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Author Topic: Constant Upstream Bitswaps Normal?  (Read 436 times)


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Constant Upstream Bitswaps Normal?
« on: March 17, 2017, 02:24:33 PM »


1st time post although long time follower of this site.

Background - I'm on outskirts of town on a 2.4 mile long BT ADSL1 line. Previously used HG612 in bridge mode to BT HH5A for routing/wireless. HG612 appeared to be very tolerant to line conditions and just worked, giving 7300 sync speed with snrm set to around 8dB to reduce errors. Happily ran for 3-4 months at a time without resync.

In January I noticed that broadband was freezing for up to 15 minutes at a time. This would happen 3-4 times a week, with no pattern regards time/usage etc. Snrm would drop to 3dB and errors go through roof. If left, line would recover by itself to original settings or a reboot would always work. Totally unrelated to these freezes, I noticed on HG612 stats that upstream bitswaps were being switched on at a constant rate of 30/min and would not recover until modem reset, only to switch on again after a few days.

Thinking that the HG612 was faulty, and reading about Zyxel routers on this site I invested 2.30!! in a VMG3925 B10B from ebay. With Rom-d cleared and latest firmware loaded, initially tried it as all in one but unimpressed by wireless coverage, so now just used as bridge to HH5A as before. After 10 days running in this mode the Zyxel does appear to work well on this line with a slightly higher sync speed and all errors are half those recorded by the HG612. And no freezes to date.

However, this morning I noted that the Zyxel also switched on constant upstream bitswaps just after midnight at the same rate 30/min. From other graphs, nothing else happened at that time.

While it does not appear to have any impact on speed, my question is - is this normal and to be expected? Or is there a fault somewhere causing this?

Attached are photos of the HG612 bitswap action from Feb and today on the VMG3925





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Re: Constant Upstream Bitswaps Normal?
« Reply #1 on: March 17, 2017, 02:55:32 PM »

Hello and welcome to the forum.

With the HG612 it is best to mount them on a vertical surface with good air flow to keep it cool, I have mounted mine on 25mm wooden battens, vertical under the rubber pads and have two long mounting screws in the wall.
Mounted with the leads at the bottom.
The modem is 25mm from the wall and this keeps my modem cool and no locking up. 

On my DG834GT I am testing on my Long ADSL2 line I have fitted an old CPU cooling fan on the unit to keep it cool. :)
I have a set of 8 fixed IP's From my Eclipse isp.
BT ADSL2 line>HG612 set as a Modem, Bridge, WAN not Bound to LAN1 or 2 >Smoothwall (Hardware Firewall and routing) > Ethernet LAN, DMZ,WiFI LAN and Spare LAN .
DSLstats LAN2  linked Ethernet


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Re: Constant Upstream Bitswaps Normal?
« Reply #2 on: March 17, 2017, 06:56:11 PM »

Hi tickmike and thanks for the welcome.

Agreed, was aware of potential cooling issues with HG612 and mounted vertically to wall batten with long nylon bushes in an unheated room. This modem has operated perfectly for the last 2 years and when locking problems arose in January I did give it a blast with compressed air to ensure no dust build up.

But consigned to the spares box now as very happy with the new VMG3925 performance as a modem. My only query is with these US bitswaps. These have been zero for 9 days and then suddenly switch to constant 30/min. Haven't been monitoring this aspect previously so not sure what the cause/trigger is and whether a hardware fault, reporting error or otherwise. Have just reset modem so will see if they reappear.

Netgears never worked on my line, DGN2200 and DG834GT would both constantly resync several times per day. Seem to recall they both gave weird DS attenuation figures which may be related to performance.