Switched ISP

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Switched ISP

Robert A Wooldridge
We recently switched to ATT from Windstream.  After the switch there is
a very large difference between accessing sites through squid compared
to bypassing squid (squid is slower).  However it is not completely
uniform.  Some sites are extremely slow and do not load at all.
news.yahoo.com is an example.  Is there anything I should be aware of
when switching to a different ISP?  Would the lack of a PTR record on
the proxy server have any effect on this? Should I clear squid's cache?

Thanks?

--
Bob Wooldridge
EDM Incorporated

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Re: Switched ISP

Alex Rousskov
On 12/30/19 4:08 PM, Robert A Wooldridge wrote:
> We recently switched to ATT from Windstream.  After the switch there is
> a very large difference between accessing sites through squid compared
> to bypassing squid (squid is slower).  However it is not completely
> uniform.  Some sites are extremely slow and do not load at all.
> news.yahoo.com is an example.  Is there anything I should be aware of
> when switching to a different ISP?  Would the lack of a PTR record on
> the proxy server have any effect on this? Should I clear squid's cache?

0. A lack of PTR record will slow down origin servers that try to
resolve your proxy IP address and (slowly?) fail. I do not know how
typical such sites are.

1. Are the problems related to sites that have IPv6 addresses (even
though access.log may show IPv4 transactions)? YMMV, but some ISP
networks enable IPv6 while not supporting it well, leading to random
IPv6 connection establishment timeouts.

2. Are you using AT&T's DNS resolver? YMMV, but some ISP DNS resolvers
overwrite NXDOMAIN responses. Such overwrites might have unexpected side
effects on complex sites.

Your best bet may be in triaging a single easier-to-reproduce problem
and extrapolating from there.

AFAICT, it should not be necessary to purge Squid's cache when switching
ISPs, but you can easily test by setting that cache aside and starting
Squid without it.


HTH,

Alex.
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Re: Switched ISP

Amos Jeffries
Administrator
On 31/12/19 11:51 am, Alex Rousskov wrote:

> On 12/30/19 4:08 PM, Robert A Wooldridge wrote:
>> We recently switched to ATT from Windstream.  After the switch there is
>> a very large difference between accessing sites through squid compared
>> to bypassing squid (squid is slower).  However it is not completely
>> uniform.  Some sites are extremely slow and do not load at all.
>> news.yahoo.com is an example.  Is there anything I should be aware of
>> when switching to a different ISP?  Would the lack of a PTR record on
>> the proxy server have any effect on this? Should I clear squid's cache?
>
> 0. A lack of PTR record will slow down origin servers that try to
> resolve your proxy IP address and (slowly?) fail. I do not know how
> typical such sites are.
>
> 1. Are the problems related to sites that have IPv6 addresses (even
> though access.log may show IPv4 transactions)? YMMV, but some ISP
> networks enable IPv6 while not supporting it well, leading to random
> IPv6 connection establishment timeouts.
>
> 2. Are you using AT&T's DNS resolver? YMMV, but some ISP DNS resolvers
> overwrite NXDOMAIN responses. Such overwrites might have unexpected side
> effects on complex sites.
>

Of Googles 8.8.8.8 resolver? it produces different types of result based
on where one queries from.

There is also the possibility of route engineering by the two ISP being
different for some destination networks. That could changes some traffic
in ways that are visible on inspection.

Or also on the network layer side of things oddities in the particular
routers each ISP uses may result in differences in MTU, ECN etc handling
that also affects some traffic routes in different ways for each of the
two ISP.

Amos
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