1、 CEA Standard Control Network Protocol Specification CEA-709.1-C August 2010 Provided by IHSNot for Resale-,-,-NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between m
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3、pect preclude any member or nonmember of CEA from manufacturing or selling products not conforming to such Standards, Bulletins or other technical publications, nor shall the existence of such Standards, Bulletins and other technical publications preclude their voluntary use by those other than CEA
4、members, whether the standard is to be used either domestically or internationally. Standards, Bulletins and other technical publications are adopted by CEA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, CEA does not assume any liability to any pat
5、ent owner, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. This CEA Standard is considered to have International Standardization implication, but the International Electrotechnical Commission activity has not progressed to the poi
6、nt where a valid comparison between the CEA Standard and the IEC document can be made. This Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safet
7、y and health practices and to determine the applicability of regulatory limitations before its use. (Formulated under the cognizance of the CEAs R7.1 HCS1 Subcommittee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2010 Technology Phone 800-854-7179; Fax 303-397-2740; Internet http:/; Email 3 Rela
8、ted Documents For complementary specifications, see references listed in the bibliography at the end of this document. 4 Definitions and Symbols 4.1 Use of Terms The following section introduces the basic terminology employed throughout this document. Moreover the terms must, must not, should, shoul
9、d not, and may when they appear in this doc-ument are used to convey requirements of conformance in accordance with the definitions in 4 (RFC 2119). Most of it is commonly used and the terms have the same meaning in both the gen-eral and the CEA-709 context. However, for some terms, there are subtle
10、 differences. For ex-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHSCEA-709.1-C 2ample, in general, bridges do selective forwarding based on the layer 2 destination address. There are no layer 2 addresses in the CEA-709 protocol, so bridges forward all p
11、ackets, as long as the domain address in the packet matches a domain of which the bridge is a member. Routers, in general, perform network address modification so that two protocols with the same transport layer but different network layers can be connected to form a single logical network. CEA-709
12、routers may perform network address modification, but typically they only examine the network address fields and selectively forward packets based on the network layer address fields. 4.2 Definitions Channel: A physical unit of bandwidth linking one or more communication nodes. Refer to Annex E for
13、further explanation of the relationship between an CEA-709 channel and a sub-net. Physical Repeater: Device that reconditions the incoming physical layer signal on one chan-nel and retransmits it on to another channel. Store-and-Forward Repeater: Device that stores and then reproduces data packets o
14、n to a second channel. Bridge: Device that connects two channels (x and y); forwards all packets from x to y and vice versa, as long as the packets originate on one of the domain(s) that the bridge belongs to. Configuration: The non-volatile information used by the device to customize its operation.
15、 There is configuration data for the correct operation of the protocol in each device, and op-tionally, for application operation. The network configuration data stored in each device has a checksum associated with the data. Examples of network configuration data are node ad-dresses, communication m
16、edia parameters such as priority settings, etc. Application configu-ration information is application specific. Domain: A virtual network that is the network unit of management and administration. Group and subnet (see below) addresses are assigned by the administrator responsible for the do-main, a
17、nd they have meaning only in the context of that domain. Flexible Domain: Used in conjunction with Unique_Node_ID and broadcast addressing. A node responds to a Unique_Node_ID-addressed message if the address matches, regardless of the domain on which the message was sent. To respond so that the sen
18、der receives it, the re-sponse must be sent on the domain in which it was received. Furthermore, this domain must be remembered for the duration of the transaction so that duplicate detection of any retries is possible. This transitory domain entry at a node is called the flexible domain. How many f
19、lexible domain entries a node supports is up to the implementation. However, a minimum of 1 is required. Subnet: A set of nodes accessible through the same link layer protocol; a routing abstraction for a channel; CEA-709 subnets are limited to a maximum of 127 nodes. Valid subnet ad-dresses are wit
20、hin the range of 1-255. Subnet address zero is reserved and means that the subnet address is unknown. Nodes that have not had their network addresses configured have their subnet addresses initialized to zero. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
21、IHSCEA-709.1-C 3Node: An abstraction for a physical node that represents the highest degree of address resol-vability on a network. A node is identified (addressed) within a subnet by its (logical) node identifier. A physical node may belong to more than one subnet; when it does, it is assigned one
22、(logical) node number for each subnet to which it belongs. A physical node may belong to at most two subnets; these subnets must be in different domains. A node may also be iden-tified (absolutely) within a network by its Unique_Node_ID. Group: A uniquely identifiable set of nodes within a domain. W
23、ithin this set, individual members are identified by their member number. Groups facilitate one-to-many communica-tion and are intended to support functional addressing. Router: Device that routes data packets to their respective destinations by selectively for-warding from subnet to subnet; a route
24、r always connects two (sets of) subnets; routers may modify network layer address fields. Routers may be set to one of four modes: repeater mode, bridge mode, learning mode, and configured mode. In repeater mode, packets are for-warded if they are received with no errors. In bridge mode, packets are
25、 forwarded if they are received with no errors and match a domain that the router is a member of. Routers in learn-ing mode learn the topology by examining packet traffic, while routers that are set to confi-gured mode have the network topology stored in their memory and make their routing deci-sion
26、s solely upon the contents of their configured tables. (Application) Gateway: Interconnects networks at their highest protocol layers (often two different protocols). Two domains can also be connected through an application gateway. Beta1: Period immediately following the end of a packet cycle. A no
27、de attempting to trans-mit monitors the state of the channel, and if it detects no transmission during the Beta1 pe-riod, it determines the channel to be idle. Beta2: Randomizing slot. A node wishing to transmit generates a random delay T. This delay is an integer number of randomizing slots of dura
28、tion Beta2. Network Variable: A variable in an application program whose value is automatically propa-gated over the network whenever a new value is assigned to it. Standard Network Variable Types (SNVTs): Variables with agreed-upon semantics. These variables are interpreted by all applications in t
29、he same way, and are the basis for interopera-bility. Definition of specific SNVTs is beyond the scope of this document. Manual service request Message: A network management message containing a nodes Unique_Node_ID. Used by a network management device that receives this message to in-stall and conf
30、igure the node. May be generated by application or system code. May be trig-gered by external hardware event, e.g., driving a “manual service request” input low. Transaction: A sequence of messages that are correlated together. For example, a request and the responses to the request are all part of
31、a single transaction. A transaction succeeds when all the expected messages from every node involved in the transaction are received at least once. A transaction fails in CEA-709 if any of the expected messages within the transaction are not received. Retries of messages within a transaction are use
32、d to increase the probability of success of a transaction in the presence of transient errors. Provided by IHSNot for Resale-,-,-CEA-709.1-C 44.3 Symbols and Graphical Representations Figure 1 shows the basic topology of networks based on this protocol and the symbolic repre-sentations used in this
33、document. BridgeStore and ForwardRepeaterChannelSubnetSubnet A, ASubnet B, BRouterNodesDomain A Domain BGatewayFigure 1 Network Topology routers with confi-gured tables may operate on topologies with physical loops, as long as the communication paths are logically tree-like. In this topology, a pack
34、et may never appear more than once at the router on the side on which the packet originated. The unicast routing algorithm uses learning for mi-nimal overhead and no additional routing traffic. Use of configured routing tables is supported for both unicast and group addresses, although in many appli
35、cations a simple flooding of group addressed messages is sufficient. The heart of the protocol hierarchy is the Transport and Session layers. A common Transaction Control Sublayer handles transaction ordering and duplicate detection for both. The Transport layer is connection-less and provides relia
36、ble message delivery to both single and multiple des-tinations. Authentication of the message senders identity is included as a transport layer ser-vice, for use when the security of sender authentication is required. The authentication server requires only the Transaction Control Sublayer to accomp
37、lish its function. Thus Transport and Provided by IHSNot for Resale-,-,-CEA-709.1-C 7Session layer messages may be authenticated using all of the addressing modes other than broadcast. The session layer provides a simple Request-Response mechanism for access to remote servers. This mechanism provide
38、s a platform upon which application specific remote procedure calls can be built. The CEA-709 network management protocol, for example, depends upon the Request-Response mechanism in the Session layer. A transport layer acknowledged message expects indication of message delivery from remote destinat
39、ion(s). A session layer Request message expects indication that application-specific re-mote task(s) have been completed. A given message uses only one or the other type of service, but not both. This specification includes the Presentation Layer and the lowest level of the Application Layer. These
40、layers provide services for sending and receiving application messages including network variables, and other types of messages such as network management and diagnostic messages and foreign frames (see 11). For a network variable update, the APDU header pro-vides information on how to interpret the
41、 APDU. This application-independent interpretation of the data allows data to be shared among nodes without prior arrangement. 6 MAC Sublayer There are two MAC sublayers allowed within this standard. The first is descibed immediately below. The other alternative is to use CEA-852 and follow the inst
42、ructions for the implementa-tion of CEA-709.1. An implementation must support at least one of these two alternatives. CEA-852 describes a means for tunneling control network packets such as those defined in this standard across an IP network. When using an IP network as, in effect, the physical laye
43、r of CEA-709.1, the p-persistent CSMA defined in this standard is not used. Instead, the media access provided by the underlying IP network is used for packet transmission. 6.1 Service Provided The CEA-709 Media Access Control (MAC) sublayer facilitates media access with optional priority and option
44、al collision detection/collision resolution. It uses a protocol called Predictive p-persistent CSMA (Carrier Sense, Multiple Access), that has some resemblance to the p-persistent CSMA protocol family. Predictive p-persistent CSMA is a collision avoidance technique that randomizes channel access usi
45、ng knowledge of the expected channel load. A node wishing to transmit always accesses the channel with a random delay in the range (0w). To avoid throughput degradation under high load, the size of the randomizing window, w, is a function of estimated channel backlog BL: w = (BL*Wbase) 1), where Wba
46、seis the base window size. Wbase is measured in time. Its duration, derived from Beta2 (see 6.7), equals 16 Beta2 slots. Provided by IHSNot for Resale-,-,-CEA-709.1-C 86.2 Interface to the Link Layer The MAC sublayer is closely coupled to the Link layer, described in 6. With the MAC sublayer being r
47、esponsible for media access, the Link layer deals with all other layer 2 issues, including framing and error detection. For explanatory purposes, the interface between the two layers is described in the form shown in Figure 4. Figure 4 Interface between the MAC and Link Layers Although the service i
48、nterface primitives are defined using a syntax similar to programming language procedure calls, no implementation technique is implied. Frame reception is handled entirely by the Link layer, that notifies the MAC sublayer about the backlog increment via the Frame_OK() primitive. The following servic
49、e interface primitives facilitate the interface between the Link and the MAC layers: M_Data_Request (Priority, delta_BL, ALT_Path, LPDU) This primitive is used by the Link layer to pass an outbound LPDU/MPDU to the MAC sublayer. Priority defines the priority with which the frame is to be transmitted; delta_BL is the backlog increment expected as a result of delivering this MPDU. ALT_Path is a bi-nary flag indicating whether the LPDU is to be
