Mobile Ad hoc Networks Working I. Chakeres Group E. Belding-Royer Internet-Draft UC Santa Barbara Expires: July 5, 2005 C. Perkins Nokia January 2005 Dynamic MANET On-demand Routing Protocol (DYMO) draft-ietf-manet-dymo-00 Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. 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 become aware will be disclosed, in accordance with RFC 3668. 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 July 5, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The Dynamic MANET On-demand (DYMO) routing protocol is intended for use by mobile nodes in wireless multihop networks. It offers quick adaptation to dynamic conditions, low processing and memory overhead, low network utilization, and determines unicast routes between nodes within the network. Chakeres, et al. Expires July 5, 2005 [Page 1] Internet-Draft DYMO January 2005 Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 Conceptual Data Structures . . . . . . . . . . . . . . . . 6 3.1.1 Route Table Entry . . . . . . . . . . . . . . . . . . 6 3.2 DYMO Message Elements . . . . . . . . . . . . . . . . . . 6 3.2.1 Fixed Portion of DYMO Elements . . . . . . . . . . . . 6 3.2.2 Routing Element (RE) . . . . . . . . . . . . . . . . . 7 3.2.3 Route Error (RERR) . . . . . . . . . . . . . . . . . . 8 3.2.4 Unsupported-element Error (UERR) . . . . . . . . . . . 8 3.3 Field Descriptions . . . . . . . . . . . . . . . . . . . . 8 4. Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 12 4.1 Sequence Numbers . . . . . . . . . . . . . . . . . . . . . 12 4.1.1 Maintaining a Sequence Number . . . . . . . . . . . . 12 4.1.2 Incrementing a Sequence Number . . . . . . . . . . . . 12 4.1.3 Sequence Number Rollover . . . . . . . . . . . . . . . 12 4.1.4 Actions After Sequence Number Loss . . . . . . . . . . 12 4.2 DYMO Routing Table Operations . . . . . . . . . . . . . . 12 4.2.1 Creating or Updating a Route Table Entry from Routing Element Information . . . . . . . . . . . . . 12 4.2.2 Route Table Entry Timeouts . . . . . . . . . . . . . . 13 4.3 DYMO General Processing . . . . . . . . . . . . . . . . . 13 4.3.1 DYMO Control Packet Processing . . . . . . . . . . . . 13 4.3.2 Generic Element Pre-processing . . . . . . . . . . . . 14 4.3.3 Processing Unsupported DYMO Elements . . . . . . . . . 14 4.3.3.1 Generating an Unsupported-element Error . . . . . 14 4.3.4 Generic Element Post-processing . . . . . . . . . . . 15 4.3.5 DYMO Control Packet Transmission . . . . . . . . . . . 15 4.4 Routing Element . . . . . . . . . . . . . . . . . . . . . 15 4.4.1 Routing Element Creation . . . . . . . . . . . . . . . 15 4.4.2 Appending Additional Routing Information to an Existing Routing Element . . . . . . . . . . . . . . . 15 4.4.3 Routing Element Processing . . . . . . . . . . . . . . 16 4.5 Route Discovery . . . . . . . . . . . . . . . . . . . . . 16 4.6 Route Maintenance . . . . . . . . . . . . . . . . . . . . 17 4.6.1 Link Breaks . . . . . . . . . . . . . . . . . . . . . 17 4.6.2 Updating Route Lifetimes . . . . . . . . . . . . . . . 17 4.6.3 Extending Route Lifetimes . . . . . . . . . . . . . . 17 4.6.4 Route Error Generation . . . . . . . . . . . . . . . . 18 4.6.5 Route Error Processing . . . . . . . . . . . . . . . . 18 4.7 Routing Prefix . . . . . . . . . . . . . . . . . . . . . . 19 4.8 Internet Attachment . . . . . . . . . . . . . . . . . . . 19 4.9 Multiple Interfaces . . . . . . . . . . . . . . . . . . . 19 Chakeres, et al. Expires July 5, 2005 [Page 2] Internet-Draft DYMO January 2005 4.10 Packet Generation Limits . . . . . . . . . . . . . . . . . 20 5. Configuration Parameters . . . . . . . . . . . . . . . . . . . 21 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 7. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25 9.1 Normative References . . . . . . . . . . . . . . . . . . . 25 9.2 Informative References . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 25 Intellectual Property and Copyright Statements . . . . . . . . 27 Chakeres, et al. Expires July 5, 2005 [Page 3] Internet-Draft DYMO January 2005 1. Overview The Dynamic MANET On-demand (DYMO) routing protocol enables dynamic, reactive, multihop routing between participating nodes wishing to communicate. The basic operations of the protocol are route discovery and management. During route discovery the originating node causes dissemination of a Routing Element (RE) throughout the network to find the target node. During dissemination each intermediate node creates a route to the originating node. When the target node receives the RE it responds with RE unicast toward originating node. During propagation each node creates a route to the target node. When the originating node is reached routes have been established between the originating node and the target node in both directions. In order to react quickly to changes in the network topology nodes should maintain their routes and monitor their links. When a packet is received for a route that is no longer available the source of the packet should be notified. A Route Error (RERR) is sent to the packet source to indicate the current route is broken. Once the source receives the RERR, it will re-initiate route discovery if it still has packets to deliver. In order to enable extension of the base specification, DYMO defines the handling of unsupported extensions. By defining default handling, future extensions are handled in a predetermined understood fashion. DYMO uses sequence numbers to ensure loop freedom [3]. All DYMO packets are transmitted via UDP on port TBD. Chakeres, et al. Expires July 5, 2005 [Page 4] Internet-Draft DYMO January 2005 2. Terminology IPBroadcastAddress Transmit the packet to the IP Limited Broadcast address, 255.255.255.255 (IPv4) or FF:FF:FF:FF:FF:FF (IPv6). IPDestinationAddress The destination of a packet, indicated by examining the IP header. IPSourceAddress The source of a packet, indicated by examining the IP header. MANETcast Transmit the packet to all MANET nodes within reception range. In a simple implementation MANETcast packets are sent to the IPBroadcastAddress. MANETcast SHOULD preform duplicate suppression. Valid Route A known route where the RouteValidTimeout is larger than the current time. Chakeres, et al. Expires July 5, 2005 [Page 5] Internet-Draft DYMO January 2005 3. Data Structures 3.1 Conceptual Data Structures 3.1.1 Route Table Entry o RouteAddress o RouteDeleteTimeout o RouteHopCnt o RouteIsGateway o RouteNextHopAddress o RouteNextHopInterface o RoutePrefix o RouteSeqNum o RouteValidTimeout 3.2 DYMO Message Elements 3.2.1 Fixed Portion of DYMO Elements All DYMO message elements must conform to the fixed data structure below. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ElemType |T|I| Res | ElemTTL | ElemLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . ElemTargetAddress . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . ElemNotifyAddress (Only ElemTypes with M-bit set) . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . ElemData . . ElemType-Specific Payload . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Chakeres, et al. Expires July 5, 2005 [Page 6] Internet-Draft DYMO January 2005 3.2.2 Routing Element (RE) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ElemType |T|I| Res | ElemTTL | ElemLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . ElemTargetAddress . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ElemTargetSeqNum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|G| Prefix1 | Res | REHopCnt1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . RENodeAddress1 . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RENodeSeqNum1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R|G| PrefixN | Res | REHopCntN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . Additional RENodeAddressN (if needed) . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional RENodeSeqNumN (if needed) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ElemType: 1. Nodes MUST implement the Routing Element. Chakeres, et al. Expires July 5, 2005 [Page 7] Internet-Draft DYMO January 2005 3.2.3 Route Error (RERR) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ElemType |T|I| Res | ElemTTL | ElemLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . ElemTargetAddress . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . UNodeAddress1 . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | UNodeSeqNum1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . Additional UNodeAddress (if needed) . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional UNodeSeqNum (if needed) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ElemType: 2. Nodes not implementing RERR will ignore the element and continue. 3.2.4 Unsupported-element Error (UERR) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ElemType |T|I| Res | ElemTTL | ElemLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . ElemTargetAddress . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . UElemTargetAddress . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . UERRNodeAddress . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | UElemType | +-+-+-+-+-+-+-+-+ ElemType: 3. Nodes not implementing UERR will ignore the element and continue. 3.3 Field Descriptions A-bit (A) 1-bit selector indicating whether this RE requires an answer RE by the ElemTargetAddress. If A=1 an answer is required. The instructions for generating an answer RE are described in Section 4.4.3. Chakeres, et al. Expires July 5, 2005 [Page 8] Internet-Draft DYMO January 2005 Element Data (ElemData) ElemType-specific payload. Element Length (ElemLen) 12-bit field that indicates the size of the element in bytes, including the fixed portion. Element Notify Address (ElemNotifyAddress) The node to send a UERR if the ElemType is unsupported. The ElemNotifyAddress field is only present if the ElemType has the M-bit is set to one (1). Element Target Address (ElemTargetAddress) The node that is the ultimate destination of the element. Element Time to Live (ElemTTL) 6-bit field that identifies the maximum number of times the element is to be retransmitted. The ElemTTL field operates similar to IPTTL (MaxCount) and is decremented at each hop. When ElemTTL reaches zero (0) the element is dropped. Element Type (ElemType) 0 0 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ | ElemType | = |M| H | | +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ The ElemType field identifies the element as well as the handling by nodes that do not implement or understand the element. The MSB bit, M-bit, denotes whether the element requires notification via an Unsupported-element Error (UERR) when the element is not understood or handled by a particular node. The next two bits, H-bits, identify how the ElemType MUST be handled by nodes not implementing the ElemType, regardless of UERR delivery. Section 4.3.3 describes the handling behavior based on the ElemType. G-bit (G) 1-bit selector to indicate whether the RENodeAddress1 is a gateway. If G=1 RENodeAddress1 is a gateway. For more information on gateway operation see Section 4.8. I-bit (I) 1-bit selector indicating whether the element has been ignored. If I=1 the element has been ignored. For a description of processing for unsupported elements by ElemType see Section 4.3.3. Prefix Size (Prefix) 6-bit field that specifies the size of the subnet reachable through the associated node, see Section 4.7. The definition of Prefix is different for gateways. Chakeres, et al. Expires July 5, 2005 [Page 9] Internet-Draft DYMO January 2005 Routing Element Block Hop Count (REHopCnt) 6-bit field that identifies the number of intermediate nodes the associated RE block has passed through. Routing Element Node Address (RENodeAddress) The IP address of the node that appending its RENodeAddress. Routing Element Node Sequence Number (RENodeSeqNum) The sequence number of the node appending its RENodeSeqNum. Reserved (Res, R) Reserved bits. These bits are set to zero (0) during element creation and ignored during processing. Route Node Address (RouteNodeAddress) The IP address of the node associated with the routing table entry. Route Delete Timeout (RouteDeleteTimeout) The corresponding routing table entry MUST be deleted if the current time is after RouteDeleteTimeout. Route Hop Count (RouteHopCnt) The number of intermediate node hops before reaching the RouteNodeAddress. Route Is Gateway (RouteIsGateway) 1-bit selector indicating whether the RouteNodeAddress is a gateway. Route Next Hop Address (RouteNextHopAddress) The IP address of the next node on the path toward the RouteNodeAddress. Route Next Hop Interface (RouteNextHopInterface) The interface to send packets toward the RouteNodeAddress. Route Prefix (RoutePrefix) 6-bit field that specifies the size of the subnet reachable through the RouteNodeAddress, see Section 4.7. The definition of the Prefix field is different for gateways. Route Sequence Number (RouteSeqNum) The sequence number of the RouteNodeAddress. RouteValidTimeout The routing table entry is no longer considered valid if the current time is after RouteValidTimeout. T-bit (T) 1-bit selector indicating how the element must be transmitted. If T=0 the element is unicast toward the ElemTargetAddress. Otherwise, if T=1 the element is MANETcast. Unreachable Node Address (UNodeAddress) The IP address of the unreachable node. Unreachable Node Sequence Number (UNodeSeqNum) The sequence number of the unreachable node, if known; otherwise, zero (0). Unsupported-element Node Address (UERRNodeAddress) The IP address of the node that generated the UERR. Chakeres, et al. Expires July 5, 2005 [Page 10] Internet-Draft DYMO January 2005 Unsupported-element Target Address (UElemTargetAddress) Address of the destination of the element that caused delivery of the UERR. Unsupported-element Type (UElemType) The ElemType that required generation of the UERR. Chakeres, et al. Expires July 5, 2005 [Page 11] Internet-Draft DYMO January 2005 4. Detailed Operation 4.1 Sequence Numbers 4.1.1 Maintaining a Sequence Number DYMO requires each node in the network maintain its own sequence number (OwnSeqNum). The circumstances for a node to change its OwnSeqNum are described in Section 4.4.1. 4.1.2 Incrementing a Sequence Number When a node increments its OwnSeqNum (as proscribed in Section 4.4.1 and Section 4.4.3) it MUST do so by treating the sequence number value as if it were an unsigned number. The sequence number zero (0) is reserved and is used in several DYMO data structures to represent an unknown sequence number. 4.1.3 Sequence Number Rollover To accomplish sequence number rollover, if the sequence number has been assigned to be the largest possible number representable as a 32-bit unsigned integer (i.e., 4294967295), then the sequence number when incremented MUST be set to one (1). 4.1.4 Actions After Sequence Number Loss If a node's OwnSeqNum is lost it MUST NOT participate in the MANET network (forward any data or issue any DYMO control packets) until it is sure that all other nodes have deleted any sequence number information about it. If RouteDeleteTimeout is set to ROUTE_DELETE_TIMEOUT + the current time (as described in Section 4.2.1), nodes should avoid participation for at least ROUTE_DELETE_TIMEOUT after sequence number loss. 4.2 DYMO Routing Table Operations 4.2.1 Creating or Updating a Route Table Entry from Routing Element Information While processing a RE, as described in Section 4.4.3, a node checks its routing table for an entry to the RENodeAddress using longest-prefix matching. In the event that there is no corresponding entry for the node, an entry is created. The routing information about RENodeAddress contained in the RE block is considered stale if: Chakeres, et al. Expires July 5, 2005 [Page 12] Internet-Draft DYMO January 2005 o the result of subtracting the RouteSeqNum from RENodeSeqNum is less than zero (0) using signed 32-bit arithmetic, OR o the result of subtracting the RouteSeqNum from RENodeSeqNum is equal to zero (0) using signed 32-bit arithmetic AND the REHopCnt is greater than RouteHopCnt. If the information is stale and this RE block is the first node in the RE (RENodeAddress1) this DYMO packet dropped. Otherwise, the RENodeAddress and RENodeSeqNum are removed from this RE. If the route information for RENodeAddress is not stale, then the following actions occur to the route table entry for RENodeAddress: o the RouteDeleteTimeout is set to the current time + ROUTE_DELETE_TIMEOUT, o the RouteNextHopAddress is set to the node that transmitted this DYMO packet (IPSourceAddress), o the RouteNextHopInterface is set to the interface that this DYMO packet was received on, o the RoutePrefix is set to Prefix, o and the RouteSeqNum is set to the RENodeSeqNum. o the RouteValidTimeout is set to the current time + ROUTE_TIMEOUT, If a valid route exists to RENodeAddress, the route can be used to send any queued data packets and to fulfill any outstanding route requests. 4.2.2 Route Table Entry Timeouts If the current time is later than a routing entry's RouteValidTimeout, the route is stale and it is not be used to route packets. If the current time is later than a routing entry's RouteDeleteTimeout, the route MUST be deleted. 4.3 DYMO General Processing 4.3.1 DYMO Control Packet Processing A DYMO packet may consist of multiple DYMO elements. Each element is processed individually and in sequence, from first to last. An incoming DYMO packet MUST be completely processed prior to any DYMO packet transmissions, resulting from the contained DYMO elements. The length of IP addresses (32-bits for IPv4 and 128-bits for IPv6) inside DYMO elements is dependent on the IP packet header. For example, if the IP header is IPv6 then all DYMO elements contained in the payload use IPv6 addresses. Chakeres, et al. Expires July 5, 2005 [Page 13] Internet-Draft DYMO January 2005 Unless specific element processing requires dropping the DYMO packet, it is retransmitted after processing. 4.3.2 Generic Element Pre-processing Each element in a DYMO packet undergoes pre-processing before the element specific processing occurs. The ElemTTL is decremented by one (1). 4.3.3 Processing Unsupported DYMO Elements This section describe the processing for unsupported DYMO ElemTypes. For unsupported DYMO elements, the ElemType field identifies the handling by nodes that do not implement or understand the element. The most significant bit (M-bit) indicates whether an Unsupported-element Error (UERR) SHOULD be sent to the ElemNotifyAddress. The next two bits (H-bits) identify how the element should be handled. 0 0 0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ | ElemType | = |M| H | | +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ If the M-bit is set is this DYMO element, a UERR is sent to the ElemNotifyAddress. This is accomplished by following the instructions in Section 4.3.3.1. Regardless of whether or not a UERR is sent in response to this unsupported ElemType, the processing node MUST also examine the H-bits to determine how this unsupported element is handled. If : o H == 00: Processing for this ElemType MUST skip the element and continue, as if the packet did not contain this element. o H == 01: Processing for this ElemType MUST remove the element (using the ElemLen) from the packet and continue, as if the packet did not include this element. o H == 10: Processing for this ElemType MUST set the ignored bit (I-bit), skip this element and continue, as if the packet did not contain this element. o H == 11: Processing for this ElemType dictates that the packet MUST be dropped. 4.3.3.1 Generating an Unsupported-element Error The ElemTargetAddress in the UERR is set to the ElemNotifyAddress from the unsupported element. The UElemTargetAddress is set to the ElemTargetAddress from the unsupported element. The UERRNodeAddress Chakeres, et al. Expires July 5, 2005 [Page 14] Internet-Draft DYMO January 2005 is set to the generating nodes IP address. The UElemType is the ElemType from the unsupported element. The ElemTTL is set to NET_DIAMETER. The UERRNodeAddress is set to the address of the node generating this UERR. The ElemLen is set to the total number of bytes in this UERR. The T-bit is set to zero (T=0). The element is then processed as described in Section 4.3.4. 4.3.4 Generic Element Post-processing If the ElemTTL is zero (0) AND this element is the first element this DYMO packet is dropped after processing of all elements in the DYMO packet. If the ElemTTL is zero (0) AND this is NOT the first element, this element is removed from the packet. If the ElemTTL is larger than zero (0), this element is re-transmitted in a DYMO packet after all elements have been processed. 4.3.5 DYMO Control Packet Transmission DYMO packet transmission is controlled by the T-bit in the first element. If T=0 the element is unicast toward the ElemTargetAddress via a routing table lookup. If the RouteNextHopAddress for the ElemTargetAddress is not known the packet is dropped. If T=1 the element is MANETcast. For all DYMO packets the IPTTL (IPMaxCount) SHOULD be set to 1 (IPTTL=1). 4.4 Routing Element 4.4.1 Routing Element Creation When a node creates a RE, it first increments its OwnSeqNum by one according to the rules specified in Section 4.1.2. Then it sets the RENodeAddress1 to its own address. The RENodeSeqNum1 is the node's OwnSeqNum. The node may advertise a prefix using the Prefix field, as described in Section 4.7. Otherwise, the Prefix field is set to zero (0). This node may advertise it is a gateway by setting the G-bit, as described in Section 4.8. Otherwise, the G-bit is set to zero (0). The ElemTTL is set to NET_DIAMETER. 4.4.2 Appending Additional Routing Information to an Existing Routing Element After processing a RE, a node MAY append its IP address and OwnSeqNum to the RE. Appending its own routing information may alleviate some route discovery procedures to this node from other nodes that process this RE. Chakeres, et al. Expires July 5, 2005 [Page 15] Internet-Draft DYMO January 2005 If this node plans to append its IP address to the RE, it first increments its OwnSeqNum as defined in Section 4.1.2. Then this node appends its IP address and OwnSeqNum to the RE. The ElemLen is also adjusted accordingly. 4.4.3 Routing Element Processing After general DYMO element pre-processing, the ElemHopCnt is incremented by one. A route to RENodeAddress1 is then created or updated using the associated RENodeSeqNum, G-bit, Prefix, and REHopCnt, as defined in Section 4.2.1. Each RENodeAddress, RENodeSeqNum, G-bit, Prefix, and REHopCnt block MAY be processed. First the REHopCnt is incremented, then a route is created or updated as defined in Section 4.2.1. Each RENodeAddress block resulting in a valid route entry may alleviate a future route discovery. Any unprocessed RENodeAddress blocks MUST be removed from the RE. If this node is the ElemTargetAddress AND the A-bit is set (A=1), this node MUST reciprocate with a RE. This node creates a new RE as described in Section 4.4.1. The ElemTargetAddress in the new RE is set to the RENodeAddress1 from the RE currently being processed. The T-bit is set to zero (T=0) and the A-bit is set to (A=0). Then the new RE undergoes post-processing, according to Section 4.3.5. If this node is not the ElemTargetAddress the current RE SHOULD be handled according to Section 4.3.4. If this node is the ElemTargetAddress the current packet and any additional elements are processed, but this packet is not retransmitted. 4.5 Route Discovery A node generates a Route Request (RREQ) to discover a valid route to a particular destination (ElemTargetAddress), other than itself. A RREQ is simply a RE with the T-bit set (T=1) to indicate that this RE is to be MANETcast. Also, the A-bit is set to one (A=1) to indicate that the TargetNode must respond with a RE. If a sequence number is known for the ElemTargetAddress it is placed in the ElemTargetSeqNum field. Otherwise, ElemTargetSeqNum is set to zero (0). Before sending the RREQ, the generating node buffers its RENodeAddress and RENodeSeqNum in its RE Table. The RE is then transmitted according to the procedure defined in Section 4.3.5. After issuing the RREQ, the node waits for a route to be created to Chakeres, et al. Expires July 5, 2005 [Page 16] Internet-Draft DYMO January 2005 the TargetNode. If a route is not received within RREQ_WAIT_TIME milliseconds, this node MAY again try to discover a route by issuing another RREQ. To reduce congestion in a network, repeated attempts at route discovery for a particular TargetNode SHOULD utilize a binary exponential backoff. The first time an node issues a RREQ, it waits RREQ_WAIT_TIME milliseconds for a route to the TargetNode. If a route is not found within that time, the node may send another RREQ. If a route is not found within 2*RREQ_WAIT_TIME, another RREQ may be sent, up to a total of RREQ_TRIES. For each additional attempt, the waiting time for the previous RREP is multiplied by 2 so that the waiting time conforms to a binary exponential backoff. Data packets waiting for a route SHOULD be buffered. If a route discovery has been attempted RREQ_TRIES times without receiving a route to the TargetNode, all data packets destined for the corresponding TargetNode SHOULD be dropped from the buffer and a Destination Unreachable ICMP message SHOULD be delivered to the application. 4.6 Route Maintenance 4.6.1 Link Breaks Nodes SHOULD monitor links to active neighbors. This may be accomplished by one or several mechanisms. Such as: o Link layer feedback o Hello messages o Neighbor discovery o Route timeout Upon detecting a link break the valid routes utilizing the broken link MUST set their RouteValidTimeout to the current time. A RERR MAY be issued after detecting a broken link of an active route. RERR Generation is described in Section 4.6.4. 4.6.2 Updating Route Lifetimes To avoid route timeouts for active sources, after receiving a packet a node MAY update the RouteValidTimeout to the IPSourceAddress to be the current time + ROUTE_TIMEOUT. 4.6.3 Extending Route Lifetimes To avoid route timeouts for active routes, an originating node MAY periodically send a RE with the T-bit set to zero (0), the A-bit set Chakeres, et al. Expires July 5, 2005 [Page 17] Internet-Draft DYMO January 2005 to one (A=1) and the ElemTargetAddress set to the target node's address (RouteAddress). The resultant DYMO packet transmissions and RE processing (Section 4.2.1) will update the lifetime of routes to the originating node and target node (RouteAddress) at all intermediate nodes, if a valid route still exists. 4.6.4 Route Error Generation When a non-DYMO packet is received for a destination without a valid routing table entry, a Route Error (RERR) SHOULD be generated by this node. A RERR informs the source that the current route is no longer available in a more timely manner than RouteValidTimeout. In the RERR, the ElemTargetAddress is the node that sent the non-DYMO packet, the IPSourceAddress. The UNodeAddress1 field is the address of the unreachable node (IPDestinationAddress) from the non-DYMO packet. If the UNodeSeqNum is known, it is placed in the RERR; otherwise zero (0) is placed in the this field of the RERR. The ElemTTL is set to NET_DIAMETER. The T-bit is set to one (T=1). Additional unreachable nodes utilizing the same invalid link (routes with the same RouteNextHopAddress and RouteNextHopInterface) as the UNodeAddress1 MAY be appended to the RERR. For each unreachable node their UNodeAddress and UNodeSeqNum are appended. The ElemLen is set accordingly. The RERR is then processed as described in Section 4.3.5. 4.6.5 Route Error Processing When a node processes a RERR after generic element pre-processing, it SHOULD set the RouteValidTimeout to the current time for each route to a UNodeAddress that meet all of the following conditions: The RouteNextHopAddress is the same as the RERR IPSourceAddress. The RouteNextHopInterface is the same as the interface this RERR was received. The UNodeSeqNum is zero (0) OR if the result of subtracting RouteSeqNum from UNodeSeqNum is less than or equal to zero using signed 32-bit arithmetic If any route's RouteValidTimeout is set to the current time, this RERR MAY be handled as described in Section 4.3.4. Otherwise, the RERR is dropped. Prior to RERR element post processing a node MAY remove UNodeAddress, UNodeSeqNum pairs to decrease the element size. Chakeres, et al. Expires July 5, 2005 [Page 18] Internet-Draft DYMO January 2005 4.7 Routing Prefix Any node can advertise connectivity to a subset of nodes within its address space by using the prefix field in RE. The nodes within the advertised prefix SHOULD NOT participate in the MANET, and MUST be reachable by forwarding packets to the node advertising connectivity. For example, 192.168.1.1 with a prefix of 16 indicates all nodes with the prefix 192.168.X.X are reachable through 192.168.1.1. If the G-bit is set the meaning of the prefix field is altered. For a gateway the prefix in association with the IP address indicates that nodes outside the subnet are reachable via the gateway node. For example, a gateway with IP address 192.168.1.1 and a prefix of 16 indicates all nodes with the IP address NOT matching 192.168.X.X are reachable through 192.168.1.1. 4.8 Internet Attachment Basic Internet attachment consists of a stub network of MANET nodes connected to the Internet via a single gateway node. The gateway is responsible for responding to RREQs for TargetNodes outside its configured MANET subnet, as well as delivering packets to destinations outside the MANET subnet. MANET nodes wishing to be reachable from nodes in the Internet MUST have IP addresses within the gateway's configured MANET subnet. Given a node with a globally route-able address or care-of address handled by the gateway, the gateway is responsible for performing route discovery for packets received from the Internet destined for nodes inside its MANET subnet. Since many nodes may commonly wish to communicate with the gateway, the gateway SHOULD indicate to nodes that it is a gateway by setting the gateway bit (G-bit) in the RE. The G-bit flag indicates to nodes in the MANET that the RENodeAddress is attached to the Internet and is capable of routing data packets to all nodes outside of the configured MANET subnet, described by the RENodeAddress and Prefix fields. 4.9 Multiple Interfaces It is likely that DYMO will be used with multiple wireless interfaces; therefore, the particular interface over which packets arrive must be known whenever a packet is received. Whenever a new route is created, the interface through which the RouteAddress can be reached is also recorded into the route table entry. When multiple interfaces are available, a node transmitting a Chakeres, et al. Expires July 5, 2005 [Page 19] Internet-Draft DYMO January 2005 MANETcast packet SHOULD send the packet on all interfaces that have been configured for operation in the MANET. 4.10 Packet Generation Limits To avoid congestion, a node SHOULD NOT transmit more than RATE_LIMIT control messages per second. Chakeres, et al. Expires July 5, 2005 [Page 20] Internet-Draft DYMO January 2005 5. Configuration Parameters Here are some suggested parameter values for DYMO: Parameter Name Suggested Value --------------------------- --------------- NET_DIAMETER 10 RATE_LIMIT 10 ROUTE_TIMEOUT 3000 milliseconds ROUTE_DELETE_TIMEOUT 5*ROUTE_TIMEOUT RREQ_WAIT_TIME 1000 milliseconds RREQ_TRIES 3 These parameters work well for small well-connected networks with moderate network topology changes. For other networks these DYMO parameters SHOULD be adjusted using either dynamic adaptation or experimentally determined values. For example in static networks, ROUTE_TIMEOUT may be set to a much larger value. Chakeres, et al. Expires July 5, 2005 [Page 21] Internet-Draft DYMO January 2005 6. IANA Considerations DYMO defines a ElemType field for each element within a packet sent to port TBD. A new registry will be created for the values for this ElemType field, and the following values will be assigned: ElemType Value -------------------------------- ----- Routing Element (RE) 1 Route Error (RERR) 2 Unsupported-element Error (UERR) 3 Future values of the ElemType and ErrType will be allocated using standard actions as described in [1]. Chakeres, et al. Expires July 5, 2005 [Page 22] Internet-Draft DYMO January 2005 7. Security Considerations Currently, DYMO does not specify any special security measures. Routing protocols, however, are prime targets for impersonation attacks. In networks where the node membership is not known, it is difficult to determine the occurrence of impersonation attacks, and security prevention techniques are difficult at best. However, when the network membership is known and there is a danger of such attacks, DYMO elements must be protected by the use of authentication techniques, such as those involving generation of unforgeable and cryptographically strong message digests or digital signatures. While DYMO does not place restrictions on the authentication mechanism used for this purpose, IPsec Authentication Element (AH) is an appropriate choice for cases where the nodes share an appropriate security association that enables the use of AH. In particular, RE messages SHOULD be authenticated to avoid creation of spurious routes to a destination. Otherwise, an attacker could masquerade as that destination and maliciously deny service to the destination and/or maliciously inspect and consume traffic intended for delivery to the destination. RERR messages, while less dangerous, SHOULD be authenticated in order to prevent malicious nodes from disrupting active routes between communicating nodes. DYMO does not make any assumption about the method by which addresses are assigned to the mobile nodes except that they are presumed to have unique IP addresses. Therefore, no special consideration, other than what is natural because of the general protocol specifications, can be made about the applicability of IPsec authentication elements or key exchange mechanisms. However, if the mobile nodes in the ad hoc network have pre-established security associations, it is presumed that the purposes for which the security associations are created include that of authorizing the processing of DYMO control packets. Given this understanding, the mobile nodes should be able to use the same authentication mechanisms based on their IP addresses as they would have used otherwise. Chakeres, et al. Expires July 5, 2005 [Page 23] Internet-Draft DYMO January 2005 8. Acknowledgments DYMO is an decedent of the design of previous MANET reactive protocols. Special thanks to the authors of AODV [2] and DSR [4]. The authors of AODV and DSR include Charlie Perkins, Elizabeth Belding-Royer, Samir Das, David Johnson, David Maltz, Yih-Chun Hu and Jorjeta Jetcheva. Much of the DYMO protocol also stems from research and implementation of MANET reactive-routing protocols. To mention a few major contributors Sung-Ju Lee, Mahesh Marina, Erik Nordstrom, Yves Prelot, J.J. Garcia-Luna-Aceves, Marc Mosko, Manel Guerrero Zapata, Philippe Jacquet, and Chris Shiflet. Also, special thanks to Luke Klein-Berndt for extensive implementation and testing of AODV, early reviewing of DYMO, as well as several technical discussions. Chakeres, et al. Expires July 5, 2005 [Page 24] Internet-Draft DYMO January 2005 9. References 9.1 Normative References [1] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 2434, BCP 26, October 1998. [2] Perkins, C., Belding-Royer, E. and S. Das, "Ad hoc On-demand Distance Vector (AODV) Routing", RFC 3561, July 2003. 9.2 Informative References [3] Perkins, C. and E. Belding-Royer, "Ad hoc On-Demand Distance Vector (AODV) Routing", February 1999. [4] Johnson, D. and D. Maltz, "Dynamic Source Routing in Ad-hoc Wireless Networks", August 1996. Authors' Addresses Ian Chakeres University of California Santa Barbara Dept. of Electrical and Computer Engineering Santa Barbara, CA 93106 USA Phone: +1-805-893-8981 Fax: +1-805-893-8553 Email: idc@engineering.ucsb.edu Elizabeth Belding-Royer University of California Santa Barbara Dept. of Computer Science Santa Barbara, CA 93106-5110 USA Phone: +1-805-893-3411 Fax: +1-805-893-8553 Email: ebelding@cs.ucsb.edu Chakeres, et al. Expires July 5, 2005 [Page 25] Internet-Draft DYMO January 2005 Charlie Perkins Nokia Research Center 313 Fairchild Drive Mountain View, CA 94043 USA Phone: +1-650-625-2986 Fax: +1-650-625-2502 Email: charlie.perkins@nokia.com Chakeres, et al. Expires July 5, 2005 [Page 26] Internet-Draft DYMO January 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Chakeres, et al. Expires July 5, 2005 [Page 27]