draft-ietf-shim6-multihome-shim-api-09.txt   draft-ietf-shim6-multihome-shim-api-10.txt 
SHIM6 Working Group M. Komu SHIM6 Working Group M. Komu
Internet-Draft HIIT Internet-Draft HIIT
Intended status: Informational M. Bagnulo Intended status: Informational M. Bagnulo
Expires: January 14, 2010 UC3M Expires: April 29, 2010 UC3M
K. Slavov K. Slavov
S. Sugimoto, Ed. S. Sugimoto, Ed.
Ericsson Ericsson
July 13, 2009 October 26, 2009
Socket Application Program Interface (API) for Multihoming Shim Socket Application Program Interface (API) for Multihoming Shim
draft-ietf-shim6-multihome-shim-api-09 draft-ietf-shim6-multihome-shim-api-10
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on January 14, 2010. This Internet-Draft will expire on April 29, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info). publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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equipped with a conceptual sub-layer (hereafter "shim") inside the IP equipped with a conceptual sub-layer (hereafter "shim") inside the IP
layer that maintains mappings between identifiers and locators. layer that maintains mappings between identifiers and locators.
Examples of the shim are SHIM6 and HIP. Examples of the shim are SHIM6 and HIP.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. System Overview . . . . . . . . . . . . . . . . . . . . . . . 6 3. System Overview . . . . . . . . . . . . . . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Socket Options for Multihoming Shim Sub-Layer . . . . . . . . 9 5. Socket Options for Multihoming Shim Sub-layer . . . . . . . . 9
5.1. SHIM_ASSOCIATED . . . . . . . . . . . . . . . . . . . . . 13 5.1. SHIM_ASSOCIATED . . . . . . . . . . . . . . . . . . . . . 13
5.2. SHIM_DONTSHIM . . . . . . . . . . . . . . . . . . . . . . 14 5.2. SHIM_DONTSHIM . . . . . . . . . . . . . . . . . . . . . . 14
5.3. SHIM_HOT_STANDBY . . . . . . . . . . . . . . . . . . . . . 15 5.3. SHIM_HOT_STANDBY . . . . . . . . . . . . . . . . . . . . 15
5.4. SHIM_PATHEXPLORE . . . . . . . . . . . . . . . . . . . . . 15 5.4. SHIM_PATHEXPLORE . . . . . . . . . . . . . . . . . . . . 15
5.5. SHIM_LOC_LOCAL_PREF . . . . . . . . . . . . . . . . . . . 16 5.5. SHIM_LOC_LOCAL_PREF . . . . . . . . . . . . . . . . . . . 16
5.6. SHIM_LOC_PEER_PREF . . . . . . . . . . . . . . . . . . . . 17 5.6. SHIM_LOC_PEER_PREF . . . . . . . . . . . . . . . . . . . 17
5.7. SHIM_LOC_LOCAL_RECV . . . . . . . . . . . . . . . . . . . 18 5.7. SHIM_LOC_LOCAL_RECV . . . . . . . . . . . . . . . . . . . 18
5.8. SHIM_LOC_PEER_RECV . . . . . . . . . . . . . . . . . . . . 19 5.8. SHIM_LOC_PEER_RECV . . . . . . . . . . . . . . . . . . . 19
5.9. SHIM_LOC_LOCAL_SEND . . . . . . . . . . . . . . . . . . . 19 5.9. SHIM_LOC_LOCAL_SEND . . . . . . . . . . . . . . . . . . . 19
5.10. SHIM_LOC_PEER_SEND . . . . . . . . . . . . . . . . . . . . 21 5.10. SHIM_LOC_PEER_SEND . . . . . . . . . . . . . . . . . . . 21
5.11. SHIM_LOCLIST_LOCAL . . . . . . . . . . . . . . . . . . . . 21 5.11. SHIM_LOCLIST_LOCAL . . . . . . . . . . . . . . . . . . . 21
5.12. SHIM_LOCLIST_PEER . . . . . . . . . . . . . . . . . . . . 23 5.12. SHIM_LOCLIST_PEER . . . . . . . . . . . . . . . . . . . . 23
5.13. SHIM_APP_TIMEOUT . . . . . . . . . . . . . . . . . . . . . 23 5.13. SHIM_APP_TIMEOUT . . . . . . . . . . . . . . . . . . . . 23
5.14. SHIM_DEFERRED_CONTEXT_SETUP . . . . . . . . . . . . . . . 24 5.14. SHIM_DEFERRED_CONTEXT_SETUP . . . . . . . . . . . . . . . 24
5.15. Error Handling . . . . . . . . . . . . . . . . . . . . . . 25 5.15. Applicability . . . . . . . . . . . . . . . . . . . . . . 25
6. Ancillary Data for Multihoming Shim . . . . . . . . . . . . . 25 5.16. Error Handling . . . . . . . . . . . . . . . . . . . . . 25
6.1. Get Locator Information from Incoming Packet . . . . . . . 27 6. Ancillary Data for Multihoming Shim Sub-layer . . . . . . . . 26
6.2. Specify Locator Information for Outgoing Packet . . . . . 27 6.1. Get Locator from Incoming Packet . . . . . . . . . . . . 27
6.3. Notification from Application to Multihoming Shim . . . . 27 6.2. Set Locator for Outgoing Packet . . . . . . . . . . . . . 27
6.3. Notification from Application to Multihoming Shim
Sub-layer . . . . . . . . . . . . . . . . . . . . . . . . 27
6.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 28
7. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 28 7. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 28
7.1. Placeholder for Locator Information . . . . . . . . . . . 28 7.1. Placeholder for Locator Information . . . . . . . . . . . 28
7.1.1. Handling Locator behind NAT . . . . . . . . . . . . . 29 7.1.1. Handling Locator behind NAT . . . . . . . . . . . . . 29
7.2. Path Exploration Parameter . . . . . . . . . . . . . . . . 30 7.2. Path Exploration Parameter . . . . . . . . . . . . . . . 30
7.3. Feedback Information . . . . . . . . . . . . . . . . . . . 30 7.3. Feedback Information . . . . . . . . . . . . . . . . . . 31
8. Implications for Existing Socket API Extensions . . . . . . . 31 8. System Requirements . . . . . . . . . . . . . . . . . . . . . 32
9. Resolving Conflicts with Preference Values . . . . . . . . . . 32 9. Implications for Existing Socket API Extensions . . . . . . . 32
9.1. Implicit Forking . . . . . . . . . . . . . . . . . . . . . 32 10. Resolving Conflicts with Preference Values . . . . . . . . . . 33
10. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 33 10.1. Implicit Forking . . . . . . . . . . . . . . . . . . . . 33
10.1. Naming at Socket Layer . . . . . . . . . . . . . . . . . . 33 11. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 34
10.2. Additional Requirements from Applications . . . . . . . . 33 11.1. Naming at Socket Layer . . . . . . . . . . . . . . . . . 34
10.3. Issues of Header Conversion among Different Address 11.2. Additional Requirements from Applications . . . . . . . . 34
Family . . . . . . . . . . . . . . . . . . . . . . . . . . 33 11.3. Issues of Header Conversion among Different Address
10.4. Handling of Unknown Locator Provided by Application . . . 34 Family . . . . . . . . . . . . . . . . . . . . . . . . . 34
11. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 11.4. Handling of Unknown Locator Provided by Application . . . 35
11.1. Changes from version 00 to version 01 . . . . . . . . . . 34 12. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
11.2. Changes from version 01 to version 02 . . . . . . . . . . 34 12.1. Changes from version 00 to version 01 . . . . . . . . . . 35
11.3. Changes from version 02 to version 03 . . . . . . . . . . 35 12.2. Changes from version 01 to version 02 . . . . . . . . . . 35
11.4. Changes from version 03 to version 04 . . . . . . . . . . 35 12.3. Changes from version 02 to version 03 . . . . . . . . . . 36
11.5. Changes from version 04 to version 05 . . . . . . . . . . 35 12.4. Changes from version 03 to version 04 . . . . . . . . . . 36
11.6. Changes from version 05 to version 06 . . . . . . . . . . 35 12.5. Changes from version 04 to version 05 . . . . . . . . . . 36
11.7. Changes from version 06 to version 07 . . . . . . . . . . 35 12.6. Changes from version 05 to version 06 . . . . . . . . . . 36
11.8. Changes from version 07 to version 08 . . . . . . . . . . 35 12.7. Changes from version 06 to version 07 . . . . . . . . . . 36
11.9. Changes from version 08 to version 09 . . . . . . . . . . 35 12.8. Changes from version 07 to version 08 . . . . . . . . . . 36
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35 12.9. Changes from version 08 to version 09 . . . . . . . . . . 36
13. Security Considerations . . . . . . . . . . . . . . . . . . . 36 12.10. Changes from version 09 to version 10 . . . . . . . . . . 36
14. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 36 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 36 14. Security Considerations . . . . . . . . . . . . . . . . . . . 37
16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37 15. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 37
16.1. Normative References . . . . . . . . . . . . . . . . . . . 37 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 37
16.2. Informative References . . . . . . . . . . . . . . . . . . 37 17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Appendix A. Context Forking . . . . . . . . . . . . . . . . . . . 38 17.1. Normative References . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40 17.2. Informative References . . . . . . . . . . . . . . . . . 38
Appendix A. Context Forking . . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction 1. Introduction
HIP and SHIM6 have a commonality in their protocol design in the HIP and SHIM6 have a commonality in their protocol design in the
sense that the semantic roles of an IP address, i.e., an identifier sense that the semantic roles of an IP address, i.e., an identifier
and a locator, are distinguished. Separation of identifier and and a locator, are distinguished. Separation of identifier and
locator is done by introducing a "shim" inside the IP layer which locator is done by introducing a "shim" inside the IP layer which
maintains mapping of the identifier and associated locators. This maintains mapping of the identifier and associated locators. This
design principle is called "identifier/locator separation" and the design principle is called "identifier/locator separation" and the
shim is referred to as a "shim sub-layer" in this document. shim is referred to as a "shim sub-layer" in this document.
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multihomed environments. In addition, this document aims to provide multihomed environments. In addition, this document aims to provide
necessary information for developers of multihoming shim protocols to necessary information for developers of multihoming shim protocols to
implement API for enabling advanced locator management. implement API for enabling advanced locator management.
2. Terminology 2. Terminology
This section provides terminology used in this document. Basically This section provides terminology used in this document. Basically
most of the terms used in this document are taken from the following most of the terms used in this document are taken from the following
documents: documents:
o SHIM6 Protocol Specification[I-D.ietf-shim6-proto] o SHIM6 Protocol Specification[RFC5533]
o HIP Architecture[RFC4423] o HIP Architecture[RFC4423]
o Reachability Protocol (REAP)[I-D.ietf-shim6-failure-detection] o Reachability Protocol (REAP)[RFC5534]
In this document, the term "IP" refers to both IPv4 and IPv6, unless In this document, the term "IP" refers to both IPv4 and IPv6, unless
the protocol version is specifically mentioned. The following are the protocol version is specifically mentioned. The following are
definitions of terms frequently used in this document: definitions of terms frequently used in this document:
o Endpoint identifier (EID) - The identifier used by the application o Endpoint identifier (EID) - The identifier used by the application
to specify the endpoint of a given communication. Applications to specify the endpoint of a given communication. Applications
may handle EIDs in various ways such as long-lived connections, may handle EIDs in various ways such as long-lived connections,
callbacks, and referrals[I-D.ietf-shim6-app-refer]. callbacks, and referrals[I-D.ietf-shim6-app-refer].
* In the case of SHIM6, an identifier called a ULID serves as an * In the case of SHIM6, an identifier called a ULID serves as an
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serves as an EID. A Host Identifier is derived from the public serves as an EID. A Host Identifier is derived from the public
key of a given host. For the sake of backward compatibility key of a given host. For the sake of backward compatibility
with the sockets API, the Host Identifier is represented in a with the sockets API, the Host Identifier is represented in a
form of hash of public key. form of hash of public key.
o Locator - The IP address actually used to deliver IP packets. o Locator - The IP address actually used to deliver IP packets.
Locators are present in the source and destination fields of the Locators are present in the source and destination fields of the
IP header of a packet on the wire. IP header of a packet on the wire.
* List of locators - A list of locators associated with an EID. * List of locators - A list of locators associated with an EID.
There are two lists of locators stored in a given context. One There are two lists of locators stored in a given context. One
is associated with the local EID and the other is associated is associated with the local EID and the other is associated
with the remote EID. As defined in [I-D.ietf-shim6-proto], the with the remote EID. As defined in [RFC5533], the list of
list of locators associated with an EID 'A' is denoted as locators associated with an EID 'A' is denoted as Ls(A).
Ls(A).
* Preferred locator - The (source/destination) locator currently * Preferred locator - The (source/destination) locator currently
used to send packets within a given context. As defined in used to send packets within a given context. As defined in
[I-D.ietf-shim6-proto], the preferred locator of a host 'A' is [RFC5533], the preferred locator of a host 'A' is denoted as
denoted as Lp(A). Lp(A).
o Shim - The conceptual sub-layer inside the IP layer which o Shim - The conceptual sub-layer inside the IP layer which
maintains mappings between EIDs and locators. An EID can be maintains mappings between EIDs and locators. An EID can be
associated with more than one locator at a time when the host is associated with more than one locator at a time when the host is
multihomed. The term 'shim' does not refer to a specific protocol multihomed. The term 'shim' does not refer to a specific protocol
but refers to the conceptual sub-layer inside the IP layer. but refers to the conceptual sub-layer inside the IP layer.
o Identifier/locator adaptation - The adaptation performed at the o Identifier/locator adaptation - The adaptation performed at the
shim sub-layer which may end up re-writing the source and/or shim sub-layer which may end up re-writing the source and/or
destination addresses of an IP packet. In the outbound packet destination addresses of an IP packet. In the outbound packet
processing, the EID pair is converted to the associated locator processing, the EID pair is converted to the associated locator
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(faulty operation). (faulty operation).
o Working address pair - The address pair is considered to be o Working address pair - The address pair is considered to be
"working" if the packet can safely travel from the source to the "working" if the packet can safely travel from the source to the
destination where the packet contains the first address from the destination where the packet contains the first address from the
pair as the source address and the second address from the pair as pair as the source address and the second address from the pair as
the destination address. If reachability is confirmed in both the destination address. If reachability is confirmed in both
directions, the address pair is considered to be working bi- directions, the address pair is considered to be working bi-
directionally. directionally.
o Reachability protocol (REAP) - The protocol for detecting failure o Reachability protocol (REAP) - The protocol for detecting failure
and exploring reachability in a multihomed environment. REAP is and exploring reachability in a multihomed environment. REAP is
defined in [I-D.ietf-shim6-failure-detection]. defined in [RFC5534].
3. System Overview 3. System Overview
Figure 1 illustrates the system overview. The shim sub-layer and Figure 1 illustrates the system overview. The shim sub-layer and
REAP component exist inside the IP layer. Applications use the REAP component exist inside the IP layer. Applications use the
sockets API defined in this document to interface with the shim sub- sockets API defined in this document to interface with the shim sub-
layer and the transport layer for locator management, failure layer and the transport layer for locator management, failure
detection, and path exploration. detection, and path exploration.
It may also be possible that the shim sub-layer interacts with the It may also be possible that the shim sub-layer interacts with the
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* It should be possible to set a list of source and/or * It should be possible to set a list of source and/or
destination locators within a given context: Ls(local) and destination locators within a given context: Ls(local) and
Ls(remote). Ls(remote).
* It should be possible to get a list of source and/or * It should be possible to get a list of source and/or
destination locators within a given context: Ls(local) and destination locators within a given context: Ls(local) and
Ls(remote). Ls(remote).
o Notification from applications to the shim sub-layer about the o Notification from applications to the shim sub-layer about the
status of the communication. The notification occurs in an event- status of the communication. The notification occurs in an event-
based manner. Applications and/or upper layer protocols may based manner. Applications and/or upper layer protocols may
provide positive feedbacks or negative feedbacks to the shim sub- provide positive feedbacks or negative feedbacks to the shim sub-
layer. Note that these feedbacks are mentioned in layer. Note that these feedbacks are mentioned in [RFC5534]]:
[I-D.ietf-shim6-failure-detection]]:
* Applications and/or upper layer protocols (e.g., TCP) may * Applications and/or upper layer protocols (e.g., TCP) may
provide positive feedbacks to the shim sub-layer informing that provide positive feedbacks to the shim sub-layer informing that
the communication is going well. the communication is going well.
* Applications and/or upper layer protocols (e.g., TCP) may * Applications and/or upper layer protocols (e.g., TCP) may
provide negative feedbacks to the shim sub-layer informing that provide negative feedbacks to the shim sub-layer informing that
the communication status is not satisfactory. TCP may detect a the communication status is not satisfactory. TCP may detect a
problem when it does not receive any expected ACK message from problem when it does not receive any expected ACK message from
the peer. Besides, a receipt of an ICMP error message could be the peer. Besides, a receipt of an ICMP error message could be
a clue for the application to detect problems. The REAP module a clue for the application to detect problems. The REAP module
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* Apply shim. The application should be able to explicitly * Apply shim. The application should be able to explicitly
request the shim sub-layer to apply multihoming support. request the shim sub-layer to apply multihoming support.
* Don't apply shim. The application should be able to request * Don't apply shim. The application should be able to request
the shim sub-layer not to apply the multihoming support but to the shim sub-layer not to apply the multihoming support but to
apply normal IP processing at the IP layer. apply normal IP processing at the IP layer.
o An application should be able to know if the communication is now o An application should be able to know if the communication is now
being served by the shim sub-layer or not. being served by the shim sub-layer or not.
o An application should be able to use a common interface to access o An application should be able to use a common interface to access
an IPv4 locator and an IPv6 locator. an IPv4 locator and an IPv6 locator.
5. Socket Options for Multihoming Shim Sub-Layer 5. Socket Options for Multihoming Shim Sub-layer
In this section, socket options that are specific to the shim sub- In this section, socket options that are specific to the shim sub-
layer are defined. layer are defined.
Table 1 shows a list of the socket options that are specific to the Table 1 shows a list of the socket options that are specific to the
multihoming shim sub-layer. An application may use these socket multihoming shim sub-layer. An application may use these socket
options for a given socket either by the getsockopt() system call or options for a given socket either by the getsockopt() system call or
by the setsockopt() system call. All of these socket options are by the setsockopt() system call. All of these socket options are
defined at level SOL_SHIM. defined at level SOL_SHIM.
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| SHIM_CONTEXT_DEFERRED_SETUP | o | o | Get or set the | int | | SHIM_CONTEXT_DEFERRED_SETUP | o | o | Get or set the | int |
| | | | parameter which | | | | | | parameter which | |
| | | | indicates | | | | | | indicates | |
| | | | whether | | | | | | whether | |
| | | | deferred | | | | | | deferred | |
| | | | context setup | | | | | | context setup | |
| | | | is supported or | | | | | | is supported or | |
| | | | not. | | | | | | not. | |
+-----------------------------+-----+-----+-----------------+-------+ +-----------------------------+-----+-----+-----------------+-------+
Table 1: Socket options for multihoming shim Table 1: Socket options for multihoming shim sub-layer
*1: Pointer to a shim_locator which is defined in Section 7. *1: Pointer to a shim_locator which is defined in Section 7.
*2: Pointer to shim_locator data structure. *2: Pointer to shim_locator data structure.
*3: Pointer to an array of shim_locator. *3: Pointer to an array of shim_locator.
*4: Pointer to a shim_pathexplore which is defined in Section 7. *4: Pointer to a shim_pathexplore which is defined in Section 7.
Figure 2 illustrates how the shim specific socket options fit into Figure 2 illustrates how the shim specific socket options fit into
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The SHIM_APP_TIMEOUT option is used to get or set the timeout value The SHIM_APP_TIMEOUT option is used to get or set the timeout value
for application to detect failure. Hence this option is effective for application to detect failure. Hence this option is effective
only when there is a shim context associated with the socket. only when there is a shim context associated with the socket.
The data type of the option value is an integer. The value indicates The data type of the option value is an integer. The value indicates
the period of timeout in seconds to send a REAP Keepalive message the period of timeout in seconds to send a REAP Keepalive message
since the last outbound traffic. By default, the option value is set since the last outbound traffic. By default, the option value is set
to 0, meaning that the option is disabled. When the option is to 0, meaning that the option is disabled. When the option is
disabled, the REAP mechanism follows its default value of Send disabled, the REAP mechanism follows its default value of Send
Timeout value as specified in [I-D.ietf-shim6-failure-detection] Timeout value as specified in [RFC5534]
If the timeout value specified is longer than the Send Timeout If the timeout value specified is longer than the Send Timeout
configured in the REAP component, the REAP Keepalive message should configured in the REAP component, the REAP Keepalive message should
be suppressed. be suppressed.
An error ENOENT will be returned when there is no context associated An error ENOENT will be returned when there is no context associated
with the socket. with the socket.
For example, an application can set the timeout value by using the For example, an application can set the timeout value by using the
socket option as follows. socket option as follows.
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For example, an application can get the option value as follows. For example, an application can get the option value as follows.
int optval; int optval;
int len; int len;
len = sizeof(optval); len = sizeof(optval);
getsockopt(fd, SOL_SHIM, SHIM_DEFERRED_CONTEXT_SETUP, getsockopt(fd, SOL_SHIM, SHIM_DEFERRED_CONTEXT_SETUP,
&optval, &len); &optval, &len);
5.15. Error Handling 5.15. Applicability
All the socket options for the multihoming shim sub-layer are
applicable only to connected sockets. The reason behind this
restriction is that it is necessary for the multihoming shim layer to
identify a target multihoming shim context when an application gives
preference value(s) by a socket option for the multihoming shim sub-
layer. Multihoming shim contexts are, by definition, identified by a
pair of EIDs. Therefore, it is possible for the multihoming shim
sub-layer to identify the target context only when the source and
destination IP addresses of the application session are known. When
any socket options for the multihoming shim sub-layer is set for an
unconnected socket, EINVAL error code MUST be returned.
5.16. Error Handling
If successful, getsockopt() and setsockopt() return 0; otherwise, the If successful, getsockopt() and setsockopt() return 0; otherwise, the
functions return -1 and set errno to indicate an error. functions return -1 and set errno to indicate an error.
The following are new error values defined for some shim specific The following are new error values defined for some shim specific
socket options indicating that the getsockopt() or setsockopt() socket options indicating that the getsockopt() or setsockopt()
finished incompletely: finished incompletely:
EINVALIDLOCATOR EINVALIDLOCATOR
This indicates that at least one of the necessary validations This indicates that at least one of the necessary validations
inside the shim sub-layer for the specified locator has failed. inside the shim sub-layer for the specified locator has failed.
In case of SHIM6, there are two kinds of verifications required In case of SHIM6, there are two kinds of verifications required
for security reasons prior to sending an IP packet to the peer's for security reasons prior to sending an IP packet to the peer's
new locator; one is the return routability (check if the peer is new locator; one is the return routability (check if the peer is
actually willing to receive data with the specified locator) and actually willing to receive data with the specified locator) and
the other one is the verification based on crypto identifier the other one is the verification based on crypto identifier
mechanisms [RFC3972], [I-D.ietf-shim6-hba]. mechanisms [RFC3972], [RFC5535].
6. Ancillary Data for Multihoming Shim 6. Ancillary Data for Multihoming Shim Sub-layer
In this section, the definition and the usage of the ancillary data In this section, the definition and the usage of the ancillary data
specific to multihoming shim are provided. specific to multihoming shim sub-layer are provided.
As defined in the Posix standard, sendmsg() and recvmsg() input a As defined in the Posix standard, sendmsg() and recvmsg() input a
msghdr structure as their arguments. These system calls can handle msghdr structure as their arguments. These system calls can handle
control information along with data. Figure 3 shows the msghdr control information along with data. Figure 3 shows the msghdr
structure which is defined in <sys/socket.h>. The member msg_control structure which is defined in <sys/socket.h>. The member msg_control
holds a pointer to the buffer where the shim specific ancillary data holds a pointer to the buffer where the shim specific ancillary data
objects can be stored in addition to other ancillary data objects. objects can be stored in addition to other ancillary data objects.
struct msghdr { struct msghdr {
caddr_t msg_name; /* optional address */ caddr_t msg_name; /* optional address */
skipping to change at page 26, line 47 skipping to change at page 27, line 20
| SHIM_LOC_LOCAL_SEND | o | | *1 | | SHIM_LOC_LOCAL_SEND | o | | *1 |
| SHIM_LOC_PEER_SEND | o | | *1 | | SHIM_LOC_PEER_SEND | o | | *1 |
| SHIM_FEEDBACK | o | | shim_feedback{} | | SHIM_FEEDBACK | o | | shim_feedback{} |
+---------------------+-----------+-----------+-----------------+ +---------------------+-----------+-----------+-----------------+
Table 2: Shim specific ancillary data Table 2: Shim specific ancillary data
*1: cmsg_data[] should include padding (if necessary) and a single *1: cmsg_data[] should include padding (if necessary) and a single
sockaddr_in{}/sockaddr_in6{}. sockaddr_in{}/sockaddr_in6{}.
It should be noted that the above ancillary data can only be handled 6.1. Get Locator from Incoming Packet
by a UDP or a raw socket and not by a TCP socket. This is because
there is no one-to-one mapping between a single send/receive
operation and a TCP segment being transmitted/received.
6.1. Get Locator Information from Incoming Packet
An application can get locator information from the received IP An application can get locator information from the received IP
packet by specifying the shim specific socket options for the socket. packet by specifying the shim specific socket options for the socket.
When SHIM_LOC_LOCAL_RECV and/or SHIM_LOC_PEER_RECV socket options are When SHIM_LOC_LOCAL_RECV and/or SHIM_LOC_PEER_RECV socket options are
set, the application can retrieve local and/or remote locator from set, the application can retrieve local and/or remote locator from
the ancillary data. the ancillary data.
6.2. Specify Locator Information for Outgoing Packet 6.2. Set Locator for Outgoing Packet
An application can specify the locators to be used for transmitting An application can specify the locators to be used for transmitting
an IP packet by sendmsg(). When the ancillary data of cmsg_type an IP packet by sendmsg(). When the ancillary data of cmsg_type
SHIM_LOC_LOCAL_SEND and/or SHIM_LOC_PEER_SEND are specified, the SHIM_LOC_LOCAL_SEND and/or SHIM_LOC_PEER_SEND are specified, the
application can explicitly specify the source and/or the destination application can explicitly specify the source and/or the destination
locators to be used for the communication over the socket. locators to be used for the communication over the socket.
In addition, the application can specify the outgoing interface by
SHIM_IF_SEND ancillary data. The ancillary data should contain the
interface identifier of the physical interface over which the
application expects the packet to be transmitted.
Note that the effect is limited to the datagram transmitted by the Note that the effect is limited to the datagram transmitted by the
sendmsg(). sendmsg().
If the specified locator pair is verified, the shim sub-layer If the specified locator pair is verified, the shim sub-layer
overrides the locators of the IP packet. overrides the locators of the IP packet.
An error EINVALIDLOCATOR will be returned when validation of the An error EINVALIDLOCATOR will be returned when validation of the
specified locator failed. specified locator failed.
6.3. Notification from Application to Multihoming Shim 6.3. Notification from Application to Multihoming Shim Sub-layer
An application may provide feedbacks to the shim sub-layer about the An application may provide feedbacks to the shim sub-layer about the
communication status. Such feedbacks are particularly useful for the communication status. Such feedbacks are particularly useful for the
shim sub-layer in the absence of REAP mechanism to monitor the shim sub-layer in the absence of REAP mechanism to monitor the
reachability status of the currently used locator pair in a given reachability status of the currently used locator pair in a given
shim context. shim context.
The notification can be made by sendmsg() specifying a new ancillary The notification can be made by sendmsg() specifying a new ancillary
data called SHIM_FEEDBACK. The ancillary data can be handled by data called SHIM_FEEDBACK. The ancillary data can be handled by
specifying SHIM_FEEDBACK option in cmsg_type. specifying SHIM_FEEDBACK option in cmsg_type.
An error ENOENT will be returned when there is no context associated An error ENOENT will be returned when there is no context associated
with the socket. with the socket.
See Section 7.3 for details of the data structure to be used. Note See Section 7.3 for details of the data structure to be used.
that this specification does not specify the exact behavior of the
shim sub-layer when a feedback is given by an application. It is outside the scope of this document how the shim sub-layer would
react when a feedback is provided by an application.
6.4. Applicability
It is important to note that the ancillary data specified in this
section are applicable only to datagram-oriented sockets (e.g., UDP
sockets or raw sockets) and that they are not applicable to stream-
oriented sockets (e.g., TCP sockets). The reason behind this
restriction is that there is no one-to-one mapping between a single
send or receive operation and a TCP segment being transmitted or
received.
Due to the above restriction and the restriction addressed in
Section 5.15, SHIM_LOC_LOCAL_RECV or SHIM_LOC_PEER_RECV socket
options are, in practice, applicable only to connected UDP sockets.
7. Data Structures 7. Data Structures
In this section, data structures specifically defined for the In this section, data structures specifically defined for the
multihoming shim sub-layer are introduced. These data structures are multihoming shim sub-layer are introduced. These data structures are
either used as a parameter for setsockopt()/getsockopt() (as either used as a parameter for setsockopt()/getsockopt() (as
mentioned in Section 5) or as a parameter for ancillary data to be mentioned in Section 5) or as a parameter for ancillary data to be
processed by sendmsg()/recvmsg() (as mentioned in Section 6). processed by sendmsg()/recvmsg() (as mentioned in Section 6).
7.1. Placeholder for Locator Information 7.1. Placeholder for Locator Information
skipping to change at page 30, line 28 skipping to change at page 31, line 8
uint8_t pe_keepaliveto; /* Keepalive Timeout */ uint8_t pe_keepaliveto; /* Keepalive Timeout */
uint16_t pe_initprobeto; /* Initial Probe Timeout */ uint16_t pe_initprobeto; /* Initial Probe Timeout */
uint32_t pe_reserved; /* reserved */ uint32_t pe_reserved; /* reserved */
}; };
Figure 6: path explore structure Figure 6: path explore structure
pe_probenum pe_probenum
Indicates the number of initial probe messages to be sent. Indicates the number of initial probe messages to be sent.
Default value of this parameter should follow what is specified in Default value of this parameter should follow what is specified in
[I-D.ietf-shim6-failure-detection]. [RFC5534].
pe_keepaliveto pe_keepaliveto
Indicates timeout value for detecting a failure when the host does Indicates timeout value for detecting a failure when the host does
not receive any packets for a certain period of time while there not receive any packets for a certain period of time while there
is outbound traffic. When the timer expires, path exploration is outbound traffic. When the timer expires, path exploration
procedure will be carried out by sending a REAP Probe message. procedure will be carried out by sending a REAP Probe message.
Default value of this parameter should follow what is specified in Default value of this parameter should follow what is specified in
[I-D.ietf-shim6-failure-detection]. [RFC5534].
pe_initprobeto pe_initprobeto
Indicates retransmission timer of REAP Probe message in Indicates retransmission timer of REAP Probe message in
milliseconds. Note that this timer is applied before exponential milliseconds. Note that this timer is applied before exponential
back-off is started. A REAP Probe message for the same locator back-off is started. A REAP Probe message for the same locator
pair may be retransmitted. Default value of this parameter should pair may be retransmitted. Default value of this parameter should
follow what is specified in [I-D.ietf-shim6-failure-detection]. follow what is specified in [RFC5534].
pe_reserved pe_reserved
A reserved field for future extension. By default, the field A reserved field for future extension. By default, the field
should be initialized to zero. should be initialized to zero.
7.3. Feedback Information 7.3. Feedback Information
As mentioned in Section 6.3, applications can inform the shim sub- As mentioned in Section 6.3, applications can inform the shim sub-
layer about the status of unicast reachability of the locator pair layer about the status of unicast reachability of the locator pair
currently in use. The feedback information can be handled by using currently in use. The feedback information can be handled by using
ancillary data called SHIM_FEEDBACK. A new data structure named ancillary data called SHIM_FEEDBACK. A new data structure named
skipping to change at page 31, line 33 skipping to change at page 32, line 15
* 1: Unable to connect. There is no unidirectional reachability * 1: Unable to connect. There is no unidirectional reachability
between the locator pair in question. between the locator pair in question.
* 2: Unsatisfactory. The application is not satisfied with the * 2: Unsatisfactory. The application is not satisfied with the
unidirectional reachability between the locator pair in unidirectional reachability between the locator pair in
question. question.
* 3: Satisfactory. There is satisfactory unidirectional * 3: Satisfactory. There is satisfactory unidirectional
reachability between the locator pair in question. reachability between the locator pair in question.
reserved reserved
Reserved field. Must be ignored by the receiver. Reserved field. Must be ignored by the receiver.
8. Implications for Existing Socket API Extensions 8. System Requirements
As discussed in Section 5, all the socket options for multihoming
shim sub-layer are applicable only to connected sockets. To break
this down into system requirements, the operating system (kernel)
should be able to establish and maintain an association between a
socket instance and one or more multihoming shim context. It is,
however, outside the scope of this document how the operating system
would establish and maintain associations between sockets and
multihoming shim contexts. An association can be established on
creation of a multihoming shim context, or at any stage. On creation
of a shim context, the multihoming shim sub-layer on the initiator
side should be aware of the triggering packet and it should be
possible to figure out the originating socket. It is more difficult
to establish an association on the responder side.
9. Implications for Existing Socket API Extensions
Some of the socket options defined in this document are overlapping Some of the socket options defined in this document are overlapping
with existing sockets API and care should be taken for the usage not with existing sockets API and care should be taken for the usage not
to confuse with the overlapping features. to confuse with the overlapping features.
The socket options for requesting specific locators to be used for a The socket options for requesting specific locators to be used for a
given transaction (SHIM_LOC_LOCAL_PREF and SHIM_LOC_PEER_PREF) are given transaction (SHIM_LOC_LOCAL_PREF and SHIM_LOC_PEER_PREF) are
semantically similar to the existing sockets API (IPV6_PKTINFO). The semantically similar to the existing sockets API (IPV6_PKTINFO). The
socket options for obtaining the locator information from the socket options for obtaining the locator information from the
received IP packet (SHIM_LOC_LOCAL_RECV and SHIM_LOC_PEER_RECV) are received IP packet (SHIM_LOC_LOCAL_RECV and SHIM_LOC_PEER_RECV) are
skipping to change at page 32, line 18 skipping to change at page 33, line 18
incoming packets. This information is stored in ancillary data being incoming packets. This information is stored in ancillary data being
IPV6_PKTINFO specified as cmsg_type. Existing sockets API should IPV6_PKTINFO specified as cmsg_type. Existing sockets API should
continue to work above the shim sub-layer, that is, the IP addresses continue to work above the shim sub-layer, that is, the IP addresses
handled in IPV6_PKTINFO should be EIDs, not the locators. handled in IPV6_PKTINFO should be EIDs, not the locators.
Baseline is that the above existing sockets API (IP_RECVDSTADDR and Baseline is that the above existing sockets API (IP_RECVDSTADDR and
IPV6_PKTINFO) is assumed to work above the multihoming shim sub- IPV6_PKTINFO) is assumed to work above the multihoming shim sub-
layer. In other words, the IP addresses those socket options deal layer. In other words, the IP addresses those socket options deal
with are EIDs rather than locators. with are EIDs rather than locators.
9. Resolving Conflicts with Preference Values 10. Resolving Conflicts with Preference Values
Since the multihoming shim API allows application to specify Since the multihoming shim API allows application to specify
preference value for the context which is associated with the socket preference value for the context which is associated with the socket
instance, there may be a conflict with preference values specified by instance, there may be a conflict with preference values specified by
different applications. For instance, application A and B may different applications. For instance, application A and B may
establish communication with the same EID pair while both establish communication with the same EID pair while both
applications have different preference in their choice of local applications have different preference in their choice of local
locator. locator.
SHIM6 supports a notion of context forking in which a context is SHIM6 supports a notion of context forking in which a context is
split when there is a conflict with preference values specified by split when there is a conflict with preference values specified by
multiple applications. Thus, context forking can simply resolve the multiple applications. Thus, context forking can simply resolve the
conflicting situation which may be caused by the use of socket conflicting situation which may be caused by the use of socket
options for multihoming shim sub-layer. options for multihoming shim sub-layer.
9.1. Implicit Forking 10.1. Implicit Forking
Socket options defined in Section 5 may cause conflicting situation Socket options defined in Section 5 may cause conflicting situation
when the target context is shared by multiple applications. In such when the target context is shared by multiple applications. In such
case, socket handler should inform the shim sub-layer that context case, socket handler should inform the shim sub-layer that context
forking is required. In SHIM6, when a context is forked, an unique forking is required. In SHIM6, when a context is forked, an unique
identifier called Forked Instance Identifier (FII) is assigned to the identifier called Forked Instance Identifier (FII) is assigned to the
newly forked context. The forked context is then exclusively newly forked context. The forked context is then exclusively
associated with the socket through which non-default preference value associated with the socket through which non-default preference value
was specified. The forked context is maintained by the multihoming was specified. The forked context is maintained by the multihoming
shim sub-layer during the lifetime of associated socket instance. shim sub-layer during the lifetime of associated socket instance.
When the socket is closed, the multihoming shim sub-layer SHOULD When the socket is closed, the multihoming shim sub-layer SHOULD
delete associated context. In this way, garbage collection can be delete associated context. In this way, garbage collection can be
carried out to cleanup unused forked contexts. Upon garbage carried out to cleanup unused forked contexts. Upon garbage
collection, every forked context SHOULD be checked if there is no collection, every forked context SHOULD be checked if there is no
socket (process) associated with the context. If there is none, the socket (process) associated with the context. If there is none, the
forked context should be deleted. When a forked context is torn forked context should be deleted. When a forked context is torn
down, SHIM6 should notify the peer about the deletion of forked down, SHIM6 should notify the peer about the deletion of forked
context. context.
As opposed to socket options, context forking MUST NOT be triggered As opposed to socket options, context forking MUST NOT be triggered
by any use of ancillary data that is specific to multihoming shim as by any use of ancillary data that is specific to multihoming shim
defined in Section 6. sub-layer as defined in Section 6.
10. Discussion 11. Discussion
In this section, open issues are introduced. In this section, open issues are introduced.
10.1. Naming at Socket Layer 11.1. Naming at Socket Layer
The getsockname() and getpeername() system calls are used to obtain The getsockname() and getpeername() system calls are used to obtain
the 'name' of an endpoint which is actually a pair of IP address and the 'name' of an endpoint which is actually a pair of IP address and
port number assigned to a given socket. getsockname() is used when an port number assigned to a given socket. getsockname() is used when an
application wants to obtain the local IP address and port number application wants to obtain the local IP address and port number
assigned for a given socket instance. getpeername() is used when an assigned for a given socket instance. getpeername() is used when an
application obtains the remote IP address and port number. application obtains the remote IP address and port number.
The above is based on a traditional system model of the sockets API The above is based on a traditional system model of the sockets API
where an IP address is expected to play both the role of identifier where an IP address is expected to play both the role of identifier
and the role of locator. and the role of locator.
In a system model where a shim sub-layer exists inside the IP layer, In a system model where a shim sub-layer exists inside the IP layer,
both getsockname() and getpeername() deal with identifiers, namely both getsockname() and getpeername() deal with identifiers, namely
EIDs. In this sense, the shim sub-layer serves to (1) hide locators EIDs. In this sense, the shim sub-layer serves to (1) hide locators
and (2) provide access to the identifier for the application over the and (2) provide access to the identifier for the application over the
legacy socket APIs. legacy socket APIs.
10.2. Additional Requirements from Applications 11.2. Additional Requirements from Applications
At the moment, it is not certain if following requirements are common At the moment, it is not certain if following requirements are common
in all the multihomed environments (SHIM6 and HIP). These are mainly in all the multihomed environments (SHIM6 and HIP). These are mainly
identified during discussions made on SHIM6 WG mailing list. identified during discussions made on SHIM6 WG mailing list.
o The application should be able to set preferences for the o The application should be able to set preferences for the
locators, local and remote ones, and also to the preferences of locators, local and remote ones, and also to the preferences of
the local locators that will be passed to the peer. the local locators that will be passed to the peer.
10.3. Issues of Header Conversion among Different Address Family 11.3. Issues of Header Conversion among Different Address Family
The shim sub-layer performs identifier/locator adaptation. The shim sub-layer performs identifier/locator adaptation.
Therefore, in some cases, the whole IP header can be replaced with Therefore, in some cases, the whole IP header can be replaced with
new IP header of a different address family (e.g. conversion from new IP header of a different address family (e.g. conversion from
IPv4 to IPv6 or vice versa). Hence, there is an issue how to make IPv4 to IPv6 or vice versa). Hence, there is an issue how to make
the conversion with minimum impact. Note that this issue is common the conversion with minimum impact. Note that this issue is common
in other protocol conversion such as SIIT[RFC2765]. in other protocol conversion such as SIIT[RFC2765].
As addressed in SIIT specification, some of the features (IPv6 As addressed in SIIT specification, some of the features (IPv6
routing headers, hop-by-hop extension headers, or destination routing headers, hop-by-hop extension headers, or destination
headers) from IPv6 are not convertible to IPv4. In addition, notion headers) from IPv6 are not convertible to IPv4. In addition, notion
of source routing is not exactly the same in IPv4 and IPv6. Hence, of source routing is not exactly the same in IPv4 and IPv6. Hence,
there is a certain limitation in protocol conversion between IPv4 and there is a certain limitation in protocol conversion between IPv4 and
IPv6. IPv6.
The question is how should the shim sub-layer behave when it faces The question is how should the shim sub-layer behave when it faces
with limitation problem of protocol conversion. Should we introduce with limitation problem of protocol conversion. Should we introduce
new error something like ENOSUITABLELOCATOR ? new error something like ENOSUITABLELOCATOR ?
10.4. Handling of Unknown Locator Provided by Application 11.4. Handling of Unknown Locator Provided by Application
There might be a case where application provides the shim layer new There might be a case where application provides the shim layer new
locator with the SHIM_LOC_*_PREF socket options or SHIM_LOC_*_SEND locator with the SHIM_LOC_*_PREF socket options or SHIM_LOC_*_SEND
ancillary data. Then there is a question how should the shim sub- ancillary data. Then there is a question how should the shim sub-
layer treat the new locator informed by the application. layer treat the new locator informed by the application.
In principle, locator information are exchanged by the shim protocol. In principle, locator information are exchanged by the shim protocol.
However, there might be a case where application acquires information However, there might be a case where application acquires information
about the locator and prefers to use it for its communication. about the locator and prefers to use it for its communication.
11. Changes 12. Changes
11.1. Changes from version 00 to version 01 12.1. Changes from version 00 to version 01
The followings are changes from version 00 to version 01: The followings are changes from version 00 to version 01:
o Define shim_locator{} data type which is a placeholder for o Define shim_locator{} data type which is a placeholder for
locator. locator.
o Define shim_pathexplore{} data type in which a set of REAP o Define shim_pathexplore{} data type in which a set of REAP
parameters are stored. parameters are stored.
o Remove descriptions about "stickiness" of socket options. o Remove descriptions about "stickiness" of socket options.
o Deprecate SHIM_IF_RECV and SHIM_IF_SEND socket options. o Deprecate SHIM_IF_RECV and SHIM_IF_SEND socket options.
o Give default value and how to disable given socket option. o Give default value and how to disable given socket option.
11.2. Changes from version 01 to version 02 12.2. Changes from version 01 to version 02
The followings are changes from version 01 to version 02: The followings are changes from version 01 to version 02:
o Add section describing context forking. o Add section describing context forking.
o Rephrase conclusion section. o Rephrase conclusion section.
o Separate normative references from informative references. o Separate normative references from informative references.
o Remove texts from discussion section that are not relevant to the o Remove texts from discussion section that are not relevant to the
contents of the document. contents of the document.
o Add section describing change history (this section). o Add section describing change history (this section).
11.3. Changes from version 02 to version 03 12.3. Changes from version 02 to version 03
The followings are changes from version 02 to version 03: The followings are changes from version 02 to version 03:
o Add an Appendix section describing the issue of context forking. o Add an Appendix section describing the issue of context forking.
11.4. Changes from version 03 to version 04 12.4. Changes from version 03 to version 04
The followings are changes from version 03 to version 04: The followings are changes from version 03 to version 04:
o Updated reference. o Updated reference.
o Correct typo and grammatical errors. o Correct typo and grammatical errors.
11.5. Changes from version 04 to version 05 12.5. Changes from version 04 to version 05
The followings are changes from version 04 to version 05: The followings are changes from version 04 to version 05:
o Added definition of SHIM_FEEDBACK ancillary data. o Added definition of SHIM_FEEDBACK ancillary data.
o Added an example of code using the SHIM_LOCLIST_LOCAL o Added an example of code using the SHIM_LOCLIST_LOCAL
o Added SHIM_LOC_LOCAL_SEND and SHIM_LOC_PEER_SEND socket options. o Added SHIM_LOC_LOCAL_SEND and SHIM_LOC_PEER_SEND socket options.
11.6. Changes from version 05 to version 06 12.6. Changes from version 05 to version 06
The followings are changes from version 04 to version 05: The followings are changes from version 04 to version 05:
o Updated references. o Updated references.
11.7. Changes from version 06 to version 07 12.7. Changes from version 06 to version 07
The followings are changes from version 06 to version 07: The followings are changes from version 06 to version 07:
o Resolved editorial issues. o Resolved editorial issues.
11.8. Changes from version 07 to version 08 12.8. Changes from version 07 to version 08
No changes are made except for updates of the references. No changes are made except for updates of the references.
11.9. Changes from version 08 to version 09 12.9. Changes from version 08 to version 09
The followings are changes from version 08 to version 09: The followings are changes from version 08 to version 09:
o Updated texts for Section 1 and Section 5 according to the o Updated texts for Section 1 and Section 5 according to the
comments provided by Samu Varjonen. comments provided by Samu Varjonen.
o Made it clear that downgrading the multihome shim support (i.e., o Made it clear that downgrading the multihoming shim support (i.e.,
specifying value 1 with the SHIM_DONTSHIM socket option) is only specifying value 1 with the SHIM_DONTSHIM socket option) is only
allowed before the socket is connected. allowed before the socket is connected.
o Updated locator information (shim_locator{}) so that it can o Updated locator information (shim_locator{}) so that it can
contain a locator behind NAT. contain a locator behind NAT.
12. IANA Considerations 12.10. Changes from version 09 to version 10
The followings are changes from version 09 to version 10:
o Addressed applicability of socket options and ancillary data for
the multihoming shim sub-layer.
o Addressed system requirements.
o Removed unnecessary description about deprecated socket option
(SHIM_IF_RECV).
13. IANA Considerations
This document contains no IANA consideration. This document contains no IANA consideration.
13. Security Considerations 14. Security Considerations
This document does not specify any security mechanism for the shim This document does not specify any security mechanism for the shim
sub-layer. Fundamentally, the shim sub-layer has a potential to sub-layer. Fundamentally, the shim sub-layer has a potential to
impose security threats, as it changes the source and/or destination impose security threats, as it changes the source and/or destination
IP addresses of the IP packet being sent or received. Therefore, the IP addresses of the IP packet being sent or received. Therefore, the
basic assumption is that the security mechanism defined in each basic assumption is that the security mechanism defined in each
protocol of the shim sub-layer is strictly applied. protocol of the shim sub-layer is strictly applied.
14. Conclusion 15. Conclusion
In this document, the Application Program Interface (API) for In this document, the Application Program Interface (API) for
multihoming shim sub-layer is specified. The sockets API allows multihoming shim sub-layer is specified. The sockets API allows
applications to have additional control of the locator management and applications to have additional control of the locator management and
interface to the REAP mechanism inside the multihoming shim sub- interface to the REAP mechanism inside the multihoming shim sub-
layer. layer.
Socket options for multihoming shim sub-layer can be used by Socket options for multihoming shim sub-layer can be used by
getsockopt() and/or setsockopt() system calls. Besides, applications getsockopt() and/or setsockopt() system calls. Besides, applications
can use some ancillary data that are specific to multihoming shim can use some ancillary data that are specific to multihoming shim
sub-layer to get locator from received packet or to set locator for sub-layer to get locator from received packet or to set locator for
outgoing packet. outgoing packet.
From an architectural point of view, the sockets API provides extends From an architectural point of view, the sockets API provides extends
the existing sockets API framework in the face of ID/Locator the existing sockets API framework in the face of ID/Locator
separation. With regard to API that relate to IP address management, separation. With regard to API that relate to IP address management,
it is assured that existing sockets API continue to work above the it is assured that existing sockets API continue to work above the
shim sub-layer dealing with identifiers, while multihoming shim API shim sub-layer dealing with identifiers, while multihoming shim API
deals with locators. deals with locators.
15. Acknowledgments 16. Acknowledgments
Authors would like to thank Jari Arkko who participated in the Authors would like to thank Jari Arkko who participated in the
discussion that lead to the first version of this document, and discussion that lead to the first version of this document, and
Tatuya Jinmei who thoroughly reviewed the early version of this draft Tatuya Jinmei who thoroughly reviewed the early version of this draft
and provided detailed comments on sockets API related issues. Thomas and provided detailed comments on sockets API related issues. Thomas
Henderson provided valuable comments especially from HIP Henderson provided valuable comments especially from HIP
perspectives. perspectives.
Authors sincerely thank to the following people for their help to Authors sincerely thank to the following people for their help to
improve this document: Samu Varjonen and Dmitriy Kuptsov. improve this document: Samu Varjonen and Dmitriy Kuptsov.
16. References 17. References
16.1. Normative References
[I-D.ietf-shim6-failure-detection]
Arkko, J. and I. Beijnum, "Failure Detection and Locator
Pair Exploration Protocol for IPv6 Multihoming",
draft-ietf-shim6-failure-detection-13 (work in progress),
June 2008.
[I-D.ietf-shim6-proto] 17.1. Normative References
Bagnulo, M. and E. Nordmark, "Level 3 multihoming shim
protocol", draft-ietf-shim6-proto-12 (work in progress),
February 2009.
[POSIX] "IEEE Std. 1003.1-2001 Standard for Information Technology [POSIX] "IEEE Std. 1003.1-2001 Standard for Information Technology
-- Portable Operating System Interface (POSIX). Open group -- Portable Operating System Interface (POSIX). Open group
Technical Standard: Base Specifications, Issue 6, Technical Standard: Base Specifications, Issue 6,
http://www.opengroup.org/austin", December 2001. http://www.opengroup.org/austin", December 2001.
[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, [RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
"Advanced Sockets Application Program Interface (API) for "Advanced Sockets Application Program Interface (API) for
IPv6", RFC 3542, May 2003. IPv6", RFC 3542, May 2003.
[RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol
(HIP) Architecture", RFC 4423, May 2006. (HIP) Architecture", RFC 4423, May 2006.
16.2. Informative References [RFC5533] Bagnulo, M. and E. Nordmark, "Level 3 multihoming shim
protocol", RFC 5533, June 2009.
[RFC5534] Arkko, J. and I. Beijnum, "Failure Detection and Locator
Pair Exploration Protocol for IPv6 Multihoming", RFC 5534,
June 2009.
17.2. Informative References
[I-D.ietf-hip-nat-traversal] [I-D.ietf-hip-nat-traversal]
Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A.
Keranen, "Basic HIP Extensions for Traversal of Network Keranen, "Basic HIP Extensions for Traversal of Network
Address Translators", Internet Address Translators", Internet
Draft draft-ietf-hip-nat-traversal-08, June 2009. Draft draft-ietf-hip-nat-traversal-09, October 2009.
[I-D.ietf-shim6-app-refer] [I-D.ietf-shim6-app-refer]
Nordmark, E., "Shim6 Application Referral Issues", Nordmark, E., "Shim6 Application Referral Issues",
draft-ietf-shim6-app-refer-00 (work in progress), draft-ietf-shim6-app-refer-00 (work in progress),
July 2005. July 2005.
[I-D.ietf-shim6-hba]
Bagnulo, M., "Hash Based Addresses (HBA)",
draft-ietf-shim6-hba-05 (work in progress), December 2007.
[RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm [RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm
(SIIT)", RFC 2765, February 2000. (SIIT)", RFC 2765, February 2000.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005. RFC 3972, March 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006. Architecture", RFC 4291, February 2006.
[RFC5535] Bagnulo, M., "Hash Based Addresses (HBA)", RFC 5535,
June 2009.
Appendix A. Context Forking Appendix A. Context Forking
In this section, an issue concerning context forking and its relation In this section, an issue concerning context forking and its relation
to the multihoming shim API are discussed. to the multihoming shim API are discussed.
SHIM6 supports a notion of context forking. A peer may decide to SHIM6 supports a notion of context forking. A peer may decide to
fork a context for certain reason (e.g. upper layer protocol prefers fork a context for certain reason (e.g. upper layer protocol prefers
to use different locator pair than the one defined in available to use different locator pair than the one defined in available
context). The procedure of forking context is done similar to the context). The procedure of forking context is done similar to the
normal context establishment, performing the 4-way message exchange. normal context establishment, performing the 4-way message exchange.
skipping to change at page 41, line 12 skipping to change at page 42, line 12
Phone: +358 9 299 3286 Phone: +358 9 299 3286
Email: kristian.slavov@ericsson.com Email: kristian.slavov@ericsson.com
Shinta Sugimoto (editor) Shinta Sugimoto (editor)
Nippon Ericsson K.K. Nippon Ericsson K.K.
Koraku Mori Building Koraku Mori Building
1-4-14, Koraku, Bunkyo-ku 1-4-14, Koraku, Bunkyo-ku
Tokyo 112-0004 Tokyo 112-0004
Japan Japan
Phone: +81 3 3830 2241 Phone: +81 3 3830 2241
Email: shinta.sugimoto@ericsson.com Email: shinta@sfc.wide.ad.jp
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