The X.25 standard does have optional throughput classes, although
I've never seen much attention paid to them in practice. IIRC, they
go up to 2MB or 4 MB or so. They aren't, however, hard limits. I've
certainly seen X.25 running on E1's. LAP-B unquestionably is used at
higher speeds on satellite links.
As an attempt to unify the CCITT and LAN worlds, there are ISO
standards for running the OSI Connection-Oriented Network Service
over LLC, and for LLC over CONS. ISO 8881 and 8880, from memory,
although I might have them reversed. The UK's JANET network
certainly used these. So, X.25 certainly has been run over Ethernet.
I can't think of an inherent reason that there would be a hard
bandwidth limit. Last I looked, X.25 was in the process switching
path, so processor load would become a limit. I seem to remember
that there was a performance cutoff of around 8 9.6Kbps heavily
loaded X.25 links on an old 4000 router, which has a 68040 derated
from the one on the 7000.
>First up, I would like to point out that I have NO hands-on experience of
>X.25 - this is considering the question from the theoretical Cisco point of
>view, which doesn't necessarily have anything to do with the real world.
>I had a look in the Paquet BCRAN book, but couldn't find anything referring
>to maximum bandwidth of X.25. I would check the RFCs, but due to a cable
>problem internet access to most sites from Australia is currently woeful.
>However, in the BCRAN book, there is the output of a 'show int' command,
>which shows the bandwidth of a sample X.25 interface as 1544 Kbps.
>
>Maybe some carriers will only provision X.25 at up to 64 Kbps, but I
>suspect that the theoretical maximum speed is higher. X.21 will run at up
>to 2Mbps, so possibly the answer is 'E - none of the above', but my guess
>is that the Cisco answer is 1.544 Mbps.
>
>JMcL
>---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 23/11/2000
>09:16 am ---------------------------
>
>
>"Hawthorne, Mike MM" <[EMAIL PROTECTED]>@groupstudy.com on
>23/11/2000 01:11:11 am
>
>Please respond to "Hawthorne, Mike MM" <[EMAIL PROTECTED]>
>
>Sent by: [EMAIL PROTECTED]
>
>
>
>To: "'xndr'" <[EMAIL PROTECTED]>
> [EMAIL PROTECTED]
>cc:
>
>
>Subject: RE: x.25 question help
>
>
>
>
>Dean, the maximum transmission rate for X.25 is 64Kbps.
>This I have confirmed with a Telco.
>
>Cheers
>Mike
>
>-----Original Message-----
>From: xndr [mailto:[EMAIL PROTECTED]]
>Sent: Wednesday, November 22, 2000 12:22 AM
>To: [EMAIL PROTECTED]
>Subject: Re: x.25 question help
>
>Hi!
>
>X.25 is a set of CCITT recomendations for transmitting dato over PDNs
>protocol suit, including OSI Layers: Physical, Datalink & Network.
>
>The speed is on Physical Layer. At the physical layer, the X.25 standard
>assumes an X.21 interface, but can also support V.35 and the EIA RS232-D
>interfaces.
>
>X.21 bis is up to 19,2 Kbps, V.35 is up to 2Mbps, and RS232 is up about
>115,200 or something like this.
>
>> I have a question about x.25 transmit rate as following:
>> What is the maximum transmission rate for X.25?
>>
>> A. 56 Kbps
>> B. 64 Kbps
>> C. 128 Kbps
>> D. 1.544 Mbps
>>
>> Thanks
>>
>> dean
>>
>>
>
>
>
>
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