InfoMagic Standards 1993 July/Disc.iso/ccitt/1988/troff/8_3_08.tro

Text File | 1991-12-22 | 70.4 KB | 3,020 lines

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.rs
\v'|.5i'
.sp 2P
.LP
\fBRecommendation\ X.122\fR
.RT
.sp 2P
.ce 1000
\fBNUMBERING\ PLAN\ INTERWORKING\ BETWEEN\ A\ PACKET\ SWITCHED\fR
.EF '%    Fascicle\ VIII.3\ \(em\ Rec.\ X.122''
.OF '''Fascicle\ VIII.3\ \(em\ Rec.\ X.122    %'
.ce 0
.ce 1000
\fBPUBLIC\ DATA\ NETWORK\ (PSPDN)\ AND\ AN\ INTEGRATED\ SERVICES\fR
.ce 0
.ce 1000
\fBDIGITAL\ NETWORK\ (ISDN)\ OR\ PUBLIC\ SWITCHED\ TELEPHONE\ NETWORK\fR
.ce 0
.sp 1P
.ce 1000
\fB(PSTN)\ IN\ THE\ SHORT\(hyTERM\fR
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
    The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that Recommendation X.121 defines the international
numbering plan for Public Data Networks (PDNs);
.PP
(b)
that Recommendation E.164/I.331 defines the numbering
plan for the ISDN era;
.PP
(c)
that Recommendation X.300 defines the general principles and arrangements
for interworking between Public Networks, and between Public Networks and
other networks for the provision or data transmission services;
.PP
(d)
that Recommendation I.330 defines ISDN numbering and
addressing principles;
.PP
(e)
that Recommendation I.332 defines the numbering
principles for interworking between ISDNs and dedicated networks with
different numbering plans;
.PP
(
f
)
that Recommendation E.166 defines numbering and addressing interworking
in the ISDN era;
.PP
(g)
that Recommendation E.165 defines the timetable for
coordinated implementation of the full capability of Recommendation\ E.164;
.PP
(h)
the Recommendation X.110 defines the international
routing principles and routing plan for Public Data Networks (PDNs);
.PP
(i)
that Recommendation X.25 defines the interface between DTE and DCE for
terminals operating in the packet mode on PDNs and connected
to PDNs by dedicated circuit;
.PP
(
j
)
that Recommendation X.32 defines the
interface between DTE and DCE for terminals operating in the packet mode and
accessing a PSPDN through a PSTN or a Circuit Switched Public Data Network
(CSPDN);
.PP
(k)
that Recommendation X.31 defines the support of packet mode terminal equipment
by an ISDN;
.PP
(l)
that Recommendation X.75 defines the packet switched
signalling system between public networks providing data transmission
services;
.PP
(m)
that the need that DTEs can communicate through
different networks with different numbering plans for the purpose of
interworking CCITT defined services;
.sp 1P
.LP
\fI(unanimously) declares the view\fR
.sp 9p
.RT
.PP
that numbering plan interworking between PSPDNs and ISDNs or PSTNs in the
short term be in accordance with the procedures specified in this
Recommendation.
.sp 1P
.ce 1000
CONTENTS
.ce 0
.sp 1P
.sp 2P
.LP
1
    \fIIntroduction\fR
.sp 1P
.RT
.sp 1P
.LP
2
    \fIScope\fR
.sp 9p
.RT
.sp 1P
.LP
3
    \fIProcedures\fR
.sp 9p
.RT
.sp 1P
.LP
4
    \fIShort\(hyterm interworking scenarios\fR
.sp 9p
.RT
.sp 1P
.LP
\fIAnnex\ A\fR \ \(emAbbreviations
.bp
.sp 9p
.RT
.LP
\fB1\fR     \fBIntroduction\fR
.sp 1P
.RT
.PP
Numbering plan interworking is a fundamental requirement for
successful completion of call connections between networks with different
numbering plans, e.g.,\ from a PDN to an ISDN.
.PP
This Recommendation defines the general procedures applicable to
PSPDNs up to the time\ \*QT\*U as specified in Recommendation\ E.165. In
particular, this Recommendation describes the interworking scenarios for
PSPDNs with ISDNs or PSTNs for a short\(hyterm. Recommendation\ E.166 deals
with interworking
scenarios for ISDNs with other networks.
.RT
.sp 2P
.LP
\fB2\fR     \fBScope\fR
.sp 1P
.RT
.PP
2.1
The scope of this Recommendation is to define the procedures
applicable to PSPDNs for the purpose of numbering plan interworking with
networks which use the E.164 (E.163) numbering plan. In this Recommendation
it is assumed that E.163 is a subset of E.164. In the short\(hyterm the
length of the E.164 numbers are restricted to 12\ digits as per Recommendation\
E.165.
.sp 9p
.RT
.PP
2.2
This Recommendation applies to numbering plan interworking across international
boundaries. Its applicability to calls within a single country is a national
matter.
.sp 9p
.RT
.PP
2.3
The procedures specified in this Recommendation may not apply
after time\ \*QT\*U. Time\ \*QT\*U is defined in Recommendation\ E.165.
.sp 9p
.RT
.PP
2.4
Interworking involving more than two networks is included in the scope
of this Recommendation.
.sp 9p
.RT
.PP
2.5
Procedures at the man machine interface and the DCE/DTE interface are outside
the scope of this Recommendation.
.sp 9p
.RT
.LP
\fB3\fR     \fBProcedures\fR
.sp 1P
.RT
.sp 2P
.LP
3.1
    \fIUse of standardized escape codes from the X.121 numbering\fR
\fIplan\fR
.sp 1P
.RT
.sp 1P
.LP
3.1.1
    \fIGeneral\fR
.sp 9p
.RT
.PP
The terms \*Qprefix\*U and \*Qescape code\*U are defined in \(sc\(sc\ 2.5
and 2.6 of Recommendation\ X.121. The values of the escape codes for use
by PDNs should be in accordance with Table\ 2/X.121 of Recommendation\
X.121.
.PP
Two escape codes from X.121 to E.164 numbering plan have been
allocated for the following reasons:
.RT
.LP
    1)
    to provide routing criteria from PDN to PSTN and ISDN,
and
.LP
    2)
    to indicate the type of interface that has been
requested.
.PP
Specific use of escape codes is described in the following
sections.
.PP
The use of prefix digits is outside the scope of this
Recommendation.
.RT
.sp 1P
.LP
3.1.2
    \fIEscape code\fR \fI0\fR
.sp 9p
.RT
.PP
Escape code 0 is used to escape from the X.121 numbering plan to
the E.164 numbering plan. It indicates that a digital interface between the
PSPDN and the destination network (ISDN or integrated ISDN/PSTN) is requested
(see also \(sc\ 3.1.4).
.PP
An Optional Network Specific Digit(s) (ONSD) that represents the
same functionality as the internationally agreed value\ 0 may be used to
avoid any conflict with existing use of 0 within a network. When an ONSD
is used, the translation of that digit into the internationally agreed
value\ 0 at the
network boundary is the responsibility of the originating (or transit)
network.
.PP
Other number formats may be used when interworking is not across an
international boundary.
.bp
.RT
.sp 1P
.LP
3.1.3
    \fIEscape code 9\fR
.sp 9p
.RT
.PP
Escape code 9 is used to escape from the X.121 numbering plan to
the E.163 or E.164 numbering plan. It indicates that an analogue interface
on the destination network (PSTN or integrated ISDN/PSTN) is requested
(modem
required) (see also \(sc\ 3.1.4).
.PP
An Optional Network Specific Digit(s) (ONSD) that represents the same functionality
as the internationally agreed value\ 9 may be used to avoid any
conflict with existing use of 9 within a network. When an ONSD is used, the
translation of that digit into the internationally agreed value\ 9, at the
network boundary is the responsibility of the originating (or transit)
network.
.PP
Other number formats may be used when interworking is not across an
international boundary.
.bp
.RT
.PP
3.1.4
It is recognized that special situations can exist where calls
from a PSPDN to an integrated ISDN/PSTN which does not require a distinction
between digital and analogue interfaces, then only a single escape code
(i.e.\ 9 or\ 0) is required. However, all PSPDNs interworking with ISDNs,
PSTNs and
ISDN/PSTNs should support both 9 and 0 escape codes when acting as an
originating, transit or destination network.
.sp 9p
.RT
.PP
3.1.5
Alternatively, in some countries (or RPOAs) a DNIC may be
allocated to an ISDN, as it is now applicable for PSTN. The use of a DNIC
for that purpose is the decision of the country (or RPOAs). In this case,
the PDN using a DNIC to identify terminals on an interconnected ISDN should
be capable of generating escape codes\ 9 and/or\ 0 for escaping to an ISDN/PSTN
or PSTN that does not use the DNIC solution. The translation of the X.121
number to an E.164 number at the destination is permitted on a national
basis. As far as the
international subscriber is concerned, the called terminal has an X.121
number and the conversion, if required, is done in the destination country.
.sp 9p
.RT
.sp 2P
.LP
3.2
    \fIGeneral description on the use of escape codes for PSPDNs\fR
\fIto ISDN/PSTN or PSTN interworking\fR
.sp 1P
.RT
.PP
3.2.1
The DTE enters the number of the ISDN or PSTN terminal to be
called, preceded by an appropriate escape code\ N (see \(sc\(sc\ 3.1.2
and 3.1.3). The full called number, N\ +\ E.164, is sent from the DTE to
the PDN for routing to the correct network interface.
.sp 9p
.RT
.PP
3.2.2
In some networks, an Optional Network Specific Digit(s) (ONSD) may be used,
which represents the same functionality as the internationally agreed value
as described in \(sc\(sc\ 3.1.2 and\ 3.1.3. In this case an ONSD can be
used in place of N. The ONSD must be translated into N before it crosses
an
international boundary.
.sp 9p
.RT
.sp 2P
.LP
3.3
    \fIDigit analysis\fR
.sp 1P
.RT
.PP
3.3.1
For routing implications, refer to Recommendation X.110.
.sp 9p
.RT
.PP
3.3.2
The number analysis capability of a PSPDN for interworking with
ISDN, PSTN should be five digits. The need to analyze more than five digits
is for further study.
.sp 9p
.RT
.sp 2P
.LP
\fB4\fR     \fBShort\(hyterm interworking scenarios\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
    \fIGeneral\fR
.sp 9p
.RT
.PP
The short term in this Recommendation means the time period up to time
\*QT\*U specified in Recommendation\ E.165.
.PP
The following figures illustrate examples of short\(hyterm numbering plan
interworking scenarios. The scenarios are not exhaustive.
.bp
.RT
.sp 1P
.LP
    \fINote to figures\fR
.sp 9p
.RT
.PP
The presence and exact format of the called and calling addresses at the
DTE/DCE interface are network dependent, including possible use of
prefixes.
.PP
The diagrams show only number flows carried in the call request packet
and do not indicate any numbering arrangement necessary for call set up
within the ISDN or PSTN. For details of call set up arrangements refer
to
Recommendations\ X.31, X.32 and the X.300\(hyseries.
.PP
In this Recommendation when an X.31 terminal is being called using an E.164
number, it is recognized that digital interworking is required (E.164
digital) and when an X.32 terminal is being called using an E.164 number,
analogue interworking is required (E.164 analogue).
.RT
.sp 1P
.LP
    \fIKey to the figures\fR
.sp 9p
.RT
.PP
Arrows associate the number flows to that portion of the call.
.PP
The positioning of the interworking function (IWF) symbol, on the
diagram, does not imply a fixed position within a network nor make any
statement on the functionality of the IWF. The IWF is a logical representation
of the gateway process which handles required protocol translations beween
two dissimilar networks. The specific location or implementation of an
IWF should be referred to the appropriate Recommendation.
.PP
In the following scenarios, the number referred to as \*QX.121\*U is
\*QInternational Data Number\*U i.e.,\ DNIC\ +\ NTN or DCC\ +\ NN as specified
in
\(sc\ 2.3.1 of Recommendation\ X.121 and Figure\ 2/X.121.
.PP
Abbreviations used are explained in Annex A.
.RT
.sp 1P
.LP
4.2
    \fIShort\(hyterm numbering plan interworking between\fR
\fItwo dissimilar networks\fR
.sp 9p
.RT
.PP
Table 1/X.122 introduces the possible numbering plan interworking scenarios.
Reference to a specific Recommendation is for the case where its
procedures are directly applicable. The other numbers in the table indicate
the corresponding scenarios in this Recommendation.
.RT
.LP
.sp 3
.ce
\fBH.T. [T1.122]\fR
.ce
TABLEAU\ 1/X.122
.ce
\fBNumbering plan interworking (short\(hyterm) between two
.ce
networks\fR
.T&
lw(36p) | lw(24p) | lw(24p) | lw(36p) | lw(24p) | lw(24p) , ^ | l | l |
l | l | l
^  | l | l | l | l | l
^  | l | l | l | l | l.


.T&
rw(36p) | lw(24p) | lw(24p) | lw(36p) | lw(24p) | cw(24p) , ^ | l | l |
c | c | l
^  | l | c | c | c | l
^  | l | l | l | l | l.
From/To    PSPDN      X.121           CSPDN    X.121     X.121
    ISDN    \(sc 4.2.2     (Note)     E.164     PSTN    \(sc 4.2.1     (Note)     E.164     E.164
_
.T&
rw(60p) | lw(24p) | cw(36p) | cw(24p) | cw(24p) , ^  | c s s s.
NETWORK  NETWORK    PSPDN    CSPDN    ISDN    PSTN
    T{
To/From
\fINote\fR
\ \(em\ Outside the scope of this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/X.122 [T1.122], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.2.1
    \fIPSPDN to/from PSTN (X.32)\fR \| (Figure 1/X.122)
.sp 9p
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 1/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
4.2.2
    \fIPSPDN to/from ISDN (X.31)\fR
.sp 1P
.RT
.PP
4.2.2.1
Case A scenarios using permanent, or switched access from the Access Unit
(AU) to the terminal connected to the ISDN when the ISDN terminal is not
allocated an X.121 number (see Figure\ 2/X.122).
.sp 9p
.RT
.LP
.rs
.sp 21P
.ad r
\fBFigure 2/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
4.2.2.2
Case A scenarios using permanent or switched access from the
access unit (AU) to the terminal in the ISDN when the ISDN terminal is
allocated an X.121 number (see Figure\ 3/X.122).
.sp 9p
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 3/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
4.2.2.3
Case B scenarios using permanent or switched access from the
packet handler (PH) to the terminal in the ISDN (see Figure 4/X.122).
.sp 9p
.RT
.LP
.rs
.sp 22P
.ad r
\fBFigure 4/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.3
    \fINumbering plan interworking via an intermediate network \(em\fR
\fIshort term\fR
.sp 9p
.RT
.ce
\fBH.T. [T2.122]\fR
.ce
TABLE\ 2/X.122
.ce
\fBNumbering plan interworking via an intermediate network \(em short\(hyterm\fR
.ce

.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(72p) .
Scenarios     Interconnected networks
_
.T&
cw(36p) | lw(72p) .
\(sc 4.3.1    PSPDN \(em ISDN \(em PSPDN
.T&
cw(36p) | lw(72p) .
\(sc 4.3.2    ISDN \(em PSPDN \(em ISDN
.T&
cw(36p) | lw(72p) .
\(sc 4.3.3    ISDN \(em PSPDN \(em ISDN
.T&
cw(36p) | lw(72p) .
\(sc 4.3.4    ISDN \(em PSPDN \(em PSTN
.T&
cw(36p) | lw(72p) .
\(sc 4.3.5    ISDN \(em PSPDN \(em ISDN
.T&
cw(36p) | lw(72p) .
\(sc 4.3.6    T{
ISDN \(em PSPDN \(em ISDN/PSTN
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/X.122 [T2.122], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 4
.sp 1P
.LP
4.3.1
    \fIPSPDN \(em ISDN \(em PSPDN\fR \| (Figure 5/X.122)
.sp 9p
.RT
.LP
.rs
.sp 25P
.ad r
\fBFigure 5/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.3.2
    \fIISDN \(em PSPDN \(em ISDN for X.31 Case B to X.31 Case B\fR \|
(Figure 6/X.122)
.sp 9p
.RT
.LP
.rs
.sp 21P
.ad r
\fBFigure 6/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.3.3
    \fIISDN \(em PSPDN \(em ISDN for X.31 Case B to X.31 Case A\fR
\fIwhen the Case A terminal is allocated an X.121 number\fR \| (Figure 7/X.122)
.sp 9p
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 7/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.3.4
    \fIISDN \(em PSPDN \(em PSTN\fR \| (Figure 8/X.122)
.sp 9p
.RT
.LP
.rs
.sp 21P
.ad r
\fBFigure 8/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.3.5
    \fIISDN \(em PSPDN \(em ISDN for X.31 Case B to X.31 Case A\fR
\fIwhen the Case A terminal is not allocated an X.121 number\fR \|
(Figure 9/X.122)
.sp 9p
.RT
.LP
.rs
.sp 22P
.ad r
\fBFigure 9/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.3.6
    \fIISDN \(em PSPDN \(em ISDN/PSTN\fR \| (Figure 10/X.122)
.sp 9p
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 10/X.122, (N) p.\fR
.sp 1P
.RT
.ad b
.RT
.ce 1000
ANNEX\ A
.ce 0
.sp 1P
.ce 1000
(to Recommendation X.122)
.sp 1P
.RT
.ce 0
.sp 1P
.ce 1000
\fBAbbreviations\fR
.sp 1P
.RT
.ce 0
.sp 1P
.sp 2P
.LP
    A, B,
    Designation of the terminals used in the scenarios
.sp 1P
.RT
.LP
    AU
    access unit
.LP
    Cd
    called number
.LP
    Cg
    calling number
.LP
    CRP
    call request packet or equivalent
.LP
    CSPDN
    circuit switched public data network
.LP
    DCE
    data circuit terminating equipent
.LP
    DNIC
    data network identification code
.LP
    DTE
    data terminal equipment
.LP
    ISDN
    integrated service digital network
.LP
    IWF
    interworking function
.LP
    M
    modem
.LP
    ONSD
    optional network specific digit
.LP
    PDN
    public data network
.LP
    PH
    packet handler
.LP
    PSPDN
    packet switched public data network
.LP
    PSTN
    public switched telephone network
.LP
    T
    time \*QT\*U specified in Recommendation E.165
.bp
.sp 2P
.LP
\fBRecommendation\ X.130\fR
.RT
.sp 2P
.ce 1000
\fBCALL\ PROCESSING\ DELAYS\ IN\ PUBLIC\ DATA\ NETWORKS\ WHEN\ PROVIDING\fR
.EF '%    Fascicle\ VIII.3\ \(em\ Rec.\ X.130''
.OF '''Fascicle\ VIII.3\ \(em\ Rec.\ X.130    %'
.ce 0
.sp 1P
.ce 1000
\fBINTERNATIONAL\ SYNCHRONOUS\ CIRCUIT\(hySWITCHED\ DATA\ SERVICES\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva,\ 1980; amended at Malaga\(hyTorremolinos,\ 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
    The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that Recommendation X.1 specifies the user classes of
service applicable to networks offering public data services;
.PP
(b)
that Recommendation X.2 specifies the international user services and facilities
to be offered by public data networks;
.PP
(c)
that Recommendations X.21 and X.21\|\fIbis\fR define the
DTE/DCE interface for circuit switched services;
.PP
(d)
that Recommendation X.60 specifies the common channel
signalling for synchronous data networks;
.PP
(e)
that Recommendation X.71 specifies the channel
associated signalling for synchronous data networks;
.PP
(
f
)
that Recommendation X.92 specifies the
hypothetical reference connections for public data networks;
.PP
(g)
that Recommendation X.110 specifies the routing plan to be applied in the
international portions of public data networks;
.PP
(h)
that Recommendation X.213 specifies the OSI Network
Layer service;
.PP
(i)
that Recommendation X.140 specifies the user\(hyoriented
quality of service parameters applicable to data services,
.sp 1P
.LP
\fIunanimously declares\fR
.sp 9p
.RT
.PP
that when public data networks provide international
synchronous circuit\(hyswitched data services
according to
Recommendations\ X.21 and X.21\|\fIbis\fR , the values of call processing
delays
specified in this Recommendation shall be taken as provisional worst\(hycase
values that should not be exceeded under the conditions specified
therein.
.PP
\fIIntroductory note\fR \ \(em\ Design objectives that take into account
both user needs and network costs are for further study.
.sp 2P
.LP
\fB1\fR     \fBIntroduction\fR
.sp 1P
.RT
.PP
1.1
Quality of service in circuit\(hyswitched public data networks has been
considered in five basic areas as follows:
.sp 9p
.RT
.LP
    i)
    call processing delays
(Recommendation\ X.130);
.LP
    ii)
    failures due to congestion
(blocking)
(Recommendation\ X.131);
.LP
    iii)
    failures due to malfunction
;
.LP
    iv)
    loss of service
; and
.LP
    v)
    transmission performance
(including throughput).
.PP
This Recommendation specifies the objectives for\ i) above. Each
of the other areas of circuit\(hyswitching quality of service identified above
will be the subject of a separate Recommendation in the X\(hyseries.
.bp
.PP
1.2
In telecommunication networks it is necessary, for economic
reasons, to limit the resources provided for carrying the offered traffic.
This limitation may affect the quality of service to the user of circuit\(hyswitched
services in two different ways: by call processing delays and by
blocking
. Both of these aspects, that are consequences of the finite
traffic handling capacity of the network, constitute the grade of service.
Grade of service
together with malfunction, loss of service and
transmission performance constitute the quality of service.
.sp 9p
.RT
.PP
1.3
In this Recommendation the values for the network delay are
quoted for two types of connection according to Recommendation\ X.92 as
follows:
.sp 9p
.RT
.LP
    Type\ 1:
    Typical terrestrial international connection of
moderate length with no satellite circuits either in
the national or international portions
(International portion:\ 1000\ km).
.LP
    Type\ 2:
    Long distance international connection with a satellite
circuit in one national portion and two satellite
circuits in the international portion (International
portion:\ 160\|000\ km).
.PP
Where appropriate, values are also specified separately for the
following network portions:
.LP
    \(em
    originating national network,
.LP
    \(em
    international portion,
.LP
    \(em
    destination national network.
.PP
The boundaries for these portions are shown in
Figure\ 1/X.130.
.LP
.rs
.sp 16P
.ad r
\fBFigure 1/X.130, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
For the present, the values apply also to other normal routing
options within the international portion.
.PP
Following the allocation of a delay allowance to the international
portion of an international transit connection, it will be necessary to
further apportion the allowance to individual transit networks and/or their
component parts within the international portion. The means by which useful
and realistic constraints can be applied, consistent with maintaining the
maximum possible
freedom for each involved Administration in the design and implementation of
its own network, is for further study.
.RT
.PP
1.4
The values for call processing delays established in this
Recommendation are to be considered as design objectives in network planning
together with the forecast traffic for the planned period. The
actual delay performance
that will be obtained will depend on the accuracy of the
traffic estimations
. Normally, the actual delay performance will not
coincide with the one used as a basis for
planning
. Furthermore, if the network is planned for the traffic forecast at the
end of the period
considered, the actual delay performance of the network may be better than
the design value, worsening gradually to the end of the planning period
as traffic increases.
.bp
.sp 9p
.RT
.PP
The non\(hycoincidence of busy hours in originating and destination national
networks as well as in the international network will improve the
overall delay performance with respect to the sum of the nominal delays of
the constituent parts of the connection.
.PP
1.5
Delays are specified under conditions of
normal busy hour
load
and are expressed where appropriate in terms of mean and 95%
probability values. The term \*Qmean\*U is taken to be the expected value
of delay in the statistical sense. The \*Q95% probability\*U value is taken
as the limit
within which 95% of the delays fall. Delays at higher loadings are for
further study.
.sp 9p
.RT
.PP
1.6
Call processing delays are defined for a basic call which does
not include any optional user facilities, e.g. those defined in
Recommendation\ X.21.
.sp 9p
.RT
.PP
1.7
Where appropriate, separate limits are quoted for common
channel signalling and channel associated signalling between DSEs.
.sp 9p
.RT
.PP
For
common channel signalling
, the values given in this
Recommendation are also applicable to lower signalling rates (less than
4800\ bit/s), when the associated mode of operation is used.
.PP
1.8
The
quality of service
implications of regional or
national satellite systems using demand assignment for resource allocation
require further study.
.sp 9p
.RT
.sp 2P
.LP
\fB2\fR     \fBCall connection delay\fR
.sp 1P
.RT
.PP
See Annex A for an explanation of the delay elements t1
to t6.
.RT
.sp 1P
.LP
2.1
    \fITotal call connection delay (TCCD)\fR
.sp 9p
.RT
.PP
The \fBtotal call connection delay (TCCD)\fR is the time interval
between the transmission of the \fIcall request\fR signal and receipt of the
\fIready for data\fR signal by the calling DTE. A full explanation of the
elements of TCCD is contained in Annex\ A. Objectives for the network\(hydependent
components of TCCD are provided below.
.RT
.sp 1P
.LP
2.2
    \fICall request delay (t1)\fR
.sp 9p
.RT
.PP
Call request delay is considered to be a national matter and
consequently the specification of its value is not appropriate to this
Recommendation.
.RT
.sp 1P
.LP
2.3
    \fIOverall network post selection delay\fR
.sp 9p
.RT
.PP
Overall network post selection delay is the sum of t3 and t5. It
should not exceed the values given in Tables\ 1/X.130 and\ 2/X.130.
.PP
If on any call the overall network post selection delay exceeds
X\ seconds, the call will be considered for quality of service purposes
to have failed. The precise value of\ X is for further study but it should
be at least 30\ seconds.
.RT
.sp 1P
.LP
2.4
    \fINetwork portion post selection delays (t3\ +\ t5)\fR
.sp 9p
.RT
.PP
The contribution from each network portion to the overall network post
selection delay should not exceed the values given in Tables\ 3/X.130
and\ 4/X.130.
.RT
.sp 1P
.LP
2.5
    \fIReady for data delay (t6)\fR
.sp 9p
.RT
.PP
The need for specification of this parameter is for further
study.
.RT
.sp 2P
.LP
\fB3\fR     \fBCall clearing delays\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
    \fIClear request delay (CLRD)\fR
.sp 9p
.RT
.PP
\fBClear request delay (CLRD)\fR is the delay between transmission of a
\fIclear request\fR \| signal and receipt of the \fIDCE ready\fR signal
by the
clearing DTE. Clear request delay is considered to be a national matter and
consequently the specification of its value is not appropriate to this
Recommendation.
.bp
.RT
.ce
\fBH.T. [T1.130]\fR
.ce
TABLE\ 1/X.130
.ce
\fBOverall network post selection delay for common\(hychannel signalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(30p) sw(30p) , ^  | ^  | c s
^  | ^  | c | c.
User rate  (bit/s)    Statistic    Delay (ms)
        Connection type    1    2
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ \ \|600    Mean    1800    3500
    95%    2700    4400
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 2\|400    Mean    1500    3200
    95%    2200    3900
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 4\|800    Mean    1300    3000
    95%    1900    3600
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 9\|600    Mean    1300    3000
    95%    1900    3600
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
48\|000    Mean    1300    3000
    95%    1900    T{
3600
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/X.130 [T1.130], p.14\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.130]\fR
.ce
TABLE\ 2/X.130
.ce
\fBOverall network post selection delay for\fR
.ce
\fBchannel\(hyassociated signalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(30p) sw(30p) , ^  | ^  | c s
^  | ^  | c | c.
User rate  (bit/s)    Statistic    Delay (ms)
        Connection type    1    2
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ \ \|600    Mean    2200    4000
    95%    3300    5100
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 2\|400    Mean    1800    3600
    95%    2700    4500
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 4\|800    Mean    1700    3500
    95%    2500    4400
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 9\|600    Mean    1600    3400
    95%    2400    4200
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
48\|000    Mean    1500    3300
    95%    2200    T{
4100
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/X.130 [T2.130], p.15\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T3.130]\fR
.ce
TABLE\ 3/X.130
.ce
\fBContributions to network post selection delays for common\(hychannel\fR
.ce
\fBsignalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(24p) sw(24p) | cw(24p) sw(24p) | cw(24p) sw(24p) , ^  | ^  | c s | c | c s
^  | ^  | c | c | c | c | c | c.
User rate  (bit/s)    Statistic    T{
Originating national portion
(ms)
T}    T{
Destination national portion
(ms)
T}    International portion  (ms)
        Number of satellites    Number of satellites    Connection type    0    1    0    1    1    2
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ \ \|600    Mean    \ 700    1200    \ 800    1300    300    1500
    95%    1100    1600    1200    1800    500    1700
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 2\|400    Mean    \ 600    1100    \ 700    1200    200    1400
    95%    \ 900    1500    1100    1600    300    1600
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 4\|800    Mean    \ 500    1000    \ 600    1100    200    1400
    95%    \ 800    1300    \ 900    1500    300    1600
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 9\|600    Mean    \ 500    1000    \ 600    1100    200    1400
    95%    \ 800    1300    \ 900    1500    300    1600
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
48\|000    Mean    \ 500    1000    \ 600    1100    200    1400
    95%    \ 800    1300    \ 900    1500    300    T{
1600
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 3/X.130 [T3.130], p.16\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T4.130]\fR
.ce
TABLE\ 4/X.130
.ce
\fBContributions to network post selection delays for channel\(hyassociated\fR
.ce
\fBsignalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(24p) sw(24p) | cw(24p) sw(24p) | cw(24p) sw(24p) , ^  | ^  | c s | c | c s
^  | ^  | c | c | c | c | c | c.
User rate  (bit/s)    Statistic    T{
Originating national portion
(ms)
T}    T{
Destination national portion
(ms)
T}    International portion  (ms)
        Number of satellites    Number of satellites    Connection type    0    1    0    1    1    2
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ \ \|600    Mean    \ 800    1300    1000    1500    400    1700
    95%    1200    1800    1500    2100    600    2000
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 2\|400    Mean    \ 700    1200    \ 800    1300    300    1600
    95%    1100    1600    1200    1800    500    1900
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 4\|800    Mean    \ 600    1100    \ 800    1300    300    1600
    95%    \ 900    1500    1200    1800    500    1900
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 9\|600    Mean    \ 600    1100    \ 700    1200    300    1600
    95%    \ 900    1500    1100    1600    500    1900
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
48\|000    Mean    \ 600    1100    \ 700    1200    200    1500
    95%    \ 900    1500    1100    1600    400    T{
1700
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 4/X.130 [T4.130], p.17\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2
    \fINetwork clear indication delay (NCID)\fR
.sp 9p
.RT
.PP
\fBNetwork clear indication delay (NCID)\fR is the delay between
transmission of a \fIclear request\fR \| signal by the clearing DTE and
the receipt of the DCE \fIclear indication\fR signal by the cleared DTE.
It should not exceed the values given in Tables\ 5/X.130 and\ 6/X.130.
.PP
If on any call the overall network clear indication delay exceeds
Y\ seconds the call will be considered for quality of service purposes
to have failed. The precise value of\ Y is for further study but it should
be at least 30\ seconds.
.RT
.ce
\fBH.T. [T5.130]\fR
.ce
TABLE\ 5/X.130
.ce
\fBOverall network clear indication delay for common\(hychannel\fR
.ce
\fBsignalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(30p) sw(30p) , ^  | ^  | c s
^  | ^  | c | c.
User rate  (bit/s)    Statistic    Delay (ms)
        Connection type    1    2
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ \ \|600    Mean    \ 900    1900
    95%    1300    2400
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 2\|400    Mean    \ 700    1700
    95%    1100    2100
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 4\|800    Mean    \ 600    1600
    95%    \ 900    1900
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 9\|600    Mean    \ 600    1600
    95%    \ 900    1900
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
48\|000    Mean    \ 600    1600
    95%    \ 900    T{
1900
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 5/X.130 [T5.130], p.18\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 11P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T6.130]\fR
.ce
TABLE\ 6/X.130
.ce
\fBOverall network clear indication delay for channel\(hyassociated\fR
.ce
\fBsignalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(30p) sw(30p) , ^  | ^  | c s
^  | ^  | c | c.
User rate  (bit/s)    Statistic    Delay (ms)
        Connection type    1    2
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ \ \|600    Mean    1100    2100
    95%    1600    2700
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 2\|400    Mean    \ 900    1900
    95%    1300    2400
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 4\|800    Mean    \ 800    1800
    95%    1200    2300
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
\ 9\|600    Mean    \ 800    1800
    95%    1200    2300
_
.T&
cw(42p) | cw(42p) | cw(30p) | cw(30p) , ^  | c | c | c.
48\|000    Mean    \ 800    1800
    95%    1200    T{
2300
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 6/X.130 [T6.130], p.19\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3
    \fINetwork portion clear indication delay (NPCID)\fR
.sp 9p
.RT
.PP
The contribution from each network portion to the overall network clear
indication delay should not exceed the values given in Tables\ 7/X.130
and\ 8/X.130.
.RT
.ce
\fBH.T. [T7.130]\fR
.ce
TABLE\ 7/X.130
.ce
\fBContributions to network clear indication delay for common\(hychannel\fR
.ce

.ce
\fBsignalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(24p) sw(24p) | cw(24p) sw(24p) | cw(24p) sw(24p) , ^  | ^  | c s | c | c s
^  | ^  | c | c | c | c | c | c.
User rate  (bit/s)    Statistic    T{
Originating national portion
(ms)
T}    T{
Destination national portion
(ms)
T}    International portion  (ms)
        Number of satellites    Number of satellites    Connection type    0    1    0    1    1    2
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ \ \|600    Mean    300    600    400    700    200    \ 900
    95%    500    800    600    900    300    1100
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 2\|400    Mean    200    500    300    600    200    \ 900
    95%    300    600    500    800    300    1100
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 4\|800    Mean    200    500    300    600    100    \ 800
    95%    300    600    500    800    200    \ 900
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 9\|600    Mean    200    500    300    600    100    \ 800
    95%    300    600    500    800    200    \ 900
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
48\|000    Mean    200    500    300    600    100    \ 800
    95%    300    600    500    800    200    T{
\ 900
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 7/X.130 [T7.130], p.20\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 12P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T8.130]\fR
.ce
TABLE\ 8/X.130
.ce
\fBContributions to network clear indication delay for channel\(hyassociated\fR
.ce
\fBsignalling\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(24p) sw(24p) | cw(24p) sw(24p) | cw(24p) sw(24p) , ^  | ^  | c s | c | c s
^  | ^  | c | c | c | c | c | c.
User rate  (bit/s)    Statistic    T{
Originating national portion
(ms)
T}    T{
Destination national portion
(ms)
T}    International portion  (ms)
        Number of satellites    Number of satellites    Connection type    0    1    0    1    1    2
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ \ \|600    Mean    400    700    500    \ 800    200    \ 900
    95%    600    900    800    1100    300    1100
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 2\|400    Mean    300    600    400    \ 700    200    \ 900
    95%    500    800    600    \ 900    300    1100
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 4\|800    Mean    300    600    300    \ 600    200    \ 900
    95%    500    800    500    \ 800    300    1100
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
\ 9\|600    Mean    300    600    300    \ 600    200    \ 900
    95%    500    800    500    \ 800    300    1100
_
.T&
cw(42p) | cw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | c | c | c | c | c | c | c.
48\|000    Mean    300    600    300    \ 600    200    \ 900
    95%    500    800    500    \ 800    300    T{
1100
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 8/X.130 [T8.130], p.21\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 16P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.4
    \fIClear confirmation delay (CLCD)\fR
.sp 9p
.RT
.PP
\fBClear confirmation delay (CLCD)\fR is the delay between
transmission of a \fIDTE clear confirmation\fR signal and receipt of a
\fIDCE\fR
\fIready\fR signal by the cleared DTE. Clear confirmation delay is considered
to be a national matter and consequently the specification of its value
is not
appropriate to this Recommendation.
\v'6p'
.RT
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation X.130)
.sp 9p
.RT
.ce 0
.LP
A.1
    \fITotal call connection delay (TCCD) elements\fR
.sp 1P
.RT
.PP
The total call connection delay is the sum of the following
elements (see Figure\ A\(hy1/X.130):
.RT
.LP
    t1:
    delay between transmission of the \fIcall request\fR \|signal
and receipt of the \fIproceed to select\fR signal by the
calling DTE.
.LP
    t2:
    time between receipt of the \fIproceed to select\fR \|signal and
transmission of the \fIend of selection\fR signal by the
calling DTE.
.LP
    t3:
    delay between transmission of the \fIend of selection\fR \|
signal by the calling DTE and receipt of the \fIincoming\fR \fIcall\fR
signal by the called DTE.
.LP
    t4:
    delay between receipt of the \fIincoming call\fR \|signal and
transmission of the \fIcall accepted\fR signal by the called
DTE.
.LP
    and if t5\ >\ t6,
.LP
t5:
    delay between transmission of the \fIcall accepted\fR \|signal
by the called DTE and receipt of the \fIready for data\fR signal by the
calling DTE.
.LP
    or if t5\ <\ t6,
.LP
t6:
    delay between transmission of the \fIcall accepted\fR \|signal
and receipt of the \fIready for data\fR signal by the called
DTE.
.LP
.rs
.sp 24P
.ad r
\fBFigure A\(hy1/X.130, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
A.1.1
    \fIUser\(hydependent call connection delay (UCCD)\fR
.sp 9p
.RT
.PP
Considering the above elements of TCCD, t2 is dependent on the
source DTE. Similarly t4\ is dependent on the destination DTE. It is therefore
inappropriate to specify values for these times in this Recommendation,
but the following observations are relevant:
.RT
.sp 1P
.LP
A.1.1.1
    \fISelection time (t2)\fR
.sp 9p
.RT
.PP
Selection times for automatic calls from the DTE are given in
Table\ A\(hy1/X.130.
.RT
.ce
\fBH.T. [T9.130]\fR
.ce
TABLE\ A\(hy1/X.130
.ce
\fBSelection time\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) .
User rate  (bit/s)    Selection time  (t2) (ms)
_
.T&
cw(42p) | cw(42p) .
\ \ \|600    260
.T&
cw(42p) | cw(42p) .
\ 2\|400    \ 70
.T&
cw(42p) | cw(42p) .
\ 4\|800    \ 40
.T&
cw(42p) | cw(42p) .
\ 9\|600    \ 20
.T&
cw(42p) | cw(42p) .
48\|000    \ \ 5
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau A\(hy1/X.130 [T9.130], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
A.1.1.2
    \fICall acceptance delay (CAD) (t4)\fR
.sp 9p
.RT
.PP
If the CAD exceeds 500 ms with automatic answer or 60 seconds with manual
answer the DCE will initiate clearing.
.RT
.sp 1P
.LP
A.1.2
    \fINetwork\(hydependent call connection delay (NCCD)\fR
.sp 9p
.RT
.PP
Considering the elements of TCCD in \(sc A.1, it has been shown in
\(sc\ A.1.1 that\ t2 and\ t4 are user\(hydependent and are not regarded
as network
performance parameters.
.PP
The network (dependent) call connection delay is therefore the sum of the
remaining elements. Hence:
\v'6p'
.RT
.sp 1P
.ce 1000
NCCD\ =\ t1\ +\ t3\ +\ t5
.ce 0
.sp 1P
.LP
.sp 1
.sp 2P
.LP
\fBRecommendation\ X.131\fR
.RT
.sp 2P
.ce 1000
\fBCALL\ BLOCKING\ IN\ PUBLIC\ DATA\|
NETWORKS\ WHEN\ PROVIDING\fR
.EF '%    Fascicle\ VIII.3\ \(em\ Rec.\ X.131''
.OF '''Fascicle\ VIII.3\ \(em\ Rec.\ X.131    %'
.ce 0
.sp 1P
.ce 1000
\fBINTERNATIONAL\ SYNCHRONOUS\ CIRCUIT\(hySWITCHED\ DATA\ SERVICES\fR
.ce 0
.sp 1P
.ce 1000
\fI(Former X.132, Geneva,\ 1980;\fR \|
\fIamended at Malaga\(hyTorremolinos,\ 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
    The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that Recommendation X.1 specifies the user classes of
service applicable to networks offering public data services;
.PP
(b)
that Recommendation X.2 specifies the international user services and facilities
to be offered by public data networks;
.PP
(c)
that Recommendations X.21 and X.21\|\fIbis\fR \|define the
DTE/DCE interface for circuit switched services;
.bp
.PP
(d)
that Recommendation X.60 specifies the common channel
signalling for synchronous data networks;
.PP
(e)
that Recommendation X.71 specifies the channel
associated signalling for synchronous data networks;
.PP
(
f
)
that Recommendation X.92 specifies the
hypothetical reference connections for public data networks;
.PP
(g)
that Recommendation X.110 specifies the routing plan to be applied in the
international portions of public data networks;
.PP
(h)
that Recommendation X.213 specifies the OSI Network
Layer service;
.PP
(i)
that Recommendation X.140 specifies the user\(hyoriented
quality of service parameters applicable to data services,
.sp 1P
.LP
\fIunanimously declares\fR
.sp 9p
.RT
.PP
that when public data networks provide international
synchronous circuit\(hyswitched data services
, according to
Recommendations\ X.21 and X.21\|\fIbis\fR , the values of call
blocking
probability
specified in this Recommendation shall be taken as provisional, worst\(hycase
values that should not be exceeded under the conditions specified
therein.
.PP
\fIIntroductory note\fR \ \(em\ Design objectives that take into account
both user needs and network costs are for further study.
.sp 2P
.LP
\fB1\fR     \fBIntroduction\fR
.sp 1P
.RT
.PP
1.1
Quality of service in circuit\(hyswitched public data networks has
been considered in five basic areas as follows:
.sp 9p
.RT
.LP
    i)
    call processing delays
(Recommendation\ X.130);
.LP
    ii)
    failures due to congestion
(blocking)
(Recommendation\ X.131);
.LP
    iii)
    failures due to malfunction
;
.LP
    iv)
    loss of service
; and
.LP
    v)
    transmission performance
(including
throughput).
.PP
This Recommendation specifies the objectives for\ ii) above. Each of the
other areas of circuit\(hyswitching quality of service identified above
will be the subject of a separate Recommendation in the X\(hyseries.
.PP
1.2
In telecommunication networks it is necessary, for economic
reasons, to limit the resources provided for carrying the offered traffic.
This limitation may affect the quality of service to the user of circuit\(hyswitched
services in two different ways: by call processing delays and by
blocking
. Both of these aspects, that are consequences of the finite
traffic handling capacity of the network, constitute the grade of service.
Grade of service
together with malfunction, loss of service and
transmission performance constitute the quality of service.
.sp 9p
.RT
.PP
1.3
In this Recommendation the values for the network blocking are
quoted for two types of connection according to Recommendation\ X.92 as
follows:
.sp 9p
.RT
.LP
    Type\ 1:
    Typical terrestrial interconnection of moderate length
with no satellite circuits either in the national or
international portions. (International
portion:\ 1000\ km.)
.LP
    Type\ 2:
    Long distance international connection with a satellite
circuit in one national portion and two satellite
circuits in the international portion. (International
portion:\ 160\|000\ km.)
.PP
Where appropriate, values are also specified separately for the
following network portions:
.LP
    \(em
    originating national network,
.LP
    \(em
    international portion,
.LP
    \(em
    destination national network.
.bp
.PP
The boundaries for these portions are shown in
Figure\ 1/X.131.
.LP
.rs
.sp 13P
.ad r
\fBFigure 1/X.131, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
For the present, the values apply also to other normal routing
options within the international portion.
.PP
Following the allocation of a blocking allowance to the international portion
of an international transit connection, it will be necessary to further
apportion the allowance to individual transit networks and/or their component
parts within the international portion. The means by which useful and realistic
constraints can be applied, consistent with maintaining the maximum possible
freedom for each involved Administration in the design and implementation of
its own network, is for further study.
.RT
.PP
1.4
The values for blocking probability established in this
Recommendation are to be considered as design objectives in network planning
together with the forecast traffic for the planned period. The
actual
blocking performance
that will be obtained will depend on the accuracy of   the
traffic estimations
. Normally the actual blocking performance will not coincide with the one
used as a basis for planning. Furthermore, if
the network is planned for the traffic forecast at the end of the period
considered, the actual blocking performance of the network may be better
than the design value, worsening gradually to the end of the planning period
as
traffic increases.
.sp 9p
.RT
.PP
The non\(hycoincidence of busy hours in originating and destination national
networks as well as in the international network will improve the
overall blocking performance with respect to the sum of the nominal blocking
probabilities of the constituent parts of the connection.
.PP
1.5
The blocking probabilities are specified under conditions of
normal busy hour load
. Blocking probabilities for higher loadings are   for further study.
.sp 9p
.RT
.PP
1.6
Blocking probabilities are defined for a basic call which does
not include any optional user facilities, e.g. those defined in
Recommendation\ X.21.
.sp 9p
.RT
.PP
1.7
Recommendation X.21 permits the following blocking
situations:
.sp 9p
.RT
.LP
    i)
    non\(hyreception of \fIproceed to select\fR ;
.LP
    ii)
    non\(hyconnection of call.
.PP
Item i) is considered to be a national matter and consequently the specification
of its value is not appropriate to this Recommendation.
Objectives for item\ ii) are contained in \(sc\ 2 of this Recommendation.
.PP
1.8
The quality of service implications of regional or national
satellite systems using demand assignment for resource allocation require
further study.
.sp 9p
.RT
.sp 2P
.LP
\fB2\fR     \fBProbability of non\(hyconnection due to congestion (blocking\fR
\fBprobability)\fR
.sp 1P
.RT
.PP
Probability of non\(hyconnection due to congestion is the probability that
a calling DTE does not receive the \fIready for data\fR signal but does
receive a \fInetwork congestion\fR signal within 20\ seconds after transmission
of the \fIend of selection\fR signal (or within 60\ seconds when manual
answering is
permitted at the called DTE).
.bp
.RT
.sp 1P
.LP
2.1
    \fIOverall probability of non\(hyconnection due to congestion\fR
.sp 9p
.RT
.PP
The overall probability of non\(hyconnection due to congestion for an end\(hyto\(hyend
connection seen from the customer point of view should not exceed
the following values:
.PP
Connection type 1:\ 13%
.PP
Connection type 2:\ 15%
.PP
See Introductory note to this Recommendation.
.RT
.sp 1P
.LP
2.2
    \fINetwork portion probability of non\(hyconnection due to congestion\fR
.sp 9p
.RT
.PP
The contribution of each network portion to overall probability of non\(hyconnection
due to congestion should not exceed the values shown in
Table\ 1/X.131.
.RT
.ce
\fBH.T. [T1.131]\fR
.ce
TABLE\ 1/X.131
.ce
\fBContributions to network probability of non\(hyconnection\fR
.ce
\fBdue to congestion\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) | cw(24p) sw(24p) , ^  | ^  | c s
^  | ^  | c | c.
Originating national portion    Destination national portion    International portion
        Connection type    1    2
_
.T&
cw(48p) | cw(48p) | cw(24p) | cw(24p) .
5%    5%    3%    T{
5%
\fINote\fR
\ \(em\ See introductory note to this Recommendation.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/X.131 [T1.131], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 1
.sp 2P
.LP
\fBRecommendation\ X.134\fR
.RT
.sp 2P
.ce 1000
\fBPORTION\ BOUNDARIES\ AND\ PACKET\ LAYER\ REFERENCE\ EVENTS:\fR
.EF '%    Fascicle\ VIII.3\ \(em\ Rec.\ X.134''
.OF '''Fascicle\ VIII.3\ \(em\ Rec.\ X.134    %'
.ce 0
.sp 1P
.ce 1000
\fBBASIS\ FOR\ DEFINING\ PACKET\(hySWITCHED\ PERFORMANCE\ PARAMETERS\fR
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
    The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that Recommendation X.1 specifies the international user classes of service
in public data networks;
.PP
(b)
that Recommendation X.2 specifies the international data transmission services
and optional user facilities in public data networks;
.PP
(c)
that Recommendation X.25 specifies the DTE/DCE interface for packet mode
terminals connected to public data networks by dedicated
circuit;
.PP
(d)
that Recommendation X.75 specifies the packet\(hyswitched signalling system
between public networks providing data transmission
services;
.bp
.PP
(e)
that Recommendation X.323 specifies general arrangements for interworking
between packet\(hyswitched public data networks;
.PP
(
f
)
that Recommendation X.96 specifies call
progress signals in public data networks;
.PP
(g)
that Recommendation X.110 specifies the international
routing principles and routing plan for public data networks;
.PP
(h)
that Recommendation X.213 defines the OSI Network Layer  service;
.PP
(i)
that Recommendation X.140 defines general quality of
service parameters for communication via public data networks;
.PP
(
j
)
that Recommendation X.135 specifies speed
of service performance values for public data networks when providing
international packet\(hyswitched service;
.PP
(k)
that Recommendation X.136 specifies accuracy and
dependability (including blocking) performance values for public data networks
when providing international packet\(hyswitched service;
.PP
(l)
that Recommendation X.137 specifies availability
performance values for public data networks when providing international
packet\(hyswitched service,
.sp 1P
.LP
\fIunanimously declares\fR
.sp 9p
.RT
.PP
(1)
that the portion boundaries defined in this
Recommendation shall be used in apportioning the performance of an
international packet\(hyswitched data communication service provided in
accordance with Recommendations\ X.25 and\ X.75;
.PP
(2)
that the packet layer reference events specified in this Recommendation
shall be used in the definition of packet\(hyswitched performance parameters
for data communication services provided in accordance with
Recommendations\ X.25 et\ X.75.
.sp 2P
.LP
\fB1\fR     \fBIntroduction\fR
.sp 1P
.RT
.PP
1.1
This Recommendation is the first in a series of four CCITT
Recommendations (X.134\(hyX.137) that define performance parameters and
values for international packet\(hyswitched data communication services.
Figure\ 1/X.134
illustrates the scope of these four Recommendations and the relationships
among them.
.sp 9p
.RT
.PP
1.2
This Recommendation divides a virtual connection into basic
sections whose boundaries are associated with X.25 and X.75 interfaces. The
performance of collections of these basic sections can be measured using the
packet\(hyswitched performance parameters defined in Recommendations\ X.135\(hy137.
In order to apportion the performance of an international virtual connection,
Recommendation\ X.134 defines two particular collections of basic sections
for which performance values will be specified: national portions and international
portions. As defined, every international virtual connection contains two
national portions and one international portion. The performance of these
three portions can be combined in the calculation of the end\(hyto\(hyend
virtual
connection performance. These Recommendations do not specify performance
values for other collections of basic sections; however, the ability to
decompose a
virtual connection into its basic sections will be useful in planning the
performance of national and international portions.
.sp 9p
.RT
.PP
1.3
The performance parameters in Recommendations X.135\(hyX.137 are
defined in terms of packet layer reference events which can be observed
at the boundaries between basic sections and thus can be observed at the
portion
boundaries. This Recommendation defines the performance significant packet
layer reference events.
.sp 9p
.RT
.PP
1.4
For comparability and completeness, packet\(hyswitched network
performance is considered in the context of the 3\ \(mu\ 3 performance matrix
defined in Recommendation\ X.140. Three protocol\(hyindependent data communication
functions are defined in the matrix: access, user information transfer,
and
disengagement. These general functions correspond to call set\(hyup, data (and
interrupt) transfer, and call clearing in packet\(hyswitched virtual call
services conforming to the X.25 and X.75\ Recommendations. Each function
is considered
with respect to three general performance concerns (or \*Qperformance criteria\*U):
speed, accuracy, and dependability. These express, respectively, the delay
or rate, degree of correctness, and degree of certainty with which the
function is performed.
.bp
.sp 9p
.RT
.LP
.rs
.sp 39P
.ad r
\fBFigure 1/X.134, (N),  p.26\fR
.sp 1P
.RT
.ad b
.RT
.PP
1.5
Recommendation X.135 defines protocol\(hyspecific speed of service
parameters and values associated with each of the three data communication
functions. Recommendation\ X.136 defines protocol\(hyspecific accuracy and
dependability parameters and values associated with each function. The
Recommendation\ X.135 and Recommendation\ X.136 parameters are called \*Qprimary
parameters\*U to emphasize their direct derivation from packet layer reference
events.
.sp 9p
.RT
.PP
1.6
An associated two\(hystate model provides a basis for describing
overall service availability. A specified availability function compares the
values for a subset of the primary parameters with corresponding outage
thresholds to classify the service as \*Qavailable\*U (no service outage) or
\*Qunavailable\*U (service outage) during scheduled service time.
Recommendation\ X.137 specifies the availability function and defines the
availability parameters and values that characterize the resulting binary
random process.
.bp
.sp 9p
.RT
.PP
1.7
In order to relate the network performance values given in
Recommendations\ X.135 to X.137 to the service receivable at points within
the scope of the DTEs, further elements must be included.
.sp 9p
.RT
.PP
1.7.1
In particular, specification of service performance at the
layer 3/4 boundary (OSI Network Service) must include those processes within
the DTEs concerned with the transfer of packets from the physical circuit of
the DTE/DCE interface to the layer\ 3/4 boundary at each end of the virtual
connection, however they may be implemented. This processing may include
elements associated with OSI layers\ 1, 2 and 3 and may involve transmission
across private wide\(hyarea and/or local\(hyarea networks.
.sp 9p
.RT
.PP
1.7.2
Specification of service performance for the user or application, if required,
must similarly include in addition those processes within the DTEs concerned
with the transfer of information from the layer\ 3/4 boundary to the layer\
7 upper boundary beyond each of the virtual connection, however they may
be implemented. This processing may include elements associated with OSI
layers\ 4, 5, 6 and\ 7.
.sp 9p
.RT
.PP
1.7.3
Additional protocol\(hy or service\(hyspecific reference events would
need to be defined to cover these aspects, but are outside the scope of this
Recommendation. However, the parameter definitions of Recommendations\
X.135 to X.137 can readily be adapted to correspond to any extension of
scope.
.sp 9p
.RT
.sp 2P
.LP
\fB2\fR     \fBVirtual connection sections and portions\fR
.sp 1P
.RT
.PP
In the context of Recommendations X.134\(hyX.137, the following
definitions apply:
.PP
An \fBaccess circuit section\fR is the physical circuit or set of
circuits connecting a DTE to the local DSE. It does not include any parts of
the DTE or DSE. These recommendations assume that X.25 procedures are used
on an access circuit section.
.PP
An \fBinternetwork circuit section\fR is the physical circuit or set of
circuits connecting a DTE in one network with a DSE in a different network.
It does not include any parts of either DSE. These recommendations assume
that
X.75 procedures are used on an internetwork circuit section.
.PP
A \fBcircuit section\fR is either an access circuit section or an
internetwork circuit section.
.PP
A \fBnetwork section\fR consists of the network components that provide
a virtual connection between two circuit sections. The network provider
is
responsible for the performance of the network section.
.PP
An \fBaccess network section\fR is a network section connected to (at least)
one access circuit section.
.PP
A \fBtransit network section\fR is a network section between two
internetwork circuit sections.
.PP
A \fBbasic section of a virtual connection\fR is either an access
network section, a transit network section, an access circuit section, or an
internetwork circuit section.
.PP
A \fBsection boundary (or boundary)\fR separates a network section from
the adjacent circuit section or it separates an access circuit section
from the adjacent DTE.
.PP
A \fBnational portion of an international virtual connection\fR is a
collection of adjacent alternating network sections and circuit sections
entirely within the borders of one nation. The national portion connects
a DTE to an internetwork circuit section that crosses the national border.
The
national portion includes the access circuit section and excludes the
internetwork circuit section that crosses the national border. A national
portion always includes one access circuit section and one access network
section, and it may include one or more pairs of internetwork circuit sections
and transit network sections.
.PP
There are two national portions of any international virtual
circuit.
.PP
An \fBinternational portion of an international virtual connection\fR is
the set of basic sections between the two national portions. An international
portion may be a single internetwork circuit section crossing a national
border or it may be two (or more) internetwork circuit sections together
with one (or more) transit network sections.
.PP
There is one international portion of any international virtual
circuit and that international portion will cross one or more national
borders.
.bp
.PP
For purposes of allocating the performance of an international virtual
connection, this Recommendation defines a \fBportion boundary\fR as a section
boundary delimiting a national or international portion.
.PP
Figure 2/X.134 illustrates the definitions and delimitation of the
virtual connection sections and portions. A typical international virtual
connection is shown including the two access circuit sections and the two
DTEs.
.RT
.LP
.rs
.sp 23P
.ad r
\fBFigure 2/X.134, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB3\fR     \fBPacket layer reference events\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
    \fIDefinitions\fR
.sp 9p
.RT
.PP
In the context of Recommendations X.134\(hyX.137:
.PP
A \fBpacket layer reference event\fR occurs when a packet crossing a
section boundary changes the state of the packet layer interface.
.PP
\fINote\fR \ \(em\ The relevant state transitions are those defined explicitly
or implicitly in Recommendations\ X.25 and\ X.75.
.PP
Two classes of packet layer reference events are defined.
.PP
A \fBpacket entry event\fR is a packet layer reference event that
corresponds to a packet entering a network section (from a circuit section)
or a packet entering a DTE (from an access circuit section).
.PP
A \fBpacket exit event\fR is a packet layer reference event that
corresponds to a packet exiting a network section (to a circuit section)
or a packet exiting a DTE (to an access circuit section).
.PP
The time of occurrence of a packet entry event is defined to coincide with
the time at which the last bit of the closing flag of the frame carrying
the packet crosses the boundary out of the circuit section. The time of
occurrence of a packet exit event is defined to coincide with the time
at which the first bit of the address field of the frame carrying the packet
crosses the boundary into the circuit section. If frame retransmissions
occur, the packet exit event occurs with the first transmission and the
packet entry event occurs with the next transmission.
.bp
.PP
Figure 3/X.134 illustrates these terms.
.PP
A single packet crossing a boundary between two adjacent virtual
connection sections may change more than one aspect of the packet layer
interface, and consequently more than one packet layer reference event
may be created. Particular reference events are specified by identifying:
.RT
.LP
    1)
    the relevant boundary
.LP
    2)
    the type of packet transferred
.LP
    3)
    the event class (packet entry or packet exit)
.LP
    4)
    the particular aspect of the state that was changed by the   event.
.LP
.rs
.sp 23P
.ad r
\fBFigure 3/X.134, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.2
    \fIPerformance\(hysignificant reference events\fR
.sp 9p
.RT
.PP
The performance\(hysignificant reference events are the packet layer reference
events useful in defining performance parameters. Table\ 1/X.134 lists
performance\(hysignificant X.25 packet layer reference events associated
with the boundaries of access circuit sections. Table\ 2/X.134 lists
performance\(hysignificant X.75 packet\(hylayer reference events associated
with the boundaries of internetwork circuit sections. These events and
their reference numbers are used in the performance parameter definitions
specified in
Recommendations\ X.135\(hyX.137.
.PP
The entries in Tables 1\(hy2/X.134 describe the type of packet
transferred and the resulting state of the packet layer interface. With the
exception of the diagnostic and registration categories, all packet types
identified in Recommendations\ X.25 and\ X.75 are addressed in the
tables.
.PP
The states identified in the tables differ from those defined in
Recommendations\ X.25 and\ X.75 in two respects:
.RT
.LP
    1)
    Call collision states are omitted, since their specification
is not required for performance parameter definition.
.LP
    2)
    Several new ancillary states are defined, consistent with
the existing X.25 and X.75 protocol specifications, to
provide a basis for more detailed performance
description.
.bp
.PP
Three ancillary X.25 states and three ancillary X.75 states are
defined in this Recommendation to permit more accurate description of flow
control effects. The new X.25 states are \*QDCE flow controlled,\*U \*QDTE flow
controlled,\*U and \*QDTE and DCE flow controlled.\*U The new X.75 states
are \*QSTE X flow controlled,\*U \*QSTE Y flow controlled,\*U and \*QSTE
X and STE Y flow
controlled.\*U A state diagram for the ancillary X.25 flow control states is
shown in Figure\ 4/X.134. A state diagram for the ancillary X.75 flow control
states is shown in Figure\ 5/X.134. In each case, the new states are numbered
d4\(hyd6.
.PP
Three ancillary state variables are defined:
.RT
.LP
    \(em
    \fIlwt\fR \ \(em\ lower edge of the window on the transmit
side. This variable contains the latest P(R) received either in a data
packet, an RR, or an RNR. The value may be implicitly represented using
the upper
window edge (and the window size).
.LP
    \(em
    \fInpr\fR \ \(em\ next data packet to be received. This variable
contains the P(S) of the next data packet to be received.
.LP
    \(em
    \fIric\fR \ \(em\ received interrupt count. Because only one
unacknowledged interrupt packet can exist in a particular direction, the
interface must record the reception of an interrupt across the circuit
section. This variable is used to record such events. The variable is cleared
when the interrupt confirmation is transmitted.
.PP
If the state resulting from packet transfer is not the one listed in the
relevant table or the state remains unchanged as a result of the packet
transaction, the reference event does not occur. Aspects of the state other
than those listed in these tables may change during packet entry or exit,
but those events are not viewed as performance\(hysignificant reference
events.
.PP
When the tables list more than one aspect of the state that might be changed
as a result of a particular packet's entry or exit, each of those
changes represents a distinct packet layer reference event that can be
used in defining different performance parameters. For example, in Table\
1/X.134, event 9a would be used where the correct receipt of the data is
relevant, and 9b
would be used when the receipt of the acknowledgement is relevant. Event 26b
would be used in association with permanent virtual circuits and 26a with
other logical channels.
.RT
.LP
.rs
.sp 26P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 32P
.ad r
\fBFigure 4/X.134, (N), p.29\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 32P
.ad r
\fBFigure 5/X.134, (N), p.30\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T1.134]\fR
.ce
TABLE\ 1/X.134
.ce
\fBX.25 packet layer reference events\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(24p) | cw(96p) | cw(108p) .
Number    Packet type    Resulting state
_
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 1    Incoming Call    p3    (DCE Waiting)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 2    Cal Request    p2    (DTE Waiting)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 3    Call Connected    p4    (Data Transfer)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 4    Call Accepted    p4
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 5    Clear Indication    p7    (DCE Clear Indication)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 6    Clear Request    p6    (DTE Clear Request)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 7    DCE Clear Confirmation    p1    (Ready)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 8    DTE Clear Confirmation    p1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 9a    DCE Data    npr    becomes P(S)+1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 9b    DCE Data    lwt    becomes P(R)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
\ 9c    DCE Data    d1    (Flow Control Ready)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
10a    DTE Data    npr    becomes P(S)+1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
10b    DTE Data    lwt    becomes P(R)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
10c    DTE Data    dl    (Flow Control Ready)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
11    DCE Interrupt    ric    becomes 1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
12    DTE Interrupt    ric    becomes 1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
13    DCE Interrupt Confirmation    ric    becomes 0
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
14    DTE Interrupt Confirmation    ric    becomes 0
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
15a    DCE RR    lwt    becomes P(R)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
15b    DCE RR    d1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
16a    DTE RR    lwt    becomes P(R)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
16b    DTE RR    dl
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
17a    DCE RNR    lwt    becomes P(R)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
17b    DCE RNR    d5    (DTE Flow Controlled)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
17c    DCE RNR    d6    (DTE + DCE Flow Controlled)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
18a    DTE RNR    lwt    becomes P(R)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
18b    DTE RNR    d4    (DCE Flow Controlled)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
18c    DTE RNR    d6
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
19    DTE REJ    npr    becomes P(R) (Note 1)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
20    Reset Indication    d3    (DCE Reset Indication)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
21    Reset Request    d2    (DTE Reset Request)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
22    DCE Reset Confirmation    d1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
23    DTE Reset Confirmation    d1
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
24    Restart Indication    r3    (DCE Restart Indication)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
25    Restart Request    r2    (DTE Restart Request)
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
26a    DCE Restart Confirmation    pl
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
26b    DCE Restart Confirmation    dl
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
27a    DTE Restart Confirmation    pl
.T&
lw(24p) | lw(96p) | lw(12p) | lw(96p) .
27b    DTE Restart Confirmation    dl
.T&
cw(24p) | lw(96p) | lw(12p) | lw(96p) .
T{
(Note 2)
\fINote\ 1\fR
\ \(em\ This is npr from the perspective of the DTE.
.parag
\fINote\ 2\fR
\ \(em\ Diagnostic packets are for information only and they do not
change the perceived state. Reference events for registration request and
confirmation packets are left for further study.
.parag
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/X.134 [T1.134] p.31\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.134]\fR
.ce
TABLE\ 2/X.134
.ce
\fBX.75 packet layer reference events\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(18p) | cw(84p) | cw(126p) .
Number    Packet type    Resulting state
_
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 1    Call Request    p2 or p3    (STE Call Request)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 2    Call Connected    p4    (Data Transfer)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 3    Clear Request    p6 or p7    (STE Clear Request)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 4    Clear Confirmation    p1    (Ready)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 5a    Data    npr    becomes P(S)+1
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 5b    Data    lwt    becomes P(R)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 5c    Data    d1    (Flow Control Ready)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 6a    Interrupt    i2 or i3    (STE Interrupt Request)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 6b    Interrupt    i4    T{
(STE\(hyX and Y Interrupt Request)
T}
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 7a    Interrupt Confirmation    i1    (No Interrupt Request)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 7b    Interrupt Confirmation    i2 or i3
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 8a    RR    lwt    becomes P(R)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 8b    RR    d1
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 9a    RNR    lwt    becomes P(R)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 9b    RNR    d4 or d5    (STE Flow Controlled)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
\ 9c    RNR    d6    T{
(STE\(hyX and Y Flow Controlled)
T}
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
10    Reset Request    d2 or d3    (STE Reset Request)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
11    Reset Confirmation    d1
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
12    Restart Request    r2 or r3    (STE Restart Request)
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
13a    Restart Confirmation    p1
.T&
lw(18p) | lw(84p) | lw(24p) | lw(102p) .
13b    Restart Confirmation    d1
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/X.134 [T2.134] p.32\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 22P
.ad r
BLANC
.ad b
.RT
.sp 2P
.LP
\fBMONTAGE: Rec. X.135 sur le reste de cette page\fR
.sp 1P
.RT
.LP
.bp