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'6' ** Downref: Normative reference to an Informational RFC: RFC 2475 (ref. '8') ** Downref: Normative reference to an Informational RFC: RFC 1633 (ref. '10') -- Possible downref: Non-RFC (?) normative reference: ref. '12' ** Obsolete normative reference: RFC 2401 (ref. '13') (Obsoleted by RFC 4301) -- No information found for draft-issll-dclass - is the name correct? -- Possible downref: Normative reference to a draft: ref. '14' -- No information found for draft-ietf-issll-aggregation - is the name correct? -- Possible downref: Normative reference to a draft: ref. '15' -- Possible downref: Normative reference to a draft: ref. '18' Summary: 12 errors (**), 0 flaws (~~), 7 warnings (==), 11 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Y. Bernet, Microsoft 2 R. Yavatkar, Intel 3 P. Ford, Microsoft 4 F. Baker, Cisco 5 L. Zhang, UCLA 6 M. Speer, Sun Microsystems 7 R. Braden, ISI 8 B. Davie, Cisco 9 John Wroclawski, MIT LCS 10 E. Felstaine, Allot Communications 11 Internet Draft 12 Expires: March, 2000 13 Document: draft-ietf-issll-diffserv-rsvp-03.txt September, 1999 15 A Framework For Integrated Services Operation Over Diffserv Networks 17 Status of this Memo 19 This document is an Internet-Draft and is in full conformance with 20 all provisions of Section 10 of RFC2026. Internet-Drafts are 21 Working documents of the Internet Engineering Task Force (IETF), its 22 areas, and its working groups. Note that other groups may also 23 distribute working documents as Internet-Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six 26 months and may be updated, replaced, or obsoleted by other documents 27 at any time. It is inappropriate to use Internet- Drafts as 28 reference material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html. 36 Copyright Notice 38 Copyright (C) The Internet Society (1999). All Rights Reserved. 40 1. Abstract 42 The Integrated Services architecture provides a means for the 43 delivery of end-to-end QoS to applications over heterogeneous 44 networks. To support this end-to-end model, the Intserv architecture 45 must be supported over a wide variety of different types of network 46 elements. In this context, a network that supports Differentiated 47 Services (Diffserv) may be viewed as a network element in the total 48 end-to-end path. This document describes a framework by which 49 Integrated Services may be supported over Diffserv networks. 51 Bernet, ed. et al. 1 53 Integrated Services Operation Over Diffserv Networks June, 1999 55 2. Introduction 57 Work on QoS-enabled IP networks has led to two distinct approaches: 58 the Integrated Services architecture (Intserv)[10] and its 59 accompanying signaling protocol, RSVP [1], and the Differentiated 60 Services architecture (Diffserv)[8]. This document describes ways in 61 which a Diffserv network can be used in the context of the Intserv 62 architecture to support the delivery of end-to-end QOS. 64 2.1 Integrated Services Architecture 66 The integrated services architecture defined a set of extensions to 67 the traditional best effort model of the Internet with the goal of 68 allowing end-to-end QOS to be provided to applications. One of the 69 key components of the architecture is a set of service definitions; 70 the current set of services consists of the controlled load and 71 guaranteed services. The architecture assumes that some explicit 72 setup mechanism is used to convey information to routers so that 73 they can provide requested services to flows that require them. 74 While RSVP is the most widely known example of such a setup 75 mechanism, the Intserv architecture is designed to accommodate other 76 mechanisms. 78 Intserv services are implemented by _network elements_. While it is 79 common for network elements to be individual nodes such as routers 80 or links, more complex entities, such as ATM _clouds_ or 802.3 81 networks may also function as network elements. As discussed in more 82 detail below, a Diffserv network (or _cloud_) may be viewed as a 83 network element within a larger Intserv network. 85 2.3 RSVP 87 RSVP is a signaling protocol that applications may use to request 88 resources from the network. The network responds by explicitly 89 admitting or rejecting RSVP requests. Certain applications that have 90 quantifiable resource requirements express these requirements using 91 Intserv parameters as defined in the appropriate Intserv service 92 specification. As noted above, RSVP and Intserv are separable. RSVP 93 is a signaling protocol which may carry Intserv information. Intserv 94 defines the models for expressing service types, quantifying 95 resource requirements and for determining the availability of the 96 requested resources at relevant network elements (admission 97 control). 99 The current prevailing model of RSVP usage is based on a combined 100 RSVP/Intserv architecture. In this model, RSVP signals per-flow 101 resource requirements to network elements, using Intserv parameters. 102 These network elements apply Intserv admission control to signaled 103 requests. In addition, traffic control mechanisms on the network 104 element are configured to ensure that each admitted flow receives 105 the service requested in strict isolation from other traffic. To 107 Bernet, ed. et al. 2 109 Integrated Services Operation Over Diffserv Networks June, 1999 111 this end, RSVP signaling configures microflow (MF) [8] packet 112 classifiers in Intserv capable routers along the path of the traffic 113 flow. These classifiers enable per-flow classification of packets 114 based on IP addresses and port numbers. 116 The following factors have impeded deployment of RSVP (and the 117 Intserv architecture) in the Internet at large: 119 1. The use of per-flow state and per-flow processing raises 120 scalability concerns for large networks. 122 2. Only a small number of hosts currently generate RSVP signaling. 123 While this number is expected to grow dramatically, many 124 applications may never generate RSVP signaling. 126 3. The necessary policy control mechanisms -- access control, 127 authentication, and accounting _- have only recently become 128 available [17]. 130 2.4 Diffserv 132 The market is pushing for immediate deployment of a QoS solution 133 that addresses the needs of the Internet as well as enterprise 134 networks. This push led to the development of Diffserv. In contrast 135 to the per-flow orientation of RSVP, Diffserv networks classify 136 packets into one of a small number of aggregated flows or 'classes', 137 based on the Diffserv codepoint (DSCP) in the packet's IP header. 138 This is known as behavior aggregate (BA) classification [8]. At each 139 Diffserv router, packets are subjected to a 'per-hop behavior' 140 (PHB), which is invoked by the DSCP. The primary benefit of Diffserv 141 is its scalability. Diffserv eliminates the need for per-flow state 142 and per-flow processing and therefore scales well to large networks. 144 2.5 Roles of Intserv, RSVP and Diffserv 146 We view Intserv, RSVP and Diffserv as complementary technologies in 147 the pursuit of end-to-end QoS. Together, these mechanisms can 148 facilitate deployment of applications such as IP-telephony, video- 149 on-demand, and various non-multimedia mission-critical applications. 150 Intserv enables hosts to request per-flow, quantifiable resources, 151 along end-to-end data paths and to obtain feedback regarding 152 admissibility of these requests. Diffserv enables scalability across 153 large networks. 155 2.6 Components of Intserv, RSVP and Diffserv 157 Before proceeding, it is helpful to identify the following 158 components of the QoS technologies described: 160 RSVP signaling - This term refers to the standard RSVP signaling 161 protocol. RSVP signaling is used by hosts to signal application 162 resource requirements to the network (and to each other). Network 164 Bernet, ed. et al. 3 166 Integrated Services Operation Over Diffserv Networks June, 1999 168 elements use RSVP signaling to return an admission control decision 169 to hosts. RSVP signaling may or may not carry Intserv parameters. 170 Admission control at a network element may or may not be based on 171 the Intserv model. 173 MF traffic control - This term refers to traffic control which is 174 applied independently to individual traffic flows and therefore 175 requires recognizing individual traffic flows via MF classification. 177 Aggregate traffic control - This term refers to traffic control 178 which is applied collectively to sets of traffic flows. These sets 179 of traffic flows are recognized based on BA (DSCP) classification. 180 In this draft, we use the terms 'aggregate traffic control' and 181 'Diffserv' interchangeably. 183 Aggregate RSVP. While the existing definition of RSVP supports only 184 per-flow reservations, extensions to RSVP are being developed to 185 enable RSVP reservations to be made for aggregated traffic, i.e. 186 sets of flows that may be recognized by BA classification. This use 187 of RSVP may be useful in controlling the allocation of bandwidth in 188 Diffserv networks. 190 Per-flow RSVP. The conventional usage of RSVP to perform resource 191 reservations for individual microflows. 193 RSVP/Intserv - This term is used to refer to the prevailing model of 194 RSVP usage which includes RSVP signaling with Intserv parameters, 195 Intserv admission control and per-flow traffic control at network 196 elements. 198 Diffserv Region. A set of contiguous routers which support BA 199 classification and traffic control. While such a region may also 200 support MF classification, the goal of this document is to describe 201 how such a region may be used in delivery of end-to-end QOS when 202 only BA classification is performed inside the Diffserv region. 204 Non-Diffserv Region. The portions of the network outside the 205 Diffserv region. Such a region may also offer a variety of different 206 types of classification and traffic control. 208 Note that, for the purposes of this document, the defining features 209 of a Diffserv region is the type of classification and traffic 210 control that is used for the delivery of end-to-end QOS for a 211 particular application. Thus, while it may not be possible to 212 identify a certain region as _purely Diffserv_ with respect to all 213 traffic flowing through the region, it is possible to define it in 214 this way from the perspective of the treatment of traffic from a 215 single application. 217 2.7 The Framework 219 Bernet, ed. et al. 4 221 Integrated Services Operation Over Diffserv Networks June, 1999 223 In the framework we present, end-to-end, quantitative QoS is 224 provided by applying the Intserv model end-to-end across a network 225 containing one or more Diffserv regions. The Diffserv regions may, 226 but are not required to, participate in end-to-end RSVP signaling 227 for the purpose of optimizing resource allocation and supporting 228 admission control. 230 From the perspective of Intserv, Diffserv regions of the network are 231 treated as virtual links connecting Intserv capable routers or hosts 232 (much as an 802.1p network region is treated as a virtual link in 233 [5]). Within the Diffserv regions of the network routers implement 234 specific PHBs (aggregate traffic control). The total amount of 235 traffic that is admitted into the Diffserv region that will receive 236 a certain PHB may be limited by policing at the edge. As a result 237 we expect that the Diffserv regions of the network will be able to 238 support the Intserv style services requested from the periphery. 239 In our framework, we address the support of end-to-end Integrated 240 Services over the Diffserv regions of the network. Our goal is to 241 enable seamless inter-operation. As a result, the network 242 administrator is free to choose which regions of the network act as 243 Diffserv regions. In one extreme the Diffserv region is pushed all 244 the way to the periphery, with hosts alone having full Intserv 245 capability. In the other extreme, Intserv is pushed all the way to 246 the core, with no Diffserv region. 248 2.8 Contents 250 In section 3 we discuss the benefits that can be realized by using 251 the aggregate traffic control provided by Diffserv network regions 252 in the broader context of the Intserv architecture. In section 4, we 253 present the framework and the reference network. Section 5 details 254 two possible realizations of the framework. Section 6 discusses the 255 implications of the framework for Diffserv. Section 7 presents some 256 issues specific to multicast flows. 258 3. Benefits of Using Intserv with Diffserv 260 The primary benefit of Diffserv aggregate traffic control is its 261 scalability. In this section, we discuss the benefits that 262 interoperation with Intserv can bring to a Diffserv network region. 263 Note that this discussion is in the context of servicing 264 quantitative QoS applications specifically. By this we mean those 265 applications that are able to quantify their traffic and QoS 266 requirements. 268 3.1 Resource Based Admission Control 270 In Intserv networks, quantitative QoS applications use an explicit 271 setup mechanism (e.g. RSVP) to request resources from the network. 272 The network may accept or reject these requests in response. This is 273 'explicit admission control'. Explicit admission control helps to 274 assure that network resources are optimally used. To further 276 Bernet, ed. et al. 5 278 Integrated Services Operation Over Diffserv Networks June, 1999 280 understand this issue, consider a Diffserv network region providing 281 only aggregate traffic control with no signaling. In the Diffserv 282 network region, admission control is applied implicitly by 283 provisioning policing parameters at network elements. For example, a 284 network element at the ingress to a Diffserv network region could be 285 provisioned to accept only 50 Kbps of traffic for the EF DSCP. 287 While such implicit admission control does protect the network to 288 some degree, it can be quite ineffective. For example, consider that 289 there may be 10 IP telephony sessions originating outside the 290 Diffserv network region, each requiring 10 Kbps of EF service from 291 the Diffserv network region. Since the network element protecting 292 the Diffserv network region is provisioned to accept only 50 Kbps of 293 traffic for the EF DSCP, it will discard half the offered traffic. 294 This traffic will be discarded from the aggregation of traffic 295 marked EF, with no regard to the microflow from which it originated. 296 As a result, it is likely that of the ten IP telephony sessions, 297 none will obtain satisfactory service when in fact, there are 298 sufficient resources available in the Diffserv network region to 299 satisfy five sessions. 301 In the case of explicit admission control, the network will signal 302 rejection in response to requests for resources that would exceed 303 the 50 Kbps limit. As a result, upstream network elements (including 304 originating hosts) and applications will have the information they 305 require to take corrective action. The application might respond by 306 refraining from transmitting, or by requesting admission for a 307 lesser traffic profile. The host operating system might respond by 308 marking the application's traffic for the DSCP that corresponds to 309 best-effort service. Upstream network elements might respond by re- 310 marking packets on the rejected flow to a lower service level. In 311 some cases, it may be possible to reroute traffic over alternate 312 paths or even alternate networks (e.g. the PSTN for voice calls). In 313 any case, the integrity of those flows that were admitted would be 314 preserved, at the expense of the flows that were not admitted. Thus, 315 by appointing an Intserv-conversant admission control agent for the 316 Diffserv region of the network it is possible to enhance the service 317 that the network can provide to quantitative QoS applications. 319 3.2 Policy Based Admission Control 321 In network regions where RSVP is used, resource requests can be 322 intercepted by RSVP-aware network elements and can be reviewed 323 against policies stored in policy databases. These resource requests 324 securely identify the user and the application for which the 325 resources are requested. Consequently, the network element is able 326 to consider per-user and/or per-application policy when deciding 327 whether or not to admit a resource request. So, in addition to 328 optimizing the use of resources in a Diffserv network region (as 329 discussed in 3.1) RSVP conversant admission control agents can be 330 used to apply specific customer policies in determining the specific 331 customer traffic flows entitled to use the Diffserv network region's 333 Bernet, ed. et al. 6 335 Integrated Services Operation Over Diffserv Networks June, 1999 337 resources. Customer policies can be used to allocate resources to 338 specific users and/or applications. 340 By comparison, in Diffserv network regions without RSVP signaling, 341 policies are typically applied based on the Diffserv customer 342 network from which traffic originates, not on the originating user 343 or application within the customer network. 345 3.3 Assistance in Traffic Identification/Classification 347 Within Diffserv network regions, traffic is allotted service based 348 on the DSCP marked in each packet's IP header. Thus, in order to 349 obtain a particular level of service within the Diffserv network 350 region, it is necessary to effect the marking of the correct DSCP in 351 packet headers. There are two mechanisms for doing so, host marking 352 and router marking. In the case of host marking, the host operating 353 system marks the DSCP in transmitted packets. In the case of router 354 marking, routers in the network are configured to identify specific 355 traffic (typically based on MF classification) and to mark the DSCP 356 as packets transit the router. There are advantages and 357 disadvantages to each scheme. Regardless of the scheme used, 358 explicit signaling offers significant benefits. 360 3.3.1 Host Marking 362 In the case of host marking, the host operating system marks the 363 DSCP in transmitted packets. This approach has the benefit of 364 shifting per-flow classification and marking to the edge of the 365 network, where it scales best. It also enables the host to make 366 decisions regarding the mark that is appropriate for each 367 transmitted packet and hence the relative importance attached to 368 each packet. The host is generally better equipped to make this 369 decision than the network. Furthermore, if IPSEC encryption is used, 370 the host may be the only device in the network that is able to make 371 a meaningful determination of the appropriate marking for each 372 packet. 374 Host marking requires that the host be aware of the interpretation 375 of DSCPs by the network. This information can be configured into 376 each host. However, such configuration imposes a management burden. 377 Alternatively, hosts can use an explicit signaling protocol such as 378 RSVP to query the network to obtain a suitable DSCP or set of DSCPs 379 to apply to packets for which a certain Intserv service has been 380 requested. An example of how this can be achieved is described in 381 [14]. 383 3.3.2 Router Marking 385 In the case of router marking, MF classification criteria must be 386 configured in the router. This may be done dynamically, by request 387 from the host operating system, or statically via manual 388 configuration or via automated scripts. 390 Bernet, ed. et al. 7 392 Integrated Services Operation Over Diffserv Networks June, 1999 394 There are significant difficulties in doing so statically. 395 Typically, it is desirable to allot service to traffic based on the 396 application and/or user originating the traffic. At times it is 397 possible to identify packets associated with a specific application 398 by the IP port numbers in the headers. It may also be possible to 399 identify packets originating from a specific user by the source IP 400 address. However, such classification criteria may change 401 frequently. Users may be assigned different IP addresses by DHCP. 402 Applications may use transient ports. To further complicate matters, 403 multiple users may share an IP address. These factors make it very 404 difficult to manage static configuration of the classification 405 information required to mark traffic in routers. 407 An attractive alternative to static configuration is to allow host 408 operating systems to signal classification criteria to the router on 409 behalf of users and applications. As we will show later in this 410 draft, RSVP signaling is ideally suited for this task. In addition 411 to enabling dynamic and accurate updating of MF classification 412 criteria, RSVP signaling enables classification of IPSEC [13] 413 packets (by use of the SPI) which would otherwise be unrecognizable. 415 3.4 Traffic Conditioning 417 Intserv-capable network elements are able to condition traffic at a 418 per-flow granularity, by some combination of shaping and/or 419 policing. Pre-conditioning traffic in this manner before it is 420 submitted to the Diffserv region of the network is beneficial. In 421 particular, it enhances the ability of the Diffserv region of the 422 network to provide quantitative services using aggregate traffic 423 control. 425 4. The Framework 427 In the general framework we envision an Internet in which the 428 Integrated Services architecture is used to deliver end-to-end QOS 429 to applications. The network includes some combination of Intserv 430 capable nodes (in which MF classification and per-flow traffic 431 control is applied) and Diffserv regions (in which aggregate traffic 432 control is applied). Individual routers may or may not participate 433 in RSVP signaling regardless of where in the network they reside. 435 We will consider two specific realizations of the framework. In the 436 first, resources within the Diffserv regions of the network are 437 statically provisioned and these regions include no RSVP aware 438 devices. In the second, resources within the Diffserv region of the 439 network are dynamically provisioned and select devices within the 440 Diffserv network regions participate in RSVP signaling. 442 4.1 Reference Network 444 Bernet, ed. et al. 8 446 Integrated Services Operation Over Diffserv Networks June, 1999 448 The two realizations of the framework will be discussed in the 449 context of the following reference network: 451 / \ / \ / \ 452 / \ / \ / \ 453 |---| | |---| |---| |---| |---| | |---| 454 |Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx | 455 |---| | |-- | |---| |---| |---| | |---| 456 \ / \ / \ / 457 \______ / \___ _________ / \__ _____/ 459 Non-Diffserv region Diffserv region Non-Diffserv region 461 Figure 1: Sample Network Configuration 463 The reference network includes a Diffserv region in the middle of a 464 larger network supporting Intserv end-to-end. The Diffserv region 465 contains a mesh of routers, at least some of which provide aggregate 466 traffic control. The regions outside the Diffserv region (non- 467 Diffserv regions) contain meshes of routers and attached hosts, at 468 least some of which support the Integrated Services architecture. 470 In the interest of simplicity we consider a single QoS sender, Tx 471 communicating across this network with a single QoS receiver, Rx. 472 The edge routers (ER1, ER2) which are adjacent to the Diffserv 473 region interface to the border routers (BR1, BR2) within the 474 Diffserv region. 476 From an economic viewpoint, we may consider that the Diffserv region 477 sells service to the network outside the Diffserv region, which in 478 turn provides service to hosts. Thus, we may think of the non- 479 Diffserv regions as customers of the Diffserv region. In the 480 following, we use the term 'customer' for the non-Diffserv regions. 481 Note that the boundaries of the regions may or may not align with 482 administrative domain boundaries, and that a single region might 483 contain multiple administrative domains. 485 We now define the major components of the reference network. 487 4.1.1 Hosts 489 We assume that both sending and receiving hosts use RSVP to 490 communicate the quantitative QoS requirements of QoS-aware 491 applications running on the host. In principle, other mechanisms may 492 be used to establish resource reservations in Intserv-capable nodes, 493 but RSVP is clearly the prevalent mechanism for this purpose. 495 Typically, a QoS process within the host operating system generates 496 RSVP signaling on behalf of applications. This process may also 497 invoke local traffic control. 499 Bernet, ed. et al. 9 501 Integrated Services Operation Over Diffserv Networks June, 1999 503 As discussed above, traffic control in the host may mark the DSCP in 504 transmitted packets, and shape transmitted traffic to the 505 requirements of the Intserv service in use. Alternatively, the first 506 Intserv-capable router downstream from the host may provide these 507 traffic control functions. 509 4.1.2 End-to-End RSVP Signaling 511 We assume that RSVP signaling messages travel end-to-end between 512 hosts Tx and Rx to support RSVP/Intserv reservations outside the 513 Diffserv network region. We require that these end-to-end RSVP 514 messages are at least carried across the Diffserv region. Depending 515 on the specific realization of the framework, these messages may be 516 processed by none, some or all of the routers in the Diffserv 517 region. 519 4.1.3 Edge Routers 521 ER1 and ER2 are edge routers, residing adjacent to the Diffserv 522 network regions. The functionality of the edge routers varies 523 depending on the specific realization of the framework. In the case 524 in which the Diffserv network region is RSVP unaware, edge routers 525 act as admission control agents to the Diffserv network. They 526 process signaling messages from both Tx and Rx, and apply admission 527 control based on resource availability within the Diffserv network 528 region and on customer defined policy. In the case in which the 529 Diffserv network region is RSVP aware, the edge routers apply 530 admission control based on local resource availability and on 531 customer defined policy. In this case, the border routers act as the 532 admission control agent to the Diffserv network region. 534 We will later describe the functionality of the edge routers in 535 greater depth for each of the two realizations of the framework. 537 4.1.4 Border Routers 539 BR1 and BR2 are border routers, residing in the Diffserv network 540 region. The functionality of the border routers varies depending on 541 the specific realization of the framework. In the case in which the 542 Diffserv network region is RSVP-unaware, these routers act as pure 543 Diffserv routers. As such, their sole responsibility is to police 544 submitted traffic based on the service level specified in the DSCP 545 and the agreement negotiated with the customer (aggregate traffic 546 control). In the case in which the Diffserv network region is RSVP- 547 aware, the border routers participate in RSVP signaling and act as 548 admission control agents for the Diffserv network region. 550 We will later describe the functionality of the border routers in 551 greater depth for each of the two realizations of the framework. 553 Bernet, ed. et al. 10 555 Integrated Services Operation Over Diffserv Networks June, 1999 557 4.1.5 Diffserv Network Region 559 The Diffserv network region supports aggregate traffic control and 560 is assumed not to be capable of MF classification. Depending on the 561 specific realization of the framework, some number of routers within 562 the Diffserv region may be RSVP aware and therefore capable of per- 563 flow signaling and admission control. If devices in the Diffserv 564 region are not RSVP aware, they will pass RSVP messages 565 transparently with negligible performance impact (see [6]). 567 The Diffserv network region provides two or more levels of service 568 based on the DSCP in packet headers. It may be a single 569 administrative domain or may span multiple domains. 571 4.1.5 Non-Diffserv Network Regions 573 The network outside of the Diffserv region consists of Intserv 574 capable hosts and other network elements. Other elements may include 575 routers and perhaps various types of network (e.g. 802, ATM, etc.). 576 These network elements may reasonably be assumed to support Intserv, 577 although this might not be required in the case of over- 578 provisioning. Even if these elements are not Intserv capable, we 579 assume that they will pass RSVP messages unhindered. Routers outside 580 of the Diffserv network region are not precluded from providing 581 aggregate traffic control to some subset of the traffic passing 582 through them. 584 4.2 Service Mapping 586 Intserv service requests specify an Intserv service type and a set 587 of quantitative parameters known as a 'flowspec'. At each hop in an 588 Intserv network, the Intserv service requests are interpreted in a 589 form meaningful to the specific link layer medium. For example at 590 an 802.1 hop, the Intserv parameters are mapped to an appropriate 591 802.1p priority level [5]. 593 In our framework, Diffserv regions of the network are analogous to 594 the 802.1p capable switched segments described in [5]. Requests for 595 Intserv services must be mapped onto the underlying capabilities of 596 the Diffserv network region. Aspects of the mapping include: 598 - selecting an appropriate PHB, or set of PHBs, for the requested 599 service; 600 - performing appropriate policing (including, perhaps, shaping or 601 remarking) at the edges of the Diffserv region; 602 - exporting Intserv parameters from the Diffserv region (e.g. for 603 the updating of ADSPECs); 604 - performing admission control on the Intserv requests that takes 605 into account the resource availability in the Diffserv region. 607 Bernet, ed. et al. 11 609 Integrated Services Operation Over Diffserv Networks June, 1999 611 Exactly how these functions are performed will be a function of the 612 way bandwidth is managed inside the Diffserv network region, which 613 is a topic we discuss in Section 4.3. 615 When the PHB (or set of PHBs) has been selected for a particular 616 Intserv flow, it may be necessary to communicate the choice of DSCP 617 for the flow to other network elements. Two schemes may be used to 618 achieve this end, as discussed below. 620 4.2.1 Default Mapping 622 In this scheme, there is some standard, well-known mapping from 623 Intserv service type to a DSCP that will invoke the appropriate 624 behavior in the Diffserv network. 626 4.2.2 Network Driven Mapping 628 In this scheme, RSVP conversant routers in the Diffserv network 629 region (perhaps at its edge) may override the well-known mapping 630 described in 4.2.1. In the case that DSCPs are marked at the ingress 631 to the Diffserv region, the DSCPs can simply be remarked at the 632 boundary routers. However, in the case that DSCP marking occurs 633 upstream of the Diffserv region, either in a host or a router, then 634 the appropriate mapping needs to be communicated upstream, to the 635 marking device. This may be accomplished using RSVP, as described 636 in [14]. 638 The decision regarding where to mark DSCP and whether to override 639 the well-known service mapping is a mater of policy to be decided by 640 the administrator of the Diffserv network region in cooperation with 641 the administrator of the network adjacent to the Diffserv region. 643 4.2.3 Microflow Separation 645 Boundary routers residing at the edge of the Diffserv region will 646 typically police traffic submitted from the outside the Diffserv 647 region in order to protect resources within the Diffserv region. 648 This policing will be applied on an aggregate basis, with no regard 649 for the individual microflows making up each aggregate. As a result, 650 it is possible for a misbehaving microflow to claim more than its 651 fair share of resources within the aggregate, thereby degrading the 652 service provided to other microflows. This problem may be addressed 653 by: 655 1. Providing per microflow policing at the edge routers - this is 656 generally the most appropriate location for microflow policing, 657 since it pushes per-flow work to the edges of the network, where it 658 scales better. In addition, since Intserv-capable routers outside 659 the Diffserv region are responsible for providing microflow service 660 to their customers and the Diffserv region is responsible for 661 providing aggregate service to its customers, this distribution of 662 functionality mirrors the distribution of responsibility. 664 Bernet, ed. et al. 12 666 Integrated Services Operation Over Diffserv Networks June, 1999 668 2. Providing per microflow policing at the border routers - this 669 approach tends to be less scalable than the previous approach. It 670 also imposes a management burden on the Diffserv region of the 671 network. However, it may be appropriate in certain cases, for the 672 Diffserv boundary routers to offer per microflow policing as a 673 value-add to its Intserv customers. 675 3. Relying on upstream shaping and policing - in certain cases, the 676 customer may trust the shaping of certain groups of hosts 677 sufficiently to not warrant reshaping or policing at the boundary of 678 the Diffserv region. Note that, even if the hosts are shaping 679 microflows properly, these shaped flows may become distorted as they 680 transit through the non-Diffserv region of the network. Depending on 681 the degree of distortion, it may be necessary to somewhat over- 682 provision the aggregate capacities in the Diffserv region, or to re- 683 police using either 1 or 2 above. 684 The choice of one mechanism or another is a matter of policy to be 685 decided by the administrator of the network outside the Diffserv 686 region. 688 4.3 Resource Management in Diffserv Regions 690 A variety of options exist for management of resources (e.g., 691 bandwidth) in the Diffserv network regions to meet the needs of end- 692 to-end Intserv flows. These options include: 694 - statically provisioned resources; 695 - resources dynamically provisioned by RSVP; 696 - resources dynamically provisioned by other means (e.g., a form of 697 Bandwidth Broker). 699 Some of the details of using each of these different approaches are 700 discussed in the following section. 702 5. Detailed Examples of the Operation of Intserv over Diffserv Regions 704 In this section we provide detailed examples of our framework in 705 action. We discuss two examples, one in which the Diffserv network 706 region is RSVP unaware, the other in which the Diffserv network 707 region is RSVP aware. 709 5.1 Statically Provisioned Diffserv Network Region 711 In this example, no devices in the Diffserv network region are RSVP 712 aware. The Diffserv network region is statically provisioned. The 713 customer(s) of the Diffserv network regions and the owner of the 714 Diffserv network region have negotiated a static contract (service 715 level specification, or SLS) for the transmit capacity to be 716 provided to the customer at each of a number of standard Diffserv 717 service levels. The _transmit capacity_ may be simply an amount of 719 Bernet, ed. et al. 13 721 Integrated Services Operation Over Diffserv Networks June, 1999 723 bandwidth or it could be a more complex _profile_ involving a number 724 of factors such as burst size, peak rate, time of day etc. 726 It is helpful to consider each edge router in the customer network 727 as consisting of two halves, a standard Intserv half, which 728 interfaces to the customer's network regions and a Diffserv half 729 which interfaces to the Diffserv network region. The Intserv half is 730 able to identify and process traffic on per-flow granularity. 732 The Diffserv half of the router can be considered to consist of a 733 number of virtual transmit interfaces, one for each Diffserv service 734 level negotiated in the SLS. The router contains a table that 735 indicates the transmit capacity provisioned, per the SLS at each 736 Diffserv service level. This table, in conjunction with the default 737 mapping described in 4.2.1, is used to perform admission control 738 decisions on Intserv flows which cross the Diffserv network region. 740 5.1.1 Sequence of Events in Obtaining End-to-end QoS 742 The following sequence illustrates the process by which an 743 application obtains end-to-end QoS when RSVP is used by the hosts. 745 1. The QoS process on the sending host Tx generates an RSVP PATH 746 message that describes the traffic offered by the sending 747 application. 749 2. The PATH message is carried toward the receiving host, Rx. In the 750 network region to which the sender is attached, standard 751 RSVP/Intserv processing is applied at capable network elements. 753 3. At the edge router ER1, the PATH message is subjected to standard 754 RSVP processing and PATH state is installed in the router. The PATH 755 message is sent onward to the Diffserv network region. 757 4. The PATH message is ignored by routers in the Diffserv network 758 region and then processed at ER2 according to standard RSVP 759 processing rules. 761 5. When the PATH message reaches the receiving host Rx, the 762 operating system generates an RSVP RESV message, indicating interest 763 in offered traffic of a certain Intserv service type. 765 6. The RESV message is carried back towards the Diffserv network 766 region and the sending host. Consistent with standard RSVP/Intserv 767 processing, it may be rejected at any RSVP-capable node in the path 768 if resources are deemed insufficient to carry the traffic requested. 770 7. At ER2, the RESV message is subjected to standard RSVP/Intserv 771 processing. It may be rejected if resources on the downstream 772 interface of ER2 are deemed insufficient to carry the resources 773 requested. If it is not rejected, it will be carried transparently 774 through the Diffserv network region, arriving at ER1. 776 Bernet, ed. et al. 14 778 Integrated Services Operation Over Diffserv Networks June, 1999 780 8. In ER1, the RESV message triggers admission control processing. 781 ER1 compares the resources requested in the RSVP/Intserv request to 782 the resources available in the Diffserv network region at the 783 corresponding Diffserv service level. The corresponding service 784 level is determined by the Intserv to Diffserv mapping discussed 785 previously. The availability of resources is determined by the 786 capacity provisioned in the SLS. ER1 may also apply a policy 787 decision such that the resource request may be rejected based on the 788 customer's specific policy criteria, even though the aggregate 789 resources are determined to be available per the SLS. 791 9. If ER1 approves the request, the RESV message is admitted and is 792 allowed to continue upstream towards the sender. If it rejects the 793 request, the RESV is not forwarded and the appropriate RSVP error 794 messages are sent. If the request is approved, ER1 updates its 795 internal tables to indicate the reduced capacity available at the 796 admitted service level on its transmit interface. 798 10. The RESV message proceeds through the network region to which 799 the sender is attached. Any RSVP node in this region may reject the 800 reservation request due to inadequate resources or policy. If the 801 request is not rejected, the RESV message will arrive at the sending 802 host, Tx. 804 11. At Tx, the QoS process receives the RESV message. It interprets 805 receipt of the message as indication that the specified traffic flow 806 has been admitted for the specified Intserv service type (in the 807 Intserv-capable nodes). It may also learn the appropriate DSCP 808 marking to apply to packets for this flow from information provided 809 in the RESV. 811 12. Tx may mark the DSCP in the headers of packets that are 812 transmitted on the admitted traffic flow. The DSCP may be the 813 default value which maps to the Intserv service type specified in 814 the admitted RESV message, or it may be a value explicitly provided 815 in the RESV. 817 In this manner, we obtain end-to-end QoS through a combination of 818 networks that support RSVP/Intserv and networks that support 819 Diffserv. 821 5.2 RSVP-Aware Diffserv Network Region 823 In this example, the customer's edge routers are standard RSVP 824 routers. The border router, BR1 is RSVP aware. In addition, there 825 may be other routers within the Diffserv network region which are 826 RSVP aware. Note that although these routers are able to participate 827 in some form of RSVP signaling, they classify and schedule traffic 828 in aggregate, based on DSCP, not on the per-flow classification 829 criteria used by standard RSVP/Intserv routers. It can be said that 830 their control-plane is RSVP while their data-plane is Diffserv. This 832 Bernet, ed. et al. 15 834 Integrated Services Operation Over Diffserv Networks June, 1999 836 approach exploits the benefits of RSVP signaling while maintaining 837 much of the scalability associated with Diffserv. 839 In the preceding example, there is no signaling between the Diffserv 840 network region and network elements outside it. The negotiation of 841 an SLS is the only explicit exchange of resource availability 842 information between the two network regions. ER1 is configured with 843 the information represented by the SLS and as such, is able to act 844 as an admission control agent for the Diffserv network region. Such 845 configuration does not readily support dynamically changing SLSs, 846 since ER1 requires reconfiguration each time the SLS changes. It is 847 also difficult to make efficient use of the resources in the 848 Diffserv network region. This is because admission control does not 849 consider the availability of resources in the Diffserv network 850 region along the specific path that would be impacted. 852 By contrast, when the Diffserv network region is RSVP aware, the 853 admission control agent is part of the Diffserv network. As a 854 result, changes in the capacity available in the Diffserv network 855 region can be indicated to the Intserv-capable nodes outside the 856 Diffserv region via RSVP. By including routers interior to the 857 Diffserv network region in RSVP signaling, it is possible to 858 simultaneously improve the efficiency of resource usage within the 859 Diffserv region and to improve the level of confidence that the 860 resources requested at admission control are indeed available at 861 this particular point in time. This is because admission control can 862 be linked to the availability of resources along the specific path 863 that would be impacted. We refer to this benefit of RSVP signaling 864 as 'topology aware admission control'. A further benefit of 865 supporting RSVP signaling within the Diffserv network region is that 866 it is possible to effect changes in the provisioning of the Diffserv 867 network region (e.g., allocating more or less bandwidth to the EF 868 queue in a router) in response to resource requests from outside of 869 the Diffserv region. 871 Various mechanisms may be used within the Diffserv network region to 872 support dynamic provisioning and topology aware admission control. 873 These include aggregated RSVP, per-flow RSVP and bandwidth brokers, 874 as described in the following paragraphs. 876 5.2.1 Aggregated or Tunneled RSVP 878 A number of drafts [3,6,15, 16] propose mechanisms for extending 879 RSVP to reserve resources for an aggregation of flows between edges 880 of a network. Border routers may interact with core routers and 881 other border routers using aggregated RSVP to reserve resources 882 between edges of the Diffserv network region. Initial reservation 883 levels for each service level may be established between major 884 border routers, based on anticipated traffic patterns. Border 885 routers could trigger changes in reservation levels as a result of 886 the cumulative per-flow RSVP requests from the non-Diffserv regions 887 reaching high or low-water marks. 889 Bernet, ed. et al. 16 891 Integrated Services Operation Over Diffserv Networks June, 1999 893 In this approach, admission of per-flow RSVP requests from nods 894 outside the Diffserv region would be counted against the appropriate 895 aggregate reservations for the corresponding service level. The size 896 of the aggregate reservations may or may not be dynamically adjusted 897 to deal with the changes in per-flow reservations. 899 The advantage of this approach is that it offers dynamic, topology 900 aware admission control to the Diffserv network region without 901 requiring the level of RSVP signaling processing that would be 902 required to support per-flow RSVP. 904 We note that resource management of a Diffserv region using 905 aggregated RSVP is most likely to be feasible only within a single 906 administrative domain, as each domain will probably choose its own 907 mechanism to manage its resources. 909 5.2.3 Per-flow RSVP 911 In this approach, described in [3], routers in the Diffserv network 912 region respond to the standard per-flow RSVP signaling originating 913 from the Intserv-capable nodes outside the Diffserv region. This 914 approach provides the benefits of the previous approach (dynamic, 915 topology aware admission control) without requiring aggregated RSVP 916 support. Resources are also used more efficiently as a result of the 917 per-flow admission control. However, the demands on RSVP signaling 918 resources within the Diffserv network region may be significantly 919 higher than in an aggregated RSVP approach. 921 Note that per-flow RSVP and aggregated RSVP are not mutually 922 exclusive in a single Diffserv region. It is possible to use per- 923 flow RSVP at the edges of the Diffserv region and aggregation only 924 in some _core_ region within the Diffserv region. 926 5.2.4 Granularity of Deployment of RSVP Aware Routers 928 In 5.2.2 and 5.2.3 some subset of the routers within the Diffserv 929 network is RSVP signaling aware (though traffic control is 930 aggregated as opposed to per-flow). The relative number of routers 931 in the core that participate in RSVP signaling is a provisioning 932 decision that must be made by the network administrator. 934 In one extreme case, only the border routers participate in RSVP 935 signaling. In this case, either the Diffserv network region must be 936 extremely over-provisioned and therefore, inefficiently used, or 937 else it must be carefully and statically provisioned for limited 938 traffic patterns. The border routers must enforce these patterns. 940 In the other extreme case, each router in the Diffserv network 941 region might participate in RSVP signaling. In this case, resources 942 can be used with optimal efficiency, but signaling processing 943 requirements and associated overhead increase. As noted above, RSVP 945 Bernet, ed. et al. 17 947 Integrated Services Operation Over Diffserv Networks June, 1999 949 aggregation is one way to limit the signaling overhead at the cost 950 of some loss of optimality in resource utilization. 952 It is likely that some network administrators will compromise by 953 enabling RSVP signaling on some subset of routers in the Diffserv 954 network region. These routers will likely represent major traffic 955 switching points with over-provisioned or statically provisioned 956 regions of RSVP unaware routers between them. 958 5.3 Dynamically Provisioned, Non-RSVP-aware Diffserv Region 960 Border routers might not use any form of RSVP signaling within the 961 Diffserv network region but might instead use custom protocols to 962 interact with an 'oracle'. The oracle is a hypothetical agent that 963 has sufficient knowledge of resource availability and network 964 topology to make admission control decisions. The set of RSVP aware 965 routers in the previous two examples can be considered collectively 966 as a form of distributed oracle. In various definitions of the 967 'bandwidth broker' [4], it is able to act as a centralized oracle. 969 6. Implications of the Framework for Diffserv Network Regions 971 We have described a framework in which RSVP/Intserv style QoS can be 972 provided across end-to-end paths that include Diffserv network 973 regions. This section discusses some of the implications of this 974 framework for the Diffserv network region. 976 6.1 Requirements from Diffserv Network Regions 978 A Diffserv network region must meet the following requirements in 979 order for it to support the framework described in this draft. 981 1. A Diffserv network region must be able to provide support for the 982 standard Intserv QoS services between its border routers. It must be 983 possible to invoke these services by use of standard PHBs within the 984 Diffserv region and appropriate behavior at the edge of the Diffserv 985 region. 987 2. Diffserv network regions must provide admission control 988 information to their _customer_ (non-Diffserv) network regions. 989 This information can be provided by a dynamic protocol or through 990 static service level agreements enforced at the edges of the 991 Diffserv region. 993 3. Diffserv network regions must be able to pass RSVP messages, in 994 such a manner that they can be recovered at the egress of the 995 Diffserv network region. The Diffserv network region may, but is not 996 required to, process these messages. Mechanisms for transparently 997 carrying RSVP messages across a transit network are described in 998 [3,6,15, 16]. 1000 Bernet, ed. et al. 18 1002 Integrated Services Operation Over Diffserv Networks June, 1999 1004 To meet these requirements, additional work is required in the areas 1005 of: 1007 1. Mapping Intserv style service specifications to services that can 1008 be provided by Diffserv network regions. 1009 2. Definition of the functionality required in network elements to 1010 support RSVP signaling with aggregate traffic control (for network 1011 elements residing in the Diffserv network region). 1012 3. Definition of mechanisms to efficiently and dynamically provision 1013 resources in a Diffserv network region (e.g. aggregated RSVP, 1014 tunneling, MPLS, etc.). This might include protocols by which an 1015 _oracle_ conveys information about resource availability within a 1016 Diffserv region to border routers. 1018 6.2 Protection of Intserv Traffic from Other Traffic 1020 Network administrators must be able to share resources in the 1021 Diffserv network region between three types of traffic: 1023 a. End-to-end Intserv traffic - this is typically traffic 1024 associated with quantitative QoS applications. It requires a 1025 specific quantity of resources with a high degree of assurance. 1027 b. Non-Intserv traffic. The Diffserv region may allocate resources 1028 to traffic that does not make use of Intserv techniques to quantify 1029 its requirements, e.g. through the use of static provisioning and 1030 SLSs enforced at the edges of the region. Such traffic might be 1031 associated with applications whose QoS requirements are not readily 1032 quantifiable but which require a 'better than best-effort' level of 1033 service. 1035 c. All other (best-effort) traffic 1037 These three classes of traffic must be isolated from each other by 1038 the appropriate configuration of policers and classifiers at ingress 1039 points to the Diffserv network region, and by appropriate 1040 provisioning within the Diffserv network region. To provide 1041 protection for Intserv traffic in Diffserv regions of the network, 1042 we suggest that the DSCPs assigned to such traffic not overlap with 1043 the DSCPs assigned to other traffic. 1045 7. Multicast 1046 The use of integrated services over Diffserv networks is 1047 significantly more complex for multicast sessions than for unicast 1048 sessions. With respect to a multicast connection, each participating 1049 region has a single ingress router and zero, one or several egress 1050 routers. The difficulties of multicast are associated with Diffserv 1051 regions that contain several egress routers. (Support of multicast 1052 functionality outside the Diffserv region is relatively 1053 straightforward since every Intserv-capable router along the 1054 multicast tree stores state for each flow.) 1056 Bernet, ed. et al. 19 1058 Integrated Services Operation Over Diffserv Networks June, 1999 1060 Consider the following reference network: 1062 Non-Diffserv region 2 1063 ________ 1064 / \ 1065 | | |---| 1066 ________ _____________ | |-|Rx1| 1067 / \ / |--\ |---| | |---| 1068 / \ / /|BR2\-----\ER2| / 1069 |---| | |---| |---| |--|/ |---| \--|____/ 1070 |Tx |-| |ER1|---|BR1|--|RR| | ________ 1071 |---| | |-- | |---| |--|\ |---| /--| \ 1072 \ / \ \|BR3/-----|ER3| | |---| 1073 \________/ \__________|--/ |---| |-|Rx2| 1074 | | |---| 1075 Non-Diffserv region 1 Diffserv region \ / 1076 \______/ 1078 Non-Diffserv region 3 1080 Figure 2: Sample Multicast Network Configuration 1082 The reference network is similar to that of Figure 1. However, in 1083 Figure 2, copies of the packets sent by Tx are delivered to several 1084 receivers outside of the Diffserv region, namely to Rx1 and Rx2. 1085 Moreover, packets are copied within the Diffserv region in a _branch 1086 point_ router RR. In the reference network BR1 is the ingress router 1087 to the Diffserv region whereas BR2 and BR3 are the egress routers. 1089 In the simplest case the receivers, Rx1 and Rx2 in the reference 1090 network, require identical reservations. The Diffserv framework [18] 1091 supports service level specifications (SLS) from an ingress router 1092 to one, some or all of the egress routers. This calls for a _one to 1093 many_ SLS within the Diffserv region, from BR1 to BR2 and BR3. Given 1094 that the SLS is granted by the Diffserv region, the ingress router 1095 BR1, or perhaps an upstream node such as ER1, marks packets entering 1096 the Diffserv region with the appropriate DSCP. The packets are 1097 routed to the egresses of the Diffserv domain using the original 1098 multicast address. 1100 The two major problems, explained in the following, are associated 1101 with heterogeneous multicast trees containing branch points within 1102 the Diffserv region, i.e. multicast trees where the level of 1103 resource requirement is not uniform among all receivers. An example 1104 of such a scenario in the network of Figure 2 is the case where both 1105 Rx1 and Rx2 need to receive multicast data from Tx1 but only one of 1106 the receivers has requested a level of service above best effort. We 1107 consider such scenarios in the following paragraphs. 1109 7.1 Remarking of packets in branch point routers 1111 Bernet, ed. et al. 20 1113 Integrated Services Operation Over Diffserv Networks June, 1999 1115 In the above scenario, the packets that arrive at BR1 are marked 1116 with an appropriate DSCP for the requested Intserv service and are 1117 sent to RR. Packets arriving at the branch point must be sent 1118 towards BR2 with the same DSCP otherwise the service to Rx1 is 1119 degraded. However, the packets going from RR towards BR3 need not 1120 maintain the high assurance level anymore. They may be demoted to 1121 best effort so that the QoS provided to other packets along this 1122 branch of the tree is not disrupted. Several problems can be 1123 observed in the given scenario: 1125 - In the Diffserv region, DSCP marking is done at edge routers 1126 (ingress), whereas a branch point router might be a core 1127 router, which does not mark packets. 1129 - Being a core Diffserv router, RR classifies based on 1130 aggregate traffic streams (BA) _ as opposed to per flow (MF) 1131 classification. Hence, it does not necessarily have the 1132 capability to distinguish those packets which belong to a 1133 specific multicast tree and require demotion from the other 1134 packets in the behavior aggregate, which carry the same DSCP. 1136 - Since RR may be RSVP-unaware, it may not participate in the 1137 admission control process, and would thus not store any per- 1138 flow state about the reservations for the multicast tree. 1139 Hence, even if RR were able to perform MF classification and 1140 DSCP remarking, it would not know enough about downstream 1141 reservations to remark the DSCP intelligently. 1143 These problems can be tackled by the following mechanisms: 1145 1. If some Intserv-capable routers are placed within the Diffserv 1146 region, it might be possible to administer the network topology and 1147 routing parameters so as to ensure that branch points occur only 1148 within such routers. These routers would support MF classification 1149 and remarking and hold per-flow state for the heterogeneous 1150 reservations for which they are the branch point. Note that in this 1151 case, branch point routers would have essentially the same 1152 functionality as ingress routers of an RSVP-aware Diffserv domain. 1154 2. Packets sent on the _non-reserved_ branch (from RR towards BR3) 1155 are marked with the _wrong_ DSCP; that is, they are not demoted to 1156 best effort but retain their DSCP. This in turn requires over 1157 reservation of resources along that link or runs the risk of 1158 degrading service to packets that legitimately bear the same DSCP 1159 along this path. However, it allows the Diffserv routers to remain 1160 free of per-flow state. 1162 3. A combination of mechanism 1 and 2 may be an effective 1163 compromise. In this case, there are some Intserv-capable routers in 1164 the core of the network, but the network cannot be administered so 1165 that ALL branch points fall at such routers. 1167 Bernet, ed. et al. 21 1169 Integrated Services Operation Over Diffserv Networks June, 1999 1171 4. Administrators of Diffserv regions may decide not to enable 1172 heterogeneous sub-trees in their domains. In the case of different 1173 downstream reservations, a ResvErr message would be sent according 1174 to the RSVP rules. This is similar to the approach taken for Intserv 1175 over IEEE 802 Networks [2,5]. 1177 5. In [3], a scheme was introduced whereby branch point routers in 1178 the interior of the aggregation region (i.e. the Diffserv region) 1179 keep reduced state information regarding the reservations by using 1180 measurement based admission control. Under this scheme, packets are 1181 tagged by the more knowledgeable Intserv edges routers with 1182 scheduling information that is used in place of the detailed Intserv 1183 state. If the Diffserv region and branch point routers are designed 1184 following that framework, demotion of packets becomes possible. 1186 7.2 Multicast SLSs and Heterogeneous Trees 1188 Multicast flows with heterogeneous reservations present some 1189 challenges in the area of SLSs. For example, a common example of an 1190 SLS is one where a certain amount of traffic is allowed to enter a 1191 Diffserv region marked with a certain DSCP, and such traffic may be 1192 destined to any egress router of that region. We call such an SLS a 1193 homogeneous, or uniform, SLS. However, in a multicast environment, a 1194 single packet that is admitted to the Diffserv region may consume 1195 resources along many paths in the region as it is replicated and 1196 forwarded towards many egress routers; alternatively, it may flow 1197 along a single path. This situation is further complicated by the 1198 possibility described above and depicted in Figure 2, in which a 1199 multicast packet might be treated as best effort along some branches 1200 while receiving some higher QOS treatment along others. We simply 1201 note here that the specification of meaningful SLSs which meet the 1202 needs of heterogeneous flows and which can be met be providers is 1203 likely to be challenging. 1205 Dynamic SLSs may help to address these issues. For example, by using 1206 RSVP to signal the resources that are required along different 1207 branches of a multicast tree, it may be possible to more closely 1208 approach the goal of allocating appropriate resources only where 1209 they are needed rather than overprovisioning or underprovisioning 1210 along certain branches of a tree. This is essentially the approach 1211 described in [15]. 1213 8. Security Considerations 1215 8.1 General RSVP Security 1217 We are proposing that RSVP signaling be used to obtain resources in 1218 both Diffserv and non-Diffserv regions of a network. Therefore, all 1219 RSVP security considerations apply [9]. In addition, network 1221 Bernet, ed. et al. 22 1223 Integrated Services Operation Over Diffserv Networks June, 1999 1225 administrators are expected to protect network resources by 1226 configuring secure policers at interfaces with untrusted customers. 1228 8.2 Host Marking 1230 Though it does not mandate host marking of the DSCP, our proposal 1231 does allow it. Allowing hosts to set the DSCP directly may alarm 1232 network administrators. The obvious concern is that hosts may 1233 attempt to 'steal' resources. In fact, hosts may attempt to exceed 1234 negotiated capacity in Diffserv network regions at a particular 1235 service level regardless of whether they invoke this service level 1236 directly (by setting the DSCP) or indirectly (by submitting traffic 1237 that classifies in an intermediate marking router to a particular 1238 DSCP). 1240 In either case, it will generally be necessary for each Diffserv 1241 network region to protect its resources by policing to assure that 1242 customers do not use more resources than they are entitled to, at 1243 each service level (DSCP). The exception to this rule is when the 1244 host is known to be trusted, e.g. a server that is under the control 1245 of the network administrators. If an untrusted sending host does not 1246 perform DSCP marking, the boundary router (or trusted intermediate 1247 routers) must provide MF classification, mark and police. If an 1248 untrusted sending host does perform marking, the boundary router 1249 needs only to provide BA classification and to police to ensure that 1250 the customer is not exceeding the aggregate capacity negotiated for 1251 the service level. 1253 In summary, there are no additional security concerns raised by 1254 marking the DSCP at the edge of the network since Diffserv providers 1255 will have to police at their boundaries anyway. Furthermore, this 1256 approach reduces the granularity at which border routers must 1257 police, thereby pushing finer grain shaping and policing 1258 responsibility to the edges of the network, where it scales better 1259 and provides other benefits described in Section 3.3.1. The larger 1260 Diffserv network regions are thus focused on the task of protecting 1261 their networks, while the Intserv-capable nodes are focused on the 1262 task of shaping and policing their own traffic to be in compliance 1263 with their negotiated Intserv parameters. 1265 9. Acknowledgments 1267 Authors thank the following individuals for their comments that led 1268 to improvements to the previous version(s) of this draft: David 1269 Oran, Andy Veitch, Curtis Villamizer, Walter Weiss, Francois le 1270 Faucheur and Russell White. 1272 Many of the ideas in this document have been previously discussed in 1273 the original Intserv architecture document [10]. 1275 10. References 1277 Bernet, ed. et al. 23 1279 Integrated Services Operation Over Diffserv Networks June, 1999 1281 [1] Braden, R., Zhang, L., Berson, S., Herzog, S. and Jamin, S., 1282 "Resource Reservation Protocol (RSVP) Version 1 Functional 1283 Specification", RFC 2205, Proposed Standard, September 1997 1285 [2] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F. and Speer, M., 1286 "SBM (Subnet Bandwidth Manager): A Protocol For RSVP-based 1287 Admission Control Over IEEE 802 Style Networks", Internet Draft, 1288 draft-ietf-issll-is802-sbm-08.txt, May 1999 1290 [3] Berson, S. and Vincent, R., "Aggregation of Internet Integrated 1291 Services State", Internet Draft, draft-berson-rsvp-aggregation- 1292 00.txt, August 1998. 1294 [4] Nichols, K., Jacobson, V. and Zhang, L., "A Two-bit 1295 Differentiated Services Architecture for the Internet", RFC 1296 2638, July 1999. 1298 [5] Seaman, M., Smith, A., Crawley, E., and Wroclawski, J., 1299 "Integrated Service Mappings on IEEE 802 Networks", Internet 1300 Draft, draft-ietf-issll-is802-svc-mapping-04.txt, June 1999 1302 [6] Guerin, R., Blake, S. and Herzog, S., "Aggregating RSVP based 1303 QoS 1304 Requests", Internet Draft, draft-guerin-aggreg-rsvp-00.txt, 1305 November 1997. 1307 [7] Nichols, Kathleen, et al., "Definition of the Differentiated 1308 Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 1309 2474, December 1998. 1311 [8] Blake, S., et al., "An Architecture for Differentiated 1312 Services." RFC 2475, December 1998. 1314 [9] Baker, F., "RSVP Cryptographic Authentication", Internet Draft, 1315 draft-ietf-rsvp-md5-08.txt, February 1999 1317 [10] Braden, R., Clark, D. and Shenker, S., "Integrated Services in 1318 the Internet Architecture: an Overview", Internet RFC 1633, 1319 June 1994 1321 [11] Garrett, M. W., and Borden, M., "Interoperation of Controlled- 1322 Load Service and Guaranteed Service with ATM", RFC2381, August 1323 1998. 1325 [12] Weiss, Walter, Private communication, November 1998. 1327 [13] Kent, S., Atkinson, R., "Security Architecture for the Internet 1328 Protocol", RFC 2401, November 1998. 1330 [14] Bernet, Y., "Usage and Format of the DCLASS Object with RSVP 1331 Signaling", Internet Draft, draft-issll-dclass-00.txt, August 1332 1999. 1334 Bernet, ed. et al. 24 1336 Integrated Services Operation Over Diffserv Networks June, 1999 1338 [15] Baker, F., Iturralde, C., le Faucheur, F., and Davie, B. "RSVP 1339 Reservation Aggregation", Internet Draft, draft-ietf-issll- 1340 aggregation-00.txt, September 1999. 1342 [16] Terzis, A., Krawczyk, J., Wroclawski, J., Zhang, L., "RSVP 1343 Operation Over IP Tunnels", Internet Draft, draft-ietf-rsvp- 1344 tunnel-04.txt, May 1999. 1346 [17] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, D., and 1347 Sastry, A., _COPS Usage for RSVP_, Internet Draft, draft-ietf- 1348 rap-cops-rsvp-05.txt, June 1999. 1350 [18] Bernet, Y., et al., _A Framework for Differentiated Services_, 1351 Internet draft, draft-ietf-diffserv-framework-02.txt, February 1352 1999. 1354 11. Author's Addresses: 1356 Yoram Bernet 1357 Microsoft 1358 One Microsoft Way, Redmond, WA 98052 1359 Phone: (425) 936-9568 1360 Email: yoramb@microsoft.com 1362 Raj Yavatkar 1363 Intel Corporation 1364 JF3-206 2111 NE 25th. Avenue, Hillsboro, OR 97124 1365 Phone: (503) 264-9077 1366 Email: raj.yavatkar@intel.com 1368 Peter Ford 1369 Microsoft 1370 One Microsoft Way, Redmond, WA 98052 1371 Phone: (425) 703-2032 1372 Email: peterf@microsoft.com 1374 Fred Baker 1375 Cisco Systems 1376 519 Lado Drive, Santa Barbara, CA 93111 1377 Phone: (408) 526-4257 1378 Email: fred@cisco.com 1380 Lixia Zhang 1381 UCLA 1382 4531G Boelter Hall Los Angeles, CA 90095 1383 Phone: +1 310-825-2695 1384 Email: lixia@cs.ucla.edu 1386 Michael Speer 1387 Sun Microsystems 1388 901 San Antonio Road UMPK15-215 Palo Alto, CA 94303 1390 Bernet, ed. et al. 25 1392 Integrated Services Operation Over Diffserv Networks June, 1999 1394 Phone: +1 650-786-6368 1395 Email: speer@Eng.Sun.COM 1397 Bob Braden 1398 USC Information Sciences Institute 1399 4676 Admiralty Way Marina del Rey, CA 90292-6695 1400 Phone: 310-822-1511 1401 Email: braden@isi.edu 1403 Bruce Davie 1404 Cisco Systems 1405 250 Apollo Drive, Chelmsford, MA 01824 1406 Phone: (978)-244-8000 1407 Email: bsd@cisco.com 1409 Eyal Felstaine 1410 Allot Communications 1411 5 Hanagar St. 1412 Neve Ne'eman B Hod- Hasharon. 1413 45800 Israel. 1414 Phone: +972-9-7443676/ext 202 1415 Email: efelstaine@allot.com 1417 John Wroclawski 1418 MIT Laboratory for Computer Science 1419 545 Technology Sq. 1420 Cambridge, MA 02139 1421 Phone: 617-253-7885 1423 E-mail: jtw@lcs.mit.edu 1425 12. Full Copyright Statement 1427 Copyright (C) The Internet Society (1999). All Rights Reserved. 1429 This document and translations of it may be copied and furnished to 1430 others, and derivative works that comment on or otherwise explain it 1431 or assist in its implementation may be prepared, copied, published 1432 and distributed, in whole or in part, without restriction of any 1433 kind, provided that the above copyright notice and this paragraph 1434 are included on all such copies and derivative works. However, this 1435 document itself may not be modified in any way, such as by removing 1436 the copyright notice or references to the Internet Society or other 1437 Internet organizations, except as needed for the purpose of 1438 developing Internet standards in which case the procedures for 1439 copyrights defined in the Internet Standards process must be 1440 followed, or as required to translate it into languages other than 1441 English. 1443 The limited permissions granted above are perpetual and will not be 1444 revoked by the Internet Society or its successors or assigns. 1446 Bernet, ed. et al. 26 1448 Integrated Services Operation Over Diffserv Networks June, 1999 1450 This document and the information contained herein is provided on an 1451 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 1452 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 1453 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 1454 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 1455 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." 1457 This draft expires March, 2000 1459 Bernet, ed. et al. 27