ETSI ETS 300 194 ed.1 (1995-11)

SLOVENSKI STANDARD
SIST ETS 300 194 E1:2006
01-februar-2006
Satelitske zemeljske postaje in sistemi (SES) – Povezava sistemov satelitskih
terminalov z zelo majhno antensko odprtino (VSAT) s paketno komutiranimi
javnimi podatkovnimi omrežji (PSPDN)
Satellite Earth Stations and Systems (SES); The interconnection of Very Small Aperture
Terminal (VSAT) systems to Packet Switched Public Data Networks (PSPDNs)
Ta slovenski standard je istoveten z: ETS 300 194 Edition 1
ICS:
33.060.30 Radiorelejni in fiksni satelitski Radio relay and fixed satellite
komunikacijski sistemi communications systems
SIST ETS 300 194 E1:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 194 E1:2006
EUROPEAN ETS 300 194
TELECOMMUNICATION November 1995
STANDARD
Source:ETSI TC-SES Reference:DE/SES-02019
ICS: 33.060.30
interfaces, PSPDN, VSAT
Key words:
Satellite Earth Stations and Systems (SES);
The interconnection of Very Small Aperture Terminal (VSAT)
systems to Packet Switched Public Data Networks
(PSPDNs)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.
New presentation - see History box

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Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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Contents
Foreword.5
1 Scope .7
2 Normative references .7
3 Abbreviations.8
4 Interconnection scenarios.8
4.1 Real time direct connection.8
4.2 Store and forward.10
5 Interface requirements.12
6 Connection quality recommendations .12
6.1 General.12
6.2 Base for the definition of the VSAT performance parameters.12
6.2.1 Portion boundaries .12
6.2.2 Performance parameters. 13
6.2.3 System load.13
6.3 Delay performance.14
6.3.1 Call set up delay .14
6.3.2 Data packet transfer delay.16
6.3.3 Clear delay .19
6.4 Throughput performance.20
Annex A (informative): Additional elements to this ETS.23
A.1 Interface information.23
A.1.1 Level 1.23
A.1.2 Level 2.23
A.1.2.1 LAPB link.23
A.1.2.2 Invalid information frames .23
A.1.2.3 Unsolicited responses.23
A.1.3 Level 3.24
A.1.3.1 Call packet types . 24
A.1.3.2 Restart handling.24
A.1.3.3 Reset handling .24
A.1.3.4 Permanent Virtual Circuits (PVCs) .24
A.1.3.5 Packet fragmentation and concatenation .24
A.1.4 OSI network layer service.24
A.2 Addressing information .24
A.2.1 Extended address facility.24
A.2.1.1 Call user data field . 25
A.2.2 CCITT Recommendation X.121 subaddressing.25
A.3 Facilities information.25
A.3.1 DTE facilities . 25
A.3.1.1 End-to-end transit delay facility. 25
A.3.2 DCE facilities.25
A.3.3 VSAT specific facilities . 26
A.4 Additional quality of service information.26

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A.4.1 Accuracy and dependability performance .26
A.4.2 Availability performance.26
Annex B (informative): Bibliography.27
History .28

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ETS 300 194: November 1995
Foreword
This European Telecommunication Standard (ETS) has been produced by the Satellite Earth Stations and
Systems (SES) Technical Committee of the European Telecommunications Standards Institute (ETSI).
Proposed transposition dates
Date of adoption of this ETS: 15 September 1995
Date of latest announcement of this ETS (doa): 28 February 1996
Date of latest publication of new National Standard 31 August 1996
or endorsement of this ETS (dop/e):
Date of withdrawal of any conflicting National Standard (dow): 31 August 1996

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1 Scope
This European Telecommunication Standard (ETS) contains the requirements to be satisfied by Very Small
Aperture Terminal (VSAT) systems for their interconnection to Packet Switched Public Data Networks
(PSPDNs) implemented according to the CCITT Recommendation X.25 [1].
This ETS applies to the provision of Packet Switched Data Transmission services as defined in section 2 of
CCITT Recommendation X.2 [2].
This ETS is applicable to both one-way and two way VSAT networks. In the case of one-way VSAT
networks, the provision of the services as defined in section 2 of CCITT Recommendation X.2 [2] implies
the implementation of return circuits using facilities of other networks (e.g. terrestrial networks).
This ETS deals with two types of specification:
a) Interface requirements (clause 5):
Interface requirements are specified in order to ensure that the VSAT network and the PSPDN can
be connected.
b) Connection quality recommendations (see clause 6):
Connection quality recommendations are characteristics that contribute to maintaining a desirable
quality of service and a uniform approach with regard to certain interfacing aspects, addressing and
facilities.
The inability to meet the recommendations does not, by itself, prevent the equipment being
considered as compliant with this ETS.
Additional informative elements are provided in annex A.
2 Normative references
This European Telecommunication Standard (ETS) incorporates, by dated or undated reference,
provisions from other publications. These normative references are cited at the appropriate places in the
text and the publications are listed hereafter. For dated references subsequent amendments to, or
revisions of, any of these publications apply to this ETS only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies.
[1] CCITT Recommendation X.25 (1988): "Interface Between Data Terminal
Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for
terminals operating in the packet mode and connected to public data
networks by dedicated circuit".
[2] CCITT Recommendation X.2 (1988): "International data transmission
services and optional user facilities in public data networks and ISDNs".
[3] NET 2 (1988): "Approval requirements for DTEs to connect to PSPDNs
using CCITT Recommendation X.25 interface".
[4] CCITT Recommendation X.134 (1988): "Portion boundaries and packet
layer reference events: basis for defining packet-switched performance
parameters".
[5] CCITT Recommendation X.135 (1988): "Speed of service (delay and
throughput) performance values for public data networks when providing
international packet-switched services".

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[6] CCITT Recommendation X.136 (1988): "Accuracy and dependability
performance values for public data networks when providing international
packet-switched services".
[7] CCITT Recommendation X.137 (1988): "Availability performance values
for public data networks when providing international packet-switched
services".
[8] CEPT Recommendation T/CAC 4 (1989): "Monitoring of network
performance aspects of quality of international packet-switched services
using externally derived indicators".
3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
BER Bit Error Ratio
DM Disconnected Mode
DTE Data Terminal Equipment
DCE Data Circuit-Terminating Equipment
FCS Frame Check Sequence
LAPB Link Access Protocol Balanced
OSI Open System Interconnection
P/F Poll/Final bit
PSPDN Packet Switched Public Data Network
PVC Permanent Virtual Circuit
PvtDN Private Data Network
RNR Receive Not Ready
SVC Switched Virtual Circuit
VSAT Very Small Aperture Terminal
4 Interconnection scenarios
A VSAT network may be considered as a particular form of implementation of a Private Data Network
(PvtDN). This type of PvtDN is not covered by CCITT Recommendation X.327.
The VSAT Data Terminal Equipment (DTE) connected to the PSPDN appears to the PSPDN as a normal
X.25 DTE. The PSPDN makes no allowance and has no knowledge of the VSAT network.
Within the VSAT network two forms of communication are possible: real time direct connection (see
subclause 4.1) and store and forward (see subclause 4.2).
4.1 Real time direct connection
In this scenario a real time connection is established between the application served by one of the VSATs
and the application served by a DTE connected to the PSPDN. The Switched Virtual Circuit (SVC) or
Permanent Virtual Circuit (PVC) over the PSPDN is extended over the VSAT network.

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The following elements are identified in the connection and are shown in figure 1:
A: the applications (APPL) which require communication.
These applications communicate with each other by means of end-to-end protocols which are
outside the scope of this ETS.
B: The application running at the remote DTE (B) shall implement a local interface to the remote
VSAT (D).
This interface is not a subject of standardization. However the recommendations related to
connection quality defined in clause 6 are based on the assumption that this interface satisfies
CCITT Recommendation X.25 [1].
C: The remote VSAT provides an appropriate DCE interface (C).
D: The remote VSAT (D) provides the communication over the satellite.
The way in which this is done and the internal protocols of the VSAT network are outside the scope
of this ETS.
E: The Hub station.
In the case of a star network this is the central station with which all the remote VSATs
communicate.
F: The interface between the VSAT network and the PSPDN.
This is a DTE on the VSAT network side and may be implemented at either the HUB or at any of the
remote VSAT stations. Under these circumstances two types of connection over the VSAT network
can be distinguished:
- single hop connections which apply in meshed networks i.e. those that allow the direct
communication between remote VSATs, and in star networks, in which the interface to the PSPDN
is implemented exclusively at the HUB;
- double hop connections which apply in star VSAT networks which implement the DTE
interface to the PSPDN at any of the remote VSATs. In these cases all communications are routed
via the HUB and, therefore, require two satellite hops.
G: The PSPDN Data Circuit Equipment (DCE).
These are customer connection points which offer an X.25 interface to the PSPDN. These occur at
the interface to the VSAT network and also at the interface to the customer.
H: This is a generic PSPDN which may be made up of a number of national and possibly international
portions. These portions are defined in CCITT Recommendation X.134 [4] and their requirements for
quality are defined in CCITT Recommendations X.135 [5], X.136 [6] and X.137 [7].
I: The remote DTE of the customer connected to the PSPDN where the corresponding application
runs.

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G
F
D
DCE
VSAT DTE
A
A
APPL.
APPL.
(H) PSPDN
I
C E FG G
B D
DTE DCE DCE DTE
HUB
DTE DCE VSAT
R1
R2
X 25 x 25
Local Interface
R1 = Bit rate at DTE(B) - DCE(C) interface
R2 = Bit rate at DTE(F) - DCE(G) interface
Figure 1: Real time direct connection scenario
The use of the VSAT network to interconnect two PSPDNs is outside the scope of this ETS.
4.2 Store and forward
This scenario is depicted in figure 2.
In this scenario the delivery to or from the remote DTE (B) is performed over the VSAT system to a
store-and-forward gateway (J) connected to the PSPDN via a DTE (F). The delivery to or from the remote
DTE (I) takes place from the gateway over the PSPDN. The transmission of information between the DTE
(B) and the DTE(I) is performed therefore in two separate transactions. This means there is no real time
interaction between the remote DTE (B) and the remote DTE (I).
NOTE: The HUB (E) may or may not be present depending on the VSAT network architecture.

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JJ
STORE AND
FORWARD
F G
D
DCE
VSAT DTE
J
STORE AND
A A
APPL. FORWARD
APPL.
(H) PSPDN
I
C E FG G
B D
DTE DCE DCE DTE
HUB
DTE DCE VSAT
R1
R2
X 25 x 25
Local Interface
R1: Bit rate at the DTE(B) - DCE(C) interface
R2: Bit rate at the DTE(F) - DCE(G) interface
Figure 2: Store-and-forward gateway scenario
The elements involved in the connection are as defined in subclause 4.1 with one extra component:
J: the store-and-forward gateway between the VSAT system and the PSPDN.
This element is responsible for delivering the messages received from either the remote DTE (B), or
the remote DTE (I), to its counterpart.
The gateway function can incorporate protocol conversion at either low functional layers or high
functional layers. Such conversion is outside the scope of this ETS.
From the PSPDN point of view, the connection is performed with the applications residing in the
gateway. As such, the services offered by the PSPDN and their quality of service is in no way
affected by the VSAT system.
Assuming that the store-and-forward gateway is a normal DTE in the PSPDN, no special
requirements are identified for addressing purposes. This function is be considered part of the
user defined protocols and is therefore outside the scope of this ETS.

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5 Interface requirements
Specification
The interface provided by a VSAT network to be connected to a PSPDN shall comply with
CCITT Recommendation X.25 [1] at levels 1, 2 and 3.
Verification
The compliance of the interface characteristics provided by a VSAT network to be connected to a PSPDN
shall be verified following the procedures specified in NET 2 [3].
6 Connection quality recommendations
6.1 General
The inclusion of a two-way VSAT network in a PSPDN network connection has an effect on the overall
quality provided by the connection. It is therefore desirable that the portion of the connection provided by
the VSAT network meets certain quality criteria.
CCITT Recommendations X.134 [4], X.135 [5], X.136 [6] and X.137 [7] provide an adequate set of
parameters which are applicable to the definition of quality of service parameters in a VSAT network.
CEPT Recommendation T/CAC 4 [8] provides a set of verification procedures which are applicable to the
definition of the verification of the quality of service parameters in a VSAT network. The verifications should
be performed for each type of VSAT DTE interface with the PSPDN. The interfaces are those declared by
the manufacturer.
VSAT networks which are restricted in their connectivity to pre-agreed subsets of users of the PSPDN, for
instance by invoking Closed User Group (CUG) facilities, need not take consideration of these
recommendations.
6.2 Base for the definition of the VSAT performance parameters
6.2.1 Portion boundaries
The definition of the connection portion and the connection portion boundaries applicable to the connection
of a VSAT network to the PSPDN, is made along the principles defined in section 2 of CCITT
Recommendation X.134 [4].
The VSAT network should be considered as a user-provided portion of the connection. This portion of the
connection is defined as lying between:
- the local interface at the VSAT which for the purpose of this ETS should be according to CCITT
Recommendation X.25 [1];
and
- the X.25 interface between the VSAT system and the PSPDN, as required in clause 5.

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This is shown in figure 3 which is an extension of figure 2 of CCITT Recommendation X.134 [4].
PRIVATE PUBLIC
DTE DCE DTE DCE
ACCESS ACCESS
CIRCUIT CIRCUIT
USER PROVIDED
NATIONAL PORTION INTERNATIONAL PORTION
PORTION
( VSAT NETWORK )
INTERNATIONAL VIRTUAL CONNECTION
AS PER CCITT REC. X134 (Fig. 2/X134)
Figure 3: Identification of the boundaries of the user provided portion of the connection
6.2.2 Performance parameters
The definition of the performance of the user provided portion of the connection (VSAT network) is made
with respect to the occurrence of performance related events.
Those events are defined in section 3 of CCITT Recommendation X.134 [4] for the X.25 interface.
The user provided portion of the connection is expected to translate those events between the two portion
boundaries i.e. a CALL REQUEST packet at the X.25 interface of the remote terminal, becomes an
equivalent CALL REQUEST packet at the X.25 interface to the PSPDN. The same applies for the other
X.25 layer 3 packets.
6.2.3 System load
The performance recommendations are defined for VSAT networks submitted to their nominal traffic load.
This load should be declared by the manufacturer and should be quoted when claiming compliance with this
ETS.
The statement should provide at least an indication of:
a) the throughput of established traffic;
This is expressed as the number of packets per second and their size.
b) call processing load.
This is expressed as the number of call attempts and clear attempts handled by the system per unit
of time (second, hour).

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For the measurement of the VSAT network performances, the VSAT network is operated under its nominal
BER condition.
NOTE: The definition of this parameter is under study by CCITT.
6.3 Delay performance
The VSAT network should meet the overall delay requirements given in subclauses 6.3.1 to 6.3.3.
The verification of the compliance with these limits should take place under the following overall conditions:
a) the VSAT is loaded with its nominal traffic load as specified in subclause 6.2.3;
b) the VSAT DTE interface (F) is connected to a test-DCE via a standard X.25 interface as used for
customer service;
The responding X.25 port of the remote VSAT under test is a DCE port. This DCE port is connected
to a test-DTE;
The test-DCE and test-DTE can, for example, be protocol analysers;
c) the X.25 interface(s) should be unloaded, i.e. SVCs should be in state p1 (ready), and if PVCs are
defined, they should produce no traffic on the interface;
d) the interface characteristics should be as follows:
- frame level window of 7;
- default packet level window size of 2;
- default maximum data packet size of 128 octets;
- all data packets should be full i.e. 128 bytes of user data;
- D bit should be set to 0.
e) The maximum transmission delay of the DTE access circuit section of the user provided portion
should be declared by the manufacturer.
The tests should be performed in a configuration where the transmission delay of this DTE access
circuit section is maximum.
6.3.1 Call set up delay
Specification
The call set-up delay applicable to this ETS, should be as defined in section 2 of
CCITT Recommendation X.135 [5].
The packet layer reference events applicable for the user provided portion of the connection defined in
subclause 6.2.1 of this ETS, are listed in table 1.
The recommendations are based on the following assumptions:
a) the nominal traffic load is as defined in subclause 6.2.3;
b) the basic call does not require any of the facilities, available for selection by the user, as defined in
CCITT Recommendation X.25 [1]. The user data field is not used;
c) the operation of the link layer does not meet either the busy condition (RNR) or the windows closed
condition.

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Table 1: Packet layer reference events used to measure the call set up delay
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡              ‡    X.134 Packet Layer  ‡
‡              ‡     Reference Event   ‡
‡  Connection Portion    ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡  Boundary         ‡ Packet Event ‡ Packet Event ‡
‡              ‡  Initial  ‡   Final  ‡
‡              ‡       ‡       ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡              ‡       ‡       ‡
‡ Remote VSAT X.25 interface ‡  2 (X.25) ‡  3 (X.25)  ‡
‡ Calling remote VSAT    ‡       ‡       ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡              ‡       ‡       ‡
‡ Remote VSAT X.25 interface ‡  1 (X.25) ‡  4 (X.25)  ‡
‡ Called remote VSAT     ‡       ‡       ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡              ‡       ‡       ‡
‡ PSPDN-VSAT X.25 interface ‡  2 (X.25) ‡  3 (X.25)  ‡
‡ Calling VSAT DTE      ‡       ‡       ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡              ‡       ‡       ‡
‡ PSPDN-VSAT X.25 interface ‡  1 (X.25) ‡  4 (X.25)  ‡
‡ Called VSAT DTE      ‡       ‡       ‡
‡              ‡       ‡       ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
The call set-up time in the user provided portion of the connection is the difference between the call set up
time at the boundaries that limit this portion of the connection.
The values defined are an average and a 95 % value. The average value is the average of the distribution
of the call set-up time. The 95 % value is the delay value which should be satisfied for at least 95 % of all
call set-ups.
The average value and the 95 % value of the call set up time, in the user provided portion of the connection
should not exceed the limits given in table 2.
Table 2: Call set-up time recommended values
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡         ‡             ‡
‡ Statistic    ‡ User provided portion  ‡
‡         ‡             ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡         ‡             ‡
‡ Average (ms)   ‡    2 500 + X     ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡         ‡             ‡
‡ 95 % (ms)    ‡    3 500 + X     ‡
‡         ‡             ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
The value of X is given by X = 400/R1 (ms), where R1 is the data transmission bit rate expressed in Kbit/s
of the access circuit between DTE B and DCE C in figures 1 and 2.
Verification
a) Verification of call set up delay from a test-DCE to a specific VSAT (the test-DCE simulates the
Data Circuit-Terminating Equipments of the PSPDN):
The following steps are carried out:
- the test-DCE transmits a CALL REQUEST packet on a free logical channel. Except for the
necessary addressing facilities to address the specific VSAT, there is no inclusion of any user
facilities in the CALL REQUEST packet;
- the test-DCE waits for the corresponding CALL CONNECTED packet to arrive;
- the time between the start of the CALL REQUEST packet and the end of reception of the
CALL CONNECTED packet is measured as the total call set-up time Tcc-cr.

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If any unexpected packet level protocol events or any unexpected link layer protocol event is
received during a measurement, a new measurement is made.
The X.135 parameter call set up delay is estimated from this value by eliminating irrelevant delays
on the access line(s) and delays in test equipment using the following formula:
T - ([L +L ]* 8/R ) - d (ms)
cc-cr cr cc 2 p
where
T is the total call set-up time in ms;
cc-cr
L is the length of the CALL REQUEST packet in octets;
cr
L is the length of the CALL CONNECTED packet in octets;
cc
d is the processing delay(s) in the test-DCE and/or test DTE in ms;
p
R is the data transmission bit rate, in Kbit/s of the access circuit between DTE F and DCE G
2
of figures 1 and 2.
The measurement is repeated a minimum of 1 000 times.
b) Verification of call set-up delay from a VSAT to a test-DCE.
Call requests are generated by a test-DTE which is connected to the VSAT used in the test. The
procedure is as defined in subclause 6.3.1 paragraph a), except that it is now the test-DTE initiating
the call set-up packets and the test-DCE that is the responding part.
The measurements are repeated a minimum of 1 000 times.
The average and the 95 % value should be computed and checked against the reco
...