--- 1/draft-ietf-dots-requirements-04.txt 2017-06-07 10:13:12.802365463 -0700 +++ 2/draft-ietf-dots-requirements-05.txt 2017-06-07 10:13:12.842366418 -0700 @@ -1,21 +1,21 @@ DOTS A. Mortensen -Internet-Draft Arbor Networks, Inc. +Internet-Draft Arbor Networks Intended status: Informational R. Moskowitz -Expires: September 14, 2017 HTT Consulting +Expires: December 9, 2017 HTT Consulting T. Reddy - Cisco Systems, Inc. - March 13, 2017 + McAfee, Inc. + June 07, 2017 Distributed Denial of Service (DDoS) Open Threat Signaling Requirements - draft-ietf-dots-requirements-04 + draft-ietf-dots-requirements-05 Abstract This document defines the requirements for the Distributed Denial of Service (DDoS) Open Threat Signaling (DOTS) protocols coordinating attack response against DDoS attacks. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -24,21 +24,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on September 14, 2017. + This Internet-Draft will expire on December 9, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -48,76 +48,76 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Context and Motivation . . . . . . . . . . . . . . . . . 2 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. General Requirements . . . . . . . . . . . . . . . . . . 7 - 2.2. Operational Requirements . . . . . . . . . . . . . . . . 8 + 2.2. Signal Channel Requirements . . . . . . . . . . . . . . . 7 2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 11 - 2.4. Security requirements . . . . . . . . . . . . . . . . . . 12 + 2.4. Security requirements . . . . . . . . . . . . . . . . . . 13 2.5. Data Model Requirements . . . . . . . . . . . . . . . . . 13 - 3. Congestion Control Considerations . . . . . . . . . . . . . . 14 - 3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 14 + 3. Congestion Control Considerations . . . . . . . . . . . . . . 15 + 3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 15 3.2. Data Channel . . . . . . . . . . . . . . . . . . . . . . 15 4. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. 04 revision . . . . . . . . . . . . . . . . . . . . . . . 16 7.2. 03 revision . . . . . . . . . . . . . . . . . . . . . . . 16 - 7.3. 02 revision . . . . . . . . . . . . . . . . . . . . . . . 16 - 7.4. 01 revision . . . . . . . . . . . . . . . . . . . . . . . 16 + 7.3. 02 revision . . . . . . . . . . . . . . . . . . . . . . . 17 + 7.4. 01 revision . . . . . . . . . . . . . . . . . . . . . . . 17 7.5. 00 revision . . . . . . . . . . . . . . . . . . . . . . . 17 7.6. Initial revision . . . . . . . . . . . . . . . . . . . . 17 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 17 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 18 8.2. Informative References . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 1. Introduction 1.1. Context and Motivation Distributed Denial of Service (DDoS) attacks continue to plague - networks around the globe, from Tier-1 service providers on down to - enterprises and small businesses. Attack scale and frequency + network operators around the globe, from Tier-1 service providers on + down to enterprises and small businesses. Attack scale and frequency similarly have continued to increase, in part as a result of software vulnerabilities leading to reflection and amplification attacks. Once-staggering attack traffic volume is now the norm, and the impact of larger-scale attacks attract the attention of international press agencies. The greater impact of contemporary DDoS attacks has led to increased focus on coordinated attack response. Many institutions and - enterprises lack the resources or expertise to operate on-premise + enterprises lack the resources or expertise to operate on-premises attack mitigation solutions themselves, or simply find themselves constrained by local bandwidth limitations. To address such gaps, security service providers have begun to offer on-demand traffic scrubbing services, which aim to separate the DDoS traffic from legitimate traffic and forward only the latter. Today each such service offers its own interface for subscribers to request attack - mitigation, tying subscribers to proprietary implementations while - also limiting the subset of network elements capable of participating - in the attack response. As a result of incompatibility across - services, attack responses may be fragmentary or otherwise - incomplete, leaving key players in the attack path unable to assist - in the defense. + mitigation, tying subscribers to proprietary signaling + implementations while also limiting the subset of network elements + capable of participating in the attack response. As a result of + signaling interface incompatibility, attack responses may be + fragmentary or otherwise incomplete, leaving key players in the + attack path unable to assist in the defense. The lack of a common method to coordinate a real-time response among involved actors and network domains inhibits the speed and effectiveness of DDoS attack mitigation. This document describes the - required characteristics of a DOTS protocol enabling requests for - DDoS attack mitigation, reducing attack impact and leading to more + required characteristics of a protocol enabling requests for DDoS + attack mitigation, reducing attack impact and leading to more efficient defensive strategies. DOTS communicates the need for defensive action in anticipation of or in response to an attack, but does not dictate the form any defensive action takes. DOTS supplements calls for help with pertinent details about the detected attack, allowing entities participating in DOTS to form ad hoc, adaptive alliances against DDoS attacks as described in the DOTS use cases [I-D.ietf-dots-use-cases]. The requirements in this document are derived from those use cases and [I-D.ietf-dots-architecture]. @@ -167,21 +167,21 @@ attack response coordination with other DOTS-aware elements. DOTS server: A DOTS-aware software module handling and responding to messages from DOTS clients. The DOTS server SHOULD enable mitigation on behalf of the DOTS client, if requested, by communicating the DOTS client's request to the mitigator and returning selected mitigator feedback to the requesting DOTS client. A DOTS server MAY also be a mitigator. DOTS agent: Any DOTS-aware software module capable of participating - in a DOTS signaling session. + in a DOTS signal or data channel. DOTS gateway: A logical DOTS agent resulting from the logical concatenation of a DOTS server and a DOTS client, analogous to a SIP Back-to-Back User Agent (B2BUA) [RFC3261]. DOTS gateways are discussed in detail in [I-D.ietf-dots-architecture]. Signal channel: A bidirectional, mutually authenticated communication channel between DOTS agents characterized by resilience even in conditions leading to severe packet loss, such as a volumetric DDoS attack causing network congestion. @@ -197,21 +197,21 @@ Client signal: A message sent from a DOTS client to a DOTS server over the signal channel, indicating the DOTS client's need for mitigation, as well as the scope of any requested mitigation, optionally including additional attack details to supplement server-initiated mitigation. Server signal: A message sent from a DOTS server to a DOTS client over the signal channel. Note that a server signal is not a response to client signal, but a DOTS server-initiated status message sent to DOTS clients with which the server has established - signaling sessions. + signal channels. Data channel: A secure communication layer between DOTS clients and DOTS servers used for infrequent bulk exchange of data not easily or appropriately communicated through the signal channel under attack conditions. Filter: A policy matching a network traffic flow or set of flows and rate-limiting or discarding matching traffic. Blacklist: A filter list of addresses, prefixes and/or other @@ -226,158 +226,164 @@ Multi-homed DOTS client: A DOTS client exchanging messages with multiple DOTS servers, each in a separate administrative domain. 2. Requirements This section describes the required features and characteristics of the DOTS protocol. DOTS is an advisory protocol. An active DDoS attack against the entity controlling the DOTS client need not be present before - establishing DOTS communication between DOTS agents. Indeed, + establishing a communication channel between DOTS agents. Indeed, establishing a relationship with peer DOTS agents during normal network conditions provides the foundation for more rapid attack response against future attacks, as all interactions setting up DOTS, including any business or service level agreements, are already complete. - DOTS must at a minimum make it possible for a DOTS client to request - a DOTS server's aid in mounting a coordinated defense against a - suspected attack, signaling within or between domains as requested by - local operators. DOTS clients should similarly be able to withdraw - aid requests. DOTS requires no justification from DOTS clients for - requests for help, nor do DOTS clients need to justify withdrawing - help requests: the decision is local to the DOTS clients' domain. + The DOTS protocol must at a minimum make it possible for a DOTS + client to request a mitigator's aid mounting a defense, coordinated + by a DOTS server, against a suspected attack, signaling within or + between domains as requested by local operators. DOTS clients should + similarly be able to withdraw aid requests. DOTS requires no + justification from DOTS clients for requests for help, nor do DOTS + clients need to justify withdrawing help requests: the decision is + local to the DOTS clients' domain. + Regular feedback between DOTS clients and DOTS server supplement the - defensive alliance by maintaining a common understanding of DOTS peer - health and activity. Bidirectional communication between DOTS + defensive alliance by maintaining a common understanding of DOTS + agent health and activity. Bidirectional communication between DOTS clients and DOTS servers is therefore critical. - Yet DOTS must also work with a set of competing operational goals. - On the one hand, the protocol must be resilient under extremely - hostile network conditions, providing continued contact between DOTS - agents even as attack traffic saturates the link. Such resiliency - may be developed several ways, but characteristics such as small - message size, asynchronous, redundant message delivery and minimal - connection overhead (when possible given local network policy) will - tend to contribute to the robustness demanded by a viable DOTS - protocol. Operators of peer DOTS-enabled domains may enable quality- - or class-of-service traffic tagging to increase the probability of - successful DOTS signal delivery, but DOTS requires no such policies - be in place. The DOTS solution indeed must be viable especially in - their absence. + DOTS protocol implementations face competing operational goals when + maintaining this bidirectional communication stream. On the one + hand, the protocol must be resilient under extremely hostile network + conditions, providing continued contact between DOTS agents even as + attack traffic saturates the link. Such resiliency may be developed + several ways, but characteristics such as small message size, + asynchronous, redundant message delivery and minimal connection + overhead (when possible given local network policy) will tend to + contribute to the robustness demanded by a viable DOTS protocol. + Operators of peer DOTS-enabled domains may enable quality- or class- + of-service traffic tagging to increase the probability of successful + DOTS signal delivery, but DOTS requires no such policies be in place. + The DOTS solution indeed must be viable especially in their absence. On the other hand, DOTS must include protections ensuring message confidentiality, integrity and authenticity to keep the protocol from becoming another vector for the very attacks it's meant to help fight off. DOTS clients must be able to authenticate DOTS servers, and - vice versa, for DOTS to operate safely, meaning the DOTS agents must - have a way to negotiate and agree upon the terms of protocol - security. Attacks against the transport protocol should not offer a - means of attack against the message confidentiality, integrity and - authenticity. + vice versa, to avoid exposing new attack surfaces when deploying + DOTS; specifically, to prevent DDoS mitigation in response to DOTS + signaling from becoming a new form of attack. In order to provide + this level of proteection, DOTS agents must have a way to negotiate + and agree upon the terms of protocol security. Attacks against the + transport protocol should not offer a means of attack against the + message confidentiality, integrity and authenticity. The DOTS server and client must also have some common method of defining the scope of any mitigation performed by the mitigator, as well as making adjustments to other commonly configurable features, such as listen ports, exchanging black- and white-lists, and so on. - Finally, DOTS should provide sufficient extensibility to meet local, - vendor or future needs in coordinated attack defense, although this - consideration is necessarily superseded by the other operational - requirements. + Finally, DOTS should be sufficiently extensible to meet future needs + in coordinated attack defense, although this consideration is + necessarily superseded by the other operational requirements. 2.1. General Requirements GEN-001 Extensibility: Protocols and data models developed as part of DOTS MUST be extensible in order to keep DOTS adaptable to operational and proprietary DDoS defenses. Future extensions MUST - be backward compatible. + be backward compatible. DOTS protocols MUST use a version number + system to distinguish protocol revisions. Implementations of + older protocol versions SHOULD ignore information added to DOTS + messages as part of newer protocol versions. GEN-002 Resilience and Robustness: The signaling protocol MUST be designed to maximize the probability of signal delivery even under the severely constrained network conditions imposed by particular attack traffic. The protocol MUST be resilient, that is, continue operating despite message loss and out-of-order or redundant message delivery. In support signaling protocol robustness, DOTS signals SHOULD be conveyed over a transport not susceptible to Head of Line Blocking. GEN-003 Bidirectionality: To support peer health detection, to maintain an open signal channel, and to increase the probability of signal delivery during attack, the signal channel MUST be bidirectional, with client and server transmitting signals to each other at regular intervals, regardless of any client request for mitigation. Unidirectional messages MUST be supported within the bidirectional signal channel to allow for unsolicited message delivery, enabling asynchronous notifications between agents. - GEN-004 Sub-MTU Message Size: To avoid message fragmentation and the - consequently decreased probability of message delivery, signaling - protocol message size MUST be kept under signaling Path Maximum - Transmission Unit (PMTU), including the byte overhead of any - encapsulation, transport headers, and transport- or message-level - security. - - DOTS agents SHOULD attempt to learn the PMTU through mechanisms - such as Path MTU Discovery [RFC1191] or Packetization Layer Path - MTU Discovery [RFC4821]. If the PMTU cannot be discovered, DOTS - agents SHOULD assume a PMTU of 1280 bytes. If IPv4 support on - legacy or otherwise unusual networks is a consideration and PMTU - is unknown, DOTS implementations MAY rely on a PMTU of 576 bytes, - as discussed in [RFC0791] and [RFC1122]. - - GEN-005 Bulk Data Exchange: Infrequent bulk data exchange between + GEN-004 Bulk Data Exchange: Infrequent bulk data exchange between DOTS agents can also significantly augment attack response coordination, permitting such tasks as population of black- or white-listed source addresses; address or prefix group aliasing; exchange of incident reports; and other hinting or configuration supplementing attack response. As the resilience requirements for the DOTS signal channel mandate small signal message size, a separate, secure data channel utilizing a reliable transport protocol MUST be used for bulk data exchange. -2.2. Operational Requirements +2.2. Signal Channel Requirements - OP-001 Use of Common Transport Protocols: DOTS MUST operate over + SIG-001 Use of Common Transport Protocols: DOTS MUST operate over common widely deployed and standardized transport protocols. - While the User Datagram Protocol (UDP) [RFC0768] SHOULD be used - for the signal channel, the Transmission Control Protocol (TCP) - [RFC0793] MAY be used if necessary due to network policy or - middlebox capabilities or configurations. The data channel MUST - use a reliable transport; see Section 2.3 below. + While connectionless transport such as the User Datagram Protocol + (UDP) [RFC0768] SHOULD be used for the signal channel, the + Transmission Control Protocol (TCP) [RFC0793] MAY be used if + necessary due to network policy or middlebox capabilities or + configurations. - OP-002 Session Health Monitoring: Peer DOTS agents MUST regularly + SIG-002 Sub-MTU Message Size: To avoid message fragmentation and the + consequently decreased probability of message delivery over a + congested link, signaling protocol message size MUST be kept under + signaling Path Maximum Transmission Unit (PMTU), including the + byte overhead of any encapsulation, transport headers, and + transport- or message-level security. + + DOTS agents SHOULD attempt to learn the PMTU through mechanisms + such as Path MTU Discovery [RFC1191] or Packetization Layer Path + MTU Discovery [RFC4821]. If the PMTU cannot be discovered, DOTS + agents SHOULD assume a PMTU of 1280 bytes. If IPv4 support on + legacy or otherwise unusual networks is a consideration and PMTU + is unknown, DOTS implementations MAY rely on a PMTU of 576 bytes, + as discussed in [RFC0791] and [RFC1122]. + + SIG-003 Channel Health Monitoring: Peer DOTS agents MUST regularly send heartbeats to each other after mutual authentication in order - to keep the DOTS session active. A session MUST be considered - active until a DOTS agent explicitly ends the session, or either - DOTS agent fails to receive heartbeats from the other after a - mutually agreed upon timeout period has elapsed. + to keep the DOTS signal channel active. A signal channel MUST be + considered active until a DOTS agent explicitly ends the session, + or either DOTS agent fails to receive heartbeats from the other + after a mutually agreed upon timeout period has elapsed. - OP-003 Session Redirection: In order to increase DOTS operational + SIG-004 Channel Redirection: In order to increase DOTS operational flexibility and scalability, DOTS servers SHOULD be able to redirect DOTS clients to another DOTS server at any time. DOTS clients MUST NOT assume the redirection target DOTS server shares security state with the redirecting DOTS server. DOTS clients MAY attempt abbreviated security negotiation methods supported by the protocol, such as DTLS session resumption, but MUST be prepared to negotiate new security state with the redirection target DOTS server. Due to the increased likelihood of packet loss caused by link - congestion during an attack, it is RECOMMENDED DOTS servers avoid - redirecting while mitigation is enabled during an active attack - against a target in the DOTS client's domain. + congestion during an attack, DOTS servers SHOULD NOT redirect + while mitigation is enabled during an active attack against a + target in the DOTS client's domain. - OP-004 Mitigation Requests and Status: Authorized DOTS clients MUST + SIG-005 Mitigation Requests and Status: Authorized DOTS clients MUST be able to request scoped mitigation from DOTS servers. DOTS servers MUST send mitigation request status in response to DOTS clients requests for mitigation, and SHOULD accept scoped mitigation requests from authorized DOTS clients. DOTS servers MAY reject authorized requests for mitigation, but MUST include a reason for the rejection in the status message sent to the client. Due to the higher likelihood of packet loss during a DDoS attack, DOTS servers SHOULD regularly send mitigation status to authorized DOTS clients which have requested and been granted mitigation, @@ -397,58 +403,63 @@ DOTS clients SHOULD take these metrics into account when determining whether to ask the DOTS server to cease mitigation. Once a DOTS client requests mitigation, the client MAY withdraw that request at any time, regardless of whether mitigation is currently active. The DOTS server MUST immediately acknowledge a DOTS client's request to stop mitigation. To protect against route or DNS flapping caused by a client rapidly toggling mitigation, and to dampen the effect of - oscillating attacks, DOTS servers MAY continue mitigation for a - period of up to five minutes after acknowledging a DOTS client's + oscillating attacks, DOTS servers MAY allow mitigation to continue + for a limited period after acknowledging a DOTS client's withdrawal of a mitigation request. During this period, DOTS server status messages SHOULD indicate that mitigation is active - but terminating. After the five-minute period elapses, the DOTS - server MUST treat the mitigation as terminated, as the DOTS client - is no longer responsible for the mitigation. For example, if - there is a financial relationship between the DOTS client and - server domains, the DOTS client ceases incurring cost at this - point. + but terminating. - OP-005 Mitigation Lifetime: DOTS servers MUST support mitigation + The active-but-terminating period is initially 30 seconds. If the + client requests mitigation again before that 30 second window + elapses, the DOTS server MAY exponentially increase the active- + but-terminating period up to a maximum of 240 seconds (4 minutes). + After the active-but-terminating period elapses, the DOTS server + MUST treat the mitigation as terminated, as the DOTS client is no + longer responsible for the mitigation. For example, if there is a + financial relationship between the DOTS client and server domains, + the DOTS client ceases incurring cost at this point. + + SIG-006 Mitigation Lifetime: DOTS servers MUST support mitigation lifetimes, and MUST terminate a mitigation when the lifetime elapses. DOTS servers also MUST support renewal of mitigation lifetimes in mitigation requests from DOTS clients, allowing clients to extend mitigation as necessary for the duration of an attack. DOTS servers MUST treat a mitigation terminated due to lifetime expiration exactly as if the DOTS client originating the - mitigation had asked to end the mitigation, including the five- - minute termination period, as described above in OP-004. + mitigation had asked to end the mitigation, including the active- + but-terminating period, as described above in SIG-005. DOTS clients SHOULD include a mitigation lifetime in all mitigation requests. If a DOTS client does not include a mitigation lifetime in requests for help sent to the DOTS server, the DOTS server will use a reasonable default as defined by the protocol. DOTS servers SHOULD support indefinite mitigation lifetimes, enabling architectures in which the mitigator is always in the traffic path to the resources for which the DOTS client is requesting protection. DOTS servers MAY refuse mitigations with indefinite lifetimes, for policy reasons. The reasons themselves are out of scope for this document, but MUST be included in the - mitigation rejection message from the server, per OP-004. + mitigation rejection message from the server, per SIG-005. - OP-006 Mitigation Scope: DOTS clients MUST indicate desired + SIG-007 Mitigation Scope: DOTS clients MUST indicate desired mitigation scope. The scope type will vary depending on the resources requiring mitigation. All DOTS agent implementations MUST support the following required scope types: * IPv4 addresses in dotted quad format * IPv4 address prefixes in CIDR notation [RFC4632] * IPv6 addresses [RFC2373] @@ -456,57 +467,60 @@ * Domain names [RFC1035] The following mitigation scope types are OPTIONAL: * Uniform Resource Identifiers [RFC3986] DOTS agents MUST support mitigation scope aliases, allowing DOTS client and server to refer to collections of protected resources by an opaque identifier created through the data channel, direct - configuration, or other means. + configuration, or other means. Domain name and URI mitigation + scopes may be thought of as a form of scope alias, in which the + addresses to which the domain name or URI resolve represent the + full scope of the mitigation. If there is additional information available narrowing the scope of any requested attack response, such as targeted port range, protocol, or service, DOTS clients SHOULD include that information in client signals. DOTS clients MAY also include additional attack details. Such supplemental information is OPTIONAL, and DOTS servers MAY ignore it when enabling countermeasures on the mitigator. As an active attack evolves, clients MUST be able to adjust as necessary the scope of requested mitigation by refining the scope of resources requiring mitigation. - OP-007 Mitigation Efficacy: When a mitigation request by a DOTS + SIG-008 Mitigation Efficacy: When a mitigation request by a DOTS client is active, DOTS clients SHOULD transmit a metric of perceived mitigation efficacy to the DOTS server, per "Automatic or Operator-Assisted CPE or PE Mitigators Request Upstream DDoS Mitigation Services" in [I-D.ietf-dots-use-cases]. DOTS servers MAY use the efficacy metric to adjust countermeasures activated on a mitigator on behalf of a DOTS client. - OP-008 Conflict Detection and Notification: Multiple DOTS clients + SIG-009 Conflict Detection and Notification: Multiple DOTS clients controlled by a single administrative entity may send conflicting mitigation requests for pool of protected resources , as a result of misconfiguration, operator error, or compromised DOTS clients. DOTS servers attempting to honor conflicting requests may flap network route or DNS information, degrading the networks attempting to participate in attack response with the DOTS clients. DOTS servers SHALL detect such conflicting requests, and SHALL notify the DOTS clients in conflict. The notification SHOULD indicate the nature and scope of the conflict, for example, the overlapping prefix range in a conflicting mitigation request. - OP-009: Network Address Translator Traversal: The DOTS protocol MUST - operate over networks in which Network Address Translation (NAT) - is deployed. As UDP is the recommended transport for the DOTS + SIG-010: Network Address Translator Traversal: The DOTS protocol + MUST operate over networks in which Network Address Translation + (NAT) is deployed. If UDP is used as the transport for the DOTS signal channel, all considerations in "Middlebox Traversal Guidelines" in [RFC5405] apply to DOTS. Regardless of transport, DOTS protocols MUST follow established best common practices (BCPs) for NAT traversal. 2.3. Data Channel Requirements The data channel is intended to be used for bulk data exchanges between DOTS agents. Unlike the signal channel, which must operate nominally even when confronted with signal degradation due to packet @@ -536,26 +550,26 @@ modification of data channel transmissions could lead to information leaks or malicious transactions on behalf of the sending agent (see Section 4 below). Consequently data sent over the data channel MUST be encrypted and authenticated using current industry best practices. DOTS servers MUST enable means to prevent leaking operationally or privacy-sensitive data. Although administrative entities participating in DOTS may detail what data may be revealed to third-party DOTS agents, such considerations are not in scope for this document. - DATA-003 Resource Configuration: To help meet the general and - operational requirements in this document, DOTS server - implementations MUST provide an interface to configure resource - identifiers, as described in OP-007. DOTS server implementations - MAY expose additional configurability. Additional configurability - is implementation-specific. + DATA-003 Resource Configuration: To help meet the general and signal + channel requirements in this document, DOTS server implementations + MUST provide an interface to configure resource identifiers, as + described in SIG-007. DOTS server implementations MAY expose + additional configurability. Additional configurability is + implementation-specific. DATA-004 Black- and whitelist management: DOTS servers SHOULD provide methods for DOTS clients to manage black- and white-lists of traffic destined for resources belonging to a client. For example, a DOTS client should be able to create a black- or whitelist entry; retrieve a list of current entries from either list; update the content of either list; and delete entries as necessary. @@ -563,45 +577,45 @@ is not in scope. 2.4. Security requirements DOTS must operate within a particularly strict security context, as an insufficiently protected signal or data channel may be subject to abuse, enabling or supplementing the very attacks DOTS purports to mitigate. SEC-001 Peer Mutual Authentication: DOTS agents MUST authenticate - each other before a DOTS session is considered valid. The method - of authentication is not specified, but should follow current - industry best practices with respect to any cryptographic - mechanisms to authenticate the remote peer. + each other before a DOTS signal or data channel is considered + valid. The method of authentication is not specified, but should + follow current industry best practices with respect to any + cryptographic mechanisms to authenticate the remote peer. SEC-002 Message Confidentiality, Integrity and Authenticity: DOTS protocols MUST take steps to protect the confidentiality, integrity and authenticity of messages sent between client and server. While specific transport- and message-level security options are not specified, the protocols MUST follow current industry best practices for encryption and message authentication. In order for DOTS protocols to remain secure despite advancements in cryptanalysis and traffic analysis, DOTS agents MUST be able to negotiate the terms and mechanisms of protocol security, subject to the interoperability and signal message size requirements above. While the interfaces between downstream DOTS server and upstream DOTS client within a DOTS gateway are implementation-specific, those interfaces nevertheless MUST provide security equivalent to - that of the signaling sessions bridged by gateways in the - signaling path. For example, when a DOTS gateway consisting of a - DOTS server and DOTS client is running on the same logical device, - they must be within the same process security boundary. + that of the signal channels bridged by gateways in the signaling + path. For example, when a DOTS gateway consisting of a DOTS + server and DOTS client is running on the same logical device, they + must be within the same process security boundary. SEC-003 Message Replay Protection: In order to prevent a passive attacker from capturing and replaying old messages, DOTS protocols MUST provide a method for replay detection. 2.5. Data Model Requirements The value of DOTS is in standardizing a mechanism to permit elements, networks or domains under or under threat of DDoS attack to request aid mitigating the effects of any such attack. A well-structured @@ -625,58 +639,59 @@ this document. DM-003: Mitigation Status Representation: The data model MUST provide the ability to represent a request for mitigation and the withdrawal of such a request. The data model MUST also support a representation of currently requested mitigation status, including failures and their causes. DM-004: Mitigation Scope Representation: The data model MUST support representation of a requested mitigation's scope. As mitigation - scope may be represented in several different ways, per OP-006 + scope may be represented in several different ways, per SIG-007 above, the data model MUST be capable of flexible representation of mitigation scope. DM-005: Mitigation Lifetime Representation: The data model MUST support representation of a mitigation request's lifetime, including mitigations with no specified end time. DM-006: Mitigation Efficacy Representation: The data model MUST support representation of a DOTS client's understanding of the efficacy of a mitigation enabled through a mitigation request. DM-007: Acceptable Signal Loss Representation: The data model MUST be able to represent the DOTS agent's preference for acceptable - signal loss when establishing a signaling session, as described in + signal loss when establishing a signal channel, as described in GEN-002. DM-008: Heartbeat Interval Representation: The data model MUST be able to represent the DOTS agent's preferred heartbeat interval, which the client may include when establishing the signal channel, - as described in OP-002. + as described in SIG-003. DM-009: Relationship to Transport: The DOTS data model MUST NOT depend on the specifics of any transport to represent fields in the model. 3. Congestion Control Considerations 3.1. Signal Channel As part of a protocol expected to operate over links affected by DDoS attack traffic, the DOTS signal channel MUST NOT contribute - significantly to link congestion. To meet the operational - requirements above, DOTS signal channel implementations MUST support - UDP. However, UDP when deployed naively can be a source of network + significantly to link congestion. To meet the signal channel + requirements above, DOTS signal channel implementations SHOULD + support connectionless transports. However, some connectionless + transports when deployed naively can be a source of network congestion, as discussed in [RFC5405]. Signal channel - implementations using UDP MUST therefore include a congestion control - mechanism. + implementations using such connectionless transports, such as UDP, + therefore MUST include a congestion control mechanism. Signal channel implementations using TCP may rely on built-in TCP congestion control support. 3.2. Data Channel As specified in DATA-001, the data channel requires reliable, in- order message delivery. Data channel implementations using TCP may rely on the TCP implementation's built-in congestion control mechanisms. @@ -857,53 +873,52 @@ DOI 10.17487/RFC5405, November 2008, . 8.2. Informative References [I-D.ietf-dots-architecture] Mortensen, A., Andreasen, F., Reddy, T., christopher_gray3@cable.comcast.com, c., Compton, R., and N. Teague, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Architecture", draft-ietf-dots- - architecture-01 (work in progress), October 2016. + architecture-02 (work in progress), May 2017. [I-D.ietf-dots-use-cases] Dobbins, R., Fouant, S., Migault, D., Moskowitz, R., Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS - Open Threat Signaling", draft-ietf-dots-use-cases-03 (work - in progress), November 2016. + Open Threat Signaling (DDoS) Open Threat Signaling", + draft-ietf-dots-use-cases-05 (work in progress), May 2017. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487/RFC3261, June 2002, . [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet Denial-of-Service Considerations", RFC 4732, DOI 10.17487/RFC4732, December 2006, . Authors' Addresses Andrew Mortensen - Arbor Networks, Inc. + Arbor Networks 2727 S. State St Ann Arbor, MI 48104 United States Email: amortensen@arbor.net - Robert Moskowitz HTT Consulting Oak Park, MI 42837 United States Email: rgm@htt-consult.com + Tirumaleswar Reddy - Cisco Systems, Inc. - Cessna Business Park, Varthur Hobli - Sarjapur Marathalli Outer Ring Road - Bangalore, Karnataka 560103 + McAfee, Inc. + Embassy Golf Link Business Park + Bangalore, Karnataka 560071 India - Email: tireddy@cisco.com + Email: TirumaleswarReddy_Konda@McAfee.com