An Overview of ANSI C12.22 ..
2
An Overview of ANSI C12.22 By: Edward Beroset, manager of the software and test group, Elster Electri city, LLC Using the Internet to send and receive meter data is a topic of discussion at many u ilities. A number of proprietary protocols are available today, but soon, a new ANSI standard protocol will be published to cover this application. This article describes the new protocol, including its impact on both Interne t and radio networks. Imagine that you’re surfing the web and you see a web link that looks interesting to you. If you’re like most people, you probably don’t think about how that mouse click results in displaying the reques ed web page. When you click on a link with the mouse, the web browser issues a Hypertext Transfer Protocol (HTTP) GET request for that specific page. This request makes its way through the Internet network to a web server, which could be anywhere in the world. In response, the web server delivers the web page content through the Internet network to the web browser, which displays the web page. Regardl ess of how your computer is connected to the web, through a modem dial- up connection or an Ethernet connection to a local area network (LAN), the request issued by the web browser is the same. This chara cter istic of In tern et network design has signi fican t advan tage s over other possi ble desig ns. One advan tage is that only one web browser is need ed that sits on top of the underly ing ransp ort protoc ols (for example, TCP/IP over PPP over dial- up, or TCP/IP over Ethern et). This design char acter istic also help s the programmers who develop the applications that make the Internet work. T he browser programmers can concentrate on browser functions without having to worry about underlying protocols, and the pro ocol developers can do their ob without needing to know what applications are using the protocol. To explain this characteristic of Internet network design in simple terms, consider this analogy. If you send a letter to Moscow by traditional post, you are the application writing the letter and the postal carrier is implementing the underlying transport protocol. You don’t need to know any of the details of how the Russian postal system works, and the letter carrier doesn’t need to know the contents of your l etter. ANSI C12.22 is the designation of a new standard that is being developed to allow the transport of ANSI C12.19 table data over networked connections. It is part of a group of related ANSI protocols but has some fundamental differences from the other protocols within the group. This article discusses the ANSI C12.22 protocol and how it work s, but to fully unde rstan d the C12.22 proto col, it is helpf ul to consider a brie f histor y of ANSI mete r communications standards. A Brief History of ANSI Meter Communications Standards Years ago, data formats, data structures and communications protocols for electricity meters were all proprietary. But, utility companie s want ed a compatib le commun icatio n prot ocol between ANSI meter s so they were not restricted to a single electricity meter vendor. To meet this requirement, ANSI standards were created that describe meter data formats and structures (C12.19), and provide a simple optical point-topoint communications protocol (C12.18) that allowed them to communicate with ANSI standard meters. While this was a huge step forward in making a standard communication protocol for electricity meters, it wasn’t long before users wanted to be able to s end and receive ANSI tables remotely. To address that need, C12.18 was adapted to create C12.21. ANSI Standard C12.21-1999 specified a new version of C12.18 that was modified for telep hone modems. This proto col was still strict ly point -to- point commun icatio n and sessio n orien ted. Minor modifications were made to account for longer communication timeouts and for security since it could no longer be assumed that a person would be standing directly in front of the meter. How and Why is C12.22 Different? C12.18 descr ibed every deta il of the physical attr ibute s for optic al communication port s (dimensions, LED wavelength, etc.). This standard was needed to build meters with a compatible communication interface. When C12.21 was created to implement point-to-point communication between meters, the intent was to use it with alre ady existing modems. For this ANSI communication standard it did not mak e any sense for the ANS I subcommittee to describe particular modulation techniques and the physical connector used in modems because these aspects were already specified by other standards. Alt hough C12.21 is a me ter communica tions standard and not a mod em standard , some gener al attri bute s regarding modems were incorporated into the C12.21 standard. For example, initialization and dial strings were speci fied, but conne ctor specifica tion and electrical characte risti cs were not. The form at and structure of the communications packets that carry C12.21 requests and responses are described in detail in the standard, but below a certain point, the detail stops. In the language of communications standards, the C12.21 protocol is more abstract than C12.18 because it deliberately omits the lower layer details. C12.22 is different from C12.21 in the same way that C12. 21 is different from C12.1 8. C12 .22 is mo re abstract because it omits even mor e of the underlying protocol details. The reason for these differences is also related. C12.22 is intended for use over already existing communication networks just as C12.21 is intended to for use with already existing modems. Examples of such communication networks covered by C12.22 include TCP/IP over Ethernet, SMS over GSM, or UDP/IP over PPP over serial port. Just as HTTP provides a common application layer that all web browsers can use, C12.22 provides a common application layer that all meters can use. OSI Reference Model The ISO (Inte rnational Orga niza tion for Stan dard iza tion) OSI (Ope n System s In terco nnect ions ) is a set of international standards that describe how computer systems may be interconnected to support the exchange of information in a consistent fashion. It is commonly referred to as the OSI Reference Model, or the "seven layer model." It provides a standard for layering communication protocols, which makes it easier to understand and implement in product design. Seven Layer Model While many people are familiar with the OSI Reference Model, Figure 1 provides an overview of the commun ication protocols contained in each layer. Figure 1 Advertisement Advertisement Advertisement Advertisement Advertisement An Overview of ANSI C12.22 - Edward Beroset, manag er of th e softwa... htt p://w ww.electri cenergy online.com /?page=sh ow_article&mag =18&ar... 2 de 3 02/06/2010 10:4
-
Upload
alvaro-paricio -
Category
Documents
-
view
223 -
download
0
Transcript of An Overview of ANSI C12.22 ..
8/8/2019 An Overview of ANSI C12.22 ..
http://slidepdf.com/reader/full/an-overview-of-ansi-c1222- 1/2
An Overview of ANSI C12.22By: Edward Beroset, manager of the software and test group, Elster Electri city, LLC
Using the Internet to send and receive meter data is a topic of discussion at many u ilities. A number of proprietary
protocols are available today, but soon, a new ANSI standard protocol will be published to cover this application.
This article describes the new protocol, including its impact on both Internet and radio networks.
Imagine that you’re surfing the web and you see a web link that looks interesting to you. If you’re like most people,
you probably don’t think about how that mouse click results in displaying the reques ed web page. When you click
on a link with the mouse, the web browser issues a Hypertext Transfer Protocol (HTTP) GET request for that
specific page. This request makes its way through the Internet network to a web server, which could be anywherein the world. In response, the web server delivers the web page content through the Internet network to the web
browser, which displays the web page. Regardless of how your computer is connected to the web, through a
modem dial-up connection or an Ethernet connection to a local area network (LAN), the request issued by the web
browser is the same.
This characteristic of Internet network design has significant advantages over other possible designs. One
advantage is that only one web browser is needed that sits on top of the underlying ransport protocols (for
example, TCP/IP over PPP over dial-up, or TCP/IP over Ethernet). This design characteristic also helps the
programmers who develop the applications that make the Internet work. The browser programmers can concentrate
on browser functions without having to worry about underlying protocols, and the pro ocol developers can do their
ob without needing to know what applications are using the protocol.
To explain this characteristic of Internet network design in simple terms, consider this analogy. If you send a letter to
Moscow by traditional post, you are the application writing the letter and the postal carrier is implementing the
underlying transport protocol. You don’t need to know any of the details of how the Russian postal system works,
and the letter carrier doesn’t need to know the contents of your letter.
ANSI C12.22 is the designation of a new standard that is being developed to allow the transport of ANSI C12.19
table data over networked connections. It is part of a group of related ANSI protocols but has some fundamental
differences from the other protocols within the group. This article discusses the ANSI C12.22 protocol and how itworks, but to fully understand the C12.22 protocol, it is helpful to consider a brief history of ANSI meter
communications standards.
A Brief History of ANSI Meter Communications Standards
Years ago, data formats, data structures and communications protocols for electricity meters were all proprietary.
But, utility companies wanted a compatible communication protocol between ANSI meters so they were not
restricted to a single electricity meter vendor. To meet this requirement, ANSI standards were created that describe
meter data formats and structures (C12.19), and provide a simple optical point-topoint communications protocol
(C12.18) that allowed them to communicate with ANSI standard meters.
While this was a huge step forward in making a standard communication protocol for electricity meters, it wasn’t
long before users wanted to be able to send and receive ANSI tables remotely. To address that need, C12.18 was
adapted to create C12.21. ANSI Standard C12.21-1999 specified a new version of C12.18 that was modified for
telephone modems. This protocol was still strictly point-to-point communication and session oriented. Minor
modifications were made to account for longer communication timeouts and for security since it could no longer be
assumed that a person would be standing directly in front of the meter.
How and Why is C12.22 Different?
C12.18 described every detail of the physical attributes for optical communication ports (dimensions, LED
wavelength, etc.). This standard was needed to build meters with a compatible communication interface. When
C12.21 was created to implement point-to-point communication between meters, the intent was to use it with
already existing modems. For this ANSI communication standard it did not make any sense for the ANSI
subcommittee to describe particular modulation techniques and the physical connector used in modems because
these aspects were already specified by other standards.
Although C12.21 is a meter communications standard and not a modem standard, some general attributes
regarding modems were incorporated into the C12.21 standard. For example, initialization and dial strings were
specified, but connector specification and electrical characteristics were not. The format and structure of the
communications packets that carry C12.21 requests and responses are described in detail in the standard, but
below a certain point, the detail stops. In the language of communications standards, the C12.21 protocol is more
abstract than C12.18 because it deliberately omits the lower layer details. C12.22 is different from C12.21 in the
same way that C12.21 is different from C12.18. C12.22 is more abstract because it omits even more of the
underlying protocol details. The reason for these differences is also related. C12.22 is intended for use over already
existing communication networks just as C12.21 is intended to for use with already existing modems. Examples of
such communication networks covered by C12.22 include TCP/IP over Ethernet, SMS over GSM, or UDP/IP over
PPP over serial port. Just as HTTP provides a common application layer that all web browsers can use, C12.22
provides a common application layer that all meters can use.
OSI Reference ModelThe ISO (International Organization for Standardization) OSI (Open Systems Interconnections) is a set of
international standards that describe how computer systems may be interconnected to support the exchange of
information in a consistent fashion. It is commonly referred to as the OSI Reference Model, or the "seven layer
model." It provides a standard for layering communication protocols, which makes it easier to understand and
implement in product design.
Seven Layer ModelWhile many people are familiar with the OSI Reference Model, Figure 1 provides an overview of the communication
protocols contained in each layer.
Figure 1
Advertisement
Advertisement
Advertisement
Advertisement
Advertisement
Overview of ANSI C12.22 - Edward Beroset, manager of the softwa... http://www.electricenergyonline.com/?page=show_article&mag=18&ar...
3 02/06/2010 10:4
8/8/2019 An Overview of ANSI C12.22 ..
http://slidepdf.com/reader/full/an-overview-of-ansi-c1222- 2/2
Overview of ANSI C12.22 - Edward Beroset, manager of the softwa... http://www.electricenergyonline.com/?page=show_article&mag=18&ar...
3 02/06/2010 10:4
