Subject: [MIPSHOP-MIH-DT] Work for version -01

From: Telemaco Melia <[email-masked]>
Date: Mon, 29 Oct 2007 18:16:58 +0100

Dear all,

Since it seems pretty much difficult to get everybody for the AC I 
propose the following.
I already started to review the document (version -01) based on the 
received comments.
I will incorporate the editorial comments and compile a list of 
technical issues for you to comment via email. (this week)

To start with I would like to clarify the DHCP vs. DNS discovery procedure.
First question I have is whether we should compare the HA discovery and 
the MoS discovery. In my opinion we should.
Second question is why we do not support DHCP only in S1, S2, S3 and DNS 
only in S4.
We should remember that IETF does not accept a document with 2 solutions 
to the same problem.

Gabor I know that at this point in time you might be disappointed, but 
we should also consider that the DHCP solution
helps the network to perform assignment. If we run discovery via DNS, 
MoS assignment cannot be done, and we should provide it by other means.
So I guess that the implicit question is whether assignment is a 
requirement for us or not. I would say yes.

Subir, JC, all can you please comment on the above?

Let me know
Tele

-- 
Dr. Telemaco Melia			[email-masked]
Senior Research Staff Member		Tel: +49 (0) 6221 4342- 142
NEC Europe Ltd.
NEC Laboratories Europe
Network Division			
Kurfürsten-Anlage 36		
69115 Heidelberg
GERMANY	  

NEC Europe Limited | Registered Office: NEC House, 1 Victoria Road, London W3 6BL | Registered in England 2832014 

_______________________________________________
MIPSHOP-MIH-DT mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mipshop-mih-dt

---

From: Sam Xia <[email-masked]>
Date: Tue, 30 Oct 2007 09:13:29 +0800

Gabor,

What about your discussion about DNS discovery method with the opposer who
objects to utilizing DNS method to publish information for anything.

 Best Regards, Sam Xia 

> -----Original Message-----
> From: Telemaco Melia [mailto:[email-masked]] 
> Sent: Tuesday, October 30, 2007 1:17 AM
> To: [email-masked]
> Subject: [MIPSHOP-MIH-DT] Work for version -01
> 
> Dear all,
> 
> Since it seems pretty much difficult to get everybody for the 
> AC I propose the following.
> I already started to review the document (version -01) based 
> on the received comments.
> I will incorporate the editorial comments and compile a list 
> of technical issues for you to comment via email. (this week)
> 
> First question I have is whether we should compare the HA 
> discovery and the MoS discovery. In my opinion we should.
> Second question is why we do not support DHCP only in S1, S2, 
> S3 and DNS only in S4.
> We should remember that IETF does not accept a document with 
> 2 solutions to the same problem.
> 
> Gabor I know that at this point in time you might be 
> disappointed, but we should also consider that the DHCP 
> solution helps the network to perform assignment. If we run 
> discovery via DNS, MoS assignment cannot be done, and we 
> should provide it by other means.
> So I guess that the implicit question is whether assignment 
> is a requirement for us or not. I would say yes.
> 
> NEC Europe Limited | Registered Office: NEC House, 1 Victoria 
> Road, London W3 6BL | Registered in England 2832014 
> 
>

---

From: <[email-masked]>
Date: Tue, 30 Oct 2007 03:38:59 -0500

Hello,

Inline <gb> 

-----Original Message-----
From: ext Telemaco Melia [mailto:[email-masked]] 
Sent: Monday, October 29, 2007 10:17 AM
To: [email-masked]
Subject: [MIPSHOP-MIH-DT] Work for version -01

Dear all,

Since it seems pretty much difficult to get everybody for the AC I propose the following.
I already started to review the document (version -01) based on the received comments.
I will incorporate the editorial comments and compile a list of technical issues for you to comment via email. (this week)

To start with I would like to clarify the DHCP vs. DNS discovery procedure.
First question I have is whether we should compare the HA discovery and the MoS discovery. In my opinion we should.

<gb> in my opinion we should not.

Second question is why we do not support DHCP only in S1, S2, S3 and DNS only in S4.

<gb> I do not understand this question. In S4 you can only DNS for the discovery, so 'DNS only' is supported.

We should remember that IETF does not accept a document with 2 solutions to the same problem.

<gb> there are reasons for it. Most of the discoveries I am aware of specify both DNS and DHCP.

Gabor I know that at this point in time you might be disappointed, but we should also consider that the DHCP solution helps the network to perform assignment. If we run discovery via DNS, MoS assignment cannot be done, and we should provide it by other means.

<gb> What kind of assigment? MoS is an optional box, the MN would have network connectivity even without having a MoS. MoS is just to facilitate optional operations. Thus, It does not need to be assigned, but discovered. An IP address is assigned, an HA is assigned. Everything else is optional for communication.

So I guess that the implicit question is whether assignment is a requirement for us or not. I would say yes.

<gb> no, see above.

- gabor

Let me know
Tele

---

From: <[email-masked]>
Date: Tue, 30 Oct 2007 03:43:25 -0500

The comments were why do we want to use dhcp option 15 at all. They had the idea that MoS is always at home and they did not understand how using dhcp option 15 in a visited network which may give you back that the domain suffix for that visited network is 'example.com', would help in discovering MoS in the home network, eg vodafone.com. I clarified, that option 15 is intended to be used to find out the local domain and use that as an input to the naptr query.

There were no other objections to the document.

- gabor

-----Original Message-----
From: ext Sam Xia [mailto:[email-masked]] 
Sent: Monday, October 29, 2007 6:13 PM
To: Bajko Gabor (Nokia-SIR/MtView)
Cc: 'Telemaco Melia'; [email-masked]
Subject: RE: [MIPSHOP-MIH-DT] Work for version -01

Gabor,

What about your discussion about DNS discovery method with the opposer who objects to utilizing DNS method to publish information for anything.

 Best Regards, Sam Xia 

> First question I have is whether we should compare the HA discovery 
> and the MoS discovery. In my opinion we should.
> we should also consider that the DHCP solution helps the network to 
> perform assignment. If we run discovery via DNS, MoS assignment cannot 
> be done, and we should provide it by other means.
> NEC Europe Limited | Registered Office: NEC House, 1 Victoria Road, 
> London W3 6BL | Registered in England 2832014
> 
>

---

From: Telemaco Melia <[email-masked]>
Date: Wed, 31 Oct 2007 16:10:19 +0100

Guys,

I started with version -01. Yoshi's and David's comments have been accounted for.
The issues not solved are listed below. I need now to thoroughly process the paper from NIST people.
Please let's agree on the open issues via mail if we cannot setup an AC in a reasonable time.
The deadline is submission for -01 version.

Comments?

Tele

Technical issues
================

- MIHFID issue raised by Yoshi (MIHFID recomendations for the MoS but not for the MN)

- Mandating only TCP and UDP (I agree on Gabor's comment that we cannot give too may options for transport)

- Use of DHCP vs. DNS for discovery (previously mentioned in my email)

- Flow -- relation between MIH user and DHCP client (issue raised by Yoshi)

- make this example Section 7.1, and then create a Section 7.2 to include a CS/ES example as well, in which UDP is used for

transport and another MoS location scenario is in effect.

- link layer security where DHCP is used might be better 

- explanation on the TLS/DTLS/IPsec usage and terminology

Editorial issues
================

- Terminology defintions (one sentence for each of them)

- Use PoSh, PoSv, PoS3 instead of MoSv, MoSh, MoS3.

Mipshop WG                                                 T. Melia, Ed.
Internet-Draft                                                       NEC
Intended status: Standards Track                                G. Bajko
Expires: May 3, 2008                                               Nokia
                                                                  S. Das
                                                               Telcordia
                                                               N. Golmie
                                                                    NIST
                                                                  S. Xia
                                                                  Huawei
                                                              JC. Zuniga
                                                            InterDigital
                                                        October 31, 2007

              Mobility Services Transport Protocol Design
                  draft-melia-mipshop-mstp-solution-01

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on May 3, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

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Abstract

   This document describes a design solution for the IEEE 802.21 Media
   Independent Handover (MIH) protocol that addresses identified issues
   associated with the transport of MIH messages.  The document
   describes mechanisms for mobility service (MoS) discovery and
   transport layer mechanisms for the reliable delivery of MIH messages.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Deployment Scenarios . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Scenario S1: Home Network MoS  . . . . . . . . . . . . . .  5
     3.2.  Scenario S2: Visited Network MoS . . . . . . . . . . . . .  6
     3.3.  Scenario S3: Roaming MoS . . . . . . . . . . . . . . . . .  6
     3.4.  Scenario S4: Third party MoS . . . . . . . . . . . . . . .  7
   4.  Solution Overview  . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Architecture . . . . . . . . . . . . . . . . . . . . . . .  8
     4.2.  MIHF Identifiers (FQDN, NAI) . . . . . . . . . . . . . . .  9
   5.  MoS Discovery  . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  MoS Discovery when MN and MoSh are in the home network
           (Scenario S1)  . . . . . . . . . . . . . . . . . . . . . . 10
     5.2.  MoS Discovery when MIN is in visited network and MoSv
           is also in visited network (Scenario S2) . . . . . . . . . 11
     5.3.  MOS Discovery when the MN is in a visited Network and
           Services are at the Home network (Scenario S3) . . . . . . 12
     5.4.  MoS discovery when MIH services are in a 3rd party
           remote network (scenario S4) . . . . . . . . . . . . . . . 13
   6.  MIH Transport Options  . . . . . . . . . . . . . . . . . . . . 14
     6.1.  MIH Message size . . . . . . . . . . . . . . . . . . . . . 15
     6.2.  MIH Message rate . . . . . . . . . . . . . . . . . . . . . 15
     6.3.  Retransmission . . . . . . . . . . . . . . . . . . . . . . 16
     6.4.  NAT Traversal  . . . . . . . . . . . . . . . . . . . . . . 16
     6.5.  General guidelines . . . . . . . . . . . . . . . . . . . . 16
   7.  Operation Flows  . . . . . . . . . . . . . . . . . . . . . . . 17
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 20

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     11.2. Informative References . . . . . . . . . . . . . . . . . . 22
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
   Intellectual Property and Copyright Statements . . . . . . . . . . 24

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1.  Introduction

   This document proposes a solution to the issues identified in the
   problem statement document [I-D.ietf-mipshop-mis-ps] for the layer 3
   transport of IEEE 802.21 MIH protocols.

   The MIH Layer 3 transport problem is divided in two main parts: the
   discovery of a node that supports specific Mobility Services (MoS)
   and the transport of the information between a mobile node (MN) and
   the discovered node.  The discovery process is required for the MN to
   obtain the information needed for MIH protocol communication with a
   peer node.  The information includes the transport address (e.g., the
   IP address) of the peer node and the types of MoS provided by the
   peer node.

   This document lists the major MoS deployment scenarios.  It next
   describes the solution architecture, including the MSTP reference
   model and MIHF identifiers.  A description follows of MoS discovery
   procedures when the MN is in a home or remote network.  The remainder
   of the document describes the MIH transport architecture, example
   message flows for several signaling scenarios, and security issues.

2.  Terminology

   The following terminology is being used:

   MIH  Media Independent Handover

   MIHF  Media Independent Handover Function

   MIHF User  MIH client initiating and terminating MIH signalling

   MIHFID  Media Independent Handover Function Identifier

   MoS  As defined in[I-D.ietf-mipshop-mis-ps] it includes IS, CS, ES
      services defined by the IEEE 802.21 standard.

   MoSh  Mobility Services assigned in the Home Network

   MoSv  Mobility Services assigned in the Visited Network

   MoS3  Mobility Services assigned in a 3rd Party Network

   MN Mobile Node

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   MSTP  Mobility Services Transport Protocol

   IS Infomation Service

   ES Event Service

   CS Command Service

   FQDN  Fully Qualified Domain Name

   NAI  Network Address Identifier

   NAT  Network Address Translator

   DHCP  Dynamic Host Configuration Protocol

   DNS  Domain Name System

   MIH ACK  MIK acknowledgement message

   PoS  Point of Service, a network-side MIHF instance that exchanges
      MIH messages with a MN-based MIHF

3.  Deployment Scenarios

   This section describes the various possible deployment scenarios for
   the MN and the MoS.  The relative positioning of MN and MoS affects
   resource discovery as well as the performance of the MIH signaling
   service.

3.1.  Scenario S1: Home Network MoS

   In this scenario, the MN and the services are located in the home
   network.  We refer to this set of services as MoSh as in Figure 1.
   The MoSh can be located at the access point the MN uses to connect to
   the home network, or it can be located elsewhere.

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   +--------------+  +====+
   | HOME NETWORK |  |MoSh|
   +--------------+  +====+
        /\
        ||
        \/
   +--------+
   |   MN   |
   +--------+

                     Figure 1: MoS in the Home network

3.2.  Scenario S2: Visited Network MoS

   In this scenario, the MN is in the visited network and mobility
   services are also provided by the visited network.  We refer to this
   as MoSv as shown in Figure 2.

             +--------------+
             | HOME NETWORK |
             +--------------+
                   /\
                   ||
                   \/
    +====+ +-----------------+
    |MoSv| | VISITED NETWORK |
    +====+ +-----------------+
                   /\
                   ||
                   \/
               +--------+
               |   MN   |
               +--------+

                   Figure 2: MoSV in the Visited Network

3.3.  Scenario S3: Roaming MoS

   In this scenario, the MN is located in the visited network and all
   MIH services are provided by the home network, as shown in Figure 3.

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    +====+   +--------------+
    |MoSh|   | HOME NETWORK |
    +====+   +--------------+
                   /\
                   ||
                   \/
          +-----------------+
          | VISITED NETWORK |
          +-----------------+
                   /\
                   ||
                   \/
               +--------+
               |   MN   |
               +--------+

            Figure 3: MoS provided by the home while in visited

3.4.  Scenario S4: Third party MoS

   In this scenario, the MN is in its home network or in a visited
   network and services are provided by a 3rd party network.  We refer
   to this situation as MoS3 as shown in Figure 4

                                      +--------------+
                                      | HOME NETWORK |
   +====+    +--------------+         +--------------+
   |MoS3|    | THIRD PARTY  |  <===>        /\
   +====+    +--------------+               ||
                                            \/
                                    +-----------------+
                                    | VISITED NETWORK |
                                    +-----------------+
                                            /\
                                            ||
                                            \/
                                        +--------+
                                        |   MN   |
                                        +--------+

                     Figure 4: MoS form a third party

   Different types of MoS can be provided independently of other types
   and there is no strict relationship between ES, CS and IS, nor is
   there a requirement that the entities that provide these types be co-
   located.  However, while IS tends to involve large amounts of static
   information, ES and CS are dynamic services and some relationship
   between them can be expected, e.g. a handover command (CS) could be

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   issued upon reception of a link event (ES).  Hence, while in theory
   MoS can be implemented in different locations, it is expected that ES
   and CS will be co-located, whereas IS can be co-located with ES/CS or
   located elsewhere.  Therefore, having the flexibility at the MSTP to
   discover different services in different locations is an important
   feature that can be used to optimize handover performance.  Resource
   discovery is discussed in more detail in Section 5.

4.  Solution Overview

   As mentioned in Section 1 the solution space is being divided into
   two functional domains: discovery and transport.  The following
   assumptions have been made:

   o  The solution is aimed at supporting 802.21 MIH services, namely
      Information Service (IS), Event Service (ES), and Command Service
      (CS).

   o  If the MIHFID is available, FQDN or NAI's realm is used for
      mobility service discovery.  The recommendation to the IEEE 802.21
      WG is to restrict discovery to only these two.

   o  The solutions are chosen to cover all possible deployment
      scenarios as described in Section 3.

   o  MoS discovery can be performed during initial network attachment
      or thereafter.

   For the discovering the location of an MoS, the MN could either be
   pre-configured with the address of the MoS, or this address could be
   dynamically assigned through DHCP or DNS by the network.  The dynamic
   assignation methods are described in Section 5.

   The configuration of the MoS could be executed either upon network
   attachment or after successful IP configuration.  The methodology to
   be used depends on the considered deployment scenario.

   Once the MIHF peer has been discovered, MIH information can be
   exchanged between MIH peers over a trasnport protocol such as UDP or
   TCP.  The usage of transport protocols is described in Section 6.

4.1.  Architecture

   Figure 5 depicts the MSTP reference model and its components within a
   node.  The topmost layer is the MIHF user.  This set of applications
   consists of one or more MIH clients that are responsible for such
   operations as maintaining MIH databases associated with the IS,

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   processing Layer 2 triggers as part of the ES, and initiating and
   carrying out handover operations as part of the CS.  Beneath the MIHF
   user set is the MIHF itself.  This function is responsible for MoS
   discovery, as well as creating, maintaining, modifying, and
   destroying MIH signaling associations with other MIHFs located in MIH
   peer nodes.  Below the MIHF are various transport layer protocols as
   well as address resolution functions.

    +--------------------------+
    |       MIHF User          |
    +--------------------------+
                 ||
    +--------------------------+
    |           MIHF           |
    +--------------------------+
        ||         ||       ||
    +---------+ +------+ +-----+
    | TCP/UDP | | DHCP | | DNS |
    +---------+ +------+ +-----+

                            Figure 5: MN stack

   The MIHF relies on the services provided by TCP and UDP for
   transporting MIH messages, and relies on DHCP and DNS for peer
   discovery.  In cases where the peer MIHF IP address is not pre-
   configured, the source MIHF needs to discover it either via DHCP or
   DNS or a combination of both as described in Section 5.  Once the
   peer MIHF is discovered, MIHF must exchange messages with its peer
   over either UDP or TCP.  Specific recommendations regarding the
   choice of transport protocols are provided in Section 6.

   The above reference architecture however does not include other
   services such as message fragmentation and security.  Depending upon
   the MIH service type (e.g., ES, CS and IS) the message size can be
   very large.  In case where the underlying layers do not support
   fragmentation, this may be an issue.  There are no security features
   currently defined as part of the MIH protocol level.  However,
   security can be provided either at the transport or IP layer where it
   is necessary.  Section 8 provides some guidelines and recommendations
   for security.

4.2.  MIHF Identifiers (FQDN, NAI)

   An MIHFID is an identifier required to uniquely identify the MIHF end
   points for delivering the mobility services (MoS).  Thus an MIHF
   identifier needs to be unique within a domain where mobility services
   are provided and invariant to interface IP addresses.  An MIHFID MUST

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   be represented either in the form of an FQDN [RFC2181] or NAI
   [RFC4282].  An MIHFID can be pre-configured or discovered through the
   discovery methods described in Section 5.

5.  MoS Discovery

   The MoS discovery method depends on whether the MN attempts to
   discover an MoS in the visited network, in the home network (if the
   MN is in a remote network), or in a 3rd party remote network that is
   neither the home network nor the visited network.

   In case MoS is provided locally (scenarios S1 and S2) , the
   techniques [I-D.bajko-mos-dhcp-options] and
   [I-D.bajko-mos-dns-discovery] should be used to transfer MoS
   information from the network to the MN (via DHCP or DNS).  In case
   MoS is provided in the home network while the MN is in the visited
   network (scenario S3), an interaction between the DHCP and AAA
   infrastructure is required similarly to what specified in
   [I-D.ietf-mip6-bootstrapping-integrated-dhc].  It is assumed
   therefore that MoS assignment is performed during access
   authentication and authorization.  In case MoS is provided in a
   remote network other than visited or home network (scenario S4), the
   MN uses only DNS based methods.

5.1.  MoS Discovery when MN and MoSh are in the home network (Scenario
      S1)

   To discover an MoS in the home network, the MN SHOULD use the DNS
   based MoS discovery method described in
   [I-D.bajko-mos-dns-discovery].  In order to use that mechanism, the
   MN MUST first find out the domain name of its home network.  Home
   domains are usually pre-configured in the MNs, thus the MN can simply
   read its configuration data to find out the home domain name
   (scenario S1).  The DNS query option is shown in Figure 6b.
   Alternatively, the MN MAY use the DHCP options for MoS
   discovery[I-D.bajko-mos-dhcp-options] as shown inFigure 6a.

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                              +-------+
               +----+         |Domain |
               | MN |-------->|Name   |
               +----+         |Server |
                              +-------+
                [email-masked]

                             (a) using DNS Query

                            +-----+      +------+
               +----+       |     |      |DHCP  |
               | MN |<----->| DHCP|<---->|Server|
               +----+       |Relay|      |      |
                            +-----+      +------+

                             (b)  Using DHCP Option

    Figure 6: MOS Discovery (a) Using DNS query, (b) using DHCP option

5.2.  MoS Discovery when MIN is in visited network and MoSv is also in
      visited network (Scenario S2)

   To discover an MoS in the visited network, the MN SHOULD attempt to
   use the DHCP options for MoS discovery [I-D.bajko-mos-dhcp-options]
   as shown in Figure 7a.  If the DHCP method fails, the MN SHOULD
   attempt to use the DNS based MoS discovery method described in
   [[I-D.bajko-mos-dns-discovery] as shown in Figure 7b.  In order to
   use that, the MN MUST first learn the domain name of the local
   network.  There are a number of ways how the domain name of a network
   can be learned:

   DHCP --  In order to find out the domain name of the local network,
      the MN SHOULD use the dhcpv4 option 15 for learning the domain
      name [RFC1533].  A similar solution is available for dhcpv6
      [I-D.ietf-dhc-dhcpv6-opt-dnsdomain] .

   Reverse dns query --  When DHCP does not provide the required domain
      name, the MN MAY use reverse DNS (DNS PTR record) to find the
      domain name associated with the IP address it is using in the
      visited network.  Note, that when a NAT device exists between the
      MN and the visited network, the MN will first need to find out the
      external IP address of the NAT device.  Some possible methods for
      determining the NAT's external IP address are STUN [RFC3849] or
      UPnP [UPnP_IDG_DCP].  Once the MN has determined the external IP
      address of the NAT device, it MUST use that address in the reverse

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      DNS query.

                         +-----+      +------+
            +----+       |     |      |DHCP  |
            | MN |<----->| DHCP|<---->|Server|
            +----+       |Relay|      |      |
                         +-----+      +------+

                   (a) MOS Discovery using DHCP options

                           +-------+
            +----+         |Domain |
            | MN |-------->|Name   |
            +----+         |Server |
                           +-------+

                    (b) Reverse DNS Query (starting from the IP address)

         Figure 7: Discovery (a) using DHCP option, (b) Using DNS

5.3.  MOS Discovery when the MN is in a visited Network and Services are
      at the Home network (Scenario S3)

   To discover an MoS in the visited network when MIH services are
   provided by the home network, the MN SHOULD use the DHCP option along
   with network access authentication.  This procedure is shown in
   Figure 8.  Upon network access authentication and interaction with
   the NAS the home AAA (AAAh) verifies in the AAA profile that the MN
   is allowed to use the MoS in the home network.  The AAAh assigns the
   MoS in the home network and sends back the information to the NAS.
   The MN sends a DHCP information request as per [RFC3315] containing
   Home Network Identifier Option indicating the need to allocate the
   MoS in the home network.  The relay agent in the visited network
   intercepts the Information request from the MN and it forwards to the
   DHCP server inserting the MIH Relay Agent Option containing the info
   received by the AAAh.  The DHCP server can then reply to the MN by
   sending the Home Network Information Option.  The MN receives the
   MoSh address.

   It should be noted that the AAAh does not know the preferences of the
   MN, i.e. whether the MoS should be allocated in the home or in
   visited.  The MoS info is stored at the relay agent and forwarded to
   the MN according to the flags in the Home Network Identifier Option.

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                           Visited             |          Home
                                               |
                                               |
                           +-------+           |        +-------+
                           |       |           |        |       |
                           |AAAV   |-----------|--------|AAAH   |
                           |       |           |        |       |
                           |       |           |        |       |
                           +-------+           |        +-------+
                               |               |
                               |               |
                               |               |
                               |               |
                               |               |       +--------+
                               |               |       |        |
                               |               |       |  MoSh  |
                           +-----+    +------+ |       +--------+
               +----+      |     |    |DHCP  | |
               | MN |------| NAS/|----|Server| |
               +----+      | DHCP|    |      | |
                           |Relay|    |      | |
                           +-----+    +------+ |
                                               |

          AAAv -- Visited AAA
          AAAH -- Home AAA
          NAS  -- Network Access Server

   Figure 8: MOS Discovery using Network Access Authentication and DHCP
                                  options

5.4.  MoS discovery when MIH services are in a 3rd party remote network
      (scenario S4)

   To discover an MoS in a remote network other than home network, the
   MN MUST use the DNS based MoS discovery method described in
   [I-D.bajko-mos-dns-discovery].  The MN MUST first learn the domain
   name of the network containing the MoS it is searching for.  If the
   MN does not yet know the domain name of the network, learning it may
   require more than one operation, as pre-configuration and DHCP
   methods can not be used.  The MN MAY attempt to first discover an MoS
   in either the local or home network (as in Figure 9 part (a)) and
   query that MoS to find out the domain name of a specific network or
   the domain name of a network at a specific location (as in Figure 9
   part (b)).  Alternatively, the MN MAY query an MoS previously known
   to learn the domain name of the desired network (e.g., via an IS
   Query).  Finally the MN can use DNS queries to find MoS in the remote

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   network as inFigure 9 part(c).  It should be noted that step c can
   only be performed upon obtaining the domain name of the remote
   network.

                                   +-------+
                    +----+         |DHCP   |
                    | MN |-------->|       |
                    +----+         |Server |
                                   +-------+
                     [email-masked]

           (a) Discover MoS in local network with DHCP
                               +------------+
                +----+         |            |
                |    |         |Information |
                | MN |-------->| Server     |
                |    |         |(previously |
                +----+         |discovered) |
                               +------------+

      (b) Using IS query to find the FQDN on the remote network

                                 +-------+
                  +----+         |Domain |
                  | MN |-------->|Name   |
                  +----+         |Server |
                                 +-------+
                   [email-masked]

            (c) using DNS Query in the remote network

     Figure 9: MOS Discovery using (a) DHCP Options, (b) IS Query to a
                        known Server, (c) DNS Query

6.  MIH Transport Options

   Once the Mobility Services have been discovered, MIH peers MUST
   exchange information over either TCP or UDP.  While either protocol
   can provide the basic transport functionality required, there are
   performance trade-offs and unique characteristics associated with
   each that need to be considered in the context of the MIH services
   for different network loss and congestion conditions.  The objectives
   of this section are to discuss these trade-offs for different MIH
   settings such as the MIH message size and rate, and the
   retransmission parameters.  In addition, factors such as NAT
   traversal are also discussed.  Given the reliability requirements for
   the MIH transport, it is assumed in this discussion that the MIH ACK

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   mechanism is to be used in conjunction with UDP, while it is
   preferred to avoid using MIH ACKs with TCP since TCP includes
   acknowledgement and retransmission functionality

6.1.  MIH Message size

   Although the MIH message size varies widely from about 30 bytes (for
   a broadcast capability discovery request) to around 65000 bytes (for
   an IS MIH_Get_Information response primitive), a typical MIH message
   size for the ES/CS service ranges between 50 to100 bytes [IEEE80221].
   Thus, considering the effects of the MIH message size on the
   performance of the transport protocol brings us to discussing two
   main issues, related to fragmentation of long messages in the context
   of UDP and the concatenation of short messages in the context of TCP.
   Since transporting long MIH messages may require fragmentation that
   is not available in UDP, if MIH is using UDP a limit MUST be set on
   the size of the MIH message, unless fragmentation functionality is
   added to the MIH layer or IP layer fragmentation is used instead.  In
   this latter case, the loss of an IP fragment leads to the
   retransmission of an entire MIH message, which in turn leads to poor
   end-to-end delay performance in addition to wasted bandwidth
   utilization.  Additional recommendations in
   [I-D.ietf-tsvwg-udp-guidelines] apply for limiting the size of the
   MIH message when using UDP and assuming IP layer fragmentation.  In
   terms of dealing with short messages, TCP has the capability to
   concatenate very short messages in order to reduce the overall
   bandwidth overhead.  However, this reduced overhead comes at the cost
   of additional delay to complete an MIH transaction, which may not be
   acceptable for CS and ES services.  Note also that TCP is a stream
   oriented protocol and measures data flow in terms of bytes, not
   messages.  Thus it is possible to split messages across multiple TCP
   segments if they are long enough.  Even short messages can be split
   across two segments.  This can also cause unacceptable delays,
   especially if the link quality is severely degraded as is likely to
   happen when the MN is exiting a wireless access coverage area.

6.2.  MIH Message rate

   The frequency of MIH messages varies according to the MIH service
   type.  It is expected that CS/ES message arrive at a rate of one in
   hundreds of milliseconds in order to capture quick changes in the
   environment and/ or process handover commands.  On the other hand, IS
   messages are exchanged mainly every time a new network is visited
   which may be in order of hours or days.  Therefore a burst of either
   short CS/ES messages or long IS message exchanges (in the case of
   multiple MIH nodes requesting information) may lead to network
   congestion.  While the built-in rate-limiting controls available in
   TCP may be well suited for dealing with these congestion conditions,

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   this may result in large transmission delays that may be unacceptable
   for the timely delivery of ES/CS messages.  On the other hand, if UDP
   is used, a rate-limiting effect similar to the one obtained with TCP
   may be obtained by adequately adjusting the parameters of a token
   bucket regulator as defined in the MIH specifications [IEEE80221].
   Recommendations for tocken bucket parameter settings are specific to
   the scenario considered.

6.3.  Retransmission

   For TCP, the retransmission timeout is adjusted according to the
   measured RTT.  However due to the exponential backoff mechanism, the
   delay associated with retransmission timeouts may increase
   significantly with increased packet loss.

   If UDP is being used to carry MIH messages, MIH MUST use MIH ACKs.
   An MIH message is retransmitted if its corresponding MIH ACK is not
   received by the generating node within a timeout interval set by the
   MIHF.  This approach does not include an exponential backoff and
   therefore tends to degrade more gracefully than TCP when the packet
   loss rate becomes large, in the sense that the expected delay does
   not increase exponentially.  The number of retransmissions is
   limited, which reduces head-of-line blocking of other MIH messages,
   but this can cause important ES/CS messages to be lost.

6.4.  NAT Traversal

   There are no known issues for NAT traversal when using TCP.  The
   default connection timeout of 24 hours is considered adequate for MIH
   transport purposes.  However, issues with NAT traversal using UDP are
   documented in [I-D.ietf-tsvwg-udp-guidelines].  Communication
   failures are experienced when middleboxes destroy the per-flow state
   associated with an application session during periods when the
   application does not exchange any UDP traffic.  Hence, communication
   between the MN and the MoS SHOULD be able to gracefully handle such
   failures and implement mechanisms to re-establish their UDP sessions.
   In addition and in order to avoid such failures, MIH messages MAY be
   sent periodically, similarly to keep-alive messages, to attempt to
   refresh middlebox state (e.g.  ES reports could be used for this
   purpose).  As [RFC4787] requires a minimum state timeout of two
   minutes or more, MIH messages using UDP as transport SHOULD be sent
   once every two minutes.

6.5.  General guidelines

   Since ES and CS messages are small in nature and have tight latency
   requirements, UDP in combination with MIH acknowledgement SHOULD be
   used for transporting ES and CS messages.  On the other hand, IS

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   messages are more resilient in terms of latency constraints and some
   long IS messages could exceed the MTU of the path to the destination.
   Therefore, TCP SHOULD be used for transporting IS messages.  For both
   UDP and TCP cases, if a port number is not explicitly assigned (e.g.
   by the DNS SRV), MIH messages sent over UDP or TCP MUST use the
   default port number.

7.  Operation Flows

   Figure 10 gives an example operation flow between MIHF peers when an
   MIH user requests for an IS service.  Scenario 1 is in effect, i.e.
   the MoS and the MN are both in the MN's home network.  Thus DHCP is
   used for MoS discovery and TCP is used for establishing a transport
   connection to carry the IS messages.  When MOS is not pre-configured,
   the MIH user needs to discover the IP address of MOS to communicate
   with the remote MIHF.  Therefore the MIH user sends a discovery
   request message to the local MIHF as defined in [IEEE80221]

   In this example, we assume that MoS discovery is performed before a
   transport connection is established with the remote MIHF, and the
   DHCP client process is invoked via some internal APIs.  DHCP Client
   sends DHCP INFORM message according to standard DHCP and with the MoS
   option as defined in [I-D.bajko-mos-dhcp-options].  DHCP server
   replies via DHCP ACK message with the IP address of the MoS.  The MOS
   address is then passed to the MIHF locally via some internal APIs.
   MIHF generates the discovery response message and passes it on to the
   corresponding MIH user.  The MIH user generates an IS query addressed
   to the remote MoS.  MIHF invokes the underlying TCP client which
   establishes a transport connection with the remote peer.  Once the
   transport connection is established, MIHF sends the IS query via MIH
   protocol REQUEST message.  The message and query arrive at the
   destination MIHF and MIH user respectively.  The MoS MIH user
   responds to the corresponding IS query and the MoS MIHF sends the IS
   response via MIH protocol RESPONSE message.  The message arrives to
   the source MIHF which passes the IS response on to the corresponding
   MIH user.

                   MN                                             MoS
|======================================|    |======|   |======================|
+------+   +-----+   +------+  +------+     +------+   +------+  +----+  +----+
| MIH  |   |MIHF |   | TCP  |  |DHCP  |     |DHCP  |   | TCP  |  |MIHF|  |MIH |
| User |   |     |   |Client|  |Client|     |Server|   |Server|  |    |  |User|
+------+   +-----+   +------+  +------+     +------+   +------+  +----+  +----+
    |         |          |         |            |          |        |       |
    |Discovery|          |         |            |          |        |       |
    | Request |Invoke DHCP Client  |DHCP INFORM |          |        |       |
    |========>|===================>|===========>|          |        |       |

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    |         |  (internal process)| with MOS   |          |        |       |
    |         |          |         | option     |          |        |       |
    |         |          |         |            |          |        |       |
    |         |          |         |   DHCP ACK |          |        |       |
    |         |          |         |<===========|          |        |       |
    |         | Inform MoS address |            |          |        |       |
    |         |<===================|            |          |        |       |
    |         | (internal process) |            |          |        |       |
    |Discovery|          |         |            |          |        |       |
    |response |          |         |            |          |        |       |
    |<========|          |         |            |          |        |       |
    |         |          |         |            |          |        |       |
    |IS Query |          |         |            |          |        |       |
    |========>|          |         |            |          |        |       |
    |         |          |         |            |          |        |       |
    |         |Invoke TCP|         |            |          |        |       |
    |         |=========>|         |            |          |        |       |
    |         | client   |    TCP connection established    |        |       |
    |         |          |<===============================>|        |       |
    |         |          |         |            |          |        |       |
    |         |          |         |            |          |        |       |
    |         |          |         |            |          |        |       |
    |         |          | IS  QUERY REQUEST (via MIH protocol)     |       |
    |         |====================================================>|       |
    |         |          |         |             |         |        |IS     |
    |         |          |         |             |         |        |QUERY  |
    |         |          |         |             |         |        |REQUEST|
    |         |          |         |             |         |        |======>|
    |         |          |         |             |         |        |       |
    |         |          |         |             |         |        |QUERY  |
    |         |          |         |             |         |        |RESPONSE
    |         |          |         |             |         |        |<======|
    |         |          |         |             |         |        |       |
    |         |          |  IS QUERY RESPONSE (via MIH protocol)    |       |
    |         |<====================================================|       |
    |         |          |         |             |         |        |       |
    |    IS   |          |         |             |         |        |       |
    |RESPONSE |          |         |             |         |        |       |
    |<========|          |         |             |         |        |       |
    |         |          |         |             |         |        |       |
    |         |          |         |             |         |        |       |

          Figure 10: Example Flow of Operation Involving MIH User

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8.  Security Considerations

   There are a number of security issues that need to be taken into
   account during node discovery and information exchange via a
   transport connection [I-D.ietf-mipshop-mis-ps]

   In case where DHCP is used for node discovery and authentication of
   the source and content of DHCP messages are required, it is
   recommended that network administrators should use DHCP
   authentication option described in [RFC3118].  This will also protect
   the denial of service attacks to DHCP server.[RFC3118] provides
   mechanisms for both entity authentication and message authentication.

   In case where DNS is used for discovering MoS, fake DNS requests and
   responses may cause DoS and the inability of the MN to perform a
   proper handover, respectively.  Where networks are exposed to such
   DoS, it is recommended that DNS service providers use the Domain Name
   System Security Extensions (DNSSEC) as described in [RFC4033].
   Readers may also refer to
   [I-D.ietf-dnsop-dnssec-operational-practices] to consider the aspects
   of DNSSEC Operational Practices.

   In case where reliable transport protocol such as TCP is used for
   transport connection between two MIHF peers, TLS [RFC4346] should be
   used for message confidentiality and data integrity.  In particular,
   TLS is designed for client/server applications and to prevent
   eavesdropping, tampering, or message forgery.  Readers should also
   follow the recommendations in [RFC4366] that provides generic
   extension mechanisms for the TLS protocol suitable for wireless
   environments.

   In case where unreliable transport protocol such as UDP is used for
   transport connection between two MIHF peers, DTLS [RFC4347] should be
   used for message confidentiality and data integrity.  The DTLS
   protocol is based on the Transport Layer Security (TLS) protocol and
   provides equivalent security guarantees.

   Alternatively, generic IP layer security, such as IPSec [RFC2401] may
   be used instead of a specific transport layer secuity for a specific
   transport.

9.  IANA Considerations

   This document registers the following TCP and UDP port(s) with IANA:

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 Keyword         Decimal   Description
 -------        -------    -----------
 ieee-mih-IS    XXX/tcp    Media Independent Handover Information Services
 ieee-mih-IS    XXX/udp    Media Independent Handover Information Services
 ieee-mih-ES    XXX/tcp    Media Independent Handover Event Services
 ieee-mih-ES    XXX/udp    Media Independent Handover Event Services
 ieee-mih-CS    XXX/tcp    Media Independent Handover Command Services
 ieee-mih-CS    XXX/udp    Media Independent Handover Command Services

10.  Acknowledgements

   The authors would like to thank Patrick Stupar for his valuable
   comments and fruitful discussions.

11.  References

11.1.  Normative References

   [I-D.bajko-mos-dhcp-options]
              Bajko, G., "Dynamic Host Configuration Protocol (DHCPv4
              and DHCPv6) Options for Mobility  Servers (MoS)",
              draft-bajko-mos-dhcp-options-00 (work in progress),
              August 2007.

   [I-D.bajko-mos-dns-discovery]
              Bajko, G., "Locating Mobility Servers",
              draft-bajko-mos-dns-discovery-00 (work in progress),
              August 2007.

   [I-D.ietf-dhc-dhcpv6-opt-dnsdomain]
              Yan, R., "Domain Suffix Option for DHCPv6",
              draft-ietf-dhc-dhcpv6-opt-dnsdomain-04 (work in progress),
              June 2007.

   [I-D.ietf-dnsop-dnssec-operational-practices]
              Gieben, R. and O. Kolkman, "DNSSEC Operational Practices",
              draft-ietf-dnsop-dnssec-operational-practices-08 (work in
              progress), March 2006.

   [I-D.ietf-mip6-bootstrapping-integrated-dhc]
              Chowdhury, K. and A. Yegin, "MIP6-bootstrapping for the
              Integrated Scenario",
              draft-ietf-mip6-bootstrapping-integrated-dhc-05 (work in
              progress), July 2007.

   [I-D.ietf-mipshop-mis-ps]

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              Melia, T., "Mobility Services Transport: Problem
              Statement", draft-ietf-mipshop-mis-ps-03 (work in
              progress), August 2007.

   [I-D.ietf-tsvwg-udp-guidelines]
              Eggert, L. and G. Fairhurst, "UDP Usage Guidelines for
              Application Designers", draft-ietf-tsvwg-udp-guidelines-03
              (work in progress), September 2007.

   [IEEE80221]
              "Draft IEEE Standard for Local and Metropolitan Area
              Networks: Media Independent Handover Services", IEEE LAN/
              MAN Draft  IEEE P802.21/D07.00, July 2007.

   [RFC1533]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 1533, October 1993.

   [RFC1536]  Kumar, A., Postel, J., Neuman, C., Danzig, P., and S.
              Miller, "Common DNS Implementation Errors and Suggested
              Fixes", RFC 1536, October 1993.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, July 1997.

   [RFC2401]  Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, November 1998.

   [RFC2988]  Paxson, V. and M. Allman, "Computing TCP's Retransmission
              Timer", RFC 2988, November 2000.

   [RFC3118]  Droms, R. and W. Arbaugh, "Authentication for DHCP
              Messages", RFC 3118, June 2001.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849, July 2004.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",

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              RFC 4033, March 2005.

   [RFC4282]  Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
              Network Access Identifier", RFC 4282, December 2005.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, April 2006.

   [RFC4366]  Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)
              Extensions", RFC 4366, April 2006.

   [RFC4787]  Audet, F. and C. Jennings, "Network Address Translation
              (NAT) Behavioral Requirements for Unicast UDP", BCP 127,
              RFC 4787, January 2007.

11.2.  Informative References

Authors' Addresses

   Telemaco Melia (editor)
   NEC

   Email: [email-masked]

   Gabor Bajko
   Nokia

   Email: [email-masked]

   Subir Das
   Telcordia

   Email: [email-masked]

   Nada Golmie
   NIST

   Email: [email-masked]

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   Sam Xia
   Huawei

   Email: [email-masked]

   Juan Carlos Zuniga
   InterDigital

   Email: [email-masked]

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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
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   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
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Acknowledgment

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   Administrative Support Activity (IASA).

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---

From: "Stefano Faccin" <[email-masked]>
Date: Wed, 31 Oct 2007 08:56:05 -0700

Hello guys,
I'd like to jump into the discussion. Yes, I'm alive, I enjoyed
following your technical discussion so far. BTW, happy Halloween to
those that celebrate it.

I think at this stage it is quite difficult to justify having only the
DHCP option wrt the DNS one, or vice versa. I see that different
deployment scenarios will have different needs, therefore I do not think
that as IETF we can conclude e.g. that the DNS solution is the only way
to do. At the same time, I do not think we should conclude that the DHCP
one should be the only way to go.

Yes, options add complication, but at the same time they add
flexibility. I think this protocol requires as much flexibility as
possible to find applicability in real-life systems, therefore I would
suggest keeping both options in.

Cheers,
Stefano