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7th April 2004 at 01:37 #37859Emin GabrielyanGuest
Hi Everybody, please advice on the following situation. There is an operator running a network, based on EWSD switches. Each of the operator’s switches passes about 200 million minutes a month and have a capacity of about 1100 E1 (30) lines. This operator has a customer connected with 4 E1 ISDN interfaces. The maximal monthly traffic observed on these 4 E1s is about 950’000 minutes. May such a load on these 4 E1s result in “disequilibrium” and in “considerable influence on other customers” when talking about a EWSD switch of above mentioned capacities?
Thank you for your replies.
Emin13th April 2004 at 10:58 #37860Tony FGuest
from the information that you provide I’d say it’s unlikely that 4 E1’s with the traffic load that you mention is causing “disequiibrium” and “considerable influence on other customers”. However it is not impossible.
From what you write (and from other postings on this site which appear to be about the same subject) there are several possible reasons for the EWSD operator to say what they have said. These being:
1) They have a serious capacity problem in terms of trunking and the traffic from the 4 E1’s is contributing to this problem. From the size of the network that you describe the traffic from the E1’s alone will not be the only cause of the capacity problems. It may be that the operator is attempting to reduce traffic from other sources also. If this is the case then the operator needs to upgrade their capacity. There may be certain reasons as to why they cannot/won’t upgrade their capacity.
2) The ISDN shelf/cabinet of the EWSD that the 4 E1’s are conncted to has an internal matrix that may have been sized to handle normal business traffic rather than carrier traffic and the traffic from the 4 E1’s is causing this matrix to become blocked. Are the majority of the 950’000 minutes from the 4 E1’s sent during the standard business hours of the country in which the operator is based (from you surname and the fact that the operator uses EWSD’s I’m guessing Armenia?)?
3) The operator may want to raise the rates that you are being charged and this may be a plan to ask for higher termination charges. Alternatively they may want to stop terminating traffic from smaller operators and only take in traffic from larger operators on C7/SS7 interconnects(I’m assuming that these 4 E1’s are used to terminate internationally originated traffic). If the traffic originated is national traffic then this may be an attempt to restrict competition or to ask for higher termination rates.
4) Some larger operators now have a company policy of only connecting to other operators with a minimum number of E1’s (often 10). It may be that this is the case here and the operator wants to stop dealing with an operator with only 4 E1’s. The companies that have taken such decisions believe that dealing with smaller operators is not cost effective for them.
Hope this helps.
Tony19th April 2004 at 07:06 #37861dmckGuest
The problem may not be associated with ‘load’ so much as with ‘call attempts’. As described the problem appears to be generated by outgoing traffic on the 4 x E1. Once these 120 channels are busy the EWSD should identify the route as busy and the calll will fail. Likewise if the calls are originating from the E1’s (PABX/PBX), once all channels are busy the originating equipment will give a ‘busy-tone’ to the caller.
BUT….. if the calls are from the EWSD to the equipment on the end of the E1’s (say a PBX) there may be problems. Assume the 4E1s are connected to the PBX of a radio station that runs a competition and generates thousands of calls for a very short time period. The first call is successful and occupies a B-channel. The other 119 B channels may be free, so the EWSD tries to complete other calls ringing the competition number. There will be thousands of call attempts, maybe tens of thousands, in a vary short space of time. While there are free B-channels on the route EVERY call will generate a D-channel call set up request to the PBX, and associated D-channel messages indicating request denied because number is busy.
These set up request messages will queue in the EWSD until they are ‘serviced’ and if the processing power cannot handle it quickly, other customers in the switch will also be affected. The customers PBX may also be slowed considerably as its CPU cannot manage the avalanche of set-up requests.
I have witnessed the above scenario render a Fujitsu F640 PBX virtually unuseable (50 seconds to return dial-tone if you picked up a handset). I have no doubt other situations generating high call loads could also do similar (eg, calls to a phone-in betting shop)20th April 2004 at 08:38 #37862EminGuest
Thank you for replies.
some clarifications for the last post:
Calls are not from EWSD. All the calls are originating from the E1’s and are send to EWSD. Operator claims that our calls are causing congestions of its switches and morover result in congestions of voice trunks between the switches. Most of our calls are to mobiles (operated by the same operator) and operator claims that these calls overload also the trunks laying between the EWSD switch (we are connected to) and the switch handling the GSM mobile network.
For a network based on 4 or 5 core switches, passing 800 million minutes a month, it sounds to me very unrealistic, that only 120 simultaneous calls may overload the links between two of those core switches of the operator network.21st April 2004 at 00:44 #37863dmckGuest
It sounds as though the EWSD operator knows nothing of telecommunications!! The are willing to take your money for connecting 4 x E1 then complain because you generate too much traffic! From your description the problem is with their network being under dimensioned.21st April 2004 at 10:31 #37864Tony FGuest
even though the operator has 4 or 5 core switches and handles 800 million minutes per month it is possible that the EWSD acting as the gateway between the GSM and fixed line networks does not have sufficient trunk capacity in place or that other parts of the mobile network do not have sufficient capacity in place. This may be because the operator did not expect the levels of mobile traffic to be as high so quickly.
It is also a possibility that this is a commercial issue and that the operator wants to reduce your traffic for the reasons (or similar reasons) that I mentioned in 3) and 4) of my original posting on this topic.
Tony7th May 2004 at 14:00 #37865EminGuest
Thank you for your replies!
For Tony F:
The operator currently abandoned the idea that the EWSD switches are being congested and they moved to the version where the trunks between one of the core EWSD switches and the GSM netowrk are overloaded, exactly as you explain (note that the GSM netowrk is also owned by the operator).
However I would like to provide some figures about the transmission capacities of this operator:
The operator has its own fiber optic cable over 7000 km in length and more than 200 POPs based on SHD/DWDM technology providing nation-wide coverage.
City-rings of three major cities have actual capacity of more than 200 Gbps.
Thanks7th May 2004 at 16:32 #37866Tony FGuest
if this is a genuine congestion problem (and not a commercial issue) then the amount of transmission capacity and POP’s that the carrier has is not the issue. The carrier needs to have sufficient E1 or STM1 cards in the EWSD’s between the fixed line network and the GSM network to be able to connect extra trunks to the transmission network.
Tony7th May 2004 at 20:47 #37867EminGuest
More than 1400 Base Transceiver Stations (BTSs)
6 Mobile service Switching Centers (MSCs) in four major cities of the country.9th May 2004 at 15:34 #37868EminGuest
This operator has 4 powerful EWSD switches for its fixed network, has 6 Mobile Switching Centres. As the operator claims “all switches are interconnected to compensate for any failure that might occur”. Has an optical DWDM transmission network (not just WDM!), whose city-rings only carry a capacity of 200 Gbps.
What is the probability that this operator may have congestions only because of extra 120 calls from its telephone network to its mobile network, assuming that its network experienced no congestion problem and was very reliable before that 120 calls?10th May 2004 at 12:01 #37869Tony FGuest
with a network the size that you describe your 4 E1’s will not by themselves be causing congestion (unless the inter EWSD trunks are extremely under provisioned). Please see point number 1) of my first reply to you on 13th April – the carrier may be trying to cut back other sources of traffic and not only your traffic.
Also please see every other posting including the first in which I mention possible commercial issues. From the wording of your postings (you express doubt that such a large network could suffer from the problems that have been described to you) it would appear that you believe some form of commercial issue is the real reason for the carrier attempting to cut back your traffic.
Without having detailed insider knowledge of the carrier it is not possible to state for sure if what they are telling you is correct or not. As such any replies to you must cover all probabilities.
In summary it is possible that the carriers network does have some form of congestion but it is also possible that the carrier has commercial reasons for doing what they are doing.
To provide a more definitive answer would require the detailed traffic statistics and switch configuration information which is only available within the carrier. Without such information nobody can make a statement which supports or refutes the carriers claims of congestion.
You may want to ask the carrier questions such as:
Why is only 4 E1’s affecting the network?