. Lying in this way could provide 380 a mechanism for subverting routing strategies that base routing 381 decisions on EID information in the PHIB. 383 Note that if some Bundle Protocol implementation does not support the 384 PHIB but does not properly implement the "Discard block if it can't 385 be processed" flag, then a PHIB may unexpectedly persist for longer 386 than a single hop. 388 5. IANA Considerations 390 If the bundle protocol becomes a standards track protocol, then we 391 may want to consider having IANA establish a register of block types, 392 of which the PHIB would be one. The block type code being suggested 393 for the PHIB is 0x05. 395 6. References 397 6.1. Normative References 399 [RFC 2119] 400 Bradner, S. and J. Reynolds, "Key words for use in RFCs to 401 Indicate Requirement Levels", RFC 2119, October 1997. 403 [RFC 5050] 404 Scott, K. and S. Burleigh, "Bundle Protocol 405 Specification", RFC 5050, November 2007. 407 6.2. Informative References 409 [RFC 4838] 410 Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, 411 R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant 412 Network Architecture", RFC 4838, April 2007. 414 [DTNBSP] Symington, S., Farrell, S., Weiss, H., and P. Lovell, 415 "Bundle Security Protocol Specification", 416 draft-irtf-dtnrg-bundle-security-14.txt, work-in-progress, 417 January 2010. 419 Author's Address 421 Susan Flynn Symington 422 The MITRE Corporation 423 7515 Colshire Drive 424 McLean, VA 22102 425 US 427 Phone: +1 (703) 983-7209 428 Email: susan@mitre.org 429 URI: http://mitre.org/