Network Working Group A. Moise Internet-Draft J. Brodkin Intended Status: Informational Future DOS R&D Expires: May 16, 2010 November 16, 2009 ANSI C12.22, IEEE 1703 and MC1222 Transport Over IP draft-c1222-transport-over-ip-02.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 16, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This RFC provides a framework for transporting ANSI C12.22/IEEE 1703/ MC1222 Advanced Metering Infrastructure (AMI) Application-Layer Messages on an IP network. Moise & Brodkin Expires May 16, 2010 [Page 1] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Table of Contents 1. Introduction..................................................2 1.1. Terminology..............................................3 1.2. Definitions..............................................3 2. The C12.22 IP Network Segment.................................6 2.1. Composition of a C12.22 IP Network Segment...............6 2.2. Native IP Address........................................7 2.3. Encoding of Native IP Addresses..........................7 2.4. Standardized Port Numbers................................8 2.5. Use of UDP Source Port 0.................................9 2.6. IP Multicast.............................................9 2.7. IP Broadcast............................................11 2.8. Encoding of Multicast and Broadcast Addresses...........11 3. IP Message Transport.........................................13 3.1. C12.22 Connection Types and TCP/UDP Transport Modes.....13 3.2. IP Message Transport Details............................14 3.2.1. TCP and UDP Port Use...............................14 3.2.2. Active-listen UDP (CL=1, CL Accept=0)..............14 3.2.3. Passive-listen UDP (CL=1, CL Accept=1).............15 3.2.4. Active-OPENs TCP Mode (CO=1, CO Accept=0)..........15 3.2.5. Passive-OPENs TCP Mode (CO=1, CO Accept=1).........16 3.2.6. TCP and C12.22 Message Directionality..............16 3.3. Using IP Broadcast/Multicast............................17 3.4. Transport Protocol Decisions............................18 3.4.1. Unicast Versus Multicast Versus Broadcast..........18 3.4.2. Sending Large C12.22 APDUs Using UDP...............18 3.4.3. Choice of Protocol for C12.22 Response APDUs.......18 3.5. Quality of Service......................................18 4. Security Considerations......................................19 5. IANA Considerations..........................................19 6. References...................................................19 6.1. Normative References....................................19 6.2. Informative References..................................21 7. Acknowledgments..............................................21 8. Authors' Addresses...........................................22 1. Introduction The ANSI C12.22 standard [1] provides a set of application layer messaging services that are applicable for the enterprise and End Device components of an Advanced Metering Infrastructure (AMI) for the SmartGrid. The messaging services are tailored for, but not limited to, the exchange of the data Tables Elements defined and co- published in ANSI C12.19 [2], IEEE P1377/D1 [3], and MC1219 [4]. Moise & Brodkin Expires May 16, 2010 [Page 2] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 ANSI C12.22, which is an application-level messaging protocol, may be transported over any underlying transport network. This RFC defines the requirements governing the transmission of ANSI C12.22 Messages via the TCP and UDP transports and the IP networking. 1.1. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [5]. Throughout this document we use terms like ANSI C12.22 or ANSI C12.19, as in C12.22 Relay or ANSI C12.19 Device. These terms are interchangeable with the terms IEEE 1703 Relay and IEEE 1377 Device, respectively. However, the recent versions of the Utility End Device communication standards were developed under the auspices of ANSI C12 SC17 WG1 and ANSI C12 SC17 WG2. For that reason, the terminology used in this document is based on the ANSI C12.22-2008 [1] and ANSI C12.19-2008 [2] definitions as revised by IEEE 1703-2009 [6] and IEEE 1377-2009 [3]. 1.2. Definitions This specification uses a number of terms to refer to the roles played by participants (actors) in, and objects of, the ANSI C12.22 [1], IEEE 1703 [6], and MC1222 [7] protocol. Terms prefixed by C12.22 or C12.19, which are not defined here, can be resolved in [1] [6] [7] or [2] [3] [4]. ACSE Association Control Service Element. In the context of this specification and of [1], ACSEs are encoded per ISO/IEC 10035-1 [8] using the ASN.1 BER [9]. Active-listen UDP Active-listen UDP is a temporary process used by a local C12.22 IP Node to expect and receive incoming C12.22 Messages from a foreign C12.22 IP Node using the UDP protocol. The local C12.22 IP Node SHALL solicit the incoming C12.22 Messages from the foreign C12.22 IP Node using the foreign C12.22 IP Node's registered Native IP Address. The local C12.22 IP Node MAY exit Active-listen UDP process when it has received all of the expected C12.22 Messages or a C12.22 Message timeout has occurred. The local C12.22 IP Node SHALL receive all C12.22 Response Messages solicited from the foreign C12.22 IP Node that Moise & Brodkin Expires May 16, 2010 [Page 3] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 arrive at the local port number that matches the source port number used to solicit the C12.22 Messages from the foreign C12.22 IP Node. Active-OPEN TCP Active-OPEN TCP is a process used by a local C12.22 IP Node to establish a TCP connection with a fully-specified foreign C12.22 IP Node using the TCP protocol and the foreign C12.22 IP Node's registered Native IP Address. The Active-OPEN TCP process is identical to "local active OPEN" defined in [11]. APDU Application Protocol Data Unit. In the context of the ANSI C12.22 Application, it is an ACSE C12.22 Message. ACSE PDU ACSE Protocol Data Unit; same as APDU. ApTitle An ANSI C12.22 Application-process Title. An ApTitle is a name for a system-independent application activity that exposes application services to the application agent; e.g., a set of application service elements that together perform all or part of the communication aspects of an application process. An ApTitle is encoded as a unique registered (as per [1]) object identifier. C12.22 IP Node A C12.22 Node that is located on a C12.22 IP Network Segment and communicates using the IP protocol. C12.22 IP Network Segment A collection of all C12.22 IP Nodes that implement the IP-based protocols, as defined in this specification, and can communicate with each other using IP routers, switches, and bridges and without the use of a C12.22 Relay. C12.22 IP Relay A C12.22 IP Node that performs the functions of a C12.22 Relay. A C12.22 IP Relay acts as a bridge between a C12.22 IP Network Segment and an adjacent, C12.22 Network Segment. Moise & Brodkin Expires May 16, 2010 [Page 4] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 C12.22 Message An APDU that is also a fully assembled or a segment of a C12.22 Request Message or a C12.22 Response Message. The C12.22 Message described in this specification MUST be encoded using [9]. C12.22 Request Message A fully assembled C12.22 APDU that contains an ACSE user information element, which includes one or more EPSEM service requests. C12.22 Response Message A fully assembled C12.22 Message APDU that contains an ACSE user information element, which includes one or more EPSEM service responses. Connection A logical and physical binding between two or more users of a service (ref. [1]). EPSEM Extended Protocol Specification for Electronic Metering. EPSEM defines structures and services used to encode multiple requests and responses for use by devices such as gas, water, electricity, and related electronic modules or appliances. Initiating C12.22 IP Node A temporary role of a C12.22 IP Node in which it initiates the transmission of a C12.22 Request Message. Native Address The term Native Address refers to the network address of a C12.22 Node on its C12.22 Network Segment. In this specification, the Native Address is the IP address plus the associated port number used in communications by a C12.22 IP Node on the C12.22 IP Network Segment. Native IP Address The binary IP address and the OPTIONAL port number used by a C12.22 IP Node to encode a Native Address in a C12.22 Message or in a C12.19 Table Element of an IP Node interface. Moise & Brodkin Expires May 16, 2010 [Page 5] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Passive-listen UDP Passive-listen UDP is a process used by a local C12.22 IP Node to expect and receive incoming C12.22 Messages from any foreign C12.22 IP Node using the UDP protocol. When the Passive-listed UDP process is active, the local C12.22 IP Node SHALL accept all C12.22 Messages that arrive at the local port number that was registered by the local C12.22 IP Node. Passive-OPEN TCP Passive-OPEN TCP is a process used by a local C12.22 IP Node that wants to establish a TCP connection with an unspecified foreign C12.22 IP Node using the TCP protocol. In this case any foreign C12.22 IP Node MAY connect to the local C12.22 IP Node as long as the local port matches the port used by the foreign C12.22 IP Node. The Passive-OPEN TCP process is identical to "local passive OPEN" defined in [11]. Responding C12.22 IP Node A temporary role of a C12.22 IP Node in which it responds to the reception of a C12.22 Request Message. Target C12.22 IP Node The C12.22 IP Node that is the destination for a C12.22 Message. 2. The C12.22 IP Network Segment This section defines the characteristics of the C12.22 IP Network Segment. 2.1. Composition of a C12.22 IP Network Segment A C12.22 Network Segment is a collection of C12.22 Nodes that can communicate with each other directly - without having to forward C12.22 Messages through a C12.22 Relay. A C12.22 IP Network Segment comprises C12.22 IP Nodes and the network infrastructure that enables any one node to reach all other nodes on the same segment. All C12.22 IP Nodes on the C12.22 IP Network Segment employ the same IP address encoding scheme and the same network and transport protocols in accordance with this specification. Moise & Brodkin Expires May 16, 2010 [Page 6] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 There is no restriction on the size of a C12.22 IP Network Segment. It MAY be as small as a single LAN or subnet, or it MAY include numerous, heterogeneous LANs and WANs connected by routers, bridges, and switches. The C12.22 IP Network Segment MAY be completely private, or include communication across the global Internet. 2.2. Native IP Address The IP address and the port number of a C12.22 IP Node on a C12.22 IP Network Segment are collectively referred to as the Native IP Address. When the Native Address of a C12.22 IP Node is communicated within the payload of a C12.22 Message it SHALL be encoded as described in Section 2.3. Encoding of Native IP Addresses. The IP address of the C12.22 IP Node SHOULD be configured before the C12.22 IP Node attempts to send or receive any C12.22 Message on its C12.22 IP Network Segment. If the port number is not explicitly configured by the controlling application, it SHALL be set to the default port number, 1153 (see Section 2.4. Standardized Port Numbers). The IP address MAY be hard-coded, manually entered, or allocated automatically and/or dynamically by an IP network mechanism such as DHCP. It is beyond the scope of this specification to define the method of configuration, the configuration parameters, or any administrative controls that the system administrator may wish to implement. 2.3. Encoding of Native IP Addresses ANSI C12.22 defines binary fields for encoding a C12.22 Native Address for transport within C12.22 Messages. In this RFC the fields SHALL contain an IPv4 or an IPv6 binary native IP network address that is followed by an OPTIONAL two-byte TCP or UDP port number. ANSI C12.22 allows these fields to be conveyed in select ANSI C12.22 service elements (e.g., ANSI C12.22 Registration Service parameter, ANSI C12.22 Resolve Service response , and ANSI C12.19 INTERFACE_CTRL_TBL Element NATIVE_ADDRESS). The length of the C12.22 Native Address is qualified by an ANSI C12.22 address length field (e.g., ANSI C12.22 Registration Service parameter, ANSI C12.22 Resolve Service response , and ANSI C12.19 ACT_NETWORK_TBL Element NATIVE_ADDRESS_LEN). The binary Native IP Address fields SHALL be encoded in network byte order as shown in Figure 1. Moise & Brodkin Expires May 16, 2010 [Page 7] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Actual Native IP Address (ADDR) and Port (P) Length Octet 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+- IPv4 | 4 | | ADDR4 | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv4 + port | 6 | | ADDR4 | P | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv6 |16 | | ADDR6 | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv6 + port |18 | | ADDR6 | P | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Encoding of the Native IP Addresses for ANSI C12.22 When an ANSI C12.22 Native Address is encoded in ANSI C12.19 Tables' BINARY data Elements then the size of the native address Element is defined by ACT_NETWORK_TBL.NATIVE_ADDRESS_LEN (See [1] [2] Table 121). This is the actual number of octets that are placed inside the C12.19 BINARY Element. This value is common to all of the C12.22 Node's interfaces, including those that are not IP based (thus not conforming to this specification). For this reason the ACT_NETWORK_TBL.NATIVE_ADDRESS_LEN MAY be greater than, and SHALL NOT be smaller than, the actual length needed to encode a Native IP Address per Figure 1. When this is the case, the C12.22 Native IP Address SHALL be padded with zero (0) to fill the Table's BINARY data Element. 2.4. Standardized Port Numbers IANA (Internet Assigned Numbers Authority) has assigned port 1153 for UDP [10] and TCP [11] C12.22 IP Messages. By default, C12.22 IP Nodes SHALL send all C12.22 Application Association initiation message requests set with 1153 as the destination port number. To ensure interoperability among C12.22 IP Nodes, all C12.22 IP Relays and Master Relays SHALL monitor and accept UDP and TCP messages destined to port 1153. Moise & Brodkin Expires May 16, 2010 [Page 8] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Any IP firewalls or Access Control Lists (ACLs) shielding a C12.22 device MUST be configured to forward UDP and TCP traffic destined to port 1153 and other ports that are assigned and registered by the LAN administrator, in order to maintain the continuity of the C12.22 IP Network Segment. 2.5. Use of UDP Source Port 0 Although [10] allows for a source port number of zero (0), C12.22 IP Nodes SHALL NOT send datagrams on UDP with the source port set to zero. A C12.22 IP Node SHALL ignore and SHALL NOT respond to any C12.22 Message that it receives from source port 0. Further details of C12.22 IP Node's use of UDP, and of TCP, are given in Section 3. IP Message Transport. 2.6. IP Multicast In addition to unicast, the ANSI C12.22 protocol requires the support of a multicast message delivery service from the network. In cases where C12.22 IP Nodes MUST perform Native IP Address discovery (e.g., the discovery of the Native IP Address of C12.22 IP Relays that provide a route out of the C12.22 IP Network Segment, or the discovery of the Native IP Address of a C12.22 IP Master Relay on the C12.22 IP Network), the C12.22 IP Nodes uses IP Multicast to send a C12.22 Message that contains an EPSEM Resolve Service Request on the IP LAN. IP multicast is also desirable, for example, when a C12.22 Host needs to read a multitude of C12.22 Nodes (e.g., meters) that are configured with a common C12.22 multicast group ApTitle. Using IP multicast, the C12.22 Host MAY send a C12.22 Message containing an EPSEM Read Service Request that reaches all C12.22 Nodes on the C12.22 IP Network Segment. For these reasons, all C12.22 IP Relays and Master Relays SHALL support IP multicast and it is RECOMMENDED that all C12.22 Nodes support IP multicast. Any IPv4 C12.22 IP Node that supports IP multicast SHALL use the Internet Group Management Protocol IGMP version 1 (IGMPv1) [12] as a minimum, to report (i.e., request) membership in the C12.22 multicast group to its local router(s). It is RECOMMENDED that C12.22 IP Nodes implement IGMPv3 [13]. Any IPv6 C12.22 IP Node that supports IP multicast SHALL use Multicast Listener Discovery version 2 (MLDv2) (RFC 3810 [14] possibly within ICMPv6 RFC 4443 [15]) to report membership. Moise & Brodkin Expires May 16, 2010 [Page 9] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Routers that interconnect C12.22 IP Nodes on the C12.22 IP Network Segment, MUST support Protocol Independent Multicast Sparse Mode (PIM SM) (RFC 4601 [16]) along with IGMPv1 (RFC 1112 [12]) as a minimum for IPv4, or MLDv2 for IPv6 (RFC 3810 [14]). It is RECOMMENDED that they implement IGMPv3 [13]. It is beyond the scope of this specification to define the mechanism for selecting an initial Rendezvous Point (RP) for the C12.22 multicast group, the use of shared versus source trees, or the mechanism for inter-domain multicast routing. IANA has registered the "All C1222 Nodes" multicast group, and has assigned the IPv4 multicast address of 224.0.2.4 and the IPv6 multicast address of FF0X::204, where X represents the Scope field as defined in RFC 4291, the IP Version 6 Addressing Architecture [17]. For IPv6, all C12.22 IP Relays, C12.22 IP Master Relays, and all C12.22 IP Nodes configured to support broadcast and multicast (see Section 3.3. Using IP Broadcast/Multicast) SHALL join the global scope multicast address, FF0E::204, as well as all of the assigned, reduced scope, multicast addresses: link-local - FF02::204; admin-local - FF04::204; site-local - FF05::204; and organization-local - FF08::204. IPv6 C12.22 IP Nodes SHOULD use the minimum scope needed, when initiating IP multicast messages to reach another C12.22 IP Node on the C12.22 Network. This practice is RECOMMENDED in order to limit unnecessary propagation of C12.22 IP multicast Messages. To determine the minimum scope required to reach the closest C12.22 IP Relay on the C12.22 Node's IP Network Segment, this specification RECOMMENDS the following simple steps: 1. Starting with the smallest (local-most) scope, link-local (or a pre-configured scope), send the C12.22 EPSEM Resolve Service Request for C12.22 IP Relay discovery. 2. Listen for a response from a C12.22 IP Relay; then: a. If no response is received, assign the next wider scope level, then repeat steps (1) and (2) at the newly assigned scope. b. If a response is received then record the scope level as the minimum scope to use on the node's C12.22 IP Network Segment. A C12.22 IPv6 Node that initiates any EPSEM Service Request SHOULD use the minimum scope necessary to reach its target C12.22 IP Nodes. Moise & Brodkin Expires May 16, 2010 [Page 10] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 A C12.22 IPv6 Relay SHALL use the global scope for any C12.22 message destined for the global Internet. This specification does not preclude the use of the unassigned scope values defined in [17]; those scope values MAY be used on a private basis, or through mutual operating agreements. For IPv4, all C12.22 IP Relays, C12.22 IP Master Relays, and all C12.22 IP Nodes configured to support broadcast/multicast SHALL join the assigned multicast address of 224.0.2.4. This global address does not provide for the type of scoping discussed above for IPv6, nor is it compatible with the administratively scoped IP multicast specification in RFC 2365[18]. Therefore, a different technique to limit the propagation of C12.22 IP multicast Messages is needed. One available technique to control IPv4 multicast scope is through the use of the Time-to-Live (TTL) attribute in the IP packet header. In the implementation of this technique, an administrative domain MUST include at least one C12.22 IP Relay, and all C12.22 IP Nodes in the administrative domain SHOULD be configured with a TTL sufficiently large to reach that C12.22 IP Relay. A TTL threshold SHOULD be defined and configured on all border routers linking the administrative domain to the global Internet such that the routers forward on their Internet interfaces only those 224.0.2.4 multicast packets that have a TTL exceeding the threshold value. A C12.22 IPv4 Node that initiates any C12.22 Request Message SHOULD use the minimum TTL needed to reach its target C12.22 IP Nodes. A C12.22 IPv4 Relay SHOULD use a TTL that exceeds the threshold for any C12.22 message destined for the global Internet. 2.7. IP Broadcast IP broadcast is not generally suitable as a replacement for, or an alternative to multicast in a C12.22 IP Network Segment. IP broadcast is not supported in IPv6 and it suffers from limited scope in IPv4. This specification, however, does not preclude the use of IP network directed or limited/local scope (address 255.255.255.255) broadcast, and specifies a minimum requirement in Section 2.8. Encoding of Multicast and Broadcast Addresses. 2.8. Encoding of Multicast and Broadcast Addresses ANSI C12.22 Tables provide binary Elements for encoding a Native Broadcast or Multicast Address for transport within a C12.22 Message. The encoding of these Table Elements is identical to that defined is Section 2.3. Encoding of Native IP Addresses. These fields SHALL be used as shown in Figure 2. Moise & Brodkin Expires May 16, 2010 [Page 11] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Actual IP Address (ADDR) and Port (P) Length Octet 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 IPv4 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Broadcast | 4 | |BADDR4 | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv4 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Broadcast | 6 | |BADDR4 | P | +Port +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv4 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Multicast | 4 | |MADDR4 | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv4 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Multicast | 6 | |MADDR4 | P | +Port +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv6 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Multicast |16 | | MADDR6 | +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv6 +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Multicast |18 | | MADDR6 | P | +Port +---+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Encoding of broadcast/multicast native IP addresses The IPv4 and IPv6 multicast addresses, MADDR4 and MADDR6, respectively, are those assigned by IANA for use by ANSI C12.22. When a broadcast/multicast Native IP Address is encoded in ANSI C12.19 Tables' BINARY data Elements the size of the Native Address Element transmitted is defined by ACT_NETWORK_TBL.NATIVE_ADDRESS_LEN (See [1] [2] Table 121). This is the actual number of octets that are placed inside the C12.19 BINARY Element. This value is common to all of the C12.22 Node's interfaces, including those that are not IP based (thus not conforming to this specification). For this reason the ACT_NETWORK_TBL.NATIVE_ADDRESS_LEN MAY be greater than, and SHALL NOT be smaller than, the actual length needed to encode a native IP broadcast/multicast address per Figure 2. When this is the case, the C12.22 Native IP Address SHALL be padded with zero (0) to fill the Table's BINARY data Element. Moise & Brodkin Expires May 16, 2010 [Page 12] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 The IPv4 network directed broadcast address can be computed by performing a bitwise OR between the bit complement of the subnet mask of the target IP subnet and the IP address of any host on that IP subnet. 3. IP Message Transport This section defines a C12.22 Node's usage of the Connection-Oriented (CO) and Connectionless (CL) transport layer protocols, TCP and UDP, respectively. 3.1. C12.22 Connection Types and TCP/UDP Transport Modes A C12.22 IP Node's use of TCP and UDP is based on its registered capabilities as defined in its configuration parameters (flags) and as expressed in the Node's accepted registration attributes [1]: CL Flag = .CONNECTIONLESS_MODE_SUPPORTED; CL Accept Flag = .ACCEPT_CONNECTIONLESS; CO Flag = .CONNECTION_MODE_SUPPORTED; and CO Accept Flag = .ACCEPT_CONNECTIONS. The mapping of the connection-type parameters to the type of TCP and UDP transports that a C12.22 Node MAY support is defined in Table 1. Table 1: C12.22 Node Parameters to IP Transport Mapping CL CO CL Accept CO Accept Flag Flag Flag Flag IP Transport Mode Supported ---- ---- ---- ---- -------------------------------------- 0 0 x x Invalid 0 1 0 0 TCP, Active-OPENs 0 1 0 1 TCP, Passive- and Active-OPENs 0 1 1 0 Invalid 0 1 1 1 Invalid 1 0 0 0 UDP, Active-listen 1 0 0 1 Invalid 1 0 1 0 UDP, Passive- and Active-listen 1 0 1 1 Invalid 1 1 0 0 UDP, Active-listen; TCP Active-OPENs 1 1 0 1 UDP, Active-listen; TCP, Passive- and Active-OPENs 1 1 1 0 UDP, Passive- and Active-listen; TCP, Active-OPENs 1 1 1 1 UDP, Passive- and Active-listen; TCP, Passive- and Active-OPENs -------------------------------------------------------------------- Moise & Brodkin Expires May 16, 2010 [Page 13] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Every C12.22 IP Node MUST support at least one of unicast CO or CL operating capabilities (as advertized in Decade 12, Network Tables [1], where available, and as registered using the C12.22 Registration Service [1]). 3.2. IP Message Transport Details 3.2.1. TCP and UDP Port Use General rules: 1. A C12.22 IP Node that implements [CL Accept=1] SHALL receive incoming UDP C12.22 Messages on its registered Native IP Address (IP address and port number). 2. A C12.22 IP Node that implements [CO Accept=1] SHALL receive incoming TCP connections on its registered Native IP Address (IP address and port number). 3. A C12.22 IP Relay that forwards a UDP C12.22 Message to a C12.22 IP Node on the C12.22 IP Network Segment SHALL send the C12.22 Message to the C12.22 IP Node's registered Native IP Address (IP address and port number). 4. A C12.22 IP Relay that forwards a TCP C12.22 Message to a C12.22 IP Node on the C12.22 IP Network Segment MAY use an established TCP connection to that C12.22 IP Node, or it SHALL establish a new TCP connection to the C12.22 IP Node's registered Native IP Address (IP address and port number). 5. A C12.22 IP Node that implements [CL=1] SHOULD set the source port number in outbound UDP C12.22 Messages to its registered port number. 6. A C12.22 IP Node that implements [CL=1] MAY set the source port number in outbound UDP C12.22 Messages to a different UDP source port number if the target UDP C12.22 IP Node is reachable using direct messaging (as defined in [1]). 7. When the registered Native IP Address of a C12.22 IP Node does not include the OPTIONAL port number, then port 1153 SHALL be assumed and used as the registered port number. 8. All C12.22 IP Nodes SHOULD use port 1153 in their Native IP Address when registering. 3.2.2. Active-listen UDP (CL=1, CL Accept=0) Moise & Brodkin Expires May 16, 2010 [Page 14] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 A C12.22 IP Node that supports this mode SHALL NOT monitor for unsolicited incoming C12.22 Messages via UDP. As a result, the C12.22 IP Node is incapable of receiving unsolicited C12.22 Messages using UDP. The C12.22 IP Node MAY enter the Active-listen UDP process by initiating an unsolicited UDP transmission to a Target C12.22 IP Node, which is expected to implement the Passive-listen UDP mode. C12.22 IP Nodes SHOULD use their registered UDP port number, or if not yet registered then they SHOULD use port 1153, as the source port number for all UDP C12.22 IP Messages. 3.2.3. Passive-listen UDP (CL=1, CL Accept=1) A C12.22 IP Node that operates in this mode SHALL be capable of receiving solicited and unsolicited C12.22 Messages from other C12.22 IP Nodes. The C12.22 Node MAY change the port number that it monitors by using the parameter of the ANSI C12.22 Registration Service. The C12.22 IP Node MAY initiate unsolicited Active-listen UDP transmissions to other C12.22 IP Nodes that implement the Passive-listen UDP mode. When operating in this mode, the C12.22 IP Nodes SHALL use their registered UDP port number as the source port number for all UDP C12.22 IP Messages. All C12.22 IP Relays SHALL support the Passive-listen UDP mode. C12.22 Authentication Hosts and C12.22 Notification Hosts that implement UDP SHALL support Passive-listen UDP mode. For all other C12.22 IP Nodes, Passive-listen UDP mode is the RECOMMENDED mode when implementing UDP. 3.2.4. Active-OPENs TCP Mode (CO=1, CO Accept=0) A C12.22 IP Node that supports this mode SHALL NOT monitor for inbound TCP connections. As a result, the node is incapable of accepting incoming connections via TCP. The C12.22 IP Node MAY initiate TCP connections to Target C12.22 IP Nodes, which are expected to implement the Passive-OPENs TCP mode. In this mode, C12.22 Messages exchanged by a pair of associated C12.22 IP Nodes can only be communicated through any of the TCP connections that were initiated by the C12.22 IP Node that implements this mode. The loss or closure of a connection SHALL NOT automatically result in the termination of the C12.22 associations between the peer nodes. In order to continue exchanging C12.22 Moise & Brodkin Expires May 16, 2010 [Page 15] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 Messages without loss of association, the initiating C12.22 IP Node MAY re-establish new TCP connections with the peer node, or use existing connections to the peer node. The termination of the C12.22 Application associations is dependent upon C12.22 application timeout attributes and C12.22 link management services (such as Procedure 25 Network Interface Control [1]). 3.2.5. Passive-OPENs TCP Mode (CO=1, CO Accept=1) A C12.22 IP Node that operates in this mode SHALL monitor and accept incoming TCP connections. The C12.22 Node May change the port number that it monitors by using the parameter of the ANSI C12.22 Registration Service. The C12.22 IP Node MAY initiate Active- OPENs TCP connections to other C12.22 IP Nodes that implement the Passive-OPENs TCP mode. In this mode, C12.22 Messages exchanged by a pair of associated C12.22 IP Nodes can arrive through any of the TCP connections that were established by either node. The loss or closure of a connection SHALL NOT automatically result in the termination of the C12.22 associations between the peer nodes. In order to continue exchanging C12.22 Messages without loss of association, either C12.22 IP Node MAY re-establish new TCP connections with the peer node, or use existing connections to the peer node. The termination of the C12.22 Application associations is dependent upon C12.22 application timeout attributes and C12.22 link management services (such as Procedure 25 Network Interface Control [1]). All C12.22 IP Relays SHALL support the Passive-OPENs TCP mode. C12.22 Authentication Hosts and C12.22 Notification Hosts that implement TCP SHALL support Passive-OPENs TCP mode. For all other C12.22 IP Nodes, Passive-OPENs TCP mode is the RECOMMENDED mode when implementing TCP. 3.2.6. TCP and C12.22 Message Directionality C12.22 IP Nodes MAY use TCP in one of two ways: bi-directional traffic flow or uni-directional traffic flow. When TCP connections are used, any new or established TCP connection between the two C12.22 IP Nodes MAY be used equivalently by the C12.22 IP Nodes to send and to receive C12.22 Messages. This is the RECOMMENDED and default mode of operation, because ANSI C12.22 requires the transport network to be reliable and connectionless (per connectionless-mode ACSE). For this reason ANSI C12.22 defines peer- to-peer application associations and not peer-to-peer connections. Moise & Brodkin Expires May 16, 2010 [Page 16] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 It is known that some C12.22 implementations have been deployed in which TCP is used for uni-directional traffic flow. For these types of implementations, an established TCP connection SHALL be used by the initiator of that connection to send C12.22 Messages and by the target node (who accepted the connection) to receive C12.22 Messages. If a C12.22 IP Node wishes to send a C12.22 Message to a peer C12.22 IP Node, it MUST establish and use a new TCP connection or use an existing TCP connection that it had previously initiated, for its outbound uni-directional traffic flow. For increased interoperability, the initiator of the connection SHOULD accept incoming C12.22 Messages on that connection in case the target node attempts to use the connection for bi-directional traffic flow. Uni-directional use of TCP is a special mode of operation; it is NOT RECOMMENDED because multiple one-way channel communication is not described by ANSI C12.22, and it utilizes one-half of the TCP connection capability. As a result it doubles the number of TCP connections used to communicate C12.22 Messages, and thus could become a burden when a large number of connections is required. While this mode of operation is not explicitly supported in the ANSI C12.22 standard, it MAY be made possible through mutual operating agreements. The means by which nodes are configured to enact the uni-directional use of TCP is not defined in this specification or in the ANSI C12.22 standard; it is left for future consideration. 3.3. Using IP Broadcast/Multicast A C12.22 IP Node's use of Broadcast/Multicast is based on its capabilities as defined in its configuration parameters (flags) and as expressed in the Node's accepted registration attributes [1] (.BROADCAST_AND_MULTICAST_SUPPORTED). The mapping of the C12.22 IP Node's Broadcast/Multicast parameter (flag) to IP Broadcast/Multicast usage is defined in Table 2. Table 2: C12.22 to IP Broadcast/Multicast Mapping C12.22 Broadcast and Multicast Supported Flag IP Broadcast/Multicast Supported ---- ------------------------------------------------- 0 The C12.22 IP Node does not accept IP broadcast and it does not accept IP multicast messages. 1 The C12.22 IP Node accepts both IP broadcast (IPv4 only) and IP multicast messages (IPv4 and IPv6). Moise & Brodkin Expires May 16, 2010 [Page 17] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 If a C12.22 IP Node is configured to accept IP broadcast and multicast messages, it SHALL join the "All C1222 Nodes" multicast group (see Section 2.6. IP Multicast), and SHALL use the default port 1153. In addition it SHALL accept IP Network directed or limited (local scope) broadcast messages sent to port 1153. Note that successful communication using network directed broadcast requires configuration of network routers, which by default are not supposed to forward directed broadcasts as per RFC 2644 [19]. 3.4. Transport Protocol Decisions 3.4.1. Unicast Versus Multicast Versus Broadcast An initiating C12.22 IP Node MAY send any C12.22 Message using UDP or TCP. However, in accordance with Section 5.3.2.4.12, Resolve Service, of ANSI C12.22, this specification RECOMMENDEDS that the C12.22 Resolve Request message be transported using UDP/IP multicast when the Native IP Address of the Target C12.22 Node is not known. Use of UDP/IP multicast is preferred over the use of IP network directed or limited broadcast; therefore when UDP/IP multicast is supported its use is RECOMMENDED over network broadcast. 3.4.2. Sending Large C12.22 APDUs Using UDP When sending a large C12.22 Message via UDP, whereby the ACSE PDU size exceeds the UDP datagram maximum data length (65527 bytes), the initiating C12.22 IP Node SHALL segment the ACSE PDU in accordance with ANSI C12.22 Datagram Segmentation and Reassembly algorithm, such that each APDU segment fits within the UDP data field. 3.4.3. Choice of Protocol for C12.22 Response APDUs When a Target C12.22 IP Node receives a C12.22 Request Message from an initiating C12.22 IP Node, it SHALL send a C12.22 Response Message using the same transport protocol (i.e., TCP to TCP, UDP to UDP). In the case of UDP, the target SHALL send the C12.22 Response Message to the source IP address and port number. 3.5. Quality of Service The ANSI C12.22 standard provides a configuration parameter in the APDU's .URGENT to mark a message as urgent. There are numerous IP-based technologies that enable enhanced levels of message delivery and quality of service. This specification does not define the technology to be used to send urgent messaged over IP. Moise & Brodkin Expires May 16, 2010 [Page 18] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 4. Security Considerations The ANSI C12.22 Application layer security is defined in Section 5.3.4.13, C12.22 Security Mechanism, of the ANSI C12.22 standard. The security mechanisms include provisions for AES-128/EAX message privacy and authentication, playback rejection, and message acceptance windows as well as ANSI C12.19 [2] role-based data access and secured register mechanisms. Additional Transport or Network layer security protocols are not required but MAY be provided transparently by network integrators. However, any added Transport or IP Network layer security features SHALL act only to enhance and preserve (i.e., not be a substitute for, or an alteration of) the ANSI C12.22 and ANSI C12.19 (interoperable) security provisions. 5. IANA Considerations UDP and TCP port 1153, which is used for C12.22 communication over IP, is registered with IANA. Section 2.6. IP Multicast defines the use of multicast. The following multicast addresses have been registered by IANA for use by the ANSI C12.22 standard: IPv4 - "All C1222 Nodes" address 224.0.2.4 IPv6 - "All C1222 Nodes" address FF0X::204 6. References 6.1. Normative References [1] ANSI, "Protocol Specification for Interfacing to Data Communication Networks", ANSI C12.22-2008, approved January 9, 2009. [2] ANSI, "Utility Industry End Device Data Tables", ANSI C12.19- 2008, approved February 24, 2009. [3] IEEE, "Draft Standard for Utility Industry Metering Communication Protocol Application Layer (End Device Data Tables)", IEEE P1377/D1, June 2009. [4] Measurement Canada, "Specification for Utility Industry Metering Communication Protocol Application Layer (End Device Data Tables)", MC1219, 2009. [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Moise & Brodkin Expires May 16, 2010 [Page 19] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 [6] IEEE, "Draft Standard for Local Area Network/Wide Area Network (LAN/WAN) Node Communication Protocol to Complement the Utility Industry End Device Data Tables", IEEE 1703/D4, March 2009. [7] Measurement Canada, "Specification for Local Area Network/Wide Area Network (LAN/WAN) Node Communication Protocol to Complement the Utility Industry End Device Data Tables", MC1222, 2009. [8] ISO/IEC, "Information Technology-Open Systems Interconnection-Connectionless Protocol for the Association Control Service Element: Protocol Specification", ISO/IEC 10035-1, 1995. [9] ISO/IEC, "Information Technology-ASN.1 Encoding Rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)", ISO/IEC 8825-1, 2002. [10] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [11] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [12] Deering, S.E., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989. [13] Cain, B., Deering, S., Kouvelas, I., Fenner, B., Thyagarajan, A., "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [14] Vida, R., Costa, L., "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. [15] Conta, A., Deering, S., Gupta, M., "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC 4443, March 2006. [16] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised) ", RFC 4601, August 2006. [17] Hinden, R., Deering, S., "IP Version 6 Addressing Architecture", RFC 4291, February 2006. Moise & Brodkin Expires May 16, 2010 [Page 20] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 [18] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, RFC 2365, July 1998. [19] Senie, D., "Changing the Default for Directed Broadcasts in Routers", BCP 34, RFC 2644, August 1999. 6.2. Informative References [Will be added as appropriate] 7. Acknowledgments The authors wish to recognize Alexander Shulgin for providing valuable comments and for conducting feasibility testing in support of this work. The following people have improved this document through thoughtful comments and suggestions: Fred Baker, Vijay Gurbani, Alfred Hoenes and Michael Stuber. Moise & Brodkin Expires May 16, 2010 [Page 21] Internet Draft draft-c1222-transport-over-ip-02.txt November 2009 8. Authors' Addresses Avygdor Moise Future DOS R&D Inc. #303 - 6707 Elbow Drive SW Calgary, Alberta, T2V 0E5 Canada Email: avy@fdos.ca Jonathan Brodkin Future DOS R&D Inc. #303 - 6707 Elbow Drive SW Calgary, Alberta, T2V 0E5 Canada Email: jonathan.brodkin@fdos.ca Moise & Brodkin Expires May 16, 2010 [Page 22]