Re: L3 DSR

It's been a while, but, here's the typical way I've always know how to do
DSR:

 

You configure your server to have both a valid network IP within its network
AND the ip address of your VIP from the ADC that your client is connecting
to.  When the packet comes in the ADC doesn't change anything but forwards
it on to the appropriate server.  In order for this to work, you need to
route the packet to the server as if it is the next hop router.  When it
sees a destination address (VIP) that it also owns, it replies and uses that
IP as the source.

 

Now-if you separate the server from the load balancer via another router-you
are going to have to convince that router to route VIA the node you
selected.  You have to trick that router into thinking that everyone of your
servers are a valid route path to the VIP and to pick the one the load
balancer wanted.  Now, I'm sure there are probably ways to do this, but I
don't know of any easy ones off hand-you start getting into some very real
network voodoo IMHO.  And the real question is why would you want to/need to
do that? 

 

The other way I've seen-for http anyway-is for the load balance to select a
node and issue a redirect directly to that node instead of forwarding the
packet.  You lose ALL control of the communications, but that works-and as
longs as you account for NAT and such-it doesn't matter where the servers
are-they could even be on another site.

 

 

KJ (Ken) Salchow, Jr.  |  Manager, Technical Marketing

 

From: [email protected] [mailto:[email protected]] On Behalf Of
zep k
Sent: Tuesday, March 31, 2009 1:40 AM
To: Load Balancing Mailing List
Subject: Re: [load balancing] L3 DSR

 

SungLyeol

 

As we all know, DSR means a way of returning packets to clients. Weather
they flow back thru LB or directly to clients.

For direct return, LB should forward packets to server without chaning ip
address. 

For this forwarding method, MAC based communication should be used. Anyone
know other tech?

 

>From the discription you did below, 

Servers reside on different network. How does the LB forward packets to
Servers?

Are you asking if there is another method other than MAC communication for
DSR?

 

We need correct description.

 

Regards

Alex

 

 

 

 

2009/3/31 SungLyeol Choi <[email protected]>

Hello.

 

I think those are normal DSR even though L4 is connect to L3 and has two
different network.

my question was 

 

Clients

   |
   |       <http://192.168.10.0/24> 192.168.10.0/24, VIP : 192.168.10.100
   |

L2 or L3-SW ==== L4 SW
   |
   |      172.16.10.1/24 

L3 SW

   l
   |        <http://10.10.10.0/24> 10.10.10.0/24
Servers

 

it means Server should be located in other network. my customer told me some
vendors mentioned that.

in this topology L4 should send client traffic to Server by L3 SW.

 

thanks.

 

 

Date: Mon, 30 Mar 2009 10:22:50 -0700 (PDT)
From: Surya ARBY < <mailto:[email protected]> [email protected]>
Subject: Re: [load balancing] L3 DSR
To: Load Balancing Mailing List < <mailto:[email protected]> [email protected]>
Message-ID: < <mailto:[email protected]>
[email protected]>
Content-Type: text/plain; charset="utf-8" 



Hello.

I guess it protects against L2 broadcast because you can build L2 isolation
by constraining? return traffic to go to the routing point of the network,
thus limiting flooding, that's the only sense I take from the sentence :)

Surya

--- En date de?: Lun 30.3.09, Kenneth Salchow < <mailto:[email protected]>
[email protected]> a ?crit?: 


De: Kenneth Salchow < <mailto:[email protected]> [email protected]>
Objet: Re: [load balancing] L3 DSR
?: "Load Balancing Mailing List" < <mailto:[email protected]> [email protected]>
Date: Lundi 30 Mars 2009, 17h59












Maybe I?m forgetting something, but I believe *all*
DSR (direct server return) is L3.? L2 DSR wouldn?t be too useful
unless you had one really, really big, flat, private network, would it?

 ?

Most vendors support this type of configuration in one way or
the other?but I also don?t know of any that recommend the

configuration, except for very specific circumstances.? But?even in 


video streaming these days, there are benefits to running the traffic back
through
the ADC in order to manage out-bound traffic flow?and there are plenty of
boxes that can handle the throughput.

 ?

So?when you talk about ?protecting L2 Broadcast??what
exactly are you trying to do and why?

 ?

--and, if I?m being complete silly, please forgive me?it
is Monday morning.? J

 ?

KJ (Ken) Salchow, Jr.??|??Manager,
Technical Marketing

 ?



From:  <mailto:[email protected]> [email protected]
[mailto: <mailto:[email protected]> [email protected]] On Behalf
Of SungLyeol Choi

Sent: Monday, March 30, 2009 9:46 AM

To:  <mailto:[email protected]> [email protected]

Subject: [load balancing] L3 DSR




 ? 



Hi guys.



 ?





Have you heard about L3 DSR?





which vendors support this?





I heard L3 DSR could protect L2
broadcast. but I think LB should consider a lot of things to support that.





 ?





Thanks.







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Message: 2
Date: Mon, 30 Mar 2009 10:25:39 -0700
From: Joo Yong-Seok < <mailto:[email protected]>
[email protected]>
Subject: Re: [load balancing] L3 DSR
To: Load Balancing Mailing List < <mailto:[email protected]> [email protected]>
Message-ID:
       <
<mailto:[email protected]>
[email protected]>
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I suppsoe that L2 or L3 config doesn't matter. the important thing in DSR is
"returning packet" should
not be forwarded to L4 and L4 should not do any processing for that.

Clients
   |
   |       <http://192.168.10.0/24> 192.168.10.0/24, VIP : 192.168.10.100
   |
L3-SW ==== L4 SW
   |
   |
   |        <http://10.10.10.0/24> 10.10.10.0/24
Servers

In this topoloty, L4 can have two interfaces for  <http://192.168.10.0/24>
192.168.10.0/24 and
 <http://10.10.10.0/24> 10.10.10.0/24. In Servers point of
view, GW should be L3-SW. Client requests will be forwarded to L3 but L3
knows the VIP location (L4)
and it will forward the request via L2-fwd.

L4 will do a client processing and send the packet to Servers. In this
moment, DSR should be enabled
and request packet's DIP is not modified. and Server will received the
packet and then forward it to L3-SW
since L3-SW is a gateway for servers.

I suppose that this is L3 DSR and return packet will not traverse to L4.

Also, L4-SW is in the same network with servers, health check by using
real-mac (VIPhealth) is also
working and No mac flapping. (Since L4 is doing L3 fwd + L4 processing and
packet's SIP should be
modified. L3-SW will not have any duplicate mac-address entry in the fdb. -
Even there are same mac
in fdb, if VLAN is different, there should be no issues to do a L2-fwd).

I have no idea why L2 broadcast issue is there on DSR. (do you mean
"mac-flapping"? - this can cause
flooding in the network).

Best regards,

- yongseok

2009/3/30 SungLyeol Choi < <mailto:[email protected]> [email protected]>

> Hi guys.
> Have you heard about L3 DSR?
> which vendors support this?
> I heard L3 DSR could protect L2 broadcast. but I think LB should consider
a
> lot of things to support that.
>
> Thanks.
>
> _______________________________________________
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Message: 3
Date: Mon, 30 Mar 2009 10:43:17 -0700
From: Joo Yong-Seok < <mailto:[email protected]>
[email protected]>
Subject: Re: [load balancing] L3 DSR
To: Load Balancing Mailing List < <mailto:[email protected]> [email protected]>
Message-ID:
       <
<mailto:[email protected]>
[email protected]>
Content-Type: text/plain; charset="iso-8859-1" 



There is TYPO.

SIP ---> SMAC.

Best regards,

- yongseok

On Mon, Mar 30, 2009 at 10:25 AM, Joo Yong-Seok <
<mailto:[email protected]> [email protected]>wrote:

> I suppsoe that L2 or L3 config doesn't matter. the important thing in DSR
> is "returning packet" should
> not be forwarded to L4 and L4 should not do any processing for that.
>
> Clients
>     |
>     |       <http://192.168.10.0/24> 192.168.10.0/24, VIP : 192.168.10.100
>     |
> L3-SW ==== L4 SW
>     |
>     |
>     |        <http://10.10.10.0/24> 10.10.10.0/24
> Servers
>
> In this topoloty, L4 can have two interfaces for  <http://192.168.10.0/24>
192.168.10.0/24 and
>  <http://10.10.10.0/24> 10.10.10.0/24. In Servers point of
> view, GW should be L3-SW. Client requests will be forwarded to L3 but L3
> knows the VIP location (L4)
> and it will forward the request via L2-fwd.
>
> L4 will do a client processing and send the packet to Servers. In this
> moment, DSR should be enabled
> and request packet's DIP is not modified. and Server will received the
> packet and then forward it to L3-SW
> since L3-SW is a gateway for servers.
>
> I suppose that this is L3 DSR and return packet will not traverse to L4.
>
> Also, L4-SW is in the same network with servers, health check by using
> real-mac (VIPhealth) is also
> working and No mac flapping. (Since L4 is doing L3 fwd + L4 processing and
> packet's SIP should be
> modified. L3-SW will not have any duplicate mac-address entry in the fdb.
-
> Even there are same mac
> in fdb, if VLAN is different, there should be no issues to do a L2-fwd).
>
> I have no idea why L2 broadcast issue is there on DSR. (do you mean
> "mac-flapping"? - this can cause
> flooding in the network).
>
> Best regards,
>
> - yongseok
>
> 2009/3/30 SungLyeol Choi < <mailto:[email protected]> [email protected]>
>
>>  Hi guys.
>> Have you heard about L3 DSR?
>> which vendors support this?
>> I heard L3 DSR could protect L2 broadcast. but I think LB should consider
>> a lot of things to support that.
>>
>> Thanks.
>>

 


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