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is Cisco EPC3925 older modem than the Thompson, Im Fuming
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24-09-2012 9:11pm#1
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Meanwhile on the 60Mb pack:
What you have is not bad but clearly you are paying more for less. Were those tests done over wired or wireless?
these were wired and wireless My wireless is ASUS AC-RT-66U which has an amazing speed so wireless is exactly as wired , Really. Mind you I measure wired from UPC Cisco Modem not via the Asus router0 -
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pretty much interesting! could someone please explain why I have only 4 downstream channels instead of 8
Please confirm all are same: (Remember not to post your MAC by accident)Bootloader Revision: 2.3.0_R1 Current Software Revision: epc3925-ESIP-12-v302r125533-110830c_upc Firmware Name: epc3925-ESIP-12-v302r125533-110830c_upc.bin Firmware Build Time: Aug 30 11:09:31 2011 Cable Modem Status: Operational Wireless Network: Disable
DOCSIS Downstream Scanning: Completed DOCSIS Ranging: Completed DOCSIS DHCP: Completed DOCSIS TFTP: Completed DOCSIS Data Reg Complete: Completed DOCSIS Privacy: Enabled
My stats for comparison:Power Level: Signal to Noise Ratio: Channel 1: 1.8 dBmV 40.4 dB Channel 2: 1.5 dBmV 40.5 dB Channel 3: 1.2 dBmV 40.3 dB Channel 4: 1.6 dBmV 39.7 dB Channel 5: 4.2 dBmV 39.6 dB Channel 6: 4.0 dBmV 40.7 dB Channel 7: 4.0 dBmV 40.4 dB Channel 8: 3.5 dBmV 38.5 dB Power Level: Channel 1: 42.2 dBmV Channel 2: 0.0 dBmV Channel 3: 0.0 dBmV Channel 4: 0.0 dBmV
Ok, I also am not a cable engineer or networking specialist, but I'll try and interpret things as best I can and hopefully educate myself in the process.dBmV
dB(1 mVRMS) – voltage relative to 1 millivolt across 75 Ω. Widely used in cable television and off air antenna signals, where the nominal strength of a single TV signal at the receiver terminals is about 0 dBmV. Cable and antenna systems use 75 Ω coaxial cable, so 0 dBmV corresponds to −78.75 dBW (−48.75 dBm).
The reference level was defined in the late 1950s and references the minimum voltage required by a television tuner to produce an excellent television picture. In the early days of television, voltages generated by antennas were measured in microvolts (uV). It was decided that 1000 microvolts at the input of the television tuner was the minimum required to produce excellent video image quality. Of course other factors also affected the tuner’s performance but it was generally accepted that 1000 microvolts was the target value. In an effort to simplify the large numbers associated with using the microvolt scale, the decibel-milivolt scale was created and the 1000 microvolt requirement was represented as 0 dBmV.
Voltage values above and below the reference of 0 dBmV are incremented in decibels or “dB.” Therefore, the difference between 6 dBmV and 2 dBmV is 4 dB. Often the short-hand way of speaking about the dBmV scale confuses people. For example, the output of an amplifier may be 44 dBmV but is incorrectly stated as “44 decibels” when in fact it should be said as “44 decibel-millivolts.
Digital television tuners operate with a lower minimum requited voltage or about -12 dBmV. You will note this is 12 dB below the reference level of 0 dBmV for analog TV. Also, digital signal measurements made by newer signal level meters are the result of a sequential set of small measurements, combined and averaged to produce an “average digital power” measurement. Despite the measurement process, the result is reported as a dBmV value.
Confused? Don’t be. Just remember that for the new digital television tuners, you need a signal level between -12 dBmV and 16 dBmV.
By:
Steve Zahn, Doc. #113005C
© 2011 Used By Permission
szahnengineering@msn.com
Also this from Wiki(Hope I dont hit the character limit here)(Slightly relevant)As frequency allocation bandwidth plans differ between United States and European CATV systems, DOCSIS standards have been modified for use in Europe. These modifications were published under the name "EuroDOCSIS". The differences between the bandwidths exist because European cable TV conforms to PAL standards of 8 MHz bandwidth and North American cable TV conforms to ATSC standards which specify 6 MHz. The wider bandwidth in EuroDOCSIS architectures permits more bandwidth to be allocated to the downstream data path (toward the user).
Throughput
All of these features combined enable a total upstream throughput of 30.72 Mbit/s per 6.4 MHz channel, or 10.24 Mbit/s per 3.2 MHz channel. All three versions of the DOCSIS standard support a downstream throughput with 256-QAM of up to 42.88 Mbit/s per 6 MHz channel, or 55.62 Mbit/s per 8 MHz channel for EuroDOCSIS. (see table below)
So this suggests that working at full efficiency(never happens in any kind of analogue system) you should get 165Mbps from 3 D channels. Also this doesnt include the networking overhead. For torrenting this can be almost 10% so I'll use that for a rule of thumb here.
Going back to the top, mine and your lines are above 0dBmV, or in laymans terms better than "excellent" which is the benchmark. DECEiFER on the other hand is a little below(older copper, more people on his stem, longer stem etc) but still within cable limits for analogue tv anyways, and digital on cable works at lower thresholds should, and is fine.
You have the same SNRs as me too, and as mine is a brand new cable, and is quite short(I think we are the first or second away from the fibre in the footpath) should be in the excellent category.
So, laymans maths:
4 EuroDocsis Downstream channels gives 222 odd Mbps, theoretical limit. Say then 80% efficiency gives 177 rounded down. Take 10% for overhead and you get 159. SO, your link to the node should supply, if I'm doing it right, at least 159(say 160 with decimals included).
Your jitter is a little high, but I dont think its enough to be alarmed about. Can you sort java and test packet loss. Also, I'm only a 30Mb but I'm connected on 8, so I dont know why you wouldnt be. Possibly a filter still on the line somewhere? Are you able to trace it all the way back to the pole or nipples(four pins on a wall).
Now that I think about it, the old standard only used 4 channels, so maybe your node doesnt support any more(in which case they shouldnt have upgraded you I suspect).
Reading more now.In a DOCSIS 3.0 network implementing downstream channel bonding, the DOCSIS CMTS dynamically balances the data across the Downstream Bonding Group (DBG), which can consist of four or more downstream channels. The reason this is done is to offer subscribers the best quality of service across downstream channels with changing impairments and changing congestion at the receive side. Each outgoing packet from the CMTS is tagged with a sequence number. The sequence number becomes important for a number of reasons. Packets can be dispersed across different downstream channels and can have different time delays in arriving at the receiving cable modem. It is then the cable modem’s responsibility to re-synchronize the incoming packets based upon the sequence numbers. TCP/IP windowing acknowledgments will take care of any lost packets at Layer 3, however for UDP flows, such as voice and video, those packets will be forever lost. Further, by dynamically distributing the packets across downstreams, the CMTS can take advantage of statistical gains of many cable modems connected to the DBG. This becomes especially critical when your system has a mixture of legacy DOCSIS 1.x, 2.0 and 3.0 cable modems. The 1.x and 2.0 modems will all be receiving data from only the Primary Channel of the DBG which the DOCSIS 3.0 modems will be able to receive data from all four+ downstream channels in the DBG. So this dynamic prioritization is in effect acting like upstream load balancing in the downstream.
read read read....
THIS: When you configure a DOCSIS channel as a primary it must carry all of the DOCSIS protocol overhead, which is about a 15% to 20% loss of user data.
So overhead is higher than I guessed. So maybe then your four channels cant cope, if 80% is a good guess for the hardware layer.
The caffeine is wearing off now, but I'd say try call UPC and badger them until they put you in touch with an installation engineer(Not the tech, the actual engineer who oversees the group of new connection installers). These guys are the ones that plan and set up the nodes and connections, they understand the layer 1/2/3 tech really well, and will be able to advise you much better than the muppets working CS who probably couldnt crimp a cat5 patch cable.
gNight,
ED E0 -
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