Network Working Group J. Hadi Salim Internet-Draft ZNYX Networks Expires: May 12, 2008 K. Ogawa NTT Network Service Systems Laboratories November 9, 2007 SCTP based TML (Transport Mapping Layer) for ForCES protocol draft-ietf-forces-sctptml-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 12, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document defines the SCTP based TML (Transport Mapping Layer) for the ForCES protocol. It explains the rationale for choosing the SCTP (Stream Control Transmission Protocol) [RFC2960] and also describes how this TML addresses all the requirements described in [RFC3654] and the ForCES protocol [FE-PROTO] draft. Hadi Salim & Ogawa Expires May 12, 2008 [Page 1] Internet-Draft ForCES SCTP TML November 2007 Table of Contents 1. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Protocol Framework Overview . . . . . . . . . . . . . . . . . 3 3.1. The PL . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. The TML layer . . . . . . . . . . . . . . . . . . . . . . 5 3.2.1. TML Parameterization . . . . . . . . . . . . . . . . . 6 3.3. The TML-PL interface . . . . . . . . . . . . . . . . . . . 6 4. SCTP TML overview . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Introduction to SCTP . . . . . . . . . . . . . . . . . . . 7 4.2. Rationale for using SCTP for TML . . . . . . . . . . . . . 9 4.3. Meeting TML requirements . . . . . . . . . . . . . . . . . 9 4.3.1. Reliability . . . . . . . . . . . . . . . . . . . . . 10 4.3.2. Congestion control . . . . . . . . . . . . . . . . . . 10 4.3.3. Timeliness and prioritization . . . . . . . . . . . . 10 4.3.4. Addressing . . . . . . . . . . . . . . . . . . . . . . 10 4.3.5. HA . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.3.6. DOS prevention . . . . . . . . . . . . . . . . . . . . 11 4.3.7. Encapsulation . . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. Manageability Considerations . . . . . . . . . . . . . . . . . 11 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Hadi Salim & Ogawa Expires May 12, 2008 [Page 2] Internet-Draft ForCES SCTP TML November 2007 1. Definitions The following definitions are taken from [RFC3654]and [RFC3746]: ForCES Protocol -- The protocol used at the Fp reference point in the ForCES Framework in [RFC3746]. ForCES Protocol Layer (ForCES PL) -- A layer in ForCES protocol architecture that defines the ForCES protocol architecture and the state transfer mechanisms as defined in [FE-PROTO]. ForCES Protocol Transport Mapping Layer (ForCES TML) -- A layer in ForCES protocol architecture that specifically addresses the protocol message transportation issues, such as how the protocol messages are mapped to different transport media (like TCP, IP, ATM, Ethernet, etc), and how to achieve and implement reliability, multicast, ordering, etc. 2. Introduction The ForCES (Forwarding and Control Element Separation) working group in the IETF is defining the architecture and protocol for separation of control and forwarding elements in network elements such as routers. [RFC3654] and [RFC3746] respectively define architectural and protocol requirements for the communication between CE and FE. The ForCES protocol layer specification [FE-PROTO] describes the protocol semantics and workings. The ForCES protocol layer operates on top of an inter-connect hiding layer known as the TML. The relationship is illustrated in Figure 1. This document defines the SCTP based TML for the ForCES protocol layer. It also addresses all the requirements for the TML including security, reliability, etc as defined in [FE-PROTO]. 3. Protocol Framework Overview The reader is referred to the Framework document [RFC3746], and in particular sections 3 and 4, for an architectural overview and explanation of where and how the ForCES protocol fits in. There is some content overlap between the ForCES protocol draft [FE-PROTO] and this section in order to provide clarity. The ForCES layout constitutes two pieces: the PL and TML layer. This is depicted in Figure 1. Hadi Salim & Ogawa Expires May 12, 2008 [Page 3] Internet-Draft ForCES SCTP TML November 2007 +---------------------------------------------- | CE PL | +---------------------------------------------- | CE TML | +---------------------------------------------- ^ | ForCES | (i.e. Forces data + control PL | packets ) messages | over | specific | TML | encaps | and | transport | | v +------------------------------------------------ | FE TML | +------------------------------------------------ | FE PL | +------------------------------------------------ Figure 1: Message exchange between CE and FE to establish an NE association The PL layer is in charge of the ForCES protocol. Its semantics and message layout are defined in [FE-PROTO]. The TML Layer is necessary to connect two ForCES PL layers as shown in Figure 1. Both the PL and TML are standardized by the IETF. While only one PL is defined, different TMLs are expected to be standardized. The TML at each of the peers (CE and FE) is expected to be of the same definition in order to inter-operate. When transmitting, the PL delivers its messages to the TML. The TML then delivers the PL message to the destination peer TML(s) as defined by the addressing in the PL message. On reception of a message, the TML delivers the message to its destination PL layer(s). Hadi Salim & Ogawa Expires May 12, 2008 [Page 4] Internet-Draft ForCES SCTP TML November 2007 3.1. The PL The PL is common to all implementations of ForCES and is standardized by the IETF [FE-PROTO]. The PL layer is responsible for associating an FE or CE to an NE. It is also responsible for tearing down such associations. An FE uses the PL layer to throw various subscribed-to events to the CE PL layer as well as respond to various status requests issued from the CE PL. The CE configures both the FE and associated LFBs attributes using the PL layer. In addition the CE may send various requests to the FE to activate or deactivate it, reconfigure its HA parameterization, subscribe to specific events etc. 3.2. The TML layer The TML layer is responsible for transport of the PL layer messages. The TML provides the following services on behalf of the ForCES protocol: 1. Reliability As defined by RFC 3654, section 6 #6. 2. Security TML provides security services to the ForCES PL. The TML definition needs to define how the following are achieved: * Endpoint authentication of FE and CE * Message authentication * Confidentiality service 3. Congestion Control The congestion control mechanism defined by the TML should prevent the FE from being overloaded by the CE. Additionally, the circumstances under which notification is sent to the PL to notify it of congestion must be defined. 4. Uni/multi/broadcast addressing/delivery, if any If there is any mapping between PL and TML level uni/multi/ broadcast addressing it needs to be defined. 5. Transport High Availability It is expected that availability of transport links is the TML's responsibility. However, on config basis, the PL layer may wish to participate in link failover schemes and therefore the TML must allow for this. Hadi Salim & Ogawa Expires May 12, 2008 [Page 5] Internet-Draft ForCES SCTP TML November 2007 6. Encapsulations used Different types of TMLs will encapsulate the PL messages on different types of headers. The TML needs to specify the encapsulation used. 7. Prioritization The TML SHOULD will be able to handle up to 8 priority levels needed by the PL and will provide preferential treatment. The TML needs to define how this is achieved. 8. Protection against DoS attacks As described in the Requirements RFC 3654, section 6 It is expected more than one TML will be standardized. The different TMLs each could implement things differently based on capabilities of underlying media and transport. However, since each TML is standardized, interoperability is guaranteed as long as both endpoints support the same TML. 3.2.1. TML Parameterization It is expected that it should be possible to use a configuration reference point, such as the FEM or the CEM, to configure the TML. Some of the configured parameters may include: o PL ID o Connection Type and associated data. For example if a TML uses IP/TCP/UDP then parameters such as TCP and UDP ports and IP addresses need to be configured. o Number of transport connections o Connection Capability, such as bandwidth, etc. o Allowed/Supported Connection QoS policy (or Congestion Control Policy) 3.3. The TML-PL interface [TML-API] defines an interface between the PL and the TML layers. The end goal of [TML-API] is to provide a consistent top edge semantics for all TMLs to adhere to. Conforming to such an interface makes it easy to plug in different TMLs over time. It also allows for simplified TML parameterization requirement stated in Section 3.2.1. Hadi Salim & Ogawa Expires May 12, 2008 [Page 6] Internet-Draft ForCES SCTP TML November 2007 ,''''''''''''''''''''''| | | | PL Layer | | | |........ .............| ^ | | TML API | | V ,''''''''''''''''''''''`. | | | TML Layer | | | '`''''''''''''''''''''''' Figure 2: The TML-PL interface We are going to assume the existence of such an interface and not discuss it further. The reader is encouraged to read [TML-API] as a background. 4. SCTP TML overview 4.1. Introduction to SCTP SCTP [RFC2960] is an end-to-end transport protocol that is equivalent to TCP, UDP, or DCCP in many aspects. With a few exceptions, SCTP can do most of what UDP, TCP, or DCCP can achieve. SCTP as well can do most of what a combination of the other transport protocols can achieve (eg TCP and DCCP or TCP and UDP). Like TCP, it provides ordered, reliable, connection-oriented, flow- controlled, congestion controlled data exchange. Unlike TCP, it does not provide byte streaming and instead provides message boundaries. Like UDP, it can provide unreliable, unordered data exchange. Unlike UDP, it does not provide multicast support Like DCCP, it can provide unreliable, ordered, congestion controlled, connection-oriented data exchange. SCTP also provides other services that none of the 3 transport protocols mentioned above provide. These include: Hadi Salim & Ogawa Expires May 12, 2008 [Page 7] Internet-Draft ForCES SCTP TML November 2007 o Multi-homing An SCTP connection can make use of multiple destination IP addresses to communicate with its peer. o Runtime IP address binding With the SCTP ADDIP feature, a new address can be bound at runtime. This allows for migration of endpoints without restarting the association (valuable for high availability). o A range of reliability shades with congestion control SCTP offers a range of services from full reliability to none, and from full ordering to none. With SCTP, on a per message basis, the application can specify a message's time-to-live. When the expressed time expires, the message can be "skipped". o Built-in heartbeats SCTP has built-in heartbeat mechanism that validate the reachability of peer addresses. o Multi-streaming A known problem with TCP is head of line (HOL) blocking. If you have independent messages, TCP enforces ordering of such messages. Loss at the head of the messages implies delays of delivery of subsequent packets. SCTP allows for defining upto 64K independent streams over the same socket connection, which are ordered independently. o Message boundaries with reliability SCTP allows for easier message parsing (just like UDP but with reliability built in) because it establishes boundaries on a PL message basis. On a TCP stream, one would have to peek into the message to figure the boundaries. o Improved SYN DOS protection Unlike TCP, which does a 3 way connection setup handshake, SCTP does a 4 way handshake. This improves against SYN-flood attacks because listening sockets do not set up state until a connection is validated. o Simpler transport events An application (such as the TML) can subscribe to be notified of both local and remote transport events. Events such as indication of association changes, addressing changes, remote errors, expiry of timed messages, etc, are off by default and require explicit subscription. o Simplified replicasting Although SCTP does not allow for multicasting it allows for a Hadi Salim & Ogawa Expires May 12, 2008 [Page 8] Internet-Draft ForCES SCTP TML November 2007 single message from an application to be sent to multiple peers. This reduces the messaging that typically crosess different memory domains within a host. 4.2. Rationale for using SCTP for TML SCTP has all the features required to provide a robust TML. As a transport that is all-encompassing, it negates the need for having multiple transport protocols, as has been suggested so far in the other proposals for TMLs. As a result it allows for simpler coding and therefore reduces a lot of the interoperability concerns. SCTP is also very mature and widely deployed completing the equation that makes it a superior choice in comparison with other proposed TMLs. 4.3. Meeting TML requirements ,''''''''''''''''''''| | | | PL | | | |........ .+.........| | + TML API | ,''''''''''+'''''''''`. | | | TML | | | '`'''''''''+''''''''''' | + SCTP socket API | ,''''''''''+'''''''''`. | | | SCTP | | (over IP) | | | '`''''''''''''''''''''' Figure 3: The TML-SCTP interface Hadi Salim & Ogawa Expires May 12, 2008 [Page 9] Internet-Draft ForCES SCTP TML November 2007 Figure 3 above shows the interfacing between the TML and SCTP. There is only one socket connection open with two streams used. The first stream which is high priority will be dedicated for configuration data and the second lower priority stream is used for data path redirect. The TML will use information passed by the TML API to select which of the two streams to use when sending. The TML will also subscribe to events from SCTP associated with the two streams. 4.3.1. Reliability As mentioned earlier, a shade of reliability ranges is possible in SCTP. Therefore this requirement is met. Redirected control traffic in ForCES is not expected to be reliably delivered but MUST at the same time be congestion aware. This requirement is also met by SCTP. 4.3.2. Congestion control Congestion control is built into SCTP. Therefore, this requirement is met. 4.3.3. Timeliness and prioritization By using multiple streams in conjunction with the partial-reliability feature, both timeliness and prioritization can be achieved. 4.3.4. Addressing SCTP can be told to replicast packets to multiple destinations. The TML will translate PL level addresses, to a variety of unicast IP addresses in order to emulate multicast and broadcast. Note, however, unlike other proposed TMLs, that there are no extra headers required for SCTP. 4.3.5. HA Transport link resiliency is SCTP's strongest point (where it totally outclasses all other TML proposals). Failure detection and recovery is built in as mentioned earlier. o The SCTP multi-homing feature is used to provide path diversity. Should one of the peer IP addresses become unreachable, the other(s) are used without needing lower layer convergence (routing, for example) or even the TML becoming aware. o SCTP heartbeats and data transmission thresholds are used on a per peer IP address to detect reachability faults. The faults could Hadi Salim & Ogawa Expires May 12, 2008 [Page 10] Internet-Draft ForCES SCTP TML November 2007 be a result of an unreachable address or peer, which may be caused by a variety of reasons, like interface, network, or endpoint failures. The cause of the fault is noted. o With the ADDIP feature, one can migrate IP addresses to other nodes at runtime. This is not unlike the VRRP[RFC3768] protocol use. This feature is used in addition to multi-homing in a planned migration of activity from one FE/CE to another. In such a case, part of the provisioning recipe at the CE for replacing an FE involves migrating activity of one FE to another. 4.3.6. DOS prevention Two separate streams are used within any FE-CE setup: the higher priority one is for configuration and the lower priority one for data redirection. The design is strict priority to further guarantee that lower priority is starved if lack of resources happen. 4.3.7. Encapsulation There is no extra encapsulation added by this TML. SCTP provides for extensions to be added to it by defining new chunks. In the future, should the need arise, a new SCTP extension can be defined to meet newer ForCES requirements. 5. IANA Considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. 6. Security Considerations TBA: how to use TLS,IPSEC 7. Manageability Considerations TBA 8. Acknowledgements 9. References Hadi Salim & Ogawa Expires May 12, 2008 [Page 11] Internet-Draft ForCES SCTP TML November 2007 9.1. Normative References [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. Paxson, "Stream Control Transmission Protocol", RFC 2960, October 2000. [RFC3654] Khosravi, H. and T. Anderson, "Requirements for Separation of IP Control and Forwarding", RFC 3654, November 2003. [RFC3746] Yang, L., Dantu, R., Anderson, T., and R. Gopal, "Forwarding and Control Element Separation (ForCES) Framework", RFC 3746, April 2004. 9.2. Informative References [FE-MODEL] Halpern, J. and E. Deleganes, "ForCES Forwarding Element Model", Oct. 2007. [FE-PROTO] Doria (Ed.), A., Haas (Ed.), R., Hadi Salim (Ed.), J., Khosravi (Ed.), H., M. Wang (Ed.), W., Dong, L., and R. Gopal, "ForCES Protocol Specification", July 2007. [TML-API] M. Wang, W., Hadi Salim, J., and A. Audu, "ForCES Transport Mapping Layer (TML) Service Primitives", Feb. 2007. Authors' Addresses Jamal Hadi Salim ZNYX Networks Ottawa, Ontario Canada Email: hadi@znyx.com Hadi Salim & Ogawa Expires May 12, 2008 [Page 12] Internet-Draft ForCES SCTP TML November 2007 Kentaro Ogawa NTT Network Service Systems Laboratories 3-9-11 Midori-cho Musashino-shi, Tokyo 180-8585 Japan Email: ogawa.kentaro@lab.ntt.co.jp Hadi Salim & Ogawa Expires May 12, 2008 [Page 13] Internet-Draft ForCES SCTP TML November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Hadi Salim & Ogawa Expires May 12, 2008 [Page 14]