DOTS M. Boucadair Internet-Draft Orange Intended status: Standards Track T. Reddy Expires: November 7, 2019 McAfee P. Patil Cisco May 6, 2019 Distributed-Denial-of-Service Open Threat Signaling (DOTS) Server Discovery draft-ietf-dots-server-discovery-02 Abstract It may not be possible for a network to determine the cause for an attack, but instead just realize that some resources seem to be under attack. To fill that gap, Distributed-Denial-of-Service Open Threat Signaling (DOTS) allows a network to inform a DOTS server that it is under a potential attack so that appropriate mitigation actions are undertaken. This document specifies mechanisms to configure DOTS clients with DOTS servers. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 https://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 November 7, 2019. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. Boucadair, et al. Expires November 7, 2019 [Page 1] Internet-Draft DOTS Server Discovery May 2019 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Why Multiple Discovery Mechanisms? . . . . . . . . . . . . . 4 4. Unified DOTS Discovery Procedure . . . . . . . . . . . . . . 5 5. DHCP Options for DOTS . . . . . . . . . . . . . . . . . . . . 7 5.1. DHCPv6 DOTS Options . . . . . . . . . . . . . . . . . . . 8 5.1.1. Format of DOTS Reference Identifier Option . . . . . 8 5.1.2. Format of DOTS Address Option . . . . . . . . . . . . 8 5.1.3. DHCPv6 Client Behavior . . . . . . . . . . . . . . . 9 5.2. DHCPv4 DOTS Options . . . . . . . . . . . . . . . . . . . 10 5.2.1. Format of DOTS Reference Identifier Option . . . . . 10 5.2.2. Format of DOTS Address Option . . . . . . . . . . . . 11 5.2.3. DHCPv4 Client Behavior . . . . . . . . . . . . . . . 12 6. Discovery using Service Resolution . . . . . . . . . . . . . 13 7. DNS Service Discovery . . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8.1. DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.2. Service Resolution . . . . . . . . . . . . . . . . . . . 15 8.3. DNS Service Discovery . . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 16 9.2. DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . 16 9.3. Application Service & Application Protocol Tags . . . . . 16 9.3.1. DOTS Application Service Tag Registration . . . . . . 16 9.3.2. signal.udp Application Protocol Tag Registration . . 17 9.3.3. signal.tcp Application Protocol Tag Registration . . 17 9.3.4. data.tcp Application Protocol Tag Registration . . . 17 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 11.1. Normative References . . . . . . . . . . . . . . . . . . 18 11.2. Informative References . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Boucadair, et al. Expires November 7, 2019 [Page 2] Internet-Draft DOTS Server Discovery May 2019 1. Introduction DDoS Open Threat Signaling (DOTS) [I-D.ietf-dots-architecture] specifies an architecture, in which a DOTS client can inform a DOTS server that the network is under a potential attack and that appropriate mitigation actions are required. Indeed, because the lack of a common method to coordinate a real-time response among involved actors and network domains inhibits the effectiveness of DDoS attack mitigation, DOTS signal channel protocol [I-D.ietf-dots-signal-channel] is meant to carry requests for DDoS attack mitigation, thereby reducing the impact of an attack and leading to more efficient defensive actions in various deployment scenarios such as those discussed in [I-D.ietf-dots-use-cases]. Moreover, DOTS clients can instruct a DOTS server to install filtering rules by means of DOTS data channel [I-D.ietf-dots-data-channel]. The basic high-level DOTS architecture is illustrated in Figure 1 ([I-D.ietf-dots-architecture]): +-----------+ +-------------+ | Mitigator | ~~~~~~~~~~ | DOTS Server | +-----------+ +-------------+ | | | +---------------+ +-------------+ | Attack Target | ~~~~~~ | DOTS Client | +---------------+ +-------------+ Figure 1: Basic DOTS Architecture [I-D.ietf-dots-architecture] specifies that the DOTS client may be provided with a list of DOTS servers; each associated with one or more IP addresses. These addresses may or may not be of the same address family. The DOTS client establishes one or more DOTS sessions by connecting to the provided DOTS server addresses. This document specifies methods for DOTS clients to discover their DOTS server(s). The rationale for specifying multiple discovery mechanisms is discussed in Section 3. The discovery methods can also used by a DOTS server to locate a DOTS client in the context of DOTS Call Home [I-D.ietf-dots-signal-call-home]. Boucadair, et al. Expires November 7, 2019 [Page 3] Internet-Draft DOTS Server Discovery May 2019 Considerations for the selection of DOTS server(s) by multi-homed DOTS clients is out of scope; the reader should refer to [I-D.ietf-dots-multihoming] for more details. Likewise, happy eyeballs considerations for DOTS signal channel protocol are out of scope. The reader should refer to Section 4 of [I-D.ietf-dots-signal-channel]. This document assumes that security credentials to authenticate DOTS server(s) are provisioned to a DOTS client using a variety of means such as (but not limited to) those discussed in [I-D.ietf-netconf-zerotouch] or [I-D.ietf-anima-bootstrapping-keyinfra]. DOTS clients use those credentials for authentication purposes following the rules documented in [I-D.ietf-dots-signal-channel]. 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. The reader should be familiar with the terms defined in [I-D.ietf-dots-architecture] and [RFC3958]. DHCP refers to both DHCPv4 [RFC2131] and DHCPv6 [RFC8415]. 3. Why Multiple Discovery Mechanisms? It is tempting to specify one single discovery mechanism for DOTS. Nevertheless, the analysis of the various use cases sketched in [I-D.ietf-dots-use-cases] reveals that it is unlikely that one single discovery method can be suitable for all the sample deployments. Concretely: o Many use cases discussed in [I-D.ietf-dots-use-cases] do involve a CPE device. Multiple CPEs, connected to distinct network providers may even be considered. It is intuitive to leverage on existing mechanisms such as discovery using service resolution or DHCP to provision the CPE acting as a DOTS client with the DOTS server(s). o Resolving a DOTS server domain name offered by an upstream transit provider provisioned to a DOTS client into IP address(es) require the use of the appropriate DNS resolvers; otherwise, resolving those names will fail. The use of protocols such as DHCP does Boucadair, et al. Expires November 7, 2019 [Page 4] Internet-Draft DOTS Server Discovery May 2019 allow to associate provisioned DOTS server domain names with a list of DNS servers to be used for name resolution. Furthermore, DHCP allows to directly provision IP addresses avoiding therefore the need for extra lookup delays. o Some of the use cases may allow DOTS clients to have direct communications with upstream DOTS servers; that is no DOTS gateway is involved. Leveraging on existing features that do not require specific feature on the node embedding the DOTS client may ease DOTS deployment. Typically, the use of Straightforward-Naming Authority Pointer (S-NAPTR) lookups [RFC3958] allows the DOTS server administrators to provision the preferred DOTS transport protocol between the DOTS client and the DOTS server and allows the DOTS client to discover this preference. o The upstream network provider is not the DDoS mitigation provider for some of these use cases. It is safe to assume that for such deployments, the DOTS server(s) domain name is provided during the service subscription (i.e., manual/local configuration). o Multiple DOTS clients may be enabled within a network (e.g., enterprise network). Dynamic means to discover DOTS servers in a deterministic manner are interesting from an operational standpoint. o Some of the use cases may involve a DOTS gateway that is responsible for selecting the appropriate DOTS server(s) to relay requests received from DOTS clients. Consequently, this document describes a unified discovery logic (Section 4) which involves the following mechanisms: o Dynamic discovery using DHCP (Section 5). o A resolution mechanism based on straightforward Naming Authority Pointer (S-NAPTR) resource records in the Domain Name System (DNS) (Section 6). o DNS Service Discovery (Section 7). 4. Unified DOTS Discovery Procedure A key point in the deployment of DOTS is the ability of network operators to be able to configure DOTS clients with the correct DOTS server(s) information consistently. To accomplish this, operators will need a consistent set of ways in which DOTS clients can discover this information, and a consistent priority among these options. If some devices prefer manual configuration over dynamic discovery, Boucadair, et al. Expires November 7, 2019 [Page 5] Internet-Draft DOTS Server Discovery May 2019 while others prefer dynamic discovery over manual configuration, the result will be a process of "whack-a-mole", where the operator must find devices that are using the wrong DOTS server(s), determine how to ensure the devices are configured properly, and then reconfigure the device through the preferred method. All DOTS clients MUST support at least one of the three mechanisms below to determine a DOTS server list. All DOTS clients SHOULD implement all three, or as many as are practical for any specific device, of these ways to discover DOTS servers, in order to facilitate the deployment of DOTS in large scale environments: 1. Explicit configuration: * Local/Manual configuration: A DOTS client, will learn the DOTS server(s) by means of local or manual DOTS configuration (i.e., DOTS servers configured at the system level). Configuration discovered from a DOTS client application is considered as local configuration. An implementation may give the user an opportunity (e.g., by means of configuration file options or menu items) to specify DOTS server(s) for each address family. These MAY be specified either as IP addresses or the DNS name of a DOTS server. When only DOTS server's IP addresses are configured, a reference identifier must also be configured for authentication purposes. * Automatic configuration (e.g., DHCP, an automation system): The DOTS client attempts to discover DOTS server(s) names and/ or addresses from DHCP, as described in Section 5. 2. Service Resolution : The DOTS client attempts to discover DOTS server name(s) using service resolution, as specified in Section 6. 3. DNS SD: DNS Service Discovery. The DOTS client attempts to discover DOTS server name(s) using DNS service discovery, as specified in Section 7. Some of these mechanisms imply the use of DNS to resolve the IP address(es) of the DOTS server, while others imply an IP address of the relevant DOTS server is obtained directly. Implementation options may vary on a per device basis, as some devices may not have DNS capabilities and/or proper configuration. DOTS clients will prefer information received from the discovery methods in the order listed. Boucadair, et al. Expires November 7, 2019 [Page 6] Internet-Draft DOTS Server Discovery May 2019 On hosts with more than one interface or address family (IPv4/v6), the DOTS server discovery procedure has to be performed for each combination of interface and address family. A client MAY choose to perform the discovery procedure only for a desired interface/address combination if the client does not wish to discover a DOTS server for all combinations of interface and address family. The above procedure MUST also be followed by a DOTS gateway. The discovery method MUST be reiterated upon the following events: o Expiry of a lease associated with a discovered DOTS server. o Expiry of a DOTS server's certificate currently in use. o Attachment to a new network. 5. DHCP Options for DOTS As reported in Section 1.7.2 of [RFC6125]: "few certification authorities issue server certificates based on IP addresses, but preliminary evidence indicates that such certificates are a very small percentage (less than 1%) of issued certificates". In order to allow for PKIX-based authentication between a DOTS client and server while accommodating for the current best practices for issuing certificates, this document allows for configuring names to DOTS clients. These names can be used for two purposes: to retrieve the list of IP addresses of a DOTS server or to be presented as a reference identifier for authentication purposes. Defining the option to include a list of IP addresses would avoid a dependency on an underlying name resolution, but that design requires to also supply a name for PKIX-based authentication purposes. The design assumes that the same DOTS server is used for establishing both signal and data channels. For more customized configurations (e.g., transport-specific configuration, distinct DOTS servers for the signal and the data channels), an operator can supply only a DOTS reference identifier that will be then passed to the procedure described in Section 6. Boucadair, et al. Expires November 7, 2019 [Page 7] Internet-Draft DOTS Server Discovery May 2019 5.1. DHCPv6 DOTS Options 5.1.1. Format of DOTS Reference Identifier Option The DHCPv6 DOTS option is used to configure a name of the DOTS server. The format of this option is shown in Figure 2. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_V6_DOTS_RI | Option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | dots-server-name (FQDN) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: DHCPv6 DOTS Reference Identifier Option The fields of the option shown in Figure 2 are as follows: o Option-code: OPTION_V6_DOTS_RI (TBA1, see Section 9.1) o Option-length: Length of the dots-server-name field in octets. o dots-server-name: A fully qualified domain name of the DOTS server. This field is formatted as specified in Section 10 of [RFC8415]. An example of the dots-server-name encoding is shown in Figure 3. This example conveys the FQDN "dots.example.com.". +------+------+------+------+------+------+------+------+------+ | 0x04 | d | o | t | s | 0x07 | e | x | a | +------+------+------+------+------+------+------+------+------+ | m | p | l | e | 0x03 | c | o | m | 0x00 | +------+------+------+------+------+------+------+------+------+ Figure 3: An example of the dots-server-name Encoding 5.1.2. Format of DOTS Address Option The DHCPv6 DOTS option can be used to configure a list of IPv6 addresses of a DOTS server. The format of this option is shown in Figure 4. As a reminder, this format follows the guidelines for creating new DHCPv6 options (Section 5.1 of [RFC7227]). Boucadair, et al. Expires November 7, 2019 [Page 8] Internet-Draft DOTS Server Discovery May 2019 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_V6_DOTS_ADDRESS | Option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | DOTS ipv6-address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | DOTS ipv6-address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: DHCPv6 DOTS Address Option The fields of the option shown in Figure 4 are as follows: o Option-code: OPTION_V6_DOTS_ADDRESS (TBA2, see Section 9.1) o Option-length: Length of the 'DOTS ipv6-address(es)' field in octets. MUST be a multiple of 16. o DOTS ipv6-address: Includes one or more IPv6 addresses [RFC4291] of the DOTS server to be used by the DOTS client. Note, IPv4-mapped IPv6 addresses (Section 2.5.5.2 of [RFC4291]) are allowed to be included in this option. To return more than one DOTS servers to the requesting DHCPv6 client, the DHCPv6 server returns multiple instances of OPTION_V6_DOTS. 5.1.3. DHCPv6 Client Behavior DHCP clients MAY request options OPTION_V6_DOTS_RI and OPTION_V6_DOTS_ADDRESS, as defined in [RFC8415], Sections 18.2.1, 18.2.2, 18.2.4, 18.2.5, 18.2.6, and 21.7. As a convenience to the reader, it is mentioned here that the DHCP client includes the requested option codes in the Option Request Option. If the DHCP client receives more than one instance of OPTION_V6_DOTS_RI (or OPTION_V6_DOTS_ADDRESS) option, it MUST use only the first instance of that option. If the DHCP client receives both OPTION_V6_DOTS_RI and OPTION_V6_DOTS_ADDRESS, the content of OPTION_V6_DOTS_RI is used as Boucadair, et al. Expires November 7, 2019 [Page 9] Internet-Draft DOTS Server Discovery May 2019 reference identifier for authentication purposes (e.g., PKIX [RFC6125]), while the addresses included in OPTION_V6_DOTS_ADDRESS are used to reach the DOTS server. In other words, the name conveyed in OPTION_V6_DOTS_RI MUST NOT be passed to underlying resolution library in the presence of OPTION_V6_DOTS_ADDRESS in a response. If the DHCP client receives OPTION_V6_DOTS_RI only, but OPTION_V6_DOTS_RI option contains more than one name, as distinguished by the presence of multiple root labels, the DHCP client MUST use only the first name. Once the name is validated (Section 8 of [RFC8415]), the name is passed to a name resolution library. Moreover, that name is also used as a reference identifier for authentication purposes. If the DHCP client receives OPTION_V6_DOTS_ADDRESS only, the address(es) included in OPTION_V6_DOTS_ADDRESS is used to reach the DOTS server. In addition, these addresses can be used as identifiers for authentication. The DHCP client MUST silently discard multicast and host loopback addresses [RFC6890] conveyed in OPTION_V6_DOTS_ADDRESS. 5.2. DHCPv4 DOTS Options 5.2.1. Format of DOTS Reference Identifier Option The DHCPv4 DOTS option is used to configure a name of the DOTS server. The format of this option is illustrated in Figure 5. Code Length DOTS server name +-----+-----+-----+-----+-----+-----+-----+-- |TBA3 | n | s1 | s2 | s3 | s4 | s5 | ... +-----+-----+-----+-----+-----+-----+-----+-- The values s1, s2, s3, etc. represent the domain name labels in the domain name encoding. Figure 5: DHCPv4 DOTS Reference Identifier Option The fields of the option shown in Figure 5 are as follows: o Code: OPTION_V4_DOTS_RI (TBA3, see Section 9.2); o Length: Includes the length of the "DOTS server name" field in octets; the maximum length is 255 octets. o DOTS server name: The domain name of the DOTS server. This field is formatted as specified in Section 10 of [RFC8415]. Boucadair, et al. Expires November 7, 2019 [Page 10] Internet-Draft DOTS Server Discovery May 2019 5.2.2. Format of DOTS Address Option The DHCPv4 DOTS option can be used to configure a list of IPv4 addresses of a DOTS server. The format of this option is illustrated in Figure 6. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code=TBA4 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | List-Length | List of | +-+-+-+-+-+-+-+-+ DOTS | / IPv4 Addresses / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --- | List-Length | List of | | +-+-+-+-+-+-+-+-+ DOTS | | / IPv4 Addresses / | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . ... . optional +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | List-Length | List of | | +-+-+-+-+-+-+-+-+ DOTS | | / IPv4 Addresses / | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --- Figure 6: DHCPv4 DOTS Address Option The fields of the option shown in Figure 6 are as follows: o Code: OPTION_V4_DOTS_ADDRESS (TBA4, see Section 9.2); o Length: Length of all included data in octets. The minimum length is 5. o List-Length: Length of the "List of DOTS IPv4 Addresses" field in octets; MUST be a multiple of 4. o List of DOTS IPv4 Addresses: Contains one or more IPv4 addresses of the DOTS server to be used by the DOTS client. The format of this field is shown in Figure 7. o OPTION_V4_DOTS_ADDRESS can include multiple lists of DOTS IPv4 addresses; each list is treated separately as it corresponds to a given DOTS server. When several lists of DOTS IPv4 addresses are to be included, "List-Length" and "DOTS IPv4 Addresses" fields are repeated. Boucadair, et al. Expires November 7, 2019 [Page 11] Internet-Draft DOTS Server Discovery May 2019 0 8 16 24 32 40 48 +-----+-----+-----+-----+-----+-----+-- | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-- IPv4 Address 1 IPv4 Address 2 ... This format assumes that an IPv4 address is encoded as a1.a2.a3.a4. Figure 7: Format of the List of DOTS IPv4 Addresses OPTION_V4_DOTS_ADDRESS is a concatenation-requiring option. As such, the mechanism specified in [RFC3396] MUST be used if OPTION_V4_DOTS_ADDRESS exceeds the maximum DHCPv4 option size of 255 octets. 5.2.3. DHCPv4 Client Behavior To discover a DOTS server, the DHCPv4 client MUST include both OPTION_V4_DOTS_RI and OPTION_V4_DOTS_ADDRESS in a Parameter Request List Option [RFC2132]. If the DHCP client receives more than one instance of OPTION_V4_DOTS_RI (or OPTION_V4_DOTS_ADDRESS) option, it MUST use only the first instance of that option. If the DHCP client receives both OPTION_V4_DOTS_RI and OPTION_V4_DOTS_ADDRESS, the content of OPTION_V6_DOTS_RI is used as reference identifier for authentication purposes, while the addresses included in OPTION_V4_DOTS_ADDRESS are used to reach the DOTS server. In other words, the name conveyed in OPTION_V4_DOTS_RI MUST NOT be passed to underlying resolution library in the presence of OPTION_V4_DOTS_ADDRESS in a response. If the DHCP client receives OPTION_V4_DOTS_RI only, but OPTION_V4_DOTS_RI option contains more than one name, as distinguished by the presence of multiple root labels, the DHCP client MUST use only the first name. Once the name is validated (Section 10 of [RFC8415]), the name is passed to a name resolution library. Moreover, that name is also used as a reference identifier for authentication purposes. If the DHCP client receives OPTION_V4_DOTS_ADDRESS only, the address(es) included in OPTION_V4_DOTS_ADDRESS is used to reach the DOTS server. In addition, these addresses can be used as identifiers for authentication. The DHCP client MUST silently discard multicast and host loopback addresses conveyed in OPTION_V4_DOTS_ADDRESS. Boucadair, et al. Expires November 7, 2019 [Page 12] Internet-Draft DOTS Server Discovery May 2019 6. Discovery using Service Resolution This mechanism is performed in two steps: 1. A DNS domain name is retrieved for each combination of interface and address family. A DOTS client has to determine the domain in which it is located relying on dynamic means such as DHCP (Section 5) . Implementations MAY allow the user to specify a default name that is used, if no specific name has been configured. 2. Retrieved DNS domain names are then used for S-NAPTR lookups. Further DNS lookups may be necessary to determine DOTS server IP address(es). Once the DOTS client has retrieved client's DNS domain or discovered the DOTS server name that needs to be resolved (e.g., Section 5), an S-NAPTR lookup with 'DOTS' application service and the desired protocol tag is made to obtain information necessary to connect to the authoritative DOTS server within the given domain. This specification defines "DOTS" as an application service tag (Section 9.3.1) and "signal.udp" (Section 9.3.2), "signal.tcp" (Section 9.3.3), and "data.tcp" (Section 9.3.4) as application protocol tags. Boucadair, et al. Expires November 7, 2019 [Page 13] Internet-Draft DOTS Server Discovery May 2019 In the example below, for domain 'example.net', the resolution algorithm will result in IP address(es), port, tag and protocol tuples as follows: example.net. IN NAPTR 100 10 "" DOTS:signal.udp "" signal.example.net. IN NAPTR 200 10 "" DOTS:signal.tcp "" signal.example.net. IN NAPTR 300 10 "" DOTS:data.tcp "" data.example.net. signal.example.net. IN NAPTR 100 10 S DOTS:signal.udp "" _dots._signal._udp.example.net. IN NAPTR 200 10 S DOTS:signal.tcp "" _dots._signal._tcp.example.net. data.example.net. IN NAPTR 100 10 S DOTS:data.tcp "" _dots._data._tcp.example.net. _dots._signal._udp.example.net. IN SRV 0 0 5000 a.example.net. _dots._signal._tcp.example.net. IN SRV 0 0 5001 a.example.net. _dots._data._tcp.example.net. IN SRV 0 0 5002 a.example.net. a.example.net. IN AAAA 2001:db8::1 +-------+----------+-------------+------+--------+ | Order | Protocol | IP address | Port | Tag | +-------+----------+-------------+------+--------+ | 1 | UDP | 2001:db8::1 | 5000 | Signal | | 2 | TCP | 2001:db8::1 | 5001 | Signal | | 3 | TCP | 2001:db8::1 | 5002 | Data | +-------+----------+-------------+------+--------+ If no DOTS-specific S-NAPTR records can be retrieved, the discovery procedure fails for this domain name (and the corresponding interface and IP protocol version). If more domain names are known, the discovery procedure MAY perform the corresponding S-NAPTR lookups immediately. However, before retrying a lookup that has failed, a DOTS client MUST wait a time period that is appropriate for the encountered error (e.g., NXDOMAIN, timeout, etc.). Boucadair, et al. Expires November 7, 2019 [Page 14] Internet-Draft DOTS Server Discovery May 2019 7. DNS Service Discovery DNS-based Service Discovery (DNS-SD) [RFC6763] provides generic solutions for discovering services. DNS-SD defines a set of naming rules for certain DNS record types that they use for advertising and discovering services. Section 4.1 of [RFC6763] specifies that a service instance name in DNS-SD has the following structure: . . The portion specifies the DNS sub-domain where the service instance is registered. It may be "local.", indicating the mDNS local domain, or it may be a conventional domain name such as "example.com.". The portion of the DOTS service instance name MUST be "_dots._signal._udp" or "_dots._signal._tcp" or "_dots._data._tcp". 8. Security Considerations DOTS-related security considerations are discussed in Section 4 of [I-D.ietf-dots-architecture] is to be considered. DOTS agents must authenticate each other using (D)TLS before a DOTS session is considered valid according to the [I-D.ietf-dots-signal-channel]. 8.1. DHCP The security considerations in [RFC2131] and [RFC8415] are to be considered. 8.2. Service Resolution The primary attack against the methods described in Section 6 is one that would lead to impersonation of a DOTS server. An attacker could attempt to compromise the S-NAPTR resolution. The use of mutual authentication makes it difficult to redirect a DOTS client to an illegitimate DOTS server. 8.3. DNS Service Discovery Since DNS-SD is just a specification for how to name and use records in the existing DNS system, it has no specific additional security requirements over and above those that already apply to DNS queries and DNS updates. For DNS queries, DNS Security Extensions (DNSSEC) [RFC4033] SHOULD be used where the authenticity of information is important. For DNS updates, secure updates [RFC2136][RFC3007] SHOULD Boucadair, et al. Expires November 7, 2019 [Page 15] Internet-Draft DOTS Server Discovery May 2019 generally be used to control which clients have permission to update DNS records. 9. IANA Considerations IANA is requested to allocate the SRV service name of "_dots._signal" for DOTS signal channel over UDP or TCP, and the service name of "_dots._data" for DOTS data channel over TCP. 9.1. DHCPv6 Option IANA is requested to assign the following new DHCPv6 Option Code in the registry maintained in: http://www.iana.org/assignments/ dhcpv6-parameters. Value Description Client ORO Singleton Option TBD1 OPTION_V6_DOTS_RI Yes Yes TBD2 OPTION_V6_DOTS_ADDRESS Yes No 9.2. DHCPv4 Option IANA is requested to assign the following new DHCPv4 Option Code in the registry maintained in: http://www.iana.org/assignments/bootp- dhcp-parameters/. Option Name Value Data length Meaning ---------------------- ----- ------------ --------------------------- OPTION_V4_DOTS_RI TBA3 Variable; Includes the name of the the maximum DOTS server. length is 255 octets. OPTION_V4_DOTS_ADDRESS TBA4 Variable; Includes one or multiple the minimum lists of DOTS IP addresses; length is 5. each list is treated as a separate DOTS server. 9.3. Application Service & Application Protocol Tags This document requests IANA to make the following allocations from the registry available at: https://www.iana.org/assignments/s-naptr- parameters/s-naptr-parameters.xhtml. 9.3.1. DOTS Application Service Tag Registration o Application Protocol Tag: DOTS o Intended Usage: See Section 6 Boucadair, et al. Expires November 7, 2019 [Page 16] Internet-Draft DOTS Server Discovery May 2019 o Security Considerations: See Section 8 o Contact Information: 9.3.2. signal.udp Application Protocol Tag Registration o Application Protocol Tag: signal.udp o Intended Usage: See Section 6 o Security Considerations: See Section 8 o Contact Information: 9.3.3. signal.tcp Application Protocol Tag Registration o Application Protocol Tag: signal.tcp o Intended Usage: See Section 6 o Security Considerations: See Section 8 o Contact Information: 9.3.4. data.tcp Application Protocol Tag Registration o Application Protocol Tag: data.tcp o Intended Usage: See Section 6 o Security Considerations: See Section 8 o Contact Information: 10. Acknowledgements Thanks to Brian Carpenter for the review of the BRSKI text. Many thanks to Russ White for the review, comments, and text contribution. Thanks for Dan Wing and Pei Wei for the review and comments. Thanks to Bernie Volz for the review of the DHCP section. Boucadair, et al. Expires November 7, 2019 [Page 17] Internet-Draft DOTS Server Discovery May 2019 11. References 11.1. Normative References [I-D.ietf-dots-signal-channel] K, R., Boucadair, M., Patil, P., Mortensen, A., and N. Teague, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification", draft- ietf-dots-signal-channel-31 (work in progress), March 2019. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, DOI 10.17487/RFC2131, March 1997, . [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997, . [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, DOI 10.17487/RFC3396, November 2002, . [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application Service Location Using SRV RRs and the Dynamic Delegation Discovery Service (DDDS)", RFC 3958, DOI 10.17487/RFC3958, January 2005, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, . [RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman, "Special-Purpose IP Address Registries", BCP 153, RFC 6890, DOI 10.17487/RFC6890, April 2013, . Boucadair, et al. Expires November 7, 2019 [Page 18] Internet-Draft DOTS Server Discovery May 2019 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., Richardson, M., Jiang, S., Lemon, T., and T. Winters, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 8415, DOI 10.17487/RFC8415, November 2018, . 11.2. Informative References [I-D.ietf-anima-bootstrapping-keyinfra] Pritikin, M., Richardson, M., Behringer, M., Bjarnason, S., and K. Watsen, "Bootstrapping Remote Secure Key Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- keyinfra-19 (work in progress), March 2019. [I-D.ietf-dots-architecture] Mortensen, A., K, R., Andreasen, F., Teague, N., and R. Compton, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Architecture", draft-ietf-dots- architecture-13 (work in progress), April 2019. [I-D.ietf-dots-data-channel] Boucadair, M. and R. K, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Data Channel Specification", draft-ietf-dots-data-channel-28 (work in progress), March 2019. [I-D.ietf-dots-multihoming] Boucadair, M. and R. K, "Multi-homing Deployment Considerations for Distributed-Denial-of-Service Open Threat Signaling (DOTS)", draft-ietf-dots-multihoming-01 (work in progress), January 2019. [I-D.ietf-dots-signal-call-home] K, R., Boucadair, M., and J. Shallow, "Distributed Denial- of-Service Open Threat Signaling (DOTS) Signal Channel Call Home", draft-ietf-dots-signal-call-home-01 (work in progress), April 2019. [I-D.ietf-dots-use-cases] Dobbins, R., Migault, D., Fouant, S., Moskowitz, R., Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS Open Threat Signaling", draft-ietf-dots-use-cases-17 (work in progress), January 2019. Boucadair, et al. Expires November 7, 2019 [Page 19] Internet-Draft DOTS Server Discovery May 2019 [I-D.ietf-netconf-zerotouch] Watsen, K., Abrahamsson, M., and I. Farrer, "Secure Zero Touch Provisioning (SZTP)", draft-ietf-netconf- zerotouch-29 (work in progress), January 2019. [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, "Dynamic Updates in the Domain Name System (DNS UPDATE)", RFC 2136, DOI 10.17487/RFC2136, April 1997, . [RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic Update", RFC 3007, DOI 10.17487/RFC3007, November 2000, . [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, DOI 10.17487/RFC4033, March 2005, . [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 2011, . [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and S. Krishnan, "Guidelines for Creating New DHCPv6 Options", BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, . Authors' Addresses Mohamed Boucadair Orange Rennes 35000 France Email: mohamed.boucadair@orange.com Tirumaleswar Reddy McAfee, Inc. Embassy Golf Link Business Park Bangalore, Karnataka 560071 India Email: TirumaleswarReddy_Konda@McAfee.com Boucadair, et al. Expires November 7, 2019 [Page 20] Internet-Draft DOTS Server Discovery May 2019 Prashanth Patil Cisco Systems, Inc. Email: praspati@cisco.com Boucadair, et al. Expires November 7, 2019 [Page 21]