RFC 8612

DDoS Open Threat Signaling (DOTS) Requirements

📅 published May 2019, from ietf

DDoS Open Threat Signaling (DOTS) Requirements 🛡️✨

RFC: 8612 🎀
Authors: A. Mortensen (Arbor Networks), T. Reddy (McAfee), R. Moskowitz (Huawei) 👯
Category: Informational 📚
ISSN: 2070-1721
Date: May 2019 🗓️
Obsoletes / Updates: the header doesn't list either one 🙈

Abstract

okay bestie, the abstract is short and sweet 🍓 This document defines the requirements for the Distributed Denial-of-Service (DDoS) Open Threat Signaling (DOTS) protocols, which exist so networks can team up and respond to DDoS attacks in a coordinated way 🫶

Status of This Memo

Lowkey important: this is NOT an Internet Standards Track spec. It's published just for information 📖

It's an IETF product 🌈 It represents the consensus of the IETF community, got public review, and was approved for publication by the Internet Engineering Steering Group (IESG). Not every IESG-approved doc is a candidate for any level of Internet Standard, so see Section 2 of RFC 7841 for the deets 💅

For the current status, any errata, and how to give feedback, check https://www.rfc-editor.org/info/rfc8612 ✨

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as they stand on the publication date. Read them carefully, because they spell out your rights and restrictions for this document. Code Components pulled out of this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as the Simplified BSD License describes 📜

1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
  1.1.  Context and Motivation  . . . . . . . . . . . . . . . . .   2
  1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   5
  2.1.  General Requirements  . . . . . . . . . . . . . . . . . .   7
  2.2.  Signal Channel Requirements . . . . . . . . . . . . . . .   8
  2.3.  Data Channel Requirements . . . . . . . . . . . . . . . .  13
  2.4.  Security Requirements . . . . . . . . . . . . . . . . . .  14
  2.5.  Data Model Requirements . . . . . . . . . . . . . . . . .  16
3.  Congestion Control Considerations . . . . . . . . . . . . . .  17
  3.1.  Signal Channel  . . . . . . . . . . . . . . . . . . . . .  17
  3.2.  Data Channel  . . . . . . . . . . . . . . . . . . . . . .  17
4.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
  6.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
  6.2.  Informative References  . . . . . . . . . . . . . . . . .  20
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  21
Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  21
Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1. Introduction 🌸

1.1. Context and Motivation 💅

DDoS attacks are a real menace 😭 They hit networks connected to the Internet and wreck network operators at service providers and enterprises everywhere. High-volume attacks that saturate inbound links are everywhere now, because the scale and frequency keep going up 📈

The more these attacks hurt, the more people care about coordinated attack response 🔥 But lots of enterprises don't have the people, the know-how, or the bandwidth to run on-premise mitigation themselves. So service providers started offering on-demand traffic scrubbing services 🧽 These services are built to separate DDoS attack traffic from legit traffic and forward only the legit stuff ✨

Right now, those services use proprietary interfaces for subscribers to ask for mitigation. Those interfaces lock you into one service and limit what network elements could otherwise do to help with mitigation 🙃 Because the signaling interfaces don't match each other, attack responses can end up fragmented or incomplete, which leaves operators along the attack path unable to help defend 💀

A standardized way to coordinate a real-time response among the operators involved would make DDoS mitigation faster and more effective, and it would shrink the damage these attacks do 🌈

This document describes the characteristics that protocols need to have in order to enable attack response coordination and DDoS mitigation 🧚

DOTS communicates the need for defensive action, either ahead of an attack or in response to one, but it does not dictate how those actions get implemented 🦋 The DOTS use cases are discussed in [DOTS-USE], and the DOTS architecture is discussed in [DOTS-ARCH] 📚

1.2. Terminology 📖

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

These capitalized words are used to signify the requirements for the DOTS protocols design 🎯

This document adopts the following terms 👇

DDoS: A distributed denial-of-service attack in which traffic originating from multiple sources is directed at a target on a network. DDoS attacks are intended to cause a negative impact on the availability and/or functionality of an attack target. Denial-of-service considerations are discussed in detail in [RFC4732]. 💥
DDoS attack target: A network-connected entity that is the target of a DDoS attack. Potential targets include (but are not limited to) network elements, network links, servers, and services. 🎯
DDoS attack telemetry: Collected measurements and behavioral characteristics defining the nature of a DDoS attack. 📊
Countermeasure: An action or set of actions focused on recognizing and filtering out specific types of DDoS attack traffic while passing legitimate traffic to the attack target. Distinct countermeasures can be layered to defend against attacks combining multiple DDoS attack types. 🛡️
Mitigation: A set of countermeasures enforced against traffic destined for the target or targets of a detected or reported DDoS attack, where countermeasure enforcement is managed by an entity in the network path between attack sources and the attack target. Mitigation methodology is out of scope for this document. 🧱
Mitigator: An entity, typically a network element, capable of performing mitigation of a detected or reported DDoS attack. The means by which this entity performs these mitigations and how they are requested of it are out of scope for this document. The mitigator and DOTS server receiving a mitigation request are assumed to belong to the same administrative entity. 🤝
DOTS client: A DOTS-aware software module responsible for requesting 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 enables 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. 🧑‍💻
DOTS agent: Any DOTS-aware software module capable of participating in a DOTS signal or data channel. It can be a DOTS client, DOTS server, or, as a logical agent, a DOTS gateway. 🕵️‍♀️
DOTS gateway: A DOTS-aware software module resulting from the logical concatenation of the functionality of a DOTS server and a DOTS client into a single DOTS agent. This functionality is analogous to a Session Initiation Protocol (SIP) [RFC3261] Back-to-Back User Agent (B2BUA) [RFC7092]. A DOTS gateway has a client-facing side, which behaves as a DOTS server for downstream clients, and a server-facing side, which performs the role of a DOTS client for upstream DOTS servers. Client-domain DOTS gateways are DOTS gateways that are in the DOTS client's domain, while server-domain DOTS gateways denote DOTS gateways that are in the DOTS server's domain. A DOTS gateway may terminate multiple discrete DOTS client connections and may aggregate these into one or more connections. DOTS gateways are described further in [DOTS-ARCH]. 🚪
Signal channel: A bidirectional, mutually authenticated communication channel between DOTS agents that is resilient even in conditions leading to severe packet loss, such as a volumetric DDoS attack causing network congestion. 📡
DOTS signal: A status/control message transmitted over the authenticated signal channel between DOTS agents, used to indicate the client's need for mitigation or to convey the status of any requested mitigation. 🚨
Heartbeat: A message transmitted between DOTS agents over the signal channel, used as a keep-alive and to measure peer health. 💓
Data channel: A bidirectional, mutually authenticated communication channel between two DOTS agents used for infrequent but reliable bulk exchange of data not easily or appropriately communicated through the signal channel. Reliable bulk data exchange may not function well or at all during attacks causing network congestion. The data channel is not expected to operate in such conditions. 📦
Filter: A specification of a matching network traffic flow or set of flows. The filter will typically have a policy associated with it, e.g., rate-limiting or discarding matching traffic [RFC4949]. 🔍
Drop-list: A list of filters indicating sources from which traffic should be blocked regardless of traffic content. 🚫
Accept-list: A list of filters indicating sources from which traffic should always be allowed regardless of contradictory data gleaned in a detected attack. ✅
Multihomed DOTS client: A DOTS client exchanging messages with multiple DOTS servers, each in a separate administrative domain. 🌐

2. Requirements ✨

Okay bestie, this is where we get to the actual to-do list 💅 The layout and who-talks-to-who stuff lives in the DOTS Architecture [DOTS-ARCH] 🗺️ so go read that first.

The whole point of this requirements spec is to nail down what the DOTS signal channel and data channel protocols need to do. Those two channels have different application and transport-layer needs, so they can't be treated the same 🦋 This section lists the features and characteristics the DOTS protocols need to have.

The goal of DOTS is to enable and manage mitigation for a network domain or resource that is, or may become, the target of a DDoS attack 🛡️ You don't need an attack happening right now before setting up a channel between DOTS agents. Honestly, setting up a relationship during normal network conditions is what makes a faster response possible later, since all the setup stuff, including any business or service-level agreements, is already done 💜 Reachability info for peer DOTS agents gets handed to a DOTS client through a mix of manual and dynamic methods. Once the relationship exists, regular communication between DOTS clients and servers keeps everyone informed about each agent's health and activity 🌸

The DOTS protocol must, at a minimum, let a DOTS client ask for help defending against a suspected attack 🫶 A DOTS server can coordinate that defense, and it can include signaling within or between domains, as local operators request. DOTS clients should be able to withdraw those help requests too. DOTS doesn't need a DOTS client to justify asking for help, and a client doesn't need to justify withdrawing it either. That call is made locally, inside the client's domain 👑 Multihomed DOTS clients must be able to pick the right DOTS server(s) to send a mitigation request to. How to pick the right server in a multihomed setup is out of scope for this document 🙈

DOTS protocol implementations have to balance two goals that pull in different directions ⚖️ On one side, DOTS must have measures for message confidentiality, integrity, authenticity, and replay protection, so the protocols don't become extra attack targets themselves 😭 On the other side, the protocol has to stay resilient under extremely hostile conditions, keeping DOTS agents in contact even while attack traffic saturates the link 🔥 There are several ways to build that resiliency, but things like small message size, asynchronous notifications, redundant message delivery, and minimal connection overhead (when possible, given local network policy) tend to make a DOTS protocol robust enough to actually work ✨ Operators of peer DOTS-enabled domains may turn on either quality-of-service or class-of-service traffic tagging to boost the odds that a DOTS signal gets through. DOTS doesn't require those policies to be in place, though, and it should still work fine without them 🧚

The DOTS server and client also need some standardized way to define the scope of a mitigation, plus a way to manage other mitigation-related configurations 🎀

Last but not least, DOTS should be extensible enough to handle future needs in coordinated attack defense. That consideration always takes a back seat to the other operational requirements though 🥲

2.1. General Requirements

GEN-001 Extensibility: Protocols and data models developed as part of DOTS MUST be extensible so DOTS can keep adapting to proprietary DDoS defenses 🧩 Future extensions MUST be backward compatible. Implementations of older protocol versions MUST ignore optional information added to DOTS messages in newer protocol versions. Implementations of older protocol versions MUST reject DOTS messages that carry mandatory information added in newer protocol versions 🙅‍♀️

GEN-002 Resilience and Robustness: The signaling protocol MUST be designed to maximize the chance of signal delivery, even when attack traffic has the network severely constrained 💪 Extra ways to boost DOTS resilience SHOULD be considered, including situations where multiple DOTS servers are provisioned to the DOTS clients 🌈 The protocol MUST be resilient, meaning it keeps working despite message loss and out-of-order or redundant message delivery. To support signaling robustness, DOTS signals SHOULD be carried over transport and application protocols that are not susceptible to head-of-line blocking 🚧 These requirements are at SHOULD strength so they can handle middleboxes and firewall traversal 🧱

GEN-003 Bulk Data Exchange: Infrequent bulk data exchange between DOTS agents can seriously boost attack response coordination 📦 It allows things like populating drop- or accept-listed source addresses, address or prefix group aliasing, exchanging incident reports, and other hinting or configuration that supplements attack responses 📝

Since the resilience requirements for the DOTS signal channel call for a small signal message size, a separate, secure data channel using a reliable transport protocol MUST be used for bulk data exchange 🔐 Reliable bulk data exchange may not be possible during attacks that cause network congestion, though 😬

GEN-004 Mitigation Hinting: DOTS clients may have access to attack details that can help inform mitigation techniques 🔍 Examples include locally collected fingerprints for an ongoing attack, or anticipated or active attack focal points based on other threat intelligence. DOTS clients MAY send mitigation hints derived from attack details to DOTS servers, fully understanding that the DOTS server MAY ignore those hints 🤷‍♀️ Mitigation hints MUST be transmitted across the signal channel, since the data channel may not be working during an attack. How a DOTS server handles mitigation hints is implementation-specific 🛠️

GEN-005 Loop Handling: In certain scenarios, usually involving misconfigured DNS or routing policy, communication between DOTS agents can end up looping 🔁 Signal and data channel implementations should be prepared to detect and terminate such loops so service doesn't get disrupted 🙏

2.2. Signal Channel Requirements

SIG-001 Use of Common Transport Protocols: DOTS MUST operate over common, widely deployed, and standardized transport protocols 🌐 Connectionless transport such as the User Datagram Protocol (UDP) [RFC768] SHOULD be used for the signal channel. The Transmission Control Protocol (TCP) [RFC793] MAY be used if network policy or middlebox capabilities or configurations make it necessary 🎯

SIG-002 Sub-MTU Message Size: To avoid message fragmentation, which would lower the chance of delivery over a congested link, signaling protocol message size MUST be kept under the signaling Path Maximum Transmission Unit (PMTU). This includes the byte overhead of any encapsulation, transport headers, and transport- or message-level security 📏 If the total message size goes over the PMTU, the DOTS agent MUST split the message into separate messages. For example, the list of mitigation scope types could be split into multiple lists, with each list sent in a new message ✂️

DOTS agents can try to learn the PMTU using the procedures discussed in [IP-FRAG-FRAGILE] 🔎 If the PMTU can't be discovered, DOTS agents MUST assume a PMTU of 1280 bytes, since IPv6 requires every link in the Internet to have an MTU of 1280 octets or greater, as specified in [RFC8200] 🧠 If IPv4 support on legacy or otherwise unusual networks is a concern and the PMTU is unknown, DOTS implementations MAY assume a PMTU of 576 bytes for IPv4 datagrams. Every IPv4 host must be able to receive a packet whose length is equal to 576 bytes, as discussed in [RFC791] and [RFC1122] 🦖

SIG-003 Bidirectionality: To support peer health detection, keep an active signal channel going, and increase the chance of signal delivery during an attack, the signal channel MUST be bidirectional 🔄 The client and server transmit signals to each other at regular intervals, no matter whether the client has requested mitigation. The bidirectional signal channel MUST support unidirectional messaging so DOTS agents can send notifications 📣

SIG-004 Channel Health Monitoring: DOTS agents MUST support exchanging heartbeat messages over the signal channel to monitor channel health 💓 These keep-alives maintain any on-path NAT or Firewall bindings, so a cryptographic handshake isn't needed for new mitigation requests 🔐 The heartbeat interval during active mitigation could be negotiable based on NAT/Firewall characteristics. Without information about those characteristics, DOTS agents need to make sure their on-path NAT or Firewall bindings don't expire, by using the keep-alive frequency discussed in Section 3.5 of [RFC8085] ⏰

To support scenarios where loss of heartbeat is used to trigger mitigation, and to keep the channel active, DOTS servers MUST solicit heartbeat exchanges after successful mutual authentication 🫀 When DOTS agents are exchanging heartbeats and no mitigation request is active, either agent MAY request changes to the heartbeat rate. For example, a DOTS server might want to lower the heartbeat frequency or stop heartbeat exchanges when an active DOTS client hasn't requested mitigation, just to control load 🎛️

Following mutual authentication, a signal channel MUST be considered active until a DOTS agent explicitly ends the session 💫 When no attack traffic is present, the signal channel MUST be considered active until either DOTS agent fails to receive heartbeats from the other peer after a mutually agreed upon retransmission procedure has been exhausted. Peer DOTS agents MUST regularly send heartbeats to each other while a mitigation request is active. Heartbeat loss is much more likely during a volumetric attack, so DOTS agents SHOULD avoid terminating the signal channel when mitigation is active and heartbeats aren't received by either DOTS agent for an extended period 😤 The exceptions to ending the signal channel session during active mitigation are:

To handle a possible DOTS server restart or crash, the DOTS clients MAY attempt to establish a new signal channel session, but MUST continue to send heartbeats on the current session so the DOTS server knows the session is still alive. If the new session is successfully established, the DOTS client can terminate the current session 🔁
DOTS servers are assumed to have the ability to monitor the attack, using feedback from the mitigator and other available sources, and MAY use the absence of attack traffic and lack of client heartbeats as an indication that the signal channel is defunct 🕵️‍♀️

SIG-005 Channel Redirection 🦋: okay so, to keep DOTS operational flexibility and scalability bussin, DOTS servers SHOULD be able to redirect DOTS clients to another DOTS server at any time 💅 But bestie, DOTS clients MUST NOT assume the redirection target DOTS server shares security state with the redirecting DOTS server 🙈 Clients are totally free to try abbreviated security negotiation methods the protocol supports, like DTLS session resumption ✨ but they MUST be ready to negotiate brand new security state with the redirection target DOTS server 💜 And the redirection DOTS server and redirecting DOTS server MUST belong to the same administrative domain 🏰

Because link congestion during an attack makes packet loss way more likely 📉, DOTS servers SHOULD NOT redirect while mitigation is enabled during an active attack against a target in the DOTS client's domain 🚫

SIG-006 Mitigation Requests and Status 📬: Authorized DOTS clients MUST be able to request scoped mitigation from DOTS servers 🙌 DOTS servers MUST send status back to the clients about those mitigation requests. If a DOTS server rejects an authorized request for mitigation, it MUST include a reason for the rejection in the status message it sends to the client 🙅‍♀️

DOTS servers MUST regularly send mitigation status updates to authorized DOTS clients that have requested and been granted mitigation 🔁 If unreliable transport is used for the signal channel protocol, then since packet loss is more likely during a DDoS attack, DOTS servers need to send the mitigation status multiple times at regular intervals, following the data transmission guidelines in Section 3.1.3 of [RFC8085] 📡

When DOTS client-requested mitigation is active, DOTS server status messages MUST include the following mitigation metrics:

Total number of packets blocked by the mitigation
Current number of packets per second blocked
Total number of bytes blocked
Current number of bytes per second blocked

DOTS clients MAY take these metrics into account when deciding whether to ask the DOTS server to stop mitigating 📊

A DOTS client MAY withdraw a mitigation request at any time, whether or not mitigation is currently active 👋 The DOTS server MUST immediately acknowledge a DOTS client's request to stop mitigation ✅

To guard against route or DNS flapping caused by a client rapidly toggling mitigation, and to dampen the effect of oscillating attacks 🌊, DOTS servers MAY keep mitigation going for a limited period after acknowledging a DOTS client's withdrawal of a mitigation request. During that period, DOTS server status messages SHOULD indicate that mitigation is active but terminating 🫠 DOTS clients MAY reverse the mitigation termination during this active-but-terminating period by sending a new mitigation request for the same scope 🔄 The DOTS server MUST treat this request as a mitigation lifetime extension (see SIG-007) ⏰

The initial active-but-terminating period is both implementation- and deployment-specific, but SHOULD be sufficiently long enough to soak up the latency that route propagation adds 🛣️ If a DOTS client refreshes the mitigation before the active-but-terminating period runs out, the DOTS server MAY increase that period up to a maximum of 300 seconds (5 minutes) ⏳ Once the active-but-terminating period elapses, the DOTS server MUST treat the mitigation as terminated, since the DOTS client is no longer responsible for it 👋

SIG-007 Mitigation Lifetime 🕰️: DOTS servers MUST support mitigations for a negotiated time interval and MUST terminate a mitigation when that lifetime elapses. They also MUST support renewal of mitigation lifetimes in mitigation requests from DOTS clients, so clients can 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 active-but-terminating period, as described above in SIG-005 🤝

DOTS clients MUST include a mitigation lifetime in all mitigation requests 📝

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 clients MUST be prepared to not be granted mitigations with indefinite lifetimes 🙃 DOTS servers MAY refuse mitigations with indefinite lifetimes for policy reasons. The reasons themselves are out of scope for this document 📜 If the DOTS server does not grant a mitigation request with an indefinite mitigation lifetime, it MUST set the lifetime to a value that is configured locally. That value MUST be returned in a reply to the requesting DOTS client 🔧

SIG-008 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 prefixes [RFC4632]
IPv6 prefixes [RFC4291] [RFC5952]
Domain names [RFC1035]

The following mitigation scope type is OPTIONAL:

Uniform Resource Identifiers [RFC3986]

DOTS servers MUST be able to resolve domain names and (when supported) URIs. How name resolution is managed on the DOTS server is implementation-specific 🔍

DOTS agents MUST support mitigation scope aliases, allowing DOTS clients and servers to refer to collections of protected resources by an opaque identifier created through the data channel, direct configuration, or other means 🫧 Domain name and URI mitigation scopes may be thought of as a form of scope alias, in which the addresses that the domain name or URI resolves to represent the full scope of the mitigation 🌐

If there is additional information available narrowing the scope of any requested attack response, such as a targeted port range, protocol, or service, DOTS clients SHOULD include that information in client mitigation requests 🔬 DOTS clients MAY also include additional attack details. DOTS servers MAY ignore such supplemental information when enabling countermeasures on the mitigator 🤷‍♀️

As an active attack evolves, DOTS clients MUST be able to adjust as necessary the scope of requested mitigation by refining the scope of resources requiring mitigation 🔄

A DOTS client may obtain the mitigation scope through direct provisioning or through implementation-specific methods of discovery. DOTS clients MUST support at least one mechanism to obtain mitigation scope 💯

SIG-009 Mitigation Efficacy 📈: When a mitigation request is active, DOTS clients MUST be able to transmit a metric of perceived mitigation efficacy to the DOTS server 💬 DOTS servers MAY use the efficacy metric to adjust countermeasures activated on a mitigator on behalf of a DOTS client 🎛️

SIG-010 Conflict Detection and Notification 🚨: Multiple DOTS clients controlled by a single administrative entity may send conflicting mitigation requests as a result of misconfiguration, operator error, or compromised DOTS clients 😬 DOTS servers in the same administrative domain 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 in a single administrative domain SHALL detect such conflicting requests and SHALL notify the DOTS clients in conflict 🔔 The notification MUST indicate the nature and scope of the conflict, for example, the overlapping prefix range in a conflicting mitigation request 📍

SIG-011 Network Address Translator Traversal 🧭: DOTS clients may be deployed behind a Network Address Translator (NAT) and need to communicate with DOTS servers through the NAT 🏠 DOTS protocols MUST therefore be capable of traversing NATs 🚪

If UDP is used as the transport for the DOTS signal channel, all considerations in "Middlebox Traversal Guidelines" in [RFC8085] apply to DOTS 📦 Regardless of transport, DOTS protocols MUST follow established best common practices established in BCP 127 for NAT traversal [RFC4787] [RFC6888] [RFC7857] 📚

2.3. Data Channel Requirements ✨

okay the data channel is basically the workhorse for bulk data exchanges between DOTS agents 📦 It's not built to deal with attack conditions the way the signal channel is 💀 Since its main job is data exchange, a reliable transport is required so DOTS agents can detect whether data delivery succeeded or failed 🫶

The data channel also gives you a protocol for DOTS configuration and management 🎀 For example, a DOTS client might submit a collection of prefixes to a DOTS server that it wants to refer to by alias when requesting mitigation 🌸 The server would respond with a success status and the new prefix group alias, or with an error status and message if the DOTS client's data channel request failed 😭

DATA-001 Reliable transport 🚚: Messages sent over the data channel MUST be delivered reliably in the order sent 💌

DATA-003 Resource Configuration 🛠️: To help meet the general and signal channel requirements in Sections 2.1 and 2.2, DOTS server implementations MUST provide an interface to configure resource identifiers, as described in SIG-008. DOTS server implementations MAY expose additional configurability. Additional configurability is implementation-specific 🧩

DATA-004 Policy Management 🛡️: DOTS servers MUST provide methods for DOTS clients to manage drop- and accept-lists of traffic destined for resources belonging to a client 🚦

For example, a DOTS client should be able to create a drop- or accept-list entry, retrieve a list of current entries from either list, update the content of either list, and delete entries as necessary 📋

How a DOTS server authorizes DOTS client management of drop- and accept-list entries is implementation-specific 🔐

2.4. Security Requirements 🔐

okay bestie, DOTS has to live in a seriously strict security neighborhood 😭 because if a signal or data channel isn't protected well enough, attackers can abuse it and end up enabling or boosting the very attacks DOTS is supposed to stop 💀

SEC-001 Peer Mutual Authentication 🫶: DOTS agents MUST authenticate each other before a DOTS signal or data channel is considered valid. The method of authentication is not specified in this document but should follow current IETF best practices [RFC7525] 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 IETF best practices [RFC7525] for encryption and message authentication. Client-domain DOTS gateways are more trusted than DOTS clients, while server-domain DOTS gateways and DOTS servers share the same level of trust. A security mechanism at the transport layer (TLS or DTLS) is thus adequate to provide security between peer DOTS agents.

So that DOTS protocols stay secure even as cryptanalysis and traffic analysis get smarter, DOTS agents MUST support secure negotiation of the terms and mechanisms of protocol security, subject to the interoperability and signal message size requirements in Section 2.2 ✨

The interfaces between a downstream DOTS server and an upstream DOTS client inside a DOTS gateway are implementation-specific, but those interfaces MUST still provide security equivalent to 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, the two DOTS agents could be implemented within the same process security boundary 🧚

SEC-003 Data Privacy and Integrity 🎀: Transmissions over the DOTS protocols are likely to contain operationally or privacy-sensitive information or instructions from the remote DOTS agent. Theft, modification, or replay of message transmissions could lead to information leaks or malicious transactions on behalf of the sending agent (see Section 4). Consequently, data sent over the DOTS protocols MUST be encrypted using secure transports (TLS or DTLS). 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.

SEC-004 Message Replay Protection 🙈: To stop a passive attacker from capturing and replaying old messages, which could disrupt or influence the network policy of the receiving DOTS agent's domain, DOTS protocols MUST provide a method for replay detection and prevention.

Within the signal channel, messages MUST be uniquely identified so that replayed or duplicated messages can be detected and discarded. Unique mitigation requests MUST be processed at most once.

SEC-005 Authorization 👑: DOTS servers MUST authorize all messages from DOTS clients that pertain to mitigation, configuration, filtering, or status.

DOTS servers MUST reject mitigation requests with scopes that the DOTS client is not authorized to manage.

Likewise, DOTS servers MUST refuse to allow creation, modification, or deletion of scope aliases and drop- or accept-lists when the DOTS client is unauthorized.

The modes of authorization are implementation-specific.

2.5. Data Model Requirements 🧁

A well-structured DOTS data model is critical to building successful DOTS protocols, so let's get it right ✨

DM-001 Structure 🌸: The data-model structure for the DOTS protocol MAY be described by a single module or be divided into related collections of hierarchical modules and submodules. If the data model structure is split across modules, those distinct modules MUST allow references to describe the overall data model's structural dependencies.

DM-002 Versioning 🏷️: To ensure interoperability between DOTS protocol implementations, data models MUST be versioned. How the protocols represent data-model versions is not defined in 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 SIG-008, the data model MUST include extensible 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 signal channel. Measurements of loss might include, but are not restricted to, number of consecutive missed heartbeat messages, retransmission count, or request timeouts.

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 SIG-003.

DM-009 Relationship to Transport 🚫: The DOTS data model MUST NOT make any assumptions about specific characteristics of any given transport into the data model, but instead represent the fields in the model explicitly.

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 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 [RFC8085]. Signal channel implementations using such connectionless transports, such as UDP, therefore MUST include a congestion control mechanism.

Signal channel implementations using an IETF standard congestion-controlled transport protocol (like TCP) may rely on built-in transport 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 an IETF standard congestion-controlled transport protocol may rely on the transport implementation's built-in congestion control mechanisms 🫧

4. Security Considerations 🛡️

This document informs future protocols under development and so does not have security considerations of its own. However, operators should be aware of potential risks involved in deploying DOTS. DOTS agent impersonation and signal blocking are discussed here. Additional DOTS security considerations may be found in [DOTS-ARCH] and DOTS protocol documents.

Impersonation of either a DOTS server or a DOTS client could have catastrophic impact on operations in either domain. 😱 If an attacker has the ability to impersonate a DOTS client, that attacker can affect policy on the network path to the DOTS client's domain up to and including instantiation of drop-lists blocking all inbound traffic to networks for which the DOTS client is authorized to request mitigation.

Similarly, an impersonated DOTS server may be able to act as a sort of malicious DOTS gateway, intercepting requests from the downstream DOTS client and modifying them before transmission to the DOTS server to inflict the desired impact on traffic to or from the DOTS client's domain. Among other things, this malicious DOTS gateway might receive and discard mitigation requests from the DOTS client, ensuring no requested mitigation is ever applied. 🕵️‍♀️

To detect misuse, as detailed in Section 2.4, DOTS implementations require mutual authentication of DOTS agents in order to make agent impersonation more difficult. However, impersonation may still be possible as a result of credential theft, implementation flaws, or DOTS agents being compromised.

To detect compromised DOTS agents, DOTS operators should carefully monitor and audit DOTS agents to detect misbehavior and deter misuse while employing best current practices to secure network communications to reduce attack surface 🔍

Blocking communication between DOTS agents has the potential to disrupt the core function of DOTS, which is to request mitigation of active or expected DDoS attacks. The DOTS signal channel is expected to operate over congested inbound links, and, as described in Section 2.2, the signal channel protocol must be designed for minimal data transfer to reduce the incidence of signal loss 📦

5. IANA Considerations 🌈

This document has no IANA actions.

6. References 📚

6.1. Normative References ✨

okay so these are the receipts 🧾 the stuff this doc needs you to have read before you can even start, no cap. every single one is a must-read, bestie 💅

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [RFC791]   Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/info/rfc791>.

   [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,
              <https://www.rfc-editor.org/info/rfc1122>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
              2006, <https://www.rfc-editor.org/info/rfc4632>.

   [RFC4787]  Audet, F., Ed. and C. Jennings, "Network Address
              Translation (NAT) Behavioral Requirements for Unicast
              UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
              2007, <https://www.rfc-editor.org/info/rfc4787>.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952,
              DOI 10.17487/RFC5952, August 2010,
              <https://www.rfc-editor.org/info/rfc5952>.

   [RFC6888]  Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
              A., and H. Ashida, "Common Requirements for Carrier-Grade
              NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
              April 2013, <https://www.rfc-editor.org/info/rfc6888>.

   [RFC7857]  Penno, R., Perreault, S., Boucadair, M., Ed., Sivakumar,
              S., and K. Naito, "Updates to Network Address Translation
              (NAT) Behavioral Requirements", BCP 127, RFC 7857,
              DOI 10.17487/RFC7857, April 2016,
              <https://www.rfc-editor.org/info/rfc7857>.

   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <https://www.rfc-editor.org/info/rfc8085>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

6.2. Informative References 💖

these ones are more like bonus reading 🧚 not strictly required, but honestly so worth it, they explain the why behind everything. the two drafts are still works in progress, so they're basically spicy previews 👀

   [DOTS-ARCH]
              Mortensen, A., Ed., Reddy, T., Ed., Andreasen, F., Teague,
              N., and R. Compton, "Distributed-Denial-of-Service Open
              Threat Signaling (DOTS) Architecture", Work in Progress,
              draft-ietf-dots-architecture-13, April 2019.

   [DOTS-USE]
              Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
              Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
              Open Threat Signaling", Work in Progress, draft-ietf-dots-
              use-cases-17, January 2019.

   [IP-FRAG-FRAGILE]
              Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O.,
              and F. Gont, "IP Fragmentation Considered Fragile", Work
              in Progress, draft-ietf-intarea-frag-fragile-10, May 2019.

   [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,
              <https://www.rfc-editor.org/info/rfc3261>.

   [RFC7092]  Kaplan, H. and V. Pascual, "A Taxonomy of Session
              Initiation Protocol (SIP) Back-to-Back User Agents",
              RFC 7092, DOI 10.17487/RFC7092, December 2013,
              <https://www.rfc-editor.org/info/rfc7092>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732,
              DOI 10.17487/RFC4732, December 2006,
              <https://www.rfc-editor.org/info/rfc4732>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <https://www.rfc-editor.org/info/rfc4949>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

Acknowledgments 🎀

big thank-yous 🫶 to these legends for reading everything super carefully and giving feedback. they're the reason this doc is as solid as it is 🔥

   Thanks to Roman Danyliw, Matt Richardson, Joe Touch, Scott Bradner,
   Robert Sparks, Brian Weis, Benjamin Kaduk, Eric Rescorla, Alvaro
   Retana, Suresh Krishnan, Ben Campbell, Mirja Kuehlewind, and Jon
   Shallow for their careful reading and feedback.

Contributors 💅

these folks put in serious work on the document too, and they absolutely deserve the shoutout 🌸

   Mohamed Boucadair
      Orange

      mohamed.boucadair@orange.com

   Flemming Andreasen
      Cisco Systems, Inc.

      fandreas@cisco.com

   Dave Dolson
      Sandvine

      ddolson@sandvine.com

Authors' Addresses 🦋

and here's where you can find the authors, iykyk 🧚 just reach out if you have questions, they're chill

   Andrew Mortensen
   Arbor Networks
   2727 S. State St.
   Ann Arbor, MI  48104
   United States of America

   Email: andrewmortensen@gmail.com


   Tirumaleswar Reddy
   McAfee
   Embassy Golf Link Business Park
   Bangalore, Karnataka  560071
   India

   Email: TirumaleswarReddy_Konda@McAfee.com


   Robert Moskowitz
   Huawei
   Oak Park, MI  42837
   United States of America

   Email: rgm@htt-consult.com

📦 where this page comes from

ietf: rfc8612 2019-05
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