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advo

@comcast.net

Modem Stats -- Small packet loss/latency

Hello everyone,

I've been seeing some intermittent packet loss (not high, 1% for the most part) as well as some high packets where there isn't loss (upwards of 800ms per 10 pings) even to my first hop. I was wondering if someone could glance at my stats and see if they see anything off. (sorry for the formatting)

Channel ID 4 1 5 7
Frequency 609000000 Hz 591000000 Hz 615000000 Hz 627000000 Hz
Signal to Noise Ratio 38 dB 38 dB 38 dB 38 dB
Downstream Modulation QAM256 QAM256 QAM256 QAM256
Power Level
9 dBmV 9 dBmV 9 dBmV 10 dBmV

Upstream Bonding Channel Value
Channel ID 4 5 6
Frequency 34800000 Hz 27900000 Hz 22600000 Hz
Ranging Service ID 931 931 931
Symbol Rate 5.120 Msym/sec 5.120 Msym/sec 2.560 Msym/sec
Power Level 47 dBmV 46 dBmV 45 dBmV
Upstream Modulation [3] QPSK
[3] 64QAM
[3] QPSK
[3] 64QAM
[3] QPSK
[2] 16QAM

Ranging Status Success Success Success

Signal Stats (Codewords) Bonding Channel Value
Channel ID 4 1 5 7
Total Unerrored Codewords 18704206006 1524341260 1524341350 1524341264
Total Correctable Codewords 346 19 12 12
Total Uncorrectable Codewords 4959 686 599 690


baineschile
2600 ways to live
Premium
join:2008-05-10
Sterling Heights, MI
Its a bit tough to read your formatting. Can you post a screenshot? If not, try here.

»Comcast High Speed Internet FAQ »What should my Signal Levels be?


advo

@comcast.net
reply to advo
Just an example of what I am seeing

Reply from X.X.X.X: bytes=32 time=10ms TTL=254
Reply from X.X.X.X: bytes=32 time=9ms TTL=254
Reply from X.X.X.X: bytes=32 time=626ms TTL=254
Reply from X.X.X.X: bytes=32 time=972ms TTL=254
Reply from X.X.X.X: bytes=32 time=12ms TTL=254
Reply from X.X.X.X: bytes=32 time=10ms TTL=254
Reply from X.X.X.X: bytes=32 time=8ms TTL=254
Reply from X.X.X.X: bytes=32 time=10ms TTL=254
Reply from X.X.X.X: bytes=32 time=48ms TTL=254
Reply from X.X.X.X: bytes=32 time=33ms TTL=254
Reply from X.X.X.X: bytes=32 time=1038ms TTL=254
Reply from X.X.X.X: bytes=32 time=167ms TTL=254
Reply from X.X.X.X: bytes=32 time=10ms TTL=254
Reply from X.X.X.X: bytes=32 time=10ms TTL=254
Reply from X.X.X.X: bytes=32 time=8ms TTL=254
Reply from X.X.X.X: bytes=32 time=9ms TTL=254
Reply from X.X.X.X: bytes=32 time=9ms TTL=254
Reply from X.X.X.X: bytes=32 time=929ms TTL=254
Reply from X.X.X.X: bytes=32 time=673ms TTL=254


advo

@comcast.net
reply to baineschile
Click for full size
Modem
Screenshot


andyross
Premium,MVM
join:2003-05-04
Schaumburg, IL
reply to advo
What are you pinging on that one post? If it's your local gateway or nearby router (by the few low pings, that's what I'm guessing), it's not unusual for it to bounce around since it may give low priority to pings.

Try pinging something like google.com and see how consistent it is. Just because a local router has variable ping times to it doesn't always mean it will delay anything passing through.


advo

@comcast.net
Not my local router..if it's getting overloaded and gives a lower QOS to ICMP; we have other issues. This is my first hop beyond my residence, so the local gateway for comcast for my subnet.


AnonMan

@comcast.net
Don't ping your first hop it won't be accurate.

ICMP can be given low priority and even if not under load still result in a high ping.

My first hop tracert for example shows 20+ms for latency but doing an actual ping shows 8-9. It also jumps around.

Same for pinging the Comcast DNS server. It's normal to see time outs on those also, doesn't mean they are down.

You need to ping something further away that's not an end gateway or hub. Try google.com it's generally consistent for me.


advo

@comcast.net
The pings matched up with google basically mirror that of my first hop. The issues has subsided since earlier, and I'm not getting packet loss. Really though, if the first hop gateway is under enough stress to be dropping ICMP it needs to be upgraded. I understand a low priority with QOS, but it still won't be dropped unless there is a certain amount of load, which would have to be fairly high.

Was more curious about the modem stats than anything and making sure the levels are not on the "edge" and that's why I was seeing ht issues.


AnonMan

@comcast.net
A high end router can be configured to handle ICMP different, it's not just all QoS.

A ping on first hop being high doesn't mean that QoS is kicking in because the device is at the limit always, many other factors are involved. Also depends on the type of ping as a tracert and a ping in windows don't use the same packet types even.

That said, you signal on the DS is a bit on the high side. If it goes over 10 you generally can start to have issues. You would probably be better with like a 6db forward path attenuator. You wouldn't want to use a regular one or a splitter to lower your DS though as your US will get to high at that point.

If your DS goes above 10 and you notice issues and don't want to get a forward path attenuator yourself you can call and have them address it.

That said most modems are technically rated for -15 through +15 on the DS but between -7 and +7 are the best with 0 being ideal.

US just keep under 50.

It's okay to test how you did but just keep in mind the ping and tracert is not 100% due to the above stated reason. It can sometimes still help identify an issue so it's good you did it. Just keep an eye how it reacts during issues and when not and see if you spot the pattern on which node. Sounds like it may be either noise though or maybe bad cable/end or something between you and the ped and possible the temperature change throughout the day impacts.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
said by AnonMan :

Also depends on the type of ping as a tracert and a ping in windows don't use the same packet types even.

Are you sure ?


advo

@comcast.net
The only real other thing a router is going to do beyond any type of QOS is set a rate limit to throttle ICMP traffic to make sure a router is not getting overloaded. Unless we have a ton of ICMP packets being sent at the same time, I don't think that's the issue.

BTW, an ICMP packet is not any different from a windows machine than a cisco router. The only difference is the flags/bits that you can set (ie, timestamps, redirects, size).


AnonMan

@comcast.net
reply to EG
said by EG:

said by AnonMan :

Also depends on the type of ping as a tracert and a ping in windows don't use the same packet types even.

Are you sure ?

Guess I might be wrong. Windows tracert uses ICMP type 8 but Linux is a bit different.

That said my first hop after my modem has double the latency if I do tracert vs. ping on any Windows 8 machine. So it's doing something funky. Every hop after is the same regardless.

Different OS's can use different methods. Some may use UDP, some ICMP and various other odd balls. The routers/switches on the ISP network can be configured to handle this traffic all different. It could be setup with simple QoS, it could be setup to drop after so many hits, it could be setup to only allow a max amount of traffic via that protocol regardless of available traffic or any number of things. Each type can even be setup different.

Regardless ping/tracert generally alone is not the best to say it's an issue, but can be used as a general starting point.

It's always fun troubleshooting a network you have no control or true knowledge over. Who knows what Comcast has configured lol.