Curious question on hop identity...

Thu Dec 14 18:57:21 UTC 2006

Bah, Humbug.  Optical taps don't decrement TTLs or generate ICMP packets.

San Francisco Bay Area cable modem networks have transitioned from 
@Home to AT&T Broadband to Comcast, so there is probably all sorts of 
expedient things done to keep it working through those transitions and 
IP addresses and IN-ADDR.ARPA files don't always align with how routers 
were divided up when companies buy/sell/exchange networks.  There are 
probably still networks in NCR/Lucent/Olivette/AT&T that have odd IP
addresses from various mergers and splits over the years.

Occam's razor suggests those two hops are two routers in San Francisco 
connecting Comcast regional network to the AT&T common IP backbone for
transit to AT&T's peering connections with other Internet backbones.

Besides, why do you believe the text in an in-addr.arpa record?  Or why do 
you think the absence of an in-addr.arpa record is meaningful?

On Thu, 14 Dec 2006, bmanning at karoshi.com wrote:
> i'm sure someone knows -exactly- what those two hops are, but they may
> not be willing to say.
> http://lists.elistx.com/archives/interesting-people/200605/msg00250.html
> might be an explaination for the paranoid.
>
> On Thu, Dec 14, 2006 at 07:24:52AM +0000, Fergie wrote:
>>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> This may be far afield insofar as topic fodder, but I am curious
>> if anyone knows exactly what these two hops [9] [10] below,
>> actually are?
>>
>> [snip]
>>
>>  [...]
>>
>>   5   165 ms   161 ms   183 ms  10g-9-1-ur04.sanjose.ca.sfba.comcast.net
>> [68.87.
>> 192.49]
>>   6   155 ms   156 ms   149 ms  10g-7-1-ur03.sanjose.ca.sfba.comcast.net
>> [68.87.
>> 192.41]
>>   7     *        *      163 ms  10g-9-1-ar01.sfsutro.ca.sfba.comcast.net
>> [68.87.
>> 192.37]
>>   8   161 ms   157 ms     *     68.87.226.130
>>   9   169 ms   185 ms   171 ms  12.116.90.17
>>  10   197 ms   198 ms   196 ms  12.122.114.66
>>  11   157 ms   169 ms   175 ms  ggr3-ge110.sffca.ip.att.net [12.122.82.169]
>>  12   145 ms   149 ms   148 ms  192.205.33.82
>>  13   182 ms   196 ms   209 ms  ae-2-54.bbr2.SanJose1.Level3.net
>> [4.68.123.97]
>>  14   344 ms   332 ms   339 ms  as-0-0.mp2.Stockholm1.Level3.net
>> [4.68.128.70]
>>  15   330 ms   343 ms   390 ms  ge-1-1.car2.Stockholm1.Level3.net
>> [4.68.96.226]
>>
>>  [...]
>>
>>
>> [snip]
>>
>> I have asked SBC/AT&T folks and received no reply at all...
>>
>> Cheers,
>>
>> - - ferg
>>
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>> wj8DBQFFgPw+q1pz9mNUZTMRAiFEAJ9y481aCutAqVuQrLcMPa3iC6SoXwCgigNC
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>>
>> --
>> "Fergie", a.k.a. Paul Ferguson
>>  Engineering Architecture for the Internet
>>  fergdawg(at)netzero.net
>>  ferg's tech blog: http://fergdawg.blogspot.com/
>>
>