Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv3 (draft-wang-aospf-00) - Authors' Technical Considerations
Naiming Shen <naiming@cisco.com> Fri, 29 December 2006 23:35 UTC
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1H0RGJ-0008Tm-Oc; Fri, 29 Dec 2006 18:35:43 -0500
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1H0RGI-0008Tc-Rh for OSPF@ietf.org; Fri, 29 Dec 2006 18:35:42 -0500
Received: from sj-iport-4.cisco.com ([171.68.10.86]) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1H0RGH-0004nt-Gv for OSPF@ietf.org; Fri, 29 Dec 2006 18:35:42 -0500
Received: from sj-dkim-8.cisco.com ([171.68.10.93]) by sj-iport-4.cisco.com with ESMTP; 29 Dec 2006 15:35:41 -0800
Received: from sj-core-4.cisco.com (sj-core-4.cisco.com [171.68.223.138]) by sj-dkim-8.cisco.com (8.12.11/8.12.11) with ESMTP id kBTNZeYu023147; Fri, 29 Dec 2006 15:35:40 -0800
Received: from [127.0.0.1] (ssh-sjc-1.cisco.com [171.68.225.134]) by sj-core-4.cisco.com (8.12.10/8.12.6) with ESMTP id kBTNZRUH020523; Fri, 29 Dec 2006 15:35:36 -0800 (PST)
Message-ID: <4595A644.2060107@cisco.com>
Date: Fri, 29 Dec 2006 15:35:32 -0800
From: Naiming Shen <naiming@cisco.com>
User-Agent: Mozilla Thunderbird 1.0 (X11/20041206)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: curtis@occnc.com
Subject: Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv3 (draft-wang-aospf-00) - Authors' Technical Considerations
References: <200612292134.kBTLYCtE040008@workhorse.brookfield.occnc.com>
In-Reply-To: <200612292134.kBTLYCtE040008@workhorse.brookfield.occnc.com>
Content-Type: text/plain; charset="ISO-8859-1"; format="flowed"
Content-Transfer-Encoding: 7bit
DKIM-Signature: v=0.5; a=rsa-sha256; q=dns/txt; l=2619; t=1167435340; x=1168299340; c=relaxed/relaxed; s=sjdkim8002; h=Content-Type:From:Subject:Content-Transfer-Encoding:MIME-Version; d=cisco.com; i=naiming@cisco.com; z=From:=20Naiming=20Shen=20<naiming@cisco.com> |Subject:=20Re=3A=20[OSPF]=20Re=3A=20[AOSPF]=20Anycast=20Extension=20to=2 0OSPFv3=20(draft-wang-aospf-00)=0A=20-=20Authors'=20Technical=20Considerat ions |Sender:=20; bh=7vc/J72Ia4Z8qfw/iBp9rJu9CknvbeWkd8uPGBZTAfk=; b=rXvnj8yZR6LCIkkC4FSIeBBA6H0+wxlBkMVCUOBPnO/4lrZMow7mIZVE4RJVMPkHGSGWEFxv LS0X8WiJ4Z0KveFDQa8QnDTrUVoEESW4iScVP4+B4MZi4jAC8NL9+8RU;
Authentication-Results: sj-dkim-8; header.From=naiming@cisco.com; dkim=pass ( sig from cisco.com/sjdkim8002 verified; );
X-Spam-Score: 0.0 (/)
X-Scan-Signature: e8a67952aa972b528dd04570d58ad8fe
Cc: OSPF List <OSPF@ietf.org>
X-BeenThere: ospf@ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: The Official IETF OSPG WG Mailing List <ospf.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/ospf>, <mailto:ospf-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www1.ietf.org/pipermail/ospf>
List-Post: <mailto:ospf@ietf.org>
List-Help: <mailto:ospf-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/ospf>, <mailto:ospf-request@ietf.org?subject=subscribe>
Errors-To: ospf-bounces@ietf.org
Curtis Villamizar said the following on 12/29/2006 01:34 PM: > In message <4594A87C.6090204@cisco.com> > Naiming Shen writes: > >>>It is unfortunate that routers still allow per-packet ECMP to be >>>configured. At least providers know not to use this feature. But we >>>can all be sure that somewhere out there someone ignorant of the >>>problems has enabled it. >> >> >>I completely agree. Per-packet ECMP should not be used normally, >>especially in provider's networks. But I did experience some cases >>( a while ago ) on international links, there were some dominant >>prefixes which led to very uneven link bandwidth usages due to flow >>based algorithm. I think if folks in the routing area still think >>things like anycast having this issue, then to signal this attribute is >>useful and can be easily done; otherwise, there is absolutely no issue >>in terms of anycast prefiexes(ipv4 or ipv6). > > > > Maybe you missed the point. The alternative to per-packet ECMP is not > per-prefix ECMP. The hash based ECMP is only uneven if one or a small > number of host pairs dominate the traffic flow. > > The only time that it mattered was when one dominante vendor didn't > offer hash based ECMP. Per-prefix ECMP could be very uneven. That > was a decade ago. The majority of the router software now is certainly 4-tuple based hash, but it does not mean in all the cases even load distribution can be achieved. > > As far as anycast goes even with per-packet ECMP, everything is fine > if the application can send one packet that is returned with the > unicast address of an anycast server and use the unicast address from > then on. This sort of probe can be repeated periodically if Sure, then this involves application awareness of anycast knowledge and explicit configuration, it's error-prone to say the least. That would certainly be a big restriction. > necessary. A load influenced anycast could be done within an IGP by > changing a cost but load might tend to slosh (all to one server, then > another). What might work better for that would be an underlying > multicast with limited TTL (reaches multiple close servers, all of > which respond with their loadings). Limited deployment of multicast > might be an issue and non-optimality of a multicast tree with fixed RP > might also be an issue. There are plenty of tools in the tool box to > implement an anycast end user service without resorting to a new > address type and any change to routing. > > The WG is OSPF and we're off topic at this point. Agreed. - Naiming > > Curtis _______________________________________________ OSPF mailing list OSPF@ietf.org https://www1.ietf.org/mailman/listinfo/ospf
- [OSPF] [AOSPF] Anycast Extension to OSPFv3 (draft… Yue Wang
- Re: [OSPF] [AOSPF] Anycast Extension to OSPFv3 (d… Abhay D.S
- [OSPF] Re: [AOSPF] Anycast Extension to OSPFv3 (d… Acee Lindem
- [OSPF] Re: [AOSPF] Anycast Extension to OSPFv3 (d… Yue Wang
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Acee Lindem
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Acee Lindem
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Yue Wang
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Acee Lindem
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Yue Wang
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Yue Wang
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Paul Wells
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Acee Lindem
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Abhay D.S
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Acee Lindem
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Naiming Shen
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Naiming Shen
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Naiming Shen
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Acee Lindem
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Curtis Villamizar
- Re: [OSPF] Re: [AOSPF] Anycast Extension to OSPFv… Naiming Shen