Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

2020-02-04 Thread chuck 
They booked all those disks as assets.

From: Ken Hohhof 
Sent: Tuesday, February 4, 2020 10:41 AM
To: 'AnimalFarm Microwave Users Group' 
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

I’m a boomer and I wouldn’t use AOL.  I remember when they mailed out tons of 
signup discs though, that people used as Christmas tree ornaments and drink 
coasters.

 

But yeah, he’s an older gent.  I was impressed though, his computer was on 
Windows 10.  I was expecting 98 or Vista or something.

 

Remember when people would launch the AOL software instead of using IE or 
Netscape?


 

From: AF  On Behalf Of Steven Kenney
Sent: Tuesday, February 4, 2020 11:29 AM
To: af 
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

All modern devices yes.  But in the past I've seen it on older windows machines 
I had to manually set it.  Especially if you are talking about someone still 
using AOL they must be a boomer :) 

 

-- 
Steven Kenney
Network Operations Manager
WaveDirect Telecommunications
http://www.wavedirect.net
(519)737-WAVE (9283)

 




From: "Ken Hohhof" 
To: "af" 
Sent: Monday, February 3, 2020 4:32:04 PM
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

I don’t think anyone changes settings on the Ethernet or WiFi connection on 
their PC, the router is responsible for rewriting the advertised MSS in the TCP 
SYN packets.  So the PC advertises MSS=1460, that gets changed to 1452 or 
lower.  (MSS = MTU-40)

 

From: AF  On Behalf Of Steven Kenney
Sent: Monday, February 3, 2020 1:57 PM
To: af 
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

Something to consider.  Their operating system and devices also need to be set 
lower.  If the PC is still at 1492 and the router is lower it will cause 
issues.  I've seen this before. 

 

How these routers are using anything lower than 1492 is interesting. 

 

-- 
Steven Kenney
Network Operations Manager
WaveDirect Telecommunications
http://www.wavedirect.net
(519)737-WAVE (9283)

 




From: "Ken Hohhof" 
To: "af" 
Sent: Monday, February 3, 2020 2:28:04 PM
Subject: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

We have used both Mikrotik and Cisco tower routers as PPPoE servers for several 
years, but have recently been swapping out the remaining Ciscos.  I have run 
into a strange problem that I’m hoping somebody here knows the answer.

 

We have the max MTU and MRU set to 1492 on the PPPoE server, but in the list of 
dynamically created interfaces some of them show up as 1480, 1454, etc.  I 
didn’t think much of this because I know some router manufacturers have those 
as default settings.  If the client router wants a lower MTU, that should be OK 
as long as it clamps MSS advertisements to the lower value.  (I don’t want to 
get into MSS clamping at the server side.)

 

But I ran into a customer with an old DLink router and he was unable to get to 
www.aol.com, other websites and speedtests worked OK.  Grasping at straws, I 
had him log into his DLink to see what the MTU setting was.  It was set 
manually to 1492, the menu did not have an option to negotiate MTU 
automatically.  I had him change it to 1480 and that solved his problem.

 

I don’t want to get too deep into solving a problem with an old DLink router, 
but I’m wondering if I’ve got something configured wrong.

 

I assume if the Mikrotik PPPoE server has the PPPoE virtual interface MRU set 
to 1480, that means it won’t receive packets larger than 1480 (plus PPPoE 
headers).  Why are a few sessions getting MRU lower than 1492?  I assume that 
is what the client insists on during PPPoE negotiation?  And if so, why would a 
router with MTU set to 1492, and that appears to be doing MSS clamping based on 
1492, negotiate 1480 with the server?

 

 

And why would Mikrotik be handling this different than Cisco?  I don’t think I 
ever saw an MTU different from 1492 in the Cisco virtual interface properties.

 

I know occasionally (very rarely) I’ve had a customer say one particular 
website won’t come up, I think I had somebody complain about Yahoo once.  Now 
I’m wondering if that was an MTU problem also.  But I don’t really see anything 
under my control at the server end to fix this, other than maybe to set max MRU 
lower like 1450 or something.  I don’t really want to do that, because it would 
mean less efficiency (fewer data bytes per packet) for no apparent good reason. 
 All clients should be able to use 1492 (1500 minus 8 overhead bytes), and if 
for some reason they want a lower MTU, that should be OK as long as they clamp 
MSS advertisements to that lower number.

 


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Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

2020-02-04 Thread Ken Hohhof 
I’m a boomer and I wouldn’t use AOL.  I remember when they mailed out tons of 
signup discs though, that people used as Christmas tree ornaments and drink 
coasters.

 

But yeah, he’s an older gent.  I was impressed though, his computer was on 
Windows 10.  I was expecting 98 or Vista or something.

 

Remember when people would launch the AOL software instead of using IE or 
Netscape?

 

From: AF  On Behalf Of Steven Kenney
Sent: Tuesday, February 4, 2020 11:29 AM
To: af 
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

All modern devices yes.  But in the past I've seen it on older windows machines 
I had to manually set it.  Especially if you are talking about someone still 
using AOL they must be a boomer :) 

 

-- 
Steven Kenney
Network Operations Manager
WaveDirect Telecommunications
http://www.wavedirect.net
(519)737-WAVE (9283)

 

  _  

From: "Ken Hohhof" mailto:af...@kwisp.com> >
To: "af" mailto:af@af.afmug.com> >
Sent: Monday, February 3, 2020 4:32:04 PM
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

I don’t think anyone changes settings on the Ethernet or WiFi connection on 
their PC, the router is responsible for rewriting the advertised MSS in the TCP 
SYN packets.  So the PC advertises MSS=1460, that gets changed to 1452 or 
lower.  (MSS = MTU-40)

 

From: AF mailto:af-boun...@af.afmug.com> > On Behalf 
Of Steven Kenney
Sent: Monday, February 3, 2020 1:57 PM
To: af mailto:af@af.afmug.com> >
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

Something to consider.  Their operating system and devices also need to be set 
lower.  If the PC is still at 1492 and the router is lower it will cause 
issues.  I've seen this before. 

 

How these routers are using anything lower than 1492 is interesting. 

 

-- 
Steven Kenney
Network Operations Manager
WaveDirect Telecommunications
http://www.wavedirect.net
(519)737-WAVE (9283)

 

  _  

From: "Ken Hohhof" mailto:af...@kwisp.com> >
To: "af" mailto:af@af.afmug.com> >
Sent: Monday, February 3, 2020 2:28:04 PM
Subject: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

We have used both Mikrotik and Cisco tower routers as PPPoE servers for several 
years, but have recently been swapping out the remaining Ciscos.  I have run 
into a strange problem that I’m hoping somebody here knows the answer.

 

We have the max MTU and MRU set to 1492 on the PPPoE server, but in the list of 
dynamically created interfaces some of them show up as 1480, 1454, etc.  I 
didn’t think much of this because I know some router manufacturers have those 
as default settings.  If the client router wants a lower MTU, that should be OK 
as long as it clamps MSS advertisements to the lower value.  (I don’t want to 
get into MSS clamping at the server side.)

 

But I ran into a customer with an old DLink router and he was unable to get to 
www.aol.com <http://www.aol.com> , other websites and speedtests worked OK.  
Grasping at straws, I had him log into his DLink to see what the MTU setting 
was.  It was set manually to 1492, the menu did not have an option to negotiate 
MTU automatically.  I had him change it to 1480 and that solved his problem.

 

I don’t want to get too deep into solving a problem with an old DLink router, 
but I’m wondering if I’ve got something configured wrong.

 

I assume if the Mikrotik PPPoE server has the PPPoE virtual interface MRU set 
to 1480, that means it won’t receive packets larger than 1480 (plus PPPoE 
headers).  Why are a few sessions getting MRU lower than 1492?  I assume that 
is what the client insists on during PPPoE negotiation?  And if so, why would a 
router with MTU set to 1492, and that appears to be doing MSS clamping based on 
1492, negotiate 1480 with the server?

 

 

And why would Mikrotik be handling this different than Cisco?  I don’t think I 
ever saw an MTU different from 1492 in the Cisco virtual interface properties.

 

I know occasionally (very rarely) I’ve had a customer say one particular 
website won’t come up, I think I had somebody complain about Yahoo once.  Now 
I’m wondering if that was an MTU problem also.  But I don’t really see anything 
under my control at the server end to fix this, other than maybe to set max MRU 
lower like 1450 or something.  I don’t really want to do that, because it would 
mean less efficiency (fewer data bytes per packet) for no apparent good reason. 
 All clients should be able to use 1492 (1500 minus 8 overhead bytes), and if 
for some reason they want a lower MTU, that should be OK as long as they clamp 
MSS advertisements to that lower number.

 


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Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

2020-02-04 Thread Steven Kenney 
All modern devices yes. But in the past I've seen it on older windows machines 
I had to manually set it. Especially if you are talking about someone still 
using AOL they must be a boomer :) 

-- 
Steven Kenney 
Network Operations Manager 
WaveDirect Telecommunications 
http://www.wavedirect.net 
(519)737-WAVE (9283) 


From: "Ken Hohhof"  
To: "af"  
Sent: Monday, February 3, 2020 4:32:04 PM 
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU 



I don’t think anyone changes settings on the Ethernet or WiFi connection on 
their PC, the router is responsible for rewriting the advertised MSS in the TCP 
SYN packets. So the PC advertises MSS=1460, that gets changed to 1452 or lower. 
(MSS = MTU-40) 




From: AF  On Behalf Of Steven Kenney 
Sent: Monday, February 3, 2020 1:57 PM 
To: af  
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU 





Something to consider. Their operating system and devices also need to be set 
lower. If the PC is still at 1492 and the router is lower it will cause issues. 
I've seen this before. 





How these routers are using anything lower than 1492 is interesting. 





-- 
Steven Kenney 
Network Operations Manager 
WaveDirect Telecommunications 
[ http://www.wavedirect.net/ | http://www.wavedirect.net ] 
(519)737-WAVE (9283) 






From: "Ken Hohhof" < [ mailto:af...@kwisp.com | af...@kwisp.com ] > 
To: "af" < [ mailto:af@af.afmug.com | af@af.afmug.com ] > 
Sent: Monday, February 3, 2020 2:28:04 PM 
Subject: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU 





We have used both Mikrotik and Cisco tower routers as PPPoE servers for several 
years, but have recently been swapping out the remaining Ciscos. I have run 
into a strange problem that I’m hoping somebody here knows the answer. 



We have the max MTU and MRU set to 1492 on the PPPoE server, but in the list of 
dynamically created interfaces some of them show up as 1480, 1454, etc. I 
didn’t think much of this because I know some router manufacturers have those 
as default settings. If the client router wants a lower MTU, that should be OK 
as long as it clamps MSS advertisements to the lower value. (I don’t want to 
get into MSS clamping at the server side.) 



But I ran into a customer with an old DLink router and he was unable to get to 
[ http://www.aol.com/ | www.aol.com ] , other websites and speedtests worked 
OK. Grasping at straws, I had him log into his DLink to see what the MTU 
setting was. It was set manually to 1492, the menu did not have an option to 
negotiate MTU automatically. I had him change it to 1480 and that solved his 
problem. 



I don’t want to get too deep into solving a problem with an old DLink router, 
but I’m wondering if I’ve got something configured wrong. 



I assume if the Mikrotik PPPoE server has the PPPoE virtual interface MRU set 
to 1480, that means it won’t receive packets larger than 1480 (plus PPPoE 
headers). Why are a few sessions getting MRU lower than 1492? I assume that is 
what the client insists on during PPPoE negotiation? And if so, why would a 
router with MTU set to 1492, and that appears to be doing MSS clamping based on 
1492, negotiate 1480 with the server? 





And why would Mikrotik be handling this different than Cisco? I don’t think I 
ever saw an MTU different from 1492 in the Cisco virtual interface properties. 



I know occasionally (very rarely) I’ve had a customer say one particular 
website won’t come up, I think I had somebody complain about Yahoo once. Now 
I’m wondering if that was an MTU problem also. But I don’t really see anything 
under my control at the server end to fix this, other than maybe to set max MRU 
lower like 1450 or something. I don’t really want to do that, because it would 
mean less efficiency (fewer data bytes per packet) for no apparent good reason. 
All clients should be able to use 1492 (1500 minus 8 overhead bytes), and if 
for some reason they want a lower MTU, that should be OK as long as they clamp 
MSS advertisements to that lower number. 




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http://af.afmug.com/mailman/listinfo/af_af.afmug.com ] 

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Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

2020-02-03 Thread Ken Hohhof 
I don’t think anyone changes settings on the Ethernet or WiFi connection on 
their PC, the router is responsible for rewriting the advertised MSS in the TCP 
SYN packets.  So the PC advertises MSS=1460, that gets changed to 1452 or 
lower.  (MSS = MTU-40)

 

From: AF  On Behalf Of Steven Kenney
Sent: Monday, February 3, 2020 1:57 PM
To: af 
Subject: Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

Something to consider.  Their operating system and devices also need to be set 
lower.  If the PC is still at 1492 and the router is lower it will cause 
issues.  I've seen this before. 

 

How these routers are using anything lower than 1492 is interesting. 

 

-- 
Steven Kenney
Network Operations Manager
WaveDirect Telecommunications
http://www.wavedirect.net
(519)737-WAVE (9283)

 

  _  

From: "Ken Hohhof" mailto:af...@kwisp.com> >
To: "af" mailto:af@af.afmug.com> >
Sent: Monday, February 3, 2020 2:28:04 PM
Subject: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

 

We have used both Mikrotik and Cisco tower routers as PPPoE servers for several 
years, but have recently been swapping out the remaining Ciscos.  I have run 
into a strange problem that I’m hoping somebody here knows the answer.

 

We have the max MTU and MRU set to 1492 on the PPPoE server, but in the list of 
dynamically created interfaces some of them show up as 1480, 1454, etc.  I 
didn’t think much of this because I know some router manufacturers have those 
as default settings.  If the client router wants a lower MTU, that should be OK 
as long as it clamps MSS advertisements to the lower value.  (I don’t want to 
get into MSS clamping at the server side.)

 

But I ran into a customer with an old DLink router and he was unable to get to 
www.aol.com <http://www.aol.com> , other websites and speedtests worked OK.  
Grasping at straws, I had him log into his DLink to see what the MTU setting 
was.  It was set manually to 1492, the menu did not have an option to negotiate 
MTU automatically.  I had him change it to 1480 and that solved his problem.

 

I don’t want to get too deep into solving a problem with an old DLink router, 
but I’m wondering if I’ve got something configured wrong.

 

I assume if the Mikrotik PPPoE server has the PPPoE virtual interface MRU set 
to 1480, that means it won’t receive packets larger than 1480 (plus PPPoE 
headers).  Why are a few sessions getting MRU lower than 1492?  I assume that 
is what the client insists on during PPPoE negotiation?  And if so, why would a 
router with MTU set to 1492, and that appears to be doing MSS clamping based on 
1492, negotiate 1480 with the server?

 

 

And why would Mikrotik be handling this different than Cisco?  I don’t think I 
ever saw an MTU different from 1492 in the Cisco virtual interface properties.

 

I know occasionally (very rarely) I’ve had a customer say one particular 
website won’t come up, I think I had somebody complain about Yahoo once.  Now 
I’m wondering if that was an MTU problem also.  But I don’t really see anything 
under my control at the server end to fix this, other than maybe to set max MRU 
lower like 1450 or something.  I don’t really want to do that, because it would 
mean less efficiency (fewer data bytes per packet) for no apparent good reason. 
 All clients should be able to use 1492 (1500 minus 8 overhead bytes), and if 
for some reason they want a lower MTU, that should be OK as long as they clamp 
MSS advertisements to that lower number.

 


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http://af.afmug.com/mailman/listinfo/af_af.afmug.com

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Re: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

2020-02-03 Thread Steven Kenney 
Something to consider. Their operating system and devices also need to be set 
lower. If the PC is still at 1492 and the router is lower it will cause issues. 
I've seen this before. 

How these routers are using anything lower than 1492 is interesting. 

-- 
Steven Kenney 
Network Operations Manager 
WaveDirect Telecommunications 
http://www.wavedirect.net 
(519)737-WAVE (9283) 


From: "Ken Hohhof"  
To: "af"  
Sent: Monday, February 3, 2020 2:28:04 PM 
Subject: [AFMUG] question re: Mikrotik PPPoE server and MRU/MTU 



We have used both Mikrotik and Cisco tower routers as PPPoE servers for several 
years, but have recently been swapping out the remaining Ciscos. I have run 
into a strange problem that I’m hoping somebody here knows the answer. 



We have the max MTU and MRU set to 1492 on the PPPoE server, but in the list of 
dynamically created interfaces some of them show up as 1480, 1454, etc. I 
didn’t think much of this because I know some router manufacturers have those 
as default settings. If the client router wants a lower MTU, that should be OK 
as long as it clamps MSS advertisements to the lower value. (I don’t want to 
get into MSS clamping at the server side.) 



But I ran into a customer with an old DLink router and he was unable to get to 
[ http://www.aol.com/ | www.aol.com ] , other websites and speedtests worked 
OK. Grasping at straws, I had him log into his DLink to see what the MTU 
setting was. It was set manually to 1492, the menu did not have an option to 
negotiate MTU automatically. I had him change it to 1480 and that solved his 
problem. 



I don’t want to get too deep into solving a problem with an old DLink router, 
but I’m wondering if I’ve got something configured wrong. 



I assume if the Mikrotik PPPoE server has the PPPoE virtual interface MRU set 
to 1480, that means it won’t receive packets larger than 1480 (plus PPPoE 
headers). Why are a few sessions getting MRU lower than 1492? I assume that is 
what the client insists on during PPPoE negotiation? And if so, why would a 
router with MTU set to 1492, and that appears to be doing MSS clamping based on 
1492, negotiate 1480 with the server? 





And why would Mikrotik be handling this different than Cisco? I don’t think I 
ever saw an MTU different from 1492 in the Cisco virtual interface properties. 



I know occasionally (very rarely) I’ve had a customer say one particular 
website won’t come up, I think I had somebody complain about Yahoo once. Now 
I’m wondering if that was an MTU problem also. But I don’t really see anything 
under my control at the server end to fix this, other than maybe to set max MRU 
lower like 1450 or something. I don’t really want to do that, because it would 
mean less efficiency (fewer data bytes per packet) for no apparent good reason. 
All clients should be able to use 1492 (1500 minus 8 overhead bytes), and if 
for some reason they want a lower MTU, that should be OK as long as they clamp 
MSS advertisements to that lower number. 



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[AFMUG] question re: Mikrotik PPPoE server and MRU/MTU

2020-02-03 Thread Ken Hohhof 
We have used both Mikrotik and Cisco tower routers as PPPoE servers for
several years, but have recently been swapping out the remaining Ciscos.  I
have run into a strange problem that I'm hoping somebody here knows the
answer.

 

We have the max MTU and MRU set to 1492 on the PPPoE server, but in the list
of dynamically created interfaces some of them show up as 1480, 1454, etc.
I didn't think much of this because I know some router manufacturers have
those as default settings.  If the client router wants a lower MTU, that
should be OK as long as it clamps MSS advertisements to the lower value.  (I
don't want to get into MSS clamping at the server side.)

 

But I ran into a customer with an old DLink router and he was unable to get
to www.aol.com  , other websites and speedtests worked
OK.  Grasping at straws, I had him log into his DLink to see what the MTU
setting was.  It was set manually to 1492, the menu did not have an option
to negotiate MTU automatically.  I had him change it to 1480 and that solved
his problem.

 

I don't want to get too deep into solving a problem with an old DLink
router, but I'm wondering if I've got something configured wrong.

 

I assume if the Mikrotik PPPoE server has the PPPoE virtual interface MRU
set to 1480, that means it won't receive packets larger than 1480 (plus
PPPoE headers).  Why are a few sessions getting MRU lower than 1492?  I
assume that is what the client insists on during PPPoE negotiation?  And if
so, why would a router with MTU set to 1492, and that appears to be doing
MSS clamping based on 1492, negotiate 1480 with the server?

 

 

And why would Mikrotik be handling this different than Cisco?  I don't think
I ever saw an MTU different from 1492 in the Cisco virtual interface
properties.

 

I know occasionally (very rarely) I've had a customer say one particular
website won't come up, I think I had somebody complain about Yahoo once.
Now I'm wondering if that was an MTU problem also.  But I don't really see
anything under my control at the server end to fix this, other than maybe to
set max MRU lower like 1450 or something.  I don't really want to do that,
because it would mean less efficiency (fewer data bytes per packet) for no
apparent good reason.  All clients should be able to use 1492 (1500 minus 8
overhead bytes), and if for some reason they want a lower MTU, that should
be OK as long as they clamp MSS advertisements to that lower number.

 

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