This International Standard specifies the frame structures, the elements of procedures, the classes of procedures, the content<\/p>\n
and format of the general purpose Exchange Identification (XID) frame, and a means for resolution\/negotiation of a data link<\/p>\n
layer address in switched environments for data communication systems using bit-oriented high-level data link control<\/p>\n
(HDLC) procedures.<\/p>\n
NOTE ??The use of the phrase "bit-oriented", referring to the HDLC control procedures, pertains to the allocation of a non-integral number<\/p>\n
of bits to various subfields used for HDLC control purposes. However, the frame as an entirety may be constructed from octet-oriented units<\/p>\n
(e.g., start-stop mode) for transmission purposes.<\/p>\n
The frame structure portion defines the relative positions of the various components of the basic frame format and the nonbasic<\/p>\n
frame format. The mechanisms used to achieve bit pattern independence (transparency), where and when required, within<\/p>\n
the frame are also defined. In addition, three frame checking sequences (FCS) are specified; the rules for address field<\/p>\n
extension are defined; and the addressing conventions available are described.<\/p>\n
The elements of procedures portion specifies elements of data link control procedures for synchronous or start\/stop, codetransparent<\/p>\n
data transmission using independent frame numbering in both directions.<\/p>\n
These HDLC elements of procedures are defined specifically in terms of the actions that occur on receipt of commands at a<\/p>\n
secondary station, a tributary station, a peer station, or a combined station.<\/p>\n
This International Standard is intended to cover a wide range of applications; for example one-way, two-way alternate or twoway<\/p>\n
simultaneous data communication between data stations which are usually buffered, including operations on different<\/p>\n
types of data circuits; for example multipoint\/point-to-point, duplex\/half-duplex, switched\/non-switched, synchronous\/startstop,<\/p>\n
etc.<\/p>\n
The defined elements of procedures are to be considered as a common basis for establishing different types of data link control<\/p>\n
procedures. This International Standard does not define any single system and should not be regarded as a specification for a<\/p>\n
data communication system. Not all of the commands or responses are required for any particular system implementation.<\/p>\n
The classes of procedures portion describes the HDLC unbalanced classes of procedures, the HDLC balanced class of<\/p>\n
procedures, and the HDLC connectionless classes of procedures for synchronous or start\/stop data transmission.<\/p>\n
For the unbalanced classes, the data link consists of a primary station plus one or more secondary stations and operates in<\/p>\n
either the normal response mode or the asynchronous response mode in a point-to-point or multipoint configuration. For the<\/p>\n
balanced class, the data link consists of two combined stations and operates in the asynchronous balanced mode in a point-topoint<\/p>\n
configuration. For the unbalanced connectionless class, the data link consists of a control station plus one or more<\/p>\n
tributary stations and operates in the unbalanced connectionless-mode in a point-to-point or multipoint configuration. For the<\/p>\n
balanced connectionless class, the data link consists of two peer stations and operates in the balanced connectionless-mode in a<\/p>\n
point-to-point configuration. In each class, a basic repertoire of commands and responses is defined, but the capability of the<\/p>\n
data link may be modified by the use of optional functions.<\/p>\n
Balanced operation is intended for use in circumstances which require equal control at either end of the data link. Operational<\/p>\n
requirements are covered in accordance with the overall HDLC architecture.<\/p>\n
The content and format of the Exchange Identification (XID) frame portion builds on the fact that the principal use of the XID<\/p>\n
frame is to exchange data link information between two or more HDLC stations. For the purpose of this International Standard,<\/p>\n
ISO\/IEC 13239:2002(E)<\/b><\/p>\n
2 <\/b>\u00a9 ISO\/IEC 2002 ? All rights reserved<\/p>\n
data link information shall include any and all essential operational characteristics such as identification, authentication and\/or<\/p>\n
selection of optional functions and facilities concerning each station. This International Standard defines a single-exchange<\/p>\n
negotiation procedure for establishing operational characteristics when either one or more stations are capable of providing<\/p>\n
multiple selections.<\/p>\n
This International Standard provides a means for exchanging the necessary information to establish, at a minimum, a data link<\/p>\n
connection between two correspondents wishing to communicate. It describes a general purpose XID frame information field<\/p>\n
content and format for that purpose.<\/p>\n
It defines encoding for information related to the basic HDLC standards only. Mechanisms are provided to permit the general<\/p>\n
purpose XID frame information field to be used to negotiate private parameters in a single XID exchange simultaneously with<\/p>\n
negotiation of the defined basic parameters.<\/p>\n
This International Standard does not limit or restrict the use of the XID frame information field from defining other standard<\/p>\n
formats for use in specific applications.<\/p>\n
The following are examples of potential uses of the XID command\/response frame interchange:<\/p>\n
a) Identification of the calling and called stations when using circuit switched networks (including switched network backup<\/p>\n
applications).<\/p>\n
b) Identification of stations operating on non-switched networks requiring identification at start-up.<\/p>\n
c) The XID command frame with an individual, group or all-station address may be used to solicit XID response frame(s)<\/p>\n
from other station(s) on the data link, prior to or following data link establishment.<\/p>\n
d) Negotiation of the Frame Check Sequence (FCS) to be used for subsequent information interchange, by stations that<\/p>\n
support both 16-bit FCS and 32-bit FCS capabilities.<\/p>\n
e) Convey higher layer information that may be required prior to data link establishment.<\/p>\n
f) Transmission of an XID response frame at any respond opportunity to request an XID exchange to modify some of the<\/p>\n
operational parameters (for example, window size) following data link establishment.<\/p>\n
g) Negotiation of the number of protected bits in the frame when an Unnumbered Information with Header check (UIH)<\/p>\n
frame is used.<\/p>\n
The means for resolution\/negotiation of a data link layer address in switched environments portion is applicable to data stations<\/p>\n
employing HDLC balanced classes of procedures which provide the XID command\/response capability with the two specific<\/p>\n
parameter fields, identified below. It is used to select a pair of operational link addresses when preassigned, system designated<\/p>\n
addresses are not known on an a priori basis; e.g., switched circuited data links. Additional XID frame functions (including the<\/p>\n
exchange of operational parameters, command\/response support, higher layer information, etc.) may be accomplished in<\/p>\n
conjunction with data link layer address determination or following address determination, with additional XID frame<\/p>\n
exchanges.<\/p>\n
NOTE ??Address resolution procedures for situations where the remote DTE does not support XID frames, the "all-station"<\/p>\n
address, or complete address support capabilities as defined in clause 8 below are not within the scope of this International<\/p>\n
Standard.<\/p>\n","protected":false},"excerpt":{"rendered":"
Information technology \u2014 Telecommunications and information exchange between systems \u2014 High-level data link control (HDLC) procedures<\/b><\/p>\n\n\n
\n Published By<\/td>\n Publication Date<\/td>\n Number of Pages<\/td>\n<\/tr>\n \n ISO<\/b><\/a><\/td>\n 2002-07<\/td>\n 111<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"featured_media":632088,"template":"","meta":{"rank_math_lock_modified_date":false,"ep_exclude_from_search":false},"product_cat":[670,2634],"product_tag":[],"class_list":{"0":"post-632075","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-35-100-20","7":"product_cat-iso","9":"first","10":"instock","11":"sold-individually","12":"shipping-taxable","13":"purchasable","14":"product-type-simple"},"_links":{"self":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product\/632075","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/types\/product"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/media\/632088"}],"wp:attachment":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/media?parent=632075"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product_cat?post=632075"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product_tag?post=632075"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}