Hormuzd Khosravi Internet Draft Shuchi Chawla Document: draft-ietf-forces-tcptml-04.txt Intel Corp. Expires: January 2007 Furquan Ansari Working Group: ForCES Lucent Tech. Jon Maloy Ericsson July 2006 TCP/IP based TML (Transport Mapping Layer) for ForCES protocol 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. Copyright Notice Copyright (C) The Internet Society (2006). Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [2]. Abstract Khosravi, et al Expires January 2007 [Page 1] Internet Draft TCP/IP based TML for ForCES protocol July 2006 This document defines the IP based TML (Transport Mapping Layer) for the ForCES protocol. It explains the rationale for choosing the transport protocols and also describes how this TML addresses all the requirements described in the Forces [3] requirements and ForCES protocol [5] document. Table of Contents 1. Definitions.....................................................3 2. Introduction....................................................3 3. Protocol Framework Overview.....................................4 3.1.1. The PL layer................................................5 3.1.2. The TML layer...............................................5 4. TML Overview....................................................5 4.1. Rationale for using TCP and DCCP..............................6 4.2. Separate Control and Data channels............................6 4.3. Reliability...................................................8 4.4. Congestion Control............................................8 4.5. Security......................................................8 4.6. Addressing....................................................8 4.7. Prioritization................................................9 4.8. HA Decisions..................................................9 4.9. Encapsulations Used..........................................10 5. TML Messaging..................................................10 6. TML Interface to Upper layer Protocol..........................10 6.1. TML Service Interface Overview...............................10 6.2. Protocol Initialization and Shutdown Model...................11 6.2.1. Protocol Initialization....................................11 6.2.2. Protocol Shutdown..........................................13 6.3. Multicast Model..............................................14 6.4. Broadcast Model..............................................17 7. Security Considerations........................................17 7.1. TLS Usage for Securing TML...................................17 7.2. IPSec Usage for securing TML.................................18 8. IANA Considerations............................................18 9. Manageability..................................................18 10. References....................................................18 10.1. Normative References........................................18 10.2. Informative References......................................18 11. Acknowledgments...............................................19 Appendix A. TML Service Interface................................19 A.1. TML Initialize.............................................19 A.2. TML Channel Open...........................................20 A.3. TML Channel Close..........................................21 A.4. TML Channel Write..........................................22 A.5. TML Channel Read...........................................23 A.6. TML Multicast Group Join...................................25 Khosravi, et al Expires January 2007 [Page 2] Internet Draft TCP/IP based TML for ForCES protocol July 2006 A.7. TML Multicast Group Leave..................................25 Authors' Addresses...............................................26 1. Definitions The following definitions are taken from [3], [5] ForCES Protocol - While there may be multiple protocols used within the overall ForCES architecture, the term "ForCES protocol" refers only to the protocol used at the Fp reference point in the ForCES Framework in RFC3746 [4]. This protocol does not apply to CE-to-CE communication, FE-to-FE communication, or to communication between FE and CE managers. Basically, the ForCES protocol works in a master-slave mode in which FEs are slaves and CEs are masters. ForCES Protocol Layer (ForCES PL) -- A layer in ForCES protocol architecture that defines the ForCES protocol messages, the protocol state transfer scheme, as well as the ForCES protocol architecture itself (including requirements of ForCES TML (see below)). Specifications of ForCES PL are defined by this document. 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. This document defines an IP based ForCES TML. 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. [3 .], [4] define both architectural and protocol requirements for the communication between CE and FE. The ForCES protocol layer [5] describes the protocol specification. It is envisioned that the ForCES protocol would be independent of the interconnect technology between the CE and FE and can run over multiple transport technologies and protocol. Thus a Transport Mapping Layer (TML) has been defined in the protocol framework that will take care of mapping the protocol messages to specific transports. This document defines the IP based TML for the ForCES protocol layer. It also addresses all the requirements for the TML including security, reliability, etc. Khosravi, et al Expires January 2007 [Page 3] Internet Draft TCP/IP based TML for ForCES protocol July 2006 3. Protocol Framework Overview The reader is referred to the Framework document [4], and in particular sections 3 and 4, for architectural overview and where and how the ForCES protocol fits in. There may be some content overlap between the ForCES protocol draft [5] and this section in order to provide clarity. The ForCES protocol constitutes two pieces: the PL and TML layer. This is depicted in Figure 1 below. +------------------------------------------------ | CE PL layer | +------------------------------------------------ | CE TML layer | +------------------------------------------------ ^ | ForCES | (i.e. Forces data + control PL | packets ) messages | over | specific | TML | encaps | and | transport | | v +------------------------------------------------ | FE TML layer | +------------------------------------------------ | FE PL layer | +------------------------------------------------ Figure 1: ForCES Interface The PL layer is in fact the ForCES protocol. Its semantics and message layout are defined in [5]. The TML Layer is necessary to connect two ForCES PL layers as shown in Figure 1 above. Both the PL and TML layers are standardized by the IETF. While only one PL layer is defined, different TMLs are expected to be standardized. To interoperate the TML layer at the CE and FE are expected to be of the same definition. Khosravi, et al Expires January 2007 [Page 4] Internet Draft TCP/IP based TML for ForCES protocol July 2006 On transmit, the PL layer delivers its messages to the TML layer. The TML layer delivers the message to the destination TML layer(s). On reception, the TML delivers the message to its destination PL layer(s). 3.1.1.The PL layer The PL is common to all implementations of ForCES and is standardized by the IETF [5]. 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 it’s HA parameterization, subscribe to specific events etc. 3.1.2.The TML layer The TML layer is essentially responsible for transport of the PL layer messages. The TML is where the issues of how to achieve transport level reliability, congestion control, multicast, ordering, etc. are handled. All TMLs will deliver a standard set of services and capabilities to the PL; the PL may use any available TML. The different TMLs each could implement things differently based on capabilities of underlying media and transport. However, since all TMLs will support a standardized interface, interoperability is guaranteed as long as both endpoints support the same TML. All ForCES Protocol Layer implementations should be portable across all TMLs, because all TMLs have the same top edge semantics. 4. TML Overview The TML consists of two connections between the CE and FE over which the protocol messages are exchanged. One of the connections is called the control channel, over which control messages are exchanged, the other is called data channel over which external protocol packets, such as routing packets will be exchanged. The control channel is a TCP connection; the data channel is a DCCP connection. The TCP and DCCP connections will use unique server port numbers for each of the channels. In addition to this, this TML will provide mechanisms to prioritize the messages over the different channels. Khosravi, et al Expires January 2007 [Page 5] Internet Draft TCP/IP based TML for ForCES protocol July 2006 Some of the rationale for choosing these transport mechanisms as well as explanation of how they meet the TML requirements is explained below. The ForCES protocol defines requirements to be met by the TML. However, the requirements in the draft do not always differentiate between control versus data messaging. The assumption is that the requirements for messaging over the data channel are a subset of those specified for control messaging. When such an assumption is made, it is explicitly specified and the justification for the same stated. 4.1.Rationale for using TCP and DCCP For control messaging, TCP meets all the reliability requirements (no losses, no data corruption, no re-ordering of data) for the ForCES protocol/TML and also provides congestion control mechanism, which is important to meet the scalability requirement. In addition, it helps with interoperability since TCP is a well-understood, widely deployed transport protocol. Using TCP also enables this TML and the protocol to work seamlessly in single hop and multihop scenarios. The reliability requirements for the data channel messages are different from that of the control messages [3] i.e. they don’t require strict reliability in terms of retransmission, etc. However congestion control is important for the data channel because in case of DoS attacks, if an unreliable transport such as UDP is used for the data traffic, it can more easily overflow the physical connection, overwhelming the control traffic with congestion. Thus we need a transport protocol that provides congestion control but does not necessarily provide full reliability. Datagram Congestion Control Protocol (DCCP) [9], which is on the RFC track is a transport protocol that exactly meets this requirement. 4.2.Separate Control and Data channels The ForCES NEs are subject to Denial of Service (DoS) attacks [Requirements Section 7 #15]. A malicious system in the network can flood a ForCES NE with bogus control packets such as spurious RIP or OSPF packets in an attempt to disrupt the operation of and the communication between the CEs and FEs. In order to protect against this situation, the TML uses separate control and data channels for communication between the CEs and FEs. Figure 2 below illustrates the different communication channels between the CEs and the FEs. As an example, the communication channels for support of High Availability with redundant CEs are also included. The setup of these channels would be dependent on the High Availability model used in the NE. Khosravi, et al Expires January 2007 [Page 6] Internet Draft TCP/IP based TML for ForCES protocol July 2006 ACTIVE CE STANDBY CE +-------------------+ +-------------------+ | CE: PL | | CE: PL | +-------------------+ +-------------------+ | CE: TML | | CE: TML | +-------------------+ +-------------------+ | CE: TCP/DCCP | | CE: TCP/DCCP | +-------------------+ +-------------------+ | | | | | | | | | | | . | . | . | . | . | | | | | | | | | | | . | . | . | . | . | | | | | | Cc1’ Cd1’ Cc2’ Cd2…Ccn’ Cdn’ | . | . | . +-Cc1-----+ | | | | +-.-.-.-.-.Cdn.-+ | +-Cd1-.-.+ | . +--------Ccn---+ | | | | | | . | . +Cc2+ . | | | | | +Cd2+ | . | . | | | | +------------+ +------------+ +------------+ |FE: TCP/DCCP| |FE: TCP/DCCP| . . . |FE: TCP/DCCP| +------------+ +------------+ +------------+ | FE: TML | | FE: TML | | FE: TML | +------------+ +------------+ +------------+ | FE: PL | | FE: PL | | FE: PL | +------------+ +------------+ +------------+ FE1 FE2 FEn \-------------V------------/ FE 1+1 Redundancy Legend: ---- Cc# : Unicast Control Channel between Active CE and FE# -.-. Cd# : Unicast Data Channel between Active CE and FE# ---- Cc#’: Unicast Control Channel between Standby CE and FE# -.-. Cd#’: Unicast Data Channel between Standby CE and FE# Figure 2: CE-FE Communication Channels The data channel carries IP packets from the network needed by the CE, such as RIP, OSPF packets as outlined in Requirements [3] Section 7 #10, which are carried in ForCES Packet Redirect messages [5], between the CEs and FEs. All the other ForCES messages, which are used for configuration/capability exchanges, event notification, Khosravi, et al Expires January 2007 [Page 7] Internet Draft TCP/IP based TML for ForCES protocol July 2006 etc, are carried over the control channel. The data channel is set up only after the control channel is set up. 4.3.Reliability TCP provides the reliability (no losses, no data corruption, no re- ordering of data) required for ForCES protocol control messages. As mentioned earlier, as per [3], strict reliability is not a requirement for payload carried over the data channel. Hence, the use of DCCP is adequate for the data channel. 4.4.Congestion Control TCP provides congestion control needed to satisfy this requirement for the control channel. DCCP provides congestion control to satisfy this requirement for the data channel. DCCP supports two congestion control mechanisms – TCP like congestion control specified with a CCID of 2 and TFRC congestion control specified with a CCID of 3. The DCCP channel may use either of these mechanisms; the CE and the FE may be configured with the mechanism to be used. The default CCID to be used if none is configured is CCID 2 which provides TCP like congestion control. 4.5.Security The TML channel can be secured in multiple ways. The default mode is to support the “no security”, a mode that is commonly used when it is determined that securing the ForCES channel is not needed (e.g. closed-box scenario). For scenarios where security is important, the TML uses either the TLS [6] or the IPSec [15] mechanisms to secure the channel(s). The security mode selection is normally done through configuration on either ends. Note that the TML will operate correctly only when both the ends are configured with the same security mechanism. The security mode used by the CE and FE is dependent on the deployment scenario as per the ForCES protocol requirements draft [3 .]. Please see section 7 on security considerations for more details. 4.6.Addressing This TML uses addressing provided by IP layer. For unicast addressing/delivery of control messages, it uses the TCP connection between the CE and FE. For multicast/broadcast Khosravi, et al Expires January 2007 [Page 8] Internet Draft TCP/IP based TML for ForCES protocol July 2006 addressing/delivery of control messages, this TML uses multiple TCP connections between the CE and FEs. Additionally, the TML layer maintains the mapping between the PL layer addresses and the channel descriptors assigned by the TML layer. The PL layer is unaware of these descriptors; the PL layer only uses the PL layer addresses for all communication with the TML layer. For unicast addressing/delivery over the data channel, it uses the DCCP connection between the CE and FE. Multicast/broadcast addressing and delivery is not supported over the data channel; data messages may only be sent from the CE to the FEs using unicast FEIds. If multicast support is required, the higher level protocol being carried over the data channel is responsible for it. 4.7.Prioritization This TML provides prioritization of messages sent over control channel as compared to the data channel. This has also been found to be useful in face of DoS attacks on the protocol. Additionally the TML can support multiple levels of prioritization for control messages if it supports a multi-queue strategy. The scheduling algorithm used at the TML layer would give preferential treatment to higher priority messages. The scheduling algorithm used in the TML layer is implementation dependent. 4.8.HA Decisions The TML transports the heartbeat messages generated at the PL layer to detect liveness of the CE/FE. The TML does not generate any heartbeat messages of its own. The PL heartbeat messages are carried over the control channel. For the data channel, the TML will propagate any DCCP detected connectivity issues over the channel to the PL layer. If the PL wishes to actively monitor the data channel, it may do so by sending periodic redirect packets from the CE to the FE. This details of this mechanism are however outside the scope of the TML. TML is responsible for keeping the control and data communication channels up. It however does not have the authority to decide which CE to set up the channels with. That is outside its control. If a FE-CE communication channel goes down or connectivity is lost, the following steps are taken by the TML layer: - FE TML attempts to reestablish the communication channel Khosravi, et al Expires January 2007 [Page 9] Internet Draft TCP/IP based TML for ForCES protocol July 2006 - If the FE TML is unable to reestablish the channel (after some configured number of retries/timeout), it notifies the FE PL that the channel is down. - CE TML waits for the channel to be reestablished (since only the FE can reestablish it) for some configured timeout prior to notifying the CE PL that the channel is down. Alternatively, the PL may detect the channel is down via the use of the PL generated heartbeat messages. If the control channel or data channel goes down, PL will control initiation of a failover to a new CE – both control and data channels will be reestablished with the new CE. If an FE goes down and a standby FE exists for it, and it has communication channels set up with the CE, the CE PL may start to use the channels associated with the standby FE. This is not within the scope of TML itself, but falls in the scope of High Availability. 4.9.Encapsulations Used There is no further message encapsulation of control and data messages done at the TML layer. The PL generated control messages are transported as is by the TML layer. The ForCES protocol control messages are encapsulated with a TCP/IP header. The PL data messages carried over the data channel are encapsulated in a DCCP header. 5. TML Messaging There is no TML layer messaging. TML only transports messages from the PL layer. 6. TML Interface to Upper layer Protocol ForCES TML interfaces with an upper layer protocol, the PL Layer and a lower layer protocol, TCP (in the case of TCP TML). This section defines the interface to the upper layer protocol. This interface should be used only as a guideline in implementing the API. Additionally, although the current interface is defined mainly as a synchronous interface, the interface may be implemented to be asynchronous if desired. 6.1.TML Service Interface Overview This section provides an overview of the TML service interface to help with understanding the following sections on protocol behavior Khosravi, et al Expires January 2007 [Page 10] Internet Draft TCP/IP based TML for ForCES protocol July 2006 with respect to initialization and multicast support. Note that this is just a brief overview for understanding the protocol initialization/shutdown sequences. It is by no means complete; the complete service interface is being specified in a separate draft. More details on this interface are specified in Appendix A. tmlInit() – Enables establishment of communication channels tmlOpen() – Opens one or more communication channels for control and data messaging tmlClose() – Closes one or more communication channels used for control and data messaging tmlWrite() – Write messages to a specific CE or FE tmlRead() – Read messages from a specific CE or FE tmlMulticastGroupJoin() – Request an FE to join a multicast group tmlMulticastGroupLeave() - Request an FE to leave a multicast group 6.2.Protocol Initialization and Shutdown Model In order for the peer PL Layers to communicate, the control and data channels must be setup. This section defines a model for the setup of the channels, using the TML interface defined above. In this model, the peer TML Layers may establish the control and data channels between the FE and the CE without the involvement of the PL Layers, or if desired, the PL Layer may trigger the setup of the channels; this is left as an implementation decision. Both modes may also be supported within an implementation. 6.2.1.Protocol Initialization The control channel must be established between the FE TML and the CE TML for establishment of association to proceed. This channel will be used for messages related to the association setup and capability query. The data channel must be established no later than the response from the FE to the CE Topology query message. The following are the significant aspects associated with channel setup: - A single call by the PL layer sets up the communication channels for both control and data messaging to a specific FE. The call specifies Unicast CE Id and attributes for control and data channels. - It is up to the TML layer whether to set up a single channel for both control and data or distinct channels for control and data Khosravi, et al Expires January 2007 [Page 11] Internet Draft TCP/IP based TML for ForCES protocol July 2006 - TML sets up the appropriate channels and allocates required descriptors for the channels. TML layer maintains a mapping between the Unicast FE/CE Id and the channel descriptors and channel type (control versus data) it creates once the FEId/CEId is known. - There is no need for channel descriptors to be returned to the PL layer at either the FE or the CE. PL Layer only uses the Unicast FE/CE Id for read/write calls and specifies the type of message (control versus data) to be read/written. - If only one of the channels is setup successfully, the TML layer will have to return appropriate status that specifies which channel is setup successfully and which isn’t. Figure 4 illustrates the initialization model where the PL layer via an interface provided by the TML Layer, triggers the setup of the control and data channels. FE1 PL FE1 TML CE TML CE PL | | | | \ / | | | tmlInit() | | FE | | | |<--------------| > CE Init/ Init/ < | | | | | Bootup Bootup | | | | | / \ | | | | | tmlOpen(CeId) | | | |-------------->| | | \ | |CtrlChan(Cc) Setup | | | Setup control | |~~~~~~~~~~~~~~~~~~~~~~>| | | channel if not | | | > already setup | |CtrlChan(Cc) Setup Rsp | | | | |<~~~~~~~~~~~~~~~~~~~~~~| | | | CeId . [CcDes] | | | | | | / | | | | | |DataChan(Cd) Setup | | | Setup data | |~~~~~~~~~~~~~~~~~~~~~~>| | | channel if not | | | | > already setup | |DataChan(Cd) Setup Rsp | | | | |<~~~~~~~~~~~~~~~~~~~~~~| | | | CeId . [CcDes, | | | | | CdDes] | | / | | | | | <-- status | | | | | | | |tmlEvent(ChUp) | |tmlEvent(ChUp) | |<--.--.--.--.--| |--.--.--.--.-->| | | | | | | Asso Setup Req | | |---------------|-----------------------|-------------->| | FeId . [CcDes, | \ Khosravi, et al Expires January 2007 [Page 12] Internet Draft TCP/IP based TML for ForCES protocol July 2006 | CdDes] | | TML updates | | > its mappings | | | once FEId is | | Asso Setup Rsp | | | available. |<--------------|-----------------------|---------------| / | | | | | | Capability Query | | |<--------------|-----------------------|---------------| | | Capability Query Rsp | | |---------------|-----------------------|-------------->| | | | | | | Topology Query | | |<--------------|-----------------------|---------------| | | Topology Query Rsp | | |---------------|-----------------------|-------------->| | | | | | |STEADY STATE OPERATION | | |<--------------|-----------------------|-------------->| | | | | Legend: PL --------> PL : Protocol layer messaging PL --------> TML: TML API TML --.--.--> PL : Events/Notifications/Upcalls TML ~~~~~~~~> TML: Internal protocol communication Figure 4: Protocol Initialization (Channel Setup) 6.2.2.Protocol Shutdown The control channel teardown must occur only after the association teardown has occurred. The data channel teardown may occur no earlier than the association teardown. The PL Layer may shutdown control and data channels via invocation of the tmlClose() API. When the PL layer shuts down the channels, the channels are torn down; hence ForCES messaging between the CE and FE is no longer possible over those channels. A tmlClose() results in both control and data channels (regardless of whether they are implemented as a single channel or distinct channels in the TML layer) being shutdown; it is not possible to close just one of them. A subsequent tmlOpen() triggers establishment of the channel. The channel(s) may be shutdown by either the FE or the CE. If an FE initiates the shutdown, it specifies the CE Id associated with the channel(s) to be shutdown. If a CE initiates the shutdown, it specifies the FE Id associated with the channel(s) to be shutdown. A channel shutdown by the FE is illustrated in Figure 5 and a channel shutdown by the CE is illustrated in Figure 6. FE PL FE TML CE TML CE PL | | | | Khosravi, et al Expires January 2007 [Page 13] Internet Draft TCP/IP based TML for ForCES protocol July 2006 | |STEADY STATE OPERATION | | |<--------------|-----------------------|-------------->| | | Config Request | | |<--------------|-----------------------|---------------| | | Config Response | | |---------------|-----------------------|-------------->| | | | | | | Association Teardown | | |<--------------|-----------------------|---------------| | | | | | | | | \ |tmlClose(CeId) | | | | FE initiated: |-------------->| | | > FE specifies CE | <-- status | | | | Id associated | | | | / with channel. Legend: PL --------> PL : Protocol layer messaging PL --------> TML: TML API TML --.--.--> PL : Events/Notifications/Upcalls TML ~~~~~~~~> TML: Internal protocol communication Figure 5: Protocol Shutdown: FE Initiated FE PL FE TML CE TML CE PL | | | | | |STEADY STATE OPERATION | | |<--------------|-----------------------|-------------->| | | Config Request | | |<--------------|-----------------------|---------------| | | Config Response | | |---------------|-----------------------|-------------->| | | | | | | Association Teardown | | |<--------------|-----------------------|---------------| | | | | | | | | \ | | |tmlClose(FeId) | | CE initiated: | | |<--------------| > FE specifies CE | <-- status | | status --> | | Id associated | | | | / with channel. Legend: PL --------> PL : Protocol layer messaging PL --------> TML: TML API TML --.--.--> PL : Events/Notifications/Upcalls TML ~~~~~~~~> TML: Internal protocol communication Figure 6: Protocol Shutdown: CE Initiated 6.3.Multicast Model Khosravi, et al Expires January 2007 [Page 14] Internet Draft TCP/IP based TML for ForCES protocol July 2006 The TML layer provides support for multicast of control messages. In the ForCES model, support is required to multicast to the FEs from a CE; in this case, the CE is the source or root of the multicast and the FEs are the leaves. Support for multicast requires that a channel for supporting multicast be opened between an FE and the CE. In the case of TCP TML, the same channel is used for both unicast and multicast messaging since multicast mode is simulated using unicast channels in this case. Once the channel is open, a CE may request FEs to join and leave specified multicast groups. Multicast support is CE- initiated. FEs can join a multicast group only if the CE requests them to join the group. TML maintains the mapping between PL layer IDs and channel descriptors for multicast. The following are the significant steps for adding or removing members from a multicast group: - CE PL communicates with FE PL for requesting the FE to join or leave a multicast group. - FE PL informs FE TML regarding the join or leave request. - FE TML updates the multicast group information. It updates the mapping between the FE Multicast Id and the channel descriptor to be used for multicast for that FE. This mapping may be from [Multicast FE Id] . [FE Id] . [Channel descriptor] or directly from [Multicast FE Id] . [Channel descriptor]. This is implementation dependent. - FE PL responds to CE PL informing it of the status of the join or leave request. - If the join or leave request was successful, CE PL informs CE TML regarding the update to the multicast group membership. - CE TML updates the multicast group membership. It updates the mapping between the FE Multicast Id and the set of channel descriptors to be used for multicast to the FEs that are members of this group. This mapping may be from [Multicast FE Id] . [Set of FE Ids] . [Set of channel descriptors] or directly from [Multicast FE Id] . [Set of channel descriptors]. This is implementation dependent. - There is no need for any descriptors to be returned to the PL layer at either the FE or the CE. PL Layer only uses the Multicast FE Id for write calls and specifies the type of message (control versus data) to be written. A tmlWrite() on a unicast FE Id results in a unicast message being sent to the FE associated with the channel. A tmlWrite() on a multicast FE Id results in multicast messaging. Figures 7 and 8 illustrate multicast scenarios with 2 FEs, FE1 and FE2. In Figure 7, the CE requests FE1 to join a multicast group. Although not Khosravi, et al Expires January 2007 [Page 15] Internet Draft TCP/IP based TML for ForCES protocol July 2006 shown as a separate figure, if FE2 were to join the same group, the join procedure would be the same as in Figure 7; it would result in the multicast group membership being updated at the TML layer on the CE to include FE2 in the group. In Figure 8, the CE requests FE1 to leave the multicast group, thus resulting in only FE2 being a member of the multicast group. Multicast Scenario with FE1 joining group: New group created FE1 PL FE1 TML CE TML CE PL | | | | | | | | \ | MC Grp Join Req (McId) | | |<--------------|-------------------|---------------| | CE:PL Level multicast group [TML | tmlJoin(McId) | | | | join request sent to each updates |-------------->| | | | FE:PL that needs to be part MC grp | McId = {FE1_ChDes} | | > of a multicast group, McId, info] | | | | | where McId specifies a | <-- status | | | | multicast group Id at the | | | | | PL layer. | MC Grp Join Rsp (status) | | |---------------|-------------------|-------------->| / | | | | | | | | \ | | |tmlJoin(McId) | | TML updates multicast | | |<--------------| | group membership. PL is | | McId = {FE1_ChDes} | > only aware of PL layer | | | | | multicast group Id, that is, | | | status --> | | McId] | | | | / Figure 7: Multicast Support: FE1 Joins Group Multicast Scenario with FE1 leaving group: Group membership updated to exclude FE1 FE1 PL FE1 TML CE TML CE PL | | | | | | | | \ | MC Grp Leave Req (McId, FE1) | | |<--------------|-------------------|---------------| | CE:PL Level multicast group [TML | tmlLeave(McId)| | | | leave request sent to FE1:PL removes |-------------->| | | | that needs to be removed MC grp | McId = {} | | > from multicast group, McId, info] | | | | | where McId specifies a | <-- status | | | | multicast group Id at the | | | | | PL layer. | MC Grp Leave Rsp (status) | | |---------------|-------------------|-------------->| / | | | | | | | | \ | | |tmlLeave(McId) | | TML removes FE1 from | | |<--------------| | multicast group McId. | | McId = {FE2_ChDes} | > That leaves only FE2 Khosravi, et al Expires January 2007 [Page 16] Internet Draft TCP/IP based TML for ForCES protocol July 2006 | | | | | in the group. | | | status --> | | | | | | / Figure 8: Multicast Support: FE1 Leaves Group 6.4.Broadcast Model The TML layer provides support for broadcast of control messages. In the ForCES model, support is required to broadcast to the FEs from a CE. The broadcast model is just a special case of multicast, where all FEs are included. This TML does not support CE or NE broadcast. 7. Security Considerations If the CE or FE are in a single box and network operator is running under a secured environment then it is up to the network administrator to turn off all the security functions. This is configured during the pre-association phase of the protocol. This mode is called “no security” mode of operation. When the CEs, FEs are running over IP networks or in an insecure environment, the operator has the choice of configuring either TLS [6] or IPSec [15] to provide security. The security association between the CEs and FEs MUST be established before any ForCES protocol messages are exchanged between the CEs and FEs. 7.1.TLS Usage for Securing TML This section is applicable for CE or FE endpoints that use the TML with TLS [6] to secure communication. Since CE is master and FEs are slaves, the FEs are TLS clients and CEs are TLS server. The endpoints that implement TLS MUST perform mutual authentication during TLS session establishment process. CE must request certificate from FE and FE needs to pass the requested information. We recommend “TLS-RSA-with-AES-128-CBC-SHA” cipher suite, but CE or FE may negotiate other TLS cipher suites. With this TML, TLS is used only for the control channel while the data channel is left unsecured since the data packets (e.g. routing protocol packets) may contain their own security mechanisms. Further, TLS has not yet been defined for usage with DCCP. Khosravi, et al Expires January 2007 [Page 17] Internet Draft TCP/IP based TML for ForCES protocol July 2006 7.2.IPSec Usage for securing TML This section is applicable for CE or FE endpoints that use the TML with IPSec [15] to secure their respective communication. IPSec is transparent to the higher-layer applications and can provide security for any transport layer protocol. This mechanism is can be used to secure just the control or both the control and the data channel simultaneously. 8. IANA Considerations This TML needs to have a one well-defined TCP port number for control messaging, which needs to be assigned by IANA. The control port is referred to as the TCP_TML_CONTROL_PORT. Similarly, TML requires one well-defined DCCP port number for data messaging. This data port is referred to as the DCCP_TML_DATA_PORT. 9. Manageability TBD 10. References 10.1.Normative References 1. S. Bradner, "The Internet Standards Process -Revision 3", RFC 2026, October 1996. 2. S. Bradner, "Keywords for use in RFCs to Indicate Requirement Levels", RFC2119 (BCP), IETF, March 1997. 3. Khosravi, et al., ’’Requirements for Separation of IP Control and Forwarding”, RFC 3654, November 2003. 4. L. Yang, et al., ” ForCES Architectural Framework”, RFC 3746, April 2004. 5. A. Doria, et al., ”ForCES protocol specification”, draft-ietf- forces-protocol-06.txt, December 2005. 10.2.Informative References 6. Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January 1999. Khosravi, et al Expires January 2007 [Page 18] Internet Draft TCP/IP based TML for ForCES protocol July 2006 7. Jungmaier, A., Rescorla, E. and M. Tuexen, "Transport Layer Security over Stream Control Transmission Protocol", RFC 3436, December 2002. 8. R. Stewart, et al., “Stream Control Transmission Protocol (SCTP)”, RFC 2960, October 2000. 9. E. Kohler, M. Handley, S. Floyd, J. Padhye, “Datagram Congestion Control Protocol (DCCP)”, draft-ietf-dccp-spec-13.txt, December 2005. 10.Floyd, S., “Congestion Control Principles”, RFC 2914, September 2000. 11.A. Doria, F. Hellstrand, K. Sundell, T. Worster, “General Switch Management Protocol (GSMP) V3”, RFC 3292, June 2002. 12.H. Balakrishnan, et al. “The Congestion Manager”, RFC 3124, June 2001. 13.H. Khosravi, S. Lakkavali, “Analysis of protocol design issues for open standards based programmable routers and switches” [SoftCOM 2004] 14.S. Lakkavali, H. Khosravi, “ForCES protocol design analysis for protection against DoS attacks” [ICCCN 2004] 15.S. Kent, R. Atkinson, “Security Architecture for the Internet Protocol”, RFC 2401 11. Acknowledgments Appendix A. TML Service Interface Note that this is just an overview for understanding the protocol initialization/shutdown sequences. It is by no means complete; the complete service interface is being specified in a separate draft. A.1. TML Initialize status tmlInit( in channelType, in initAttributes) Input Parameters: Khosravi, et al Expires January 2007 [Page 19] Internet Draft TCP/IP based TML for ForCES protocol July 2006 channelType: control versus data channel initAttributes: initialization parameters Output Parameters: none Returns: status: SUCCESS Errors TBD Synopsis: tmlInit() enables establishment of communication channels on the entity that this API is invoked. Optionally specifies attributes if any, for initialization. This call does not however result in the setup of any channels. ForCES Usage Model: In the case of ForCES which follows a client-server model, this API would be invoked on the CE, which functions as the server. It is invoked once for every class of TML channels on a per channel type basis (control channel versus data channel). For example, say for control messaging, the CE communicates with five FEs using TCP TML and with another two FEs, using UDP TML. tmlInit() will need to be invoked twice, once for the TCP TML attributes and once for the UDP TML attributes for the control channel setup with all of the FEs. The same holds true for the data channel setup in the above case. A.2. TML Channel Open status tmlOpen( in elementId, in channelMode, in ctrlChannelAttributes, in dataChannelAttributes, in eventHandlerCallBack) Input Parameters: elementId: Specific CE for which channel needs to be setup channelMode: unicast versus multicast ctrlChannelAttributes: control channel establishment parameters dataChannelAttributes: data channel establishment parameters eventHandlerCallback: Callback function to be invoked on event generation Output Parameters: none Khosravi, et al Expires January 2007 [Page 20] Internet Draft TCP/IP based TML for ForCES protocol July 2006 Returns: status: SUCCESS Errors TBD Synopsis: tmlOpen() results in one or more communication channels for control and data messaging being established with the specified elementId. It is up to the TML layer implementation whether to setup a single channel for both control and data messaging or distinct channels for each. The channel may be specified as unicast or multicast via channelMode. This call may either trigger the establishment of the channel(s), or if the channel(s) are already established, it only results in a registration for the channel(s). In either case, if successful, status is returned to indicate successful creation/registration of the control and data channels. No descriptors are returned to the PL layer since the TML layer maintains the mapping between the PL provided elementId and the descriptors it allocates. If this call triggers the establishment of the control and data channels, the channels are established using the ctrlChannelAttributes and dataChannelAttributes parameters respectively, specified to the call. Once the channel(s) are setup (or if already setup prior to this call), the caller of this API is also capable of receiving TML events via the specified event handling callback function. If this call is invoked multiple times on a channel that has already been opened and registered, a return status of ALREADY_REGISTERED is returned, with no change to registration. ForCES Usage Model: In the case of ForCES which follows a client-server model, this API would be invoked on the FE by FE PL, which functions as the client. On each FE, it is invoked once for both control and data channels that the FE wishes to setup with the CE. Notes: In the case of TCP TML for the control channel, since there is no inherent support for multicast, regardless of the channelMode specified, the specified channel would be setup as a unicast channel; however, the unicast channel would be able to support pseudo multicast. Hence, TCP TML has no need to set up distinct channels for unicast and multicast communication; they are both mapped to the same TCP connection. In the case of DCCP TML for the data channel, multicast mode is not being supported. Hence, channelMode would be ignored. A.3. TML Channel Close Khosravi, et al Expires January 2007 [Page 21] Internet Draft TCP/IP based TML for ForCES protocol July 2006 status tmlClose( in elementId, in mode) Input Parameters: elementId: address of element with which communication channel is to be terminated mode: mode of operation for the close – forced versus controlled Output Parameters: none Returns: status: SUCCESS Errors TBD Synopsis: Tears down/terminates communication channels connecting to the specified elementId. This API closes both control and data channels (regardless of whether they are implemented as a single channel or distinct channels in the TML layer); it is not possible to close just one of them. No further CE PL – FE PL messaging is possible after this. If the mode is specified as controlled, current messages that are pending in the TML layer shall be sent, but no new messages shall be accepted by the TML layer on this channel. In the forced mode, messages pending in the TML layer shall be discarded. Since the channel was terminated, a subsequent tmlOpen() will trigger establishment of the channel. ForCES Usage Model: This API may be invoked by either the CE or the FE. If the FE PL invokes it, it specifies a CE ID for the elementId. If the CE PL invokes it, it specifies an FE ID for the elementId. A.4. TML Channel Write status tmlWrite( in elementId, in msgType, in msg, in msgSize, in timeout, out bytesWritten) Input Parameters: elementId: address of element to be written to; may be a unicast, multicast or broadcast address Khosravi, et al Expires January 2007 [Page 22] Internet Draft TCP/IP based TML for ForCES protocol July 2006 msgType: control versus data message msg: message to be sent msgSize: size of message to be sent timeout: specifies blocking or non-blocking write. Value of -1 implies blocking write (wait forever), value of 0 implies non- blocking write Output Parameters: bytesWritten: number of bytes actually transmitted Returns: status: SUCCESS Errors TBD Synopsis: Sends message to the address specified by elementId. If the specified elementId is associated with a multicast group, the message will be sent to all members of the group. Similarly, if the elementId specified is a broadcast address, the message is sent to all elements associated with the broadcast address. The msgType parameter is used to specify whether the message is a control or data type of message. Based on the message type, the TML will send the message over the appropriate channel. The TML layer uses the address specified by elementId and the msgType to map to the appropriate channel to be used for sending the message. The message is queued in the appropriate queue for transmission. Once this call returns, the message buffer may be freed. If TML’s message queues are full, the timeout will be used to determine how long to wait prior to returning; if the specified timeout expires, and no message buffer becomes available, the API returns with an error. ForCES Usage Model: This API may be invoked by either the FE PL or the CE PL. If the FE PL invokes it, it specifies a CE ID for the elementId. If the CE PL invokes it, it specifies an (unicast/multicast/broadcast) FE ID for the elementId. In the case of TCP TML since there is a single channel used for unicast, multicast and broadcast messaging, the same channel is used for sending messages regardless of the address specified. In other cases where there are distinct channels for unicast versus multicast, the channel to be written to will differ based on the address specified. A.5. TML Channel Read status tmlRead( in elementId, Khosravi, et al Expires January 2007 [Page 23] Internet Draft TCP/IP based TML for ForCES protocol July 2006 in msgType, in msgBuf, in timeout, out bytesRead) Input Parameters: elementId: address of element to be read from; may be a unicast, multicast or broadcast address msgType: control versus data message msgBuf: buffer into which message is to be read timeout: specifies blocking or non-blocking read. Value of -1 implies blocking read (wait forever), value of 0 implies non- blocking read Output Parameters: bytesRead: number of bytes actually read Returns: status: SUCCESS Errors TBD Synopsis: Reads message from the specified address. The msgType parameter is used to specify whether the message to be read is a control or data type of message. The TML layer uses the address specified by elementId and the msgType to map to the appropriate channel to be used for reading the message. Once the message is copied into msgBuf specified by the call, the TML message buffer may be freed. If TML’s message queues are empty (no message is available), the timeout will be used to determine how long to wait prior to returning; if the specified timeout expires, and no message becomes available, the API returns with an error. If a non-blocking read is executed, the caller of the API is notified via an upcall when a message becomes available. ForCES Usage Model: This API may be invoked by either the CE or the FE. If the FE PL invokes it, it specifies a CE ID for the elementId. If the CE PL invokes it, it specifies an (unicast/multicast/broadcast) FE ID for the elementId. In the case of TCP TML since there is a single channel used for unicast, multicast and broadcast messaging, the same channel is used for reading messages regardless of the address specified. In other cases where there are distinct channels for unicast versus multicast, the channel to be read from will differ based on the address specified. Khosravi, et al Expires January 2007 [Page 24] Internet Draft TCP/IP based TML for ForCES protocol July 2006 A.6. TML Multicast Group Join status tmlMulticastGroupJoin( in groupId, in groupAttributes) Input Parameters: groupId: address of multicast group to join groupAttributes: attributes associated with the multicast group to be joined Output Parameters: none Returns: status: SUCCESS Errors TBD Synopsis: Joins the multicast group specified by groupId as leaf node in the group. Once a member of this group, the entity calling this API will be capable of receiving messages addressed to this multicast group. The TML layer on each end (CE/FE) maintains the mapping between the PL layer multicast address and the descriptors. The TML layer on the element which is the root of the multicast updates the set of elements that are members of the group specified by groupId. ForCES Usage Model: This API would be invoked on both the CE and the FE. Initially, the intent is to only support FE multicast. In such a case. on the FE the API is invoked once the PL layer on the FE receives a request from the PL layer on the CE to join a specified multicast group. On the CE it is invoked after the FE has successfully joined the multicast group. A.7. TML Multicast Group Leave status tmlMulticastGroupLeave( in groupId) Input Parameters: groupId: address of multicast group to leave Output Parameters: none Returns: Khosravi, et al Expires January 2007 [Page 25] Internet Draft TCP/IP based TML for ForCES protocol July 2006 status: SUCCESS Errors TBD Synopsis: Leaves the multicast group specified by groupId it had previously joined. Once an entity is not a member of the multicast group, it is no longer capable of receiving messages addressed to group. The TML layer on each end (CE/FE) updates the mapping between the PL layer multicast address and the descriptors. The TML layer on the element which is the root of the multicast updates the set of elements that are members of the group specified by groupId. ForCES Usage Model: This API would be invoked on both the CE and the FE. Initially, the intent is to only support FE multicast. In such a case, on the FE the API is invoked once the PL layer on the FE receives a request from the PL layer on the CE to leave a specified multicast group. On the CE it is invoked after the FE has successfully left the multicast group. Authors' Addresses Hormuzd Khosravi Intel 2111 NE 25th Avenue Hillsboro, OR 97124 Phone: 1-503-264-0334 Email: hormuzd.m.khosravi@intel.com Furquan Ansari 101 Crawfords Corner Road Holmdel, NJ 07733 USA Phone: +1 732-949-5249 Email: furquan@lucent.com Jon Maloy Ericsson Research Canada 8400 Boul Decarie Ville Mont-Royal, Quebec H4P 2N2 Canada Phone: 1-514-345-7900 Email: jon.maloy@ericsson.com Shuchi Chawla Intel Khosravi, et al Expires January 2007 [Page 26] Internet Draft TCP/IP based TML for ForCES protocol July 2006 2111 NE 25th Avenue Hillsboro, OR 97124 Phone: 1-503-712-4539 Email: shuchi.chawla@intel.com Copyright Statement Copyright (C) The Internet Society (2006). 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. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Khosravi, et al Expires January 2007 [Page 27]