cheng@cbnewsh.ATT.COM (wan-hong.steve.cheng) (06/05/89)
Is there any difference between DDN X.25 interface and CCITT X.25 interface standard (198?) ? I understand there is a certification procedure to pass before connection to DDN can be done. Does anyone know the details? Thanks for your information.
lars@salt.acc.com (Lars J Poulsen) (06/10/89)
In article <1152@cbnewsh.att.com> cheng@cbnewsh.ATT.COM (wan-hong.steve.cheng) writes: >Is there any difference between DDN X.25 interface and CCITT X.25 interface >standard (198?) ? I understand there is a certification procedure to pass >before connection to DDN can be done. Does anyone know the details? Thanks >for your information. The DDN (MilNet, APRAnet and clones) is a bona fide CCITT X.25 1984 compliant network (although it does not seem to have a DNIC). Due to the requirements for stability of the applications that run on this network, the owners have instituted a certification program. Most X.25 network operators will not allow connection of customer equipment without prior certification, but the DDN certification procedure is the most rigorous I have seen. (It tests the error detection and error handling capability of the host as well as normal operation). What is special about the DDN is that most of the traffic is known to be TCP/IP, and the network is optimized for TCP/IP traffic. Special ports are available to hosts that speak no X.25 but speak BBN-1822 AHIP (ARPAnet Host-to-Imp-Protocol), and the network performs protocol conversion as needed. In order to be able to exchange traffic with these hosts, most TCP/IP hosts specify "Standard Mode Facility" at call setup time. Also, there is an algorithmic correspondence between physical attachment point (PSN number, port number), IP address and X.25 address. Also, instead of PADs for asynch terminals, DDN has TACs; i.e. dial-up asynch terminal service uses TELENT protocol instead of X.29. / Lars Poulsen <lars@salt.acc.com> (800) 222-7308 or (805) 963-9431 ext 358 ACC Customer Service Affiliation stated for identification only My employer probably would not agree if he knew what I said !!
barns@GATEWAY.MITRE.ORG (Bill Barns) (06/12/89)
The DDN X.25 interface is generally along the lines of CCITT X.25
(1980), with many 1984 features available. It is really pretty close
to an X.25 (1984) implementation. The certification procedure involves
mostly rather low-level tests. DDN X.25 has notions of "Basic" and
"Standard" service. Basic resembles commercial X.25. Standard entails
a few special facilities and magic values which are used in the places
CCITT X.25 provides for such extensions. The intent is that Standard
service is to be used for TCP/IP support; the DDN backbone provides
interworking of Standard connections with BBN 1822-style interfaces.
Basic service is to be used for "raw X.25" needs and for OSI (GOSIP)
support. This last point is of interest because it means that a vendor
intending to sell both TCP/IP and OSI services on top of DDN X.25 will
need to provide for simultaneous Basic and Standard operation, with
the appropriate higher layer interface functions for each.
Certification for DDN connection used to be done by DCA or a DCA
contractor, but now is going to be done through the NVLAP program.
This means that you contract with an accredited laboratory which
performs the official testing. Realistically, it is normal to acquire
a copy of the test software, and the appropriate hardware (Tekelec
Chameleon) yourself, and do your own testing beforehand. When you are
done, you get an official test done by the NVLAP-accredited laboratory
of your choice and send the paperwork to DCA.
The DCA publication covering layer 2 and 3 qualification testing for
DDN is DCA Circular 370-P195-5. I have a "Draft" version dated 8 Sep
1988; I understand that an essentially identical "official" version is
due back from the printer any day now. If you plan to get this
qualification done, you will eventually have to deal with an accredited
laboratory, so you might as well touch base with those people early in
the cycle; perhaps you will receive useful advice. Here is a list of
accredited labs for this set of tests (as of 31 Mar 89):
BBNCC Testnet
150 Cambridge Park Drive
Cambridge, MA 02140
POC: Mark Whitney (617) 873-2874
Downey, Dalton, Inc.
135 Bellevue Street
Boston, MA 02132
POC: June Downey (617) 325-8425
J.G. Van Dyke and Associates, Inc.
8975 Guilford Road
Suite 100
Columbia, MD 21046
POC: Robert Smith (301) 596-7510
You can start your own laboratory and get it accredited, but you cannot
qualify your own products. It is imaginable that two unaffiliated
vendors could each set up labs, get them accredited, and test each
other's products. This may or may not be cheaper than dealing with one
of the existing accredited labs. Accreditation is a function of NIST;
I don't have any specific contact information, but DCA would probably
help you track it down if you were seriously interested.
The DDN X.25 Host Interface Specification (1983 edition) is obtainable
from the Defense Technical Information Center as document number
AD-A137427; phone number is (703) 274-7633. This specification is
correct as far as it goes, but the DDN now actually supports some
additional facilities beyond those described in the document. I know
of no impact this could have upon testing, but I can't guarantee it -
there's just too much fine print which I haven't studied closely.
Nowadays there is also mandatory conformance testing for new
acquisitions of IP, TCP, TELNET, FTP, SMTP implementations. This
also comes under NVLAP. Someday there will be COS testing for GOSIP
items, and a general intention exists to make that mandatory too.
Hope this info is of some use. As you might expect, all of this came
from various DCA sources of eminence and distinction, but I shall not
name them here (in order to avoid embarrassment to them or me should
there be any error here...) If you need to contact DCA and are having
problems doing so, let me know and I will try to point you to some
appropriate person.
Bill Barns / MITRE-Washington / barns@gateway.mitre.org