Re: [16NG] WG last call on draft-ietf-16ng-ipv4-over-802-dot-16-ipcs-02 + RE: regarding my comments on MTUs

[Wesley George <[e-mail]>]

Samita, others - is a new version of this ID going to be posted ahead of 
IETF Dublin? I can't attend Dublin in person and would like to review and 
provide comments, since I've been one of the more vocal objectors to the 
current language.

Thanks,
Wes

On Fri, 11 Apr 2008, Riegel, Maximilian (NSN - DE/Muenich) wrote:

> If 'L2 tunneling' is replaced by 'L3 tunneling' I am fine with option 3.
> There are too many protocols and options in 'L2 tunneling', to make a
> recommendation without providing further details. Burcak may have one
> particular solution for fixed and nomadic deployments in mind, which
> works well, and I see issues with L2 tunneling in a mobile environment.
>
> Bye
> Max
>
> -----Original Message-----
> From: ext Samita Chakrabarti [mailto:[e-mail]]
> Sent: Thursday, April 10, 2008 11:01 PM
> To: Riegel, Maximilian (NSN - DE/Muenich); 'Burcak Beser'; 'Wesley
> George'
> Cc: 'Samita Chakrabarti'; 'gabriel montenegro'; [e-mail]
> Subject: RE: [16NG] WG last call on
> draft-ietf-16ng-ipv4-over-802-dot-16-ipcs-02 + RE: regarding my comments
> on MTUs
>
> Hi Max,
>
> Not clear to me whether you are also supporting option 3 as suggested
> below
> by Burcak. Please confirm.
>
> Thanks,
> -Samita
>
>> -----Original Message-----
>> From: Riegel, Maximilian (NSN - DE/Muenich)
>> [mailto:[e-mail]]
>> Sent: Thursday, March 27, 2008 10:17 AM
>> To: Burcak Beser; Samita Chakrabarti; Wesley George
>> Cc: Samita Chakrabarti; gabriel montenegro; [e-mail]
>> Subject: RE: [16NG] WG last call on
> draft-ietf-16ng-ipv4-over-802-dot-16-
>> ipcs-02 + RE: regarding my comments on MTUs
>>
>> I would also support to prevent MTU limitations in the I-D, which would
>> be easy based on L3 tunneling, e.g. GRE over IP (IP can fragment and
>> reassemble the tunneled payload inside the access network). L2
> tunneling
>> is much more critical, because L2 technologies often miss the
>> functionality to fragment and reassembly packets over a link. If L2
>> breaks, there is no way to recover.
>>
>> Bye
>> Max
>>
>> -----Original Message-----
>> From: [e-mail] [mailto:[e-mail]] On Behalf Of
>> ext Burcak Beser
>> Sent: Tuesday, March 25, 2008 8:33 PM
>> To: Samita Chakrabarti; 'Wesley George'
>> Cc: 'Samita Chakrabarti'; 'gabriel montenegro'; [e-mail]
>> Subject: Re: [16NG] WG last call on
>> draft-ietf-16ng-ipv4-over-802-dot-16-ipcs-02 + RE: regarding my
> comments
>> on MTUs
>>
>> As far as I can see we tree options:
>>
>> 1. Get WiMAX Forum to handle 1500 byte packets. I am not sure how this
>> may be achieved other than traveling back in time to impact NWG v1.
>>
>> 2. Change this draft to 'personal'-ipv4-over-wimax-ipcs and use 1400
>> byte limitation from WiMAX Forum NWG v1.
>>
>> 3. Write the draft for IPCS  assuming L2 tunneling and no MTU
>> limitations; and put the 1400 byte case on the appendix stating that
>> WiMAX is expected to be the widest 802.16 deployment and NWG v1 has the
>> 1400 byte limitation as a special case, and offer the remedies and
> state
>> the problems.
>>
>> Personally I like the option 3 which is cleaner and straight forward.
>>
>> -burcak
>> ________________________________________
>> From: Samita Chakrabarti [[e-mail]]
>> Sent: Friday, March 21, 2008 4:07 PM
>> To: 'Wesley George'; Burcak Beser
>> Cc: 'gabriel montenegro'; 'Jari Arkko'; 'Samita Chakrabarti';
>> [e-mail]
>> Subject: RE: [16NG] WG last call on
>> draft-ietf-16ng-ipv4-over-802-dot-16-ipcs-02 + RE: [16NG] regarding my
>> comments on MTUs
>>
>> Hi Wes,
>>
>> Please see in-line.
>>
>>>
>>> Samita, your proposed update merely adds more words to say the
>>> same thing that the current draft says - host MTU should be 1400. It's
>>> helpful in that it adds more justification to your argument, but I
>> still
>>> disagree
>>> with the underlying conclusion.
>>>
>>> My recommendation was to treat MTU as something that must be taken
> into
>>> consideration at the design phase of a WiMax network and the
>>> initial configuration of the devices, not a hard and fast limit based
>> on
>>> the limitations and assumptions of ONE case out of many, especially
>> since
>>> the
>>> 806.16 over Ethernet draft completely contradicts your recommendation.
>> It
>>> views MTU as non-negotiable (must be at least 1500), and puts the
>>> responsibility on the network operator to ensure that they've build
> the
>>> network to support the right underlying MTU or deal with the
>>> fragmentation that will be inevitable.
>>> I don't see why we wouldn't be doing the same thing here.
>> [SC>]
>>       As far as I know for IPCS network WiMAX forum has decided that
>> their
>> default link MTU would be 1400 bytes. Checkout RFC 5121 (appendix D)
>> which
>> chose the same value 1400 bytes for that reason. But one difference
> from
>> IPv6 case is that IPv6 specification requires to send RA with MTU
> option
>> if
>> the MTU supported by the link is not the default value. Thus by
>> following
>> IETF specification WiMAX AR can send MTU option with 1400 value to the
>> clients and the clients can adjust the MTU accordingly; while RFC 5121
>> can
>> specify 1500 bytes as the default MTU.
>>
>> Now IPV4CS would be happy to set the same default 1500 bytes following
>> RFC5121 example - the only major issue is that there is no IPv4
>> mandatory
>> requirement from the server to communicate (through RA or DHCP option
>> etc.)
>> the non-default link MTU unless the client itself asks for it.
>>
>> The problem that Jari and others are pointing to is that if we specify
>> 1500
>> bytes and the clients do not know that they are in WiMAX link and start
>> sending packets over 1400 bytes, the packets will not be delivered at
>> all.
>> Those clients will not operate in the WiMAX network.
>>
>> Please note that WiMAX forum can change their default MTU value in the
>> next
>> revision, but the current specifications (Rls 1.1) cannot change.
>>
>> This is the data behind the decision on 1400 bytes as initial value; it
>> matches the criteria that was given by Jari on the list. This IPv4CS
>> recommends the new clients to request MTU option from DHCP requests for
>> efficiency.
>>
>> If you or Burcak can work with WiMAX forum and produce a note from the
>> chair
>> that 1500byte  IPv4CS payload is OK for WiMAX network for the current
>> NWG
>> releases in the next one or two weeks, we can really appreciate that
> and
>> change to 1500 bytes. Currently, I do not know of any other deployment
>> of
>> IPv4CS other than WMF.
>>
>>
>>
>>>
>>> Also, I do not understand how the statement
>>> "The WiMAX forum [WMF] has specified the Max SDU size as 1522 octets."
>>> aligns with the current statement in your draft
>>> "The Length parameter of IEEE 802.16 MAC frame has a size of 11 bits.
>>> Hence the total PDU size is 2048 bytes.  The IPv4 payload can be a
>>> maximum value of 2038 bytes ( Total PDU size (2048) - (MAC Header (6)
> +
>>> CRC (4)), which is the maximum possible MTU."
>>>
>>> Where are those other ~500 octets going? Forgive my ignorance, but is
>>> there some layer between SDU and PDU that has that sort of overhead,
> or
>> is
>>> this another example of arbitrary limits that conflict with each
> other?
>> [SC>]
>>      I do not know why WMF has specified 1522 bytes as MAX SDU and not
>> beyond that. You need to ask that question to the WiMAX forum. For
>> reference, please check RFC 5121 Appendix D.
>>
>>
>> Thanks,
>> -Samita
>>
>>
>>
>>
>>
>>>
>>> On Thu, 20 Mar 2008, Burcak Beser wrote:
>>>
>>>> I have to admit that I fail to understand the reason for the MTU
>>> limitation in the first place. The draft talks about Layer 2 tunnels
>>> between BS and AR, and than GRE is being given as an example which
>> causes
>>> the problems in the first place. Instead of GRE, if 802.1Q VLANs are
> to
>> be
>>> used this artificial limitation will not be taken into considereation.
>>>>
>>>> Is it possible to clarify the sentence "Hence if a IPv4CS MS is
>>> configured for 1500 bytes it will have to be communicated by the
> access
>>> router(AR) about the default link MTU (1400 bytes) in WiMAX network."?
>> Due
>>> to fragmentation support in the 802.16 transport aribitrary PDU sizes
>> are
>>> supported even when the maximum SDU size is limited. In the light of
>>> fragmentation the "The WiMAX forum [WMF] has specified the Max SDU
> size
>> as
>>> 1522 octets." only means that a 1600 byte PDU will be transmitted in
> at
>>> least two chunks. The 802.16 transport will carry almost anything that
>> the
>>> underlying native protocol can.
>>>>
>>>> The normative 'should' in the sentence "Therefore, IEEE 802.16 frame
>>> SHOULD support for 1500 byte IP payload..." is unnecessary.
>>>>
>>>> The use of normative 'should' in ".. IPv4 and IPV4CS clients SHOULD
>>> implement DHCP interface MTU option..." sentence looks like
>> conditionally
>>> mandating the use of DHCP as well. A clear requirement will be better.
>> The
>>> inclusion of IPv4 clients is first not correct since ARP would work,
>> and
>>> second is out of scope for this draft by definition.
>>>>
>>>> I understand that IPv4CS cannot transmit ARP messages but "An IPv4CS
>>> client is not capable of doing ARP probing either to find out the link
>>> MTU." looks like stating that "IPv4CS client MUST NOT use ARP
>> messages". At
>>> the same time IPv4CS client has to be defined.
>>>>
>>>> "Consequently, the clients are encouraged to run PMTU[RFC 1191]
>> algorithm
>>> or PPMTUD[RFC 4821] for appropriating the bandwidth usage over the
>> route-
>>> path or end-to-end transport layers. However, PMTU mechanism has
>> inherent
>>> problems of packet loss due to ICMP messages not reaching the sender
>> and
>>> IPv4 routers not fragmenting the packets due to DF bit being set in
> the
>> IP
>>> packet." Can we state this sentence in normative manner?
>>>>
>>>> I have to admit that the draft struggles around the artificial MTU
>>> limitation which is not justified, and omits other important subjects.
>>>>
>>>> -burcak
>>>>
>>>> -----Original Message-----
>>>> From: [e-mail] [mailto:[e-mail]] On Behalf
>> Of
>>> Samita Chakrabarti
>>>> Sent: Thursday, March 20, 2008 7:18 PM
>>>> To: 'Wesley George'; 'gabriel montenegro'; 'Jari Arkko'
>>>> Cc: 'Samita Chakrabarti'; [e-mail]
>>>> Subject: Re: [16NG] regarding my comments on MTUs
>>>>
>>>> Hi Jari and Gabriel,
>>>> Thanks for the guidelines on re-wording the text on MTU
> determination
>> for
>>> IP4CS link. Thanks to Wes for your proposed text as well; I have taken
>> some
>>> ideas from your text.
>>>>
>>>>
>>>> Here is the proposed text on MTU based on the wg discussion and the
>> AD
>>>> guideline:
>>>> ------------------------------------
>>>>
>>>> 5. Maximum Transmission Unit considerations for IPv4CS link
>>>>
>>>> [RFC894] specifies 1500 bytes as a maximum length of IPv4 over
>> Ethernet
>>> and encourages to support full-length packets. Therefore, IEEE 802.16
>> frame
>>> SHOULD support for 1500 byte IP payload in the IPv4CS link by
>> supporting
>>> larger than 1500 bytes link MTU between the MS and the Access router
>> (AR).
>>>> The extra overhead that IEEE 802.16 frame should support in this
>> case,
>>> depends on the tunneling protocols or any other virtual or
>> pseudo-wiring
>>> protocols packet overhead.
>>>>
>>>>   The current architecture of IPv4CS in IEEE 802.16 networks is
>> defined
>>> in
>>>>   the WiMAX (Worldwide Interoperability for Microwave Access) forum
>> [WMF].
>>>>   The addressing and operation of IPv4CS described in this document
>> are
>>>>   applicable to the WiMAX networks as well. The WiMAX forum [WMF]
> has
>>>>   specified the Max SDU size as 1522 octets. However, it is
>> recommended
>>>>   that IP-payload in WiMAX architecture [WMF] specified network is
>> 1400
>>>>   bytes due to overhead of GRE tunnel and possible
>>>>   additional over-head of different types of tunneling (such as
>> IPSec/UDP
>>>>   tunneling) between the base station (BS) and Access Router.
>>>>
>>>>   Hence  if a IPv4CS MS is configured for 1500 bytes it will have to
>> be
>>>>   communicated by the access router(AR) about the default link MTU
>> (1400
>>>>   bytes) in WiMAX network.
>>>>   However, currently in IPv4 client architecture a node is not
>> required
>>>>   to ask for MTU option in its DHCP messages nor the
>>>>   IPv4 router-advertisements
>>>>   are required to advertise link MTU option when the link does not
>>> support
>>>>   1500 byte de-facto MTU size. An IPv4CS client is not capable of
>> doing
>>> ARP
>>>>
>>>>   probing either to find out the link MTU.
>>>>   Thus current specifications of WiMAX network access routers cannot
>>>>   communicate its link MTU to the IPV4CS MS. On the other hand, it
> is
>>>>   imperative for an MS to know the link MTU size if it is not the
>> default
>>>>   MTU value for de-facto standard in order to
>>>>   successfully send packets in the network towards the first hop.
>>>>   This document can not also assume that the legacy IPv4 client
>>>>   implementation with IEEE 802.16 layer 2 support,
>>>>   would be able to dynamically sense IPv4CS WiMAX network and adjust
>>>>   their MTU size  accordingly.
>>>>
>>>>   Thus for IPv4CS over IEEE 802.16 the default MTU size is 1400
>> bytes.
>>>>
>>>>   This document recommends that all future implementations of IPv4
>> and
>>>>   IPV4CS clients SHOULD implement DHCP interface MTU option
> [RFC2132]
>> in
>>>>   order to configure its interface MTU according to the access
>> network in
>>>>   order to maximize the capacity of the bandwidth of
>>>>   the network. Consequently, the clients are encouraged to run
>>>>   PMTU[RFC 1191] algorithm or PPMTUD[RFC 4821] for
>>>>   appropriating the bandwidth usage over the route-path or
> end-to-end
>>>>   transport layers. However, PMTU mechanism has inherent problems of
>>> packet
>>>>
>>>>   loss due to ICMP messages not reaching the
>>>>   sender and IPv4 routers not fragmenting the packets due to DF bit
>> being
>>>>   set in the IP packet. The above mentioned path MTU mechanisms will
>> take
>>>>   care of the MTU size between the MS and its correspondent node
>> across
>>>>   different flavors of convergence layers in the WiMAX networks,
>>>>   IEEE 802.16 networks and other types of networks such as Wi-Fi,
>>>>   Ethernet or 3G networks.
>>>>
>>>> --------------------------
>>>>
>>>> Review comments are welcome.
>>>>
>>>> Regards,
>>>> -Samita
>>>>
>>>>> -----Original Message-----
>>>>> From: [e-mail] [mailto:[e-mail]] On
> Behalf
>> Of
>>>>> Wesley George
>>>>> Sent: Thursday, March 20, 2008 8:24 AM
>>>>> To: gabriel montenegro
>>>>> Cc: Samita Chakrabarti; [e-mail]
>>>>> Subject: Re: [16NG] regarding my comments on MTUs
>>>>>
>>>>> I have been thinking about the discussions regarding MTU, and would
>>>>> like to propose some alternate language for section 5 of the ipcs
>>>>> draft. I will caveat this by saying that it is my first attempt at
>> an
>>>>> ID (or a part of
>>>>> one) but I thought that it might be helpful to propose an
>> alternative
>>>>> rather than simply saying that the language that is in the -02
> draft
>>>>> currently in Last Call that IMO is not adequate, due to its
> conflict
>>>>> with the .16 over ethernet draft.
>>>>>
>>>>> ** proposed draft language to replace the first paragraph of
> section
>> 5
>>>>> **
>>>>>
>>>>> When considering end host MTU, there are two points at which MTU
>> must
>>>>> be considered. First, the end to end path MTU between one IP host
>> and
>>>>> another. In 802.16, this is expected to follow existing convention
>> [rfc
>>>>> citation needed?] for fragmentation and path MTU discovery between
>> end
>>>>> hosts, and will not be treated here.
>>>>>
>>>>> The point at which MTU must be considered and will be treated by
>> this
>>>>> document is the path between the Base Station (BS) and the ASN
>> Gateway
>>>>> or HA, where traffic is usually encapsulated using one of several
>>>>> methods before being allowed to transit the remaining path as
> native
>> IP
>>>>> traffic.
>>>>> On this portion of the path, there are two cases which must be
>>> considered:
>>>>>
>>>>> 1) Where the underlying MTU of the transport mechanism between the
>> BS
>>>>> and the ASN GW or HA is configurable to a value > 1600 bytes or is
>>>>> known to support the same
>>>>> 2) Where the underlying MTU of the transport mechanism between the
>> BS
>>>>> and the ASN GW or HA is not a known value, or is not able to be
>>>>> configured to MTU > 1600 bytes
>>>>>
>>>>> In case 1, the end host MTU SHOULD be set to at least 1500 bytes,
>> but
>>>>> can be set to any higher value supported by the underlying network
>> up
>>>>> to the maximum supported size on 802.16 of 2038 bytes.
>>>>>
>>>>> With an end host MTU of 1500 bytes or more, the underlying network
>> MUST
>>>>> support an MTU of at least 1500 bytes plus the overhead of the
>> chosen
>>>>> encapsulation method between the BS and the ASN GW or HA. For ease
>> of
>>>>> standardization, the underlying network SHOULD support an MTU of at
>>>>> least 100 bytes larger than the chosen host MTU value, as this is
>> large
>>>>> enough to ensure that there is no dropping or fragmentation of
>> oversize
>>>>> packets regardless of the encapsulation method.
>>>>>
>>>>> In case 2, the end host MTU SHOULD be set to 1400 bytes to ensure
>> that
>>>>> there is no dropping or fragmentation of oversize packets
> regardless
>> of
>>>>> the encapsulation method. If the end host MTU is set higher, or the
>> MTU
>>>>> of the underlying transport network is lower than 1500 bytes, the
>>>>> network MUST be able to accept any fragmentation of packets larger
>> than
>>>>> the supported transport MTU, or MUST employ a method of MTU
>> discovery
>>>>> to prevent oversize packets from being generated by the end host.
>>>>>
>>>>> In order to preserve the defacto standard of MTU 1500 bytes for end
>>>>> host use, case 1 SHOULD be followed if at all possible. If adhering
>> to
>>>>> case 1 is not possible, case 2 is presented as an alternative.
>>>>>
>>>>> ** end proposed draft language **
>>>>>
>>>>> The second paragraph of section 5 can remain as-is.
>>>>>
>>>>> Some additional comments:
>>>>> It may be a good idea to add in language from the background slides
>>>>> that were presented in Philadelphia which identify why 100 bytes is
>> the
>>>>> recommended padding between host MTU andNetwork MTU for further
>>>>> clarification.
>>>>>
>>>>> I concede that it's not really feasible to rely on an MTU discovery
>>>>> method to compensate for MTU on the transport network that is not
>>>>> capable of supporting the full 1500 bytes of host MTU. However, I
>> think
>>>>> that the proposed language provides ways to work this based on
>> whether
>>>>> that is a known value or not (via the two different cases) and
>>>>> addresses that concern. I think that this is much closer in idea
>> with
>>>>> the way that the EthernetCS draft is written, treating 1500 as the
>>>>> defacto standard that we should prefer, but covering what the
>> reasoning
>>>>> is for MTU settings and identifying ways to compensate for
>> limitations
>>>>> in the underlying transport network, rather than simply assuming
>> that
>>>>> those limitations exist and catering to the lowest common
>> denominator.
>>>>>
>>>>> Thanks,
>>>>> Wes
>>>>>
>>>>> _________________________________________
>>>>>   Wesley George
>>>>>       Sprint IP Engineering
>>>>>   703-689-7505 (O)  703-864-4902 (PCS)
>>>>>         http://www.sprint.net
>>>>> _________________________________________
>>>>>
>>>>>
>>>>> On Tue, 18 Mar 2008, gabriel montenegro wrote:
>>>>>
>>>>>> For the IPv4 case, I have no problem with the MTU staying at 1400
>>>>>> bytes
>>>>> per the current draft.
>>>>>> There is no sure-fire way to indicate to the MS what the MTU is.
>> The
>>>>> draft currently says:
>>>>>>
>>>>>>   The MTU value of the MS can be configured via Path MTU Discovery
>> [6],
>>>>>>   Packetization layer path MTU discovery [7], DHCP MTU option [8]
>> or
>>>>>>   static configuration of each MS.As pointed out by Jari, what
>> we're
>>>>> talking about is the *interface* MTU, not the *path* MTU
>>>>>> (minimum hop MTU of all the hops in a path). Accordingly, when
>>>>>> applying
>>>>> [6] or [7]
>>>>>> to discover the interface MTU, they must be used between the MS
> and
>>>>>> its
>>>>> immediate IP hop,
>>>>>> the access router. Of course, in order to use [6] or [7], some
>>>>>> interface
>>>>> MTU must be assumed
>>>>>> to begin the discovery process.
>>>>>>
>>>>>> 1400 is a very reasonable value for this initial default MTU.
> Given
>>>>>> the
>>>>> well-known issues with PMTU,
>>>>>> and the scant support for the DHCP Interface MTU option, 1400 will
>>>>>> work
>>>>> well in the absence of
>>>>>> any further MTU discovery or configuration. It will also avoid
>>>>> fragmentation in what is expected
>>>>>> to be the most common deployment for 802.16: WiMAX networks. 1500
>>>>>> bytes,
>>>>> the other MTU value
>>>>>> folks have proposed for IPv4 CS does not have this virtue and will
>>>>>> incur
>>>>> fragmentation.
>>>>>>
>>>>>> Notice that for DHCP we should really say "Interface MTU option"
>>>>>> to clarify that we're talking about option 26 (Section 5.1,
>> RFC2132).
>>>>>>
>>>>>> Going forward we may have a more reliable and less time consuming
>>>>> mechanism to
>>>>>> derive the interface IP MTU by learning the layer 2 maximum SDU
> via
>> a
>>>>>> new
>>>>> TLV in the SBC exchange
>>>>>> in 802.16. This is being proposed  this week at the Orlando IEEE
>>> meeting.
>>>>>>
>>>>>> As for the ethernet CS MTU, as Max said during his presentation
>> last
>>>> week,
>>>>> there is no choice. We must
>>>>>> preserve the ethernet MTU as expected from "Ethernet" CS,
>> regardless
>>>>>> of
>>>>> the fact that 1500 byte IP packets will incur
>>>>>> fragmentation in common WiMAX networks.
>>>>>>
>>>>>>
>>>>>> -gabriel
>>>>>>
>>>>>>
>>>>>> ----- Original Message ----
>>>>>> From: Jari Arkko <[e-mail]>
>>>>>> To: [e-mail]
>>>>>> Sent: Thursday, March 13, 2008 1:18:55 PM
>>>>>> Subject: [16NG] regarding my comments on MTUs
>>>>>>
>>>>>>
>>>>>> As a clarification of my comments during the WG meeting I would
>> like
>>>>>> to state the following:
>>>>>>
>>>>>>> From AD perspective the WG is free to decide whatever MTU value
>> that
>>>>>>> you
>>>>>> wish to have, as long as you are both aware of and document the
>>>>>> implications of this choice. Some of the implications include:
>>>>>>
>>>>>> - difficulty of manual configuration
>>>>>> - ability to raise/lower the values automatically
>>>>>> - capability of 802.16 backhaul networks to handle larger MTUs
>> (ipcs,
>>>>>> ethcs, wimax and non-wimax)
>>>>>> - ability or inability to determine what network you are in
>>>>>> - inability of L2 devices to send ICMP messages
>>>>>>
>>>>>> Hope this clarifies,
>>>>>>
>>>>>> Jari
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> 16NG mailing list
>>>>>> [e-mail]
>>>>>> https://www.ietf.org/mailman/listinfo/16ng
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> _______________________________________________
>>>>> 16NG mailing list
>>>>> [e-mail]
>>>>> https://www.ietf.org/mailman/listinfo/16ng
>>>>
>>>>
>>>>
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>>
>>
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>>
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