1、 ANSI/CEA Standard Enhanced Protocol for Tunneling Component Network Protocols over Internet Protocol Channels ANSI/CEA-852.1-A April 2014 NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating
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8、ade to CEA. (Formulated under the cognizance of the CEA R7 Home Networks Committee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2014 Technology Phone: 800-854-7179; Fax: 303-397-2740; Internet: http:/; E-mail: . IETF Documents: Internet Engineering Task Force (IETF) Secretariat, c/o Corporation f
9、or National Research Initiatives, 1895 Preston White Drive, Suite 100, Reston, VA 20191-5434, USA; (703) 620-8990 / (703) 620-9071 (FAX); URL: www.ietf.org, IETF RFCs may be downloaded from www.ietf.org/rfc.html, IETF Internet drafts may be downloaded from www.ietf.org/ID.html. 3 Introduction The pr
10、otocol described herein, that is, the CEA-852.1 protocol is a non backwards compatible enhanced replacement for the CEA-852 protocol. After several years of active use in the field, it was determined that that CEA-852 protocol needed to be upgraded primarily to enable better support for dynamic IP a
11、ddressing, NAT router support, better scalability and performance for large networks, more flexible configuration services and eventual support for IPV6. Because of the extreme difficulty in adding support for these features in both an elegant and backwards compatible way, it was decided to break ba
12、ckwards compatibility. Instead, the approach contemplated for backwards compatibility is to use Bilingual devices that can run in either 852 or 852.1 mode and correctly determine which mode to run in. Despite the fact that CEA-852.1 is not backwards compatible, it still retains much of the flavor of
13、 CEA-852 and where possible preserved field names and functionality. Because of the many similarities between the two protocols, effort was made to point out where the CEA-852.1 specification differs from CEA-852. It is expected that CEA-852 will continue to be deployed for some time and in some cas
14、es in hybrid networks that have both 852.1 and 852 channels. Unless otherwise indicated, the designator 852 refers to the latest revision of CEA-852, which at the time of this writing was CEA-852-C 5. This document provides specifications for the transporting of Component Network (CN) packets over I
15、nternet Protocol (IP) networks using a tunneling mechanism wherein the CN packets are encapsulated within the IP packets. It applies to both CN nodes and CN routers. The purpose of this specification is to insure interoperability between various CN devices that wish to use IP networks to communicate
16、 using a particular CN protocol. The specification is intended to be general enough to handle a wide range of CN protocols. In particular this specification will cover the following standard CN protocols: CEA-709.1 2 CEA-600 1 The main body of this specification is independent of the CN protocol bei
17、ng transported over the IP network. The reader is directed to Annex A and Annex B for the normative CEA-852.1-A 8 and informative, respectively, aspects of this specification that are specific to CEA-709.1 2. Likewise Annex C and Annex D are the normative and informative, respectively, aspects of th
18、is specification as they apply to CEA-600 1. Figure 1 shows a possible configuration of such CN devices and networks connected to an IP network. Figure 1 Typical CN/IP Application Figure 1 depicts two types of CN devices: CN nodes and CN routers. Note that the routers shown can route packets between
19、 typical CN channels (such as twisted pair or power line) and an IP channel or it can route CN packets between two IP channels. In this document the IP channel will be defined in such a way to allow it to be used like any other CN channel. In the above diagram the IP network can be considered to be
20、one or more IP channels. This specification covers only how CN packets are transported over IP channels. It does not cover how CN packets are routed between standard CN channels and IP channels. This specification is not intended to cover the lower layers (physical, MAC and link) layers of either st
21、andard CN or IP channels. CN/IP Router CN Channel CN Nodes CN/IP Router CN Channel CN Nodes CN/IP Router CN Channel CN Node INTERNET IP Channel IP Channel Workstation running CN Stack Embedded CN Device CN/IP to CN/IP Router CN/IP to CN/IP Router CEA-852.1-A 9 4 Requirements The following is a set o
22、f general requirements for the transporting of CN packets over IP channels: Be as efficient as possible to allow quasi real time operation. Be independent of the application level interface used to receive the packets. For example the tunneling protocol should not rely on the existence of a socket i
23、nterface or how that interface may be used. Insure that CN packet ordering is preserved. Insure that CN packets that are “stale” (outside the maximum timeout characteristics of the IP channel) are not forwarded. Detect packets that get duplicated in the IP network. Support IP routing devices that pr
24、ioritize IP packets. Optional security measures to prevent malicious users from tampering with devices. Scalable. Allow status information to be extracted from 852.1 devices. Support the exchange of configuration information between 852.1 devices and configuration servers. Provide for the bootstrapp
25、ing of hybrid 852.1/852 devices. 5 852.1 Device and Channel Specification An 852.1 device has a dual personality. From a CN point of view, it is a CN node on a CN channel and has all such characteristics. These parameters can be configured and managed using the standard CN network management procedu
26、res and messages. From the IP point of view, the 852.1 device is an IP host on an IP network and thus has to be configured like any other host on an IP network. In addition, there is configuration information that defines the logical 852.1 channel associated with that 852.1 device. In general all IP
27、 host and channel parameters will be configurable using a number of techniques and protocols. As a minimum all 852.1 devices MUST support manual configuration of the forwarding mechanism for that device in order to guarantee a minimum level of interoperability between devices that may be configured
28、in different ways. By forwarding we mean the act of tunneling as described above to the other devices on the IP channel. IP channels are not like typical CN channels that currently exist. Typical CN channels are physical busses by nature. This implies that all devices on the channel will by default
29、receive all packets transmitted on that channel. In addition when a new device is added to the channel it is not necessary that other devices on the channel become aware of it before they can exchange packets. To transmit a packet on a channel it is only necessary CEA-852.1-A 10 that a device be cap
30、able of physically transmitting the packet on the channel, nothing more. If a device is simply physically connected to a channel it is capable of exchanging packets with other devices on the channel. By contrast an IP channel is not physical, but logical in nature. There are a number of different ph
31、ysical media that can support IP communications and any of them should be capable of supporting a CN channel. Because we are dealing with a logical channel it is necessary to “construct” the channel by informing each device on the channel of the existence of the other devices on that channel. In oth
32、er words before a device can transmit a packet to some other device on an IP channel it must be made aware of how to specifically send a packet to that device, i.e. its IP address. Another significant difference between physical and logical channels is that in the case of typical physical channels i
33、t is possible to calculate fixed upper bounds on the length of time it will take a packet to traverse from one device to another once the packet is transmitted on the channel. This is not always possible for IP networks. The deviation of packet delivery times between CN devices on an IP channel are
34、much higher than those experienced with typical CN channels. As depicted in Figure 1 the IP channel is used as an intermediary transport mechanism for the CN packets by a variety of 852.1 devices. When a CN packet is transported on an IP channel, an IP packet encapsulating the CN packets is sent to
35、other 852.1 devices on that IP channel. On reception of one of the IP messages by an 852.1 device the CN packets are extracted and processed. A single IP packet may contain more than one CN packet. Therefore the IP packets must be formatted in such a way to allow the extraction of the individual CN
36、packets. This is referred to a packet “aggregation”. 852.1 devices MUST support the reception of aggregated packets. Likewise the aggregation MUST be done in such a fashion that each CN packet contained within an aggregated IP packet is complete, i.e. CN packets should not cross IP packet boundaries
37、 as a result of aggregation. It is also a requirement that intermediate IP devices be capable of unbundling aggregated CN packets and aggregating them in a different manner before forwarding them. An 852.1 device MUST behave like any standard IP host capable of exchanging IP packets with any other I
38、P host either on the same IP subnet or anywhere else in the Internet cloud. An 852.1 device MUST have at least one IP Uni-cast address and MAY be capable of belonging to as many as 32 multi-cast groups. It is OPTIONAL that an 852.1 device support multi-casting. This document does not address the rou
39、ting of IP packets between subnets or through the Internet. The CN/IP devices MUST be compatible with whatever standard mechanisms (IP routers, switches, etc.) are required to perform the IP routing functions. An 852.1 Channel is specified by a list of unique Device IDs (DID). Associated with each D
40、evice ID is the current IP addressing information that allows other 852.1 devices to communicate over the IP network to the associated Device. Because the IP address may be dynamic or the device may be behind a NAT router or both. The nature of and the manner in which the IP addressing information i
41、s used are context and time dependant. Each device, however, MUST be uniquely addressable on the IP network. CEA-852.1-A 11 The IP addressing information might be a DNS registered IP Node Name that is converted dynamically into an IP Uni-cast host and port address. For example, multiple devices MAY
42、share the same IP Uni-cast host address but MUST have unique IP ports. Conversely, multiple devices may all use the same port but must have different host addresses. When devices are behind NAT routers, more than one IP address may be needed for a given device depending on whether the communicating
43、device is also behind the NAT router or not. If every 852.1 device on an IP channel contained an updated list of the current IP Uni-cast addresses for every other 852.1 device on that IP channel, this is all that would be required to enable the tunneling of CN packets. In order to make the problem t
44、racking the changes in IP addresses tractable, CEA-852.1 assigns each device in an 852.1 channel a unique Device ID. In the most brute force approach, for each CN packet to be forwarded on the IP channel a separate IP Uni-cast message could be sent to each 852.1 device in the channel. This does not
45、scale very well, so the following techniques will be used to reduce the IP traffic: IP Multi-cast groups Selective forwarding IP multi-cast groups allow a single IP message to be sent to more than one 852.1 device. Therefore a complete definition of the 852.1 channel should contain not only the Devi
46、ce IDs and IP Uni-cast addresses of all the 852.1 devices on the channel but also the IP Multi-cast groups to which they belong. Each 852.1 device can belong to up to 32 multi-cast addresses. Selective Forwarding Selective forwarding refers to examining the contents of the CN packet before forwardin
47、g it to determine if it should be sent to a particular 852.1 device. In order to do this additional CN specific information must be known about each potential destination. If the 852.1 device is a router then the information necessary to perform selective forwarding is the routing tables of the 852.
48、1 router. If the device is simply a node then the domain, subnet, node ID, unique ID, and CN groups that the node belongs to should be known. Therefore all this information is also part of a complete 852.1 channel definition. In short a complete IP channel definition contains all known information t
49、hat may be relevant to the forwarding of packets to the other 852.1 devices in the IP channel. It is the universe of all relevant knowledge about the IP channel. It is important that whatever forwarding scheme is used by CN/IP device the following conditions are always true: 1. CN protocol packets are always received by all 852.1 devices on the IP channel that need to receive them regardless of whether they are routers or nodes. If there is any ambiguity or uncertainty concerning which 852.1 devices should receive a CN pac
