| Author |
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ns
Guest
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 Posted:
Wed Dec 15, 2004 6:19 pm Post subject:
Re: Ping slow on serial interface |
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| Quote: | Your packets have to travel 6,000 miles and you think 180 ms is slow?
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.... |
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Ivan Ostreš
Guest
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| Posted:
Wed Dec 15, 2004 7:12 pm Post subject:
Re: Ping slow on serial interface |
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In article <vPTvd.4714831$yk.708332@news.easynews.com>,
jrcdehc@nospam.hotmail.com says...
| Quote: | Because that command is the default (well, 'bandwidth 1536' is), and it is
only used so EIGRP can accurately calculate its metric.
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....and for some QoS mechanisms, and for interface load counter, and
bunch of other not well-known things.
--
-Ivan.
*** Use Rot13 to see my eMail address *** |
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Guest
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| Posted:
Wed Dec 15, 2004 9:52 pm Post subject:
Re: Ping slow on serial interface |
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Hi,
"= 164/166/168 ms it's too late !!"
Thing is, if it really is too late you will *have* to move one end
nearer to the other to help.
I am in London UK and I am happy with the numbers below. The ONLY
way to change them is to move one of - me, San Jose, a university
or similar in Australia, Imperial College in London, or Syracuse
university.
None of these is going to happen anytime soon, so I have to live with
the
result:)
It is just possible that your provider is using some weird routing and
that
your sites are not really 6000 miles apart. If this is the case you
may be able to use a different one. Upgrading to a higher speed line
will
reduce the tranmission delay, but with a 2M line that is only 8ms at
each end for a 1500 byte packet anyway so it will only bring it down to
150ms if you eliminate the transmission delay altogether.
H:\>ping www.cisco.com
Pinging www.cisco.com [198.133.219.25] with 32 bytes of data:
Reply from 198.133.219.25: bytes=32 time=155ms TTL=116
Reply from 198.133.219.25: bytes=32 time=153ms TTL=116
Reply from 198.133.219.25: bytes=32 time=153ms TTL=116
Reply from 198.133.219.25: bytes=32 time=152ms TTL=116
Ping statistics for 198.133.219.25:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 152ms, Maximum = 155ms, Average = 153ms
H:\>ping flinders.edu.au
Pinging flinders.edu.au [129.96.252.36] with 32 bytes of data:
Reply from 129.96.252.36: bytes=32 time=335ms TTL=47
Reply from 129.96.252.36: bytes=32 time=333ms TTL=47
Reply from 129.96.252.36: bytes=32 time=333ms TTL=47
Reply from 129.96.252.36: bytes=32 time=333ms TTL=47
Ping statistics for 129.96.252.36:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 333ms, Maximum = 335ms, Average = 333ms
H:\>ping www.doc.ic.ac.uk
Pinging linnet.doc.ic.ac.uk [146.169.1.10] with 32 bytes of data:
Reply from 146.169.1.10: bytes=32 time=12ms TTL=48
Reply from 146.169.1.10: bytes=32 time=12ms TTL=48
Reply from 146.169.1.10: bytes=32 time=12ms TTL=48
Reply from 146.169.1.10: bytes=32 time=11ms TTL=48
Ping statistics for 146.169.1.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 11ms, Maximum = 12ms, Average = 11ms
H:\>ping www.syracuse.edu
Pinging syracuse.edu [128.230.18.35] with 32 bytes of data:
Reply from 128.230.18.35: bytes=32 time=99ms TTL=239
Reply from 128.230.18.35: bytes=32 time=96ms TTL=239
Reply from 128.230.18.35: bytes=32 time=95ms TTL=239
Reply from 128.230.18.35: bytes=32 time=97ms TTL=239
Ping statistics for 128.230.18.35:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 95ms, Maximum = 99ms, Average = 96ms |
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Toby
Guest
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| Posted:
Wed Dec 15, 2004 10:16 pm Post subject:
Re: Ping slow on serial interface |
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"Arnold Nipper" <arnold-200411@nipper.de> wrote in message
news:cpnuar$oam$1@nntp.ilk.net...
| Quote: | On 15.12.2004 00:36 Toby wrote
The speed the signal travels depends on what it is travelling through but
usually can be thought of as 70% of the speed of light through a vacuum
(dont quote me on this figure as it is your problem so I have not googled
it, thats your job). The speed of light in a vacuum though is approx
300,000km/sec at 70% speed it would equate to 210,000km. So in 180ms the
distance travelled would be 5.xx times round the earth.
If the signal travels with 210,000 km/s and if you see a RTT of 180ms, the
distance to B-Router is 210,000 * 0.18 / 2 which gives 18,900km. This is
less than half time round the earth on a great circle.
When I do a traceroute from here (Heidelberg, Germany) 180ms RTT typically
means something on the US westcoast, 100ms - 120ms is US eastcoast, APA is
something like 300ms.
Please also bear in mind that it takes some time to serialize the packet.
On slow links and with large packetsize this takes a non negligable amount
of time.
Arnold
--
Arnold Nipper, AN45
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Arnold I did my maths wrong I forgot the round trip part and multiplied in
error instead of divided the .18 (oops It had been a long day)
It doesn't alter most of my other facts though. I was trying to point out
that delays inside a service providers network at layer2 have to be taken
into account as very few companies will be able to justify the cost of a
pure point-point link over very large distances and the SP contract has to
be taken into account over a shared medium such as a Frame-relay/ATM etc
network.
My comment on serialisation was based on the service providers trunks being
usually fast and I ignored this on the local routers bandwidth as this would
be the same delay for 1mile or 20000miles of link. But you are quite right
they should be accounted for.
If I had done my maths correctly to start with I would have noticed the
distance was infact in the terrestial range and I would have added in a
serialisation factor for a slow link in my example, I didn't because no
single hop router delay with a 3% util of a link could cause the kind of
delay to make it look like 5 times round the world.
At least I can show my kids with this example why they must show there
working in there upcomming maths exam.
Thanks for the correction
Toby |
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Erik Freitag
Guest
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| Posted:
Wed Dec 15, 2004 10:25 pm Post subject:
Re: Ping slow on serial interface |
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On Wed, 15 Dec 2004 09:57:04 +0000, Jonathan wrote:
| Quote: | Which doesn't account for encapsulation, serialization delays, frame-relay
switch latency, and FRATM latency.
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Except that he said it is a point-to-point T1, which should mean there's
no switching. The only encap/decapsulation time should be at his two
routers, serialization might be an issue but I don't think the 1700s have
big enough buffers to worry about this.
| Quote: |
There is nothing wrong with his ping times.
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Except that they are a lot longer than you would expect for a short
point-to-point T1.
| Quote: | The SLA for telcos is 120ms for a 100-byte packet, end to end from our
ingress switches.
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Which telcos? My carrier has an 80ms domestic commitment within the
continental US and Europe.
| Quote: |
He is getting about 45% higher ping times for 1400% more data being sent. He
needs to calm down.
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It is not the data size causing the long round-trip times, packet size has
more to do with throughput than latency - I get better ping times going
through the Internet - he's on a point-to-point. I agree there's no reason
to panic, but maybe he has an application that depends on better times, or
maybe he's just trying to improve his latency.
router#ping
Protocol [ip]:
Target IP address: www.yahoo.com
Translating "www.yahoo.com"...domain server (24.143.128.68) [OK]
Repeat count [5]: 30
Datagram size [100]: 1500
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 30, 1500-byte ICMP Echos to 66.94.230.34, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (30/30), round-trip min/avg/max = 16/38/144 ms |
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Erik Freitag
Guest
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| Posted:
Wed Dec 15, 2004 10:26 pm Post subject:
Re: Ping slow on serial interface |
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On Wed, 15 Dec 2004 12:54:02 +0100, ns wrote:
| Quote: | DLY = 20000 usec
Circuit : PPP
more informations a bout serial interface
======================================================
MyRouterA#sh int s0
Serial0 is up, line protocol is up
Hardware is PowerQUICC Serial
Internet address is 192.168.25.10/30
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set
Keepalive set (10 sec)
Last input 00:00:03, output 00:00:00, output hang never
Last clearing of "show interface" counters 4d19h
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 16
Queueing strategy: weighted fair
Output queue: 0/1000/64/16 (size/max total/threshold/drops)
Conversations 0/13/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 1158 kilobits/sec
======================================================
Thanks a lot
NS
How far apart are these routers? Ping times reflect latency, not bandwidth
(usually). If you do a show interface serial 0 (or whatever the serial is
called), what is the delay shown? Look for DLY 20000 usec, or something
like that. What kind of circuit connects them? PRI? Frame Relay?
Point-to-Point? The bandwidth setting is used by routing protocols and
some network management tools, but does not affect your line speed or
latency.
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So, how far apart are these routers? What kind of circuit connects them? |
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Erik Freitag
Guest
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| Posted:
Wed Dec 15, 2004 10:31 pm Post subject:
Re: Ping slow on serial interface |
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On Wed, 15 Dec 2004 12:48:44 +0100, ns wrote:
| Quote: | MyRouterA is located at Paris
MyRouterB is located at San Francisco
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OK, great circle distance 5558 miles, fiber speed 124.3 miles/ms = 44 ms,
round-trip 88 ms. Given that this is the best possible time given ideal
conditions, I would say you are doing pretty well at 180 ms. |
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ns
Guest
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| Posted:
Wed Dec 15, 2004 10:40 pm Post subject:
Re: Ping slow on serial interface |
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Thanks Eric
"Erik Freitag" <erik.freitag@pobox.com> a écrit dans le message de
news:pan.2004.12.15.17.31.18.346276@pobox.com...
| Quote: | On Wed, 15 Dec 2004 12:48:44 +0100, ns wrote:
MyRouterA is located at Paris
MyRouterB is located at San Francisco
OK, great circle distance 5558 miles, fiber speed 124.3 miles/ms = 44 ms,
round-trip 88 ms. Given that this is the best possible time given ideal
conditions, I would say you are doing pretty well at 180 ms. |
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ns
Guest
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| Posted:
Wed Dec 15, 2004 10:41 pm Post subject:
Re: Ping slow on serial interface |
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How do you know that the distance is ^ 5558 miles ?
"ns" <ns@none.ns> a écrit dans le message de
news:32bb96F3ht6ueU1@individual.net...
| Quote: | Thanks Eric
"Erik Freitag" <erik.freitag@pobox.com> a écrit dans le message de
news:pan.2004.12.15.17.31.18.346276@pobox.com...
On Wed, 15 Dec 2004 12:48:44 +0100, ns wrote:
MyRouterA is located at Paris
MyRouterB is located at San Francisco
OK, great circle distance 5558 miles, fiber speed 124.3 miles/ms = 44
ms,
round-trip 88 ms. Given that this is the best possible time given ideal
conditions, I would say you are doing pretty well at 180 ms.
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ns
Guest
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| Posted:
Wed Dec 15, 2004 10:44 pm Post subject:
Re: Ping slow on serial interface |
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| Quote: | So, how far apart are these routers?
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sorry, i don't understand your question
| Quote: | What kind of circuit connects them?
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PPP |
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Erik Freitag
Guest
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ns
Guest
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| Posted:
Wed Dec 15, 2004 11:34 pm Post subject:
Re: Ping slow on serial interface |
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Thank a lot!!
"Erik Freitag" <erik.freitag@pobox.com> a écrit dans le message de
news:pan.2004.12.15.17.53.12.77447@pobox.com...
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Arnold Nipper
Guest
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| Posted:
Thu Dec 16, 2004 1:40 am Post subject:
Re: Ping slow on serial interface |
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On 15.12.2004 12:58 ns wrote
| Quote: | I tested with default datagram size (100), 1400 and 1500 and i have
the same result. I tested with option "Set DF bit in IP header? [no]:
yes" and i have the same result
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Not so astonishing as the difference to serialize a 1500 byte packet vs.
a 100 byte packet on a T1 is only 7.2 ms
This is by far outweighted by the time to get from Paris, EU to SFO.
Arnold
--
Arnold Nipper, AN45 |
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Barry Margolin
Guest
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| Posted:
Thu Dec 16, 2004 4:07 am Post subject:
Re: Ping slow on serial interface |
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In article <pan.2004.12.15.17.25.26.382852@pobox.com>,
Erik Freitag <erik.freitag@pobox.com> wrote:
| Quote: | On Wed, 15 Dec 2004 09:57:04 +0000, Jonathan wrote:
Which doesn't account for encapsulation, serialization delays, frame-relay
switch latency, and FRATM latency.
Except that he said it is a point-to-point T1, which should mean there's
no switching. The only encap/decapsulation time should be at his two
routers, serialization might be an issue but I don't think the 1700s have
big enough buffers to worry about this.
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He said it's going from Paris to San Francisco. There may not be any
routers in the path, but there are almost certainly several telco
switches. I don't think you can buy a direct, physical connection
that's 6,000 miles long (including a transatlantic link).
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA |
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Erik Freitag
Guest
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| Posted:
Thu Dec 16, 2004 4:19 am Post subject:
Re: Ping slow on serial interface |
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On Wed, 15 Dec 2004 18:07:53 -0500, Barry Margolin wrote:
| Quote: | In article <pan.2004.12.15.17.25.26.382852@pobox.com>,
Erik Freitag <erik.freitag@pobox.com> wrote:
On Wed, 15 Dec 2004 09:57:04 +0000, Jonathan wrote:
Which doesn't account for encapsulation, serialization delays, frame-relay
switch latency, and FRATM latency.
Except that he said it is a point-to-point T1, which should mean there's
no switching. The only encap/decapsulation time should be at his two
routers, serialization might be an issue but I don't think the 1700s have
big enough buffers to worry about this.
He said it's going from Paris to San Francisco. There may not be any
routers in the path, but there are almost certainly several telco
switches. I don't think you can buy a direct, physical connection
that's 6,000 miles long (including a transatlantic link).
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Sure, but when someone says point-to-point, I usually envision something
like a DACS, not a F/R switch. A DACS may not switch very fast, but it
doesn't do it very often. I agree there will be latency at each
intermediate wiring center for his path. |
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