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Re: [lvs-users] LVS-DR generates TONS of icmp unreachables

To: Wensong Zhang <wensong@xxxxxxxxxxxx>
Subject: Re: [lvs-users] LVS-DR generates TONS of icmp unreachables
Cc: Jivko Velev <jiko@xxxxxxxxxx>, Jerry Glomph Black <black@xxxxxxxx>, Julian Anastasov <uli@xxxxxxxxxxxxxxxxxxxxxx>, lvs-users@xxxxxxxxxxxxxxxxxxxxxx
From: Joseph Mack <mack@xxxxxxxxxxx>
Date: Fri, 21 Jan 2000 09:56:46 -0500 (EST)
On Fri, 21 Jan 2000, Wensong Zhang wrote:

> No, it is not right. The director handles ICMP packets for virtual
> services long time ago, please check the ChangeLog of the code.

from ChangeLog for 0.9.3-2.2.13

        The incoming ICMP packets for virtual services will be forwarded
        to the right real servers, and outgoing ICMP packets from virtual
        services will be altered and send out correctly. This is important
        for error and control notification between clients and servers,
        such as the MTU discovery.

If a realserver goes down after the connection is established, will the
client get a dest_unreachable from the director?

If the client goes down after the connection is established, where do the
dest_unreachable icmp packets generated by the last router go?

Since icmp packets are udp, are the icmp packets routed through the
director independantly of the services that are being LVS'ed. ie if the
director is only forwarding port 80/tcp, from CIP to a particular RIP,
does the LVS code which handles the icmp forward all icmp packets from the
CIP to that RIP. What if the client has a telnet session to one realserver
and http to another realserver?

> As for VS/TUN or VS/DR, the director handles ICMP packets in the
> client-to-server half connection. If the real servers generate ICMP
> packets and want to send it to the client, they can send the ICMP
> packets to the clients directly, there is no need for the director to
> interference it.

Joe

--
Joseph Mack mack@xxxxxxxxxxx

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