[c-nsp] Fwd: IPV6 Path MTU DIscovery Test
Xu Hu
jstuxuhu0816 at gmail.com
Wed Aug 1 11:15:49 EDT 2012
Hi Oli, thanks for your inputs, will add this to my test document.
Best Regards for the NSP's help.
2012/8/1 Oliver Boehmer (oboehmer) <oboehmer at cisco.com>
> well, you don't have to use TCP, but it's the most convinient as you
> have the client prepared to react to the packet-too-big ICMP/ICMPv6
> messages from intermediate nodes, and see the effect it has on the MSS. You
> can't test this just by sending icmp packets from the CLI?! ****
>
> And to your question: yes, it is the MSS reported, and the below output
> suggests that you have PMTUD enabled on the routers and you're using a min
> MTU of 1500 along the path, otherwise the nodes would have used MSS=532 or
> something low like this..****
>
> ** **
>
> oli****
>
> ** **
>
> *From:* Xu Hu [mailto:jstuxuhu0816 at gmail.com]
> *Sent:* 01 August 2012 15:54
>
> *To:* Oliver Boehmer (oboehmer)
> *Cc:* cisco-nsp at puck.nether.net
> *Subject:* Re: [c-nsp] Fwd: IPV6 Path MTU DIscovery Test****
>
> ** **
>
> Must use the TCP packets? I want to just use the ping packet to test the
> effect of PMTUD. Is any simple way to test this feature?****
>
> ** **
>
> Another thing, if use the iBGP to test, i find one show ip bgp neighbor
> command as below, the MSS you mentioned is the "*Datagrams (max data
> segment is 1460 bytes):*" ?****
>
> ** **
>
> Thanks for your help.****
>
> Hu Xu****
>
> ** **
>
> Router# *show ip bgp neighbors 172.16.232.178*
>
>
>
> ****
>
> BGP neighbor is 172.16.232.178, remote AS 10, external link****
>
> Index 1, Offset 0, Mask 0x2****
>
> Inbound soft reconfiguration allowed****
>
> BGP version 4, remote router ID 172.16.232.178****
>
> BGP state = Established, table version = 27, up for 00:06:12****
>
> Last read 00:00:12, hold time is 180, keepalive interval is 60 seconds****
>
> Minimum time between advertisement runs is 30 seconds****
>
> Received 19 messages, 0 notifications, 0 in queue****
>
> Sent 17 messages, 0 notifications, 0 in queue****
>
> Inbound path policy configured****
>
> Route map for incoming advertisements is testing****
>
> Connections established 2; dropped 1****
>
> Connection state is ESTAB, I/O status: 1, unread input bytes: 0****
>
> Local host: 172.16.232.181, Local port: 11002****
>
> Foreign host: 172.16.232.178, Foreign port: 179****
>
>
>
> ****
>
> Enqueued packets for retransmit: 0, input: 0, saved: 0****
>
>
>
> ****
>
> Event Timers (current time is 0x530C294):****
>
> Timer Starts Wakeups Next****
>
> Retrans 12 0 0x0****
>
> TimeWait 0 0 0x0****
>
> AckHold 12 10 0x0****
>
> SendWnd 0 0 0x0****
>
> KeepAlive 0 0 0x0****
>
> GiveUp 0 0 0x0****
>
> PmtuAger 0 0 0x0****
>
>
>
> ****
>
> iss: 133981889 snduna: 133982166 sndnxt: 133982166 sndwnd: 16108****
>
> irs: 3317025518 rcvnxt: 3317025810 rcvwnd: 16093 delrcvwnd: 291****
>
>
>
> ****
>
> SRTT: 441 ms, RTTO: 2784 ms, RTV: 951 ms, KRTT: 0 ms****
>
> minRTT: 0 ms, maxRTT: 300 ms, ACK hold: 300 ms****
>
> Flags: higher precedence, nagle****
>
>
>
> ****
>
> *Datagrams (max data segment is 1460 bytes):*****
>
> Rcvd: 15 (out of order: 0), with data: 12, total data bytes: 291****
>
> Sent: 23 (retransmit: 0), with data: 11, total data bytes: 276****
>
> ** **
>
> 2012/8/1 Oliver Boehmer (oboehmer) <oboehmer at cisco.com>****
>
> Well, you need to create TCP connections to see the effect of PMTUD.. you
> could build an iBGP session across the test network, and play around with
> the minimum link MTU along the path. The MSS (shown in show bgp neighbor
> ..) should adapt as you change it..
>
> oli****
>
>
> > -----Original Message-----
> > From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> > bounces at puck.nether.net] On Behalf Of Xu Hu
> > Sent: 01 August 2012 02:33
> > To: cisco-nsp at puck.nether.net
> > Subject: [c-nsp] Fwd: IPV6 Path MTU DIscovery Test
> >
> > Anybody have any good idea?
> >
> > Thanks advance for any inputs,
> > Xu Hu
> >
> > Begin forwarded message:
> >
> > > From: TJ <trejrco at gmail.com>
> > > Date: 1 August, 2012 5:23:46 GMT+08:00
> > > To: Xu Hu <jstuxuhu0816 at gmail.com>
> > > Subject: Re: [c-nsp] IPV6 Path MTU DIscovery Test
> > > Reply-To: trejrco at gmail.com
> > >
> > > In order to test it, take one of the links along the path and change
> the
> > (IPv6) MTU to something smaller - say 1300B. Then send large packets,
> with
> > WireShark running. And no, you cannot disable PMTUD in IPv6.
> > >
> > > HTH!
> > > /TJ
> > >
> > >
> > > On Tue, Jul 31, 2012 at 6:43 AM, Xu Hu <jstuxuhu0816 at gmail.com> wrote:
> > > Hi Experts,
> > >
> > > I have some queries about the PMTU for IPv6.
> > > 1. From my understanding, path MTU discovery in IPv6 allows a host to
> > > dynamically discover and adjust to differences in the MTU size of every
> > > link along a given data path, So the fragmentation is handled by the
> > > source, if i want to test this feature in the IPv6 network, anyone have
> > any
> > > good ideas?
> > > For example, as below topology, if i want to test the Path MTU
> discovery,
> > > how to test, i can ping from CE-1 to CE--2 with a specific IPv6 packet
> > > size.
> > > CE-1------PE-1------------PE-2--------CE-2
> > >
> > > 2. If i need to configure the Path MTU discovery, just one command
> > > mentioned in Cisco.com, which is "ipv6 flowset" under configuration
> mode.
> > > So if i want to disable that in test scenario, just using the "no ipv6
> > > flowset" is okay? Cisco don't mentioned that.
> > > By default, it is enable for ip routers or not?
> > >
> > > Thanks for any inputs.
> > >
> > > Best Regards,
> > > Hu Xu
> > > _______________________________________________
> > > cisco-nsp mailing list cisco-nsp at puck.nether.net
> > > https://puck.nether.net/mailman/listinfo/cisco-nsp
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> > >
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>
> ** **
>
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