Internet DRAFT - draft-ietf-pcp-upnp-igd-interworking
draft-ietf-pcp-upnp-igd-interworking
PCP Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track R. Penno
Expires: October 28, 2013 D. Wing
Cisco
April 26, 2013
Universal Plug and Play (UPnP) Internet Gateway Device (IGD)-Port
Control Protocol (PCP) Interworking Function
draft-ietf-pcp-upnp-igd-interworking-10
Abstract
This document specifies the behavior of the UPnP IGD (Internet
Gateway Device)/PCP Interworking Function. A UPnP IGD-PCP
Interworking Function (IGD-PCP IWF) is required to be embedded in CP
(Customer Premises) routers to allow for transparent NAT control in
environments where UPnP IGD is used on the LAN side and PCP on the
external side of the CP router.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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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."
This Internet-Draft will expire on October 28, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Architecture Model . . . . . . . . . . . . . . . . . . . . . 4
4. UPnP IGD-PCP IWF: Overview . . . . . . . . . . . . . . . . . 5
4.1. UPnP IGD-PCP: State Variables . . . . . . . . . . . . . . 6
4.2. IGD-PCP: Methods . . . . . . . . . . . . . . . . . . . . 7
4.3. UPnP IGD-PCP: Errors . . . . . . . . . . . . . . . . . . 8
5. Specification of the IGD-PCP IWF . . . . . . . . . . . . . . 9
5.1. PCP Server Discovery . . . . . . . . . . . . . . . . . . 9
5.2. Control of the Firewall . . . . . . . . . . . . . . . . . 9
5.3. Port Mapping Table . . . . . . . . . . . . . . . . . . . 10
5.4. Interworking Function Without NAT in the IGD . . . . . . 10
5.5. NAT Embedded in the IGD . . . . . . . . . . . . . . . . . 10
5.6. Creating a Mapping . . . . . . . . . . . . . . . . . . . 11
5.6.1. AddAnyPortMapping() . . . . . . . . . . . . . . . . . 11
5.6.2. AddPortMapping() . . . . . . . . . . . . . . . . . . 12
5.7. Listing One or a Set of Mappings . . . . . . . . . . . . 15
5.8. Delete One or a Set of Mappings: DeletePortMapping() or
DeletePortMappingRange() . . . . . . . . . . . . . . . . 15
5.9. Renewing a Mapping . . . . . . . . . . . . . . . . . . . 18
5.10. Rapid Recovery . . . . . . . . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 21
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
PCP [I-D.ietf-pcp-base] discusses the implementation of NAT control
features that rely upon Carrier Grade NAT devices such as a DS-Lite
AFTR [RFC6333] or NAT64 [RFC6146]. Nevertheless, in environments
where UPnP IGD (Internet Gateway Device) is used in the local
network, an interworking function between UPnP IGD and PCP is
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required to be embedded in the IGD (see the example illustrated in
Figure 1).
UPnP IGD-PCP
UPnP Control Interworking
Point Function PCP Server
| IGD |
| | |
| (1) AddPortMapping | |
|--------------------->| |
| | (2) PCP MAP Request |
| |-------------------------->|
| | |
Figure 1: Flow Example
Two configurations are considered within this document:
o No NAT function is embedded in the IGD (Section 5.4). This is
required for instance in DS-Lite or NAT64 deployments;
o The IGD embeds a NAT function (Section 5.5).
The UPnP IGD-PCP Interworking Function (UPnP IGD-PCP IWF) maintains a
local mapping table that stores all active mappings constructed by
internal IGD Control Points. This design choice restricts the amount
of PCP messages to be exchanged with the PCP Server.
Triggers for deactivating the UPnP IGD-PCP IWF from the IGD and
relying on a PCP-only mode are out of scope of this document.
Considerations related to co-existence of the UPnP IGD-PCP
Interworking Function and a PCP Proxy [I-D.ietf-pcp-proxy] are out of
scope.
2. Acronyms
This document makes use of the following abbreviations:
DS-Lite - Dual-Stack Lite
IGD - Internet Gateway Device
IGD:1 - UPnP Forum's nomenclature for version 1 of IGD [IGD1]
IGD:2 - UPnP Forum's nomenclature for version 2 of IGD [IGD2]
IWF - Interworking Function
NAT - Network Address Translation
PCP - Port Control Protocol
UPnP - Universal Plug and Play
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3. Architecture Model
As a reminder, Figure 2 illustrates the architecture model as adopted
by the UPnP Forum [IGD2]. In Figure 2, the following UPnP
terminology is used:
o 'Client' refers to a host located in the local network.
o 'IGD Control Point' is a device using UPnP to control an IGD
(Internet Gateway Device).
o 'IGD' is a router supporting UPnP IGD. It is typically a NAT or a
firewall.
o 'Host' is a remote peer reachable in the Internet.
+-------------+
| IGD Control |
| Point |-----+
+-------------+ | +-----+ +------+
+---| | | |
| IGD |-------| Host |
+---| | | |
+-------------+ | +-----+ +------+
| Client |-----+
+-------------+
Figure 2: UPnP IGD Model
This model is not valid when PCP is used to control for instance a
Carrier Grade NAT (a.k.a., Provider NAT) while internal hosts
continue to use UPnP IGD. In such scenarios, Figure 3 shows the
updated model.
+-------------+
| IGD Control |
| Point |----+
+-------------+ | +-----+ +--------+ +------+
+---| IGD-| |Provider| |Remote|
| PCP |------| NAT |--<Internet>---| Host |
+---| IWF | | | | |
+-------------+ | +-----+ +--------+ +------+
| Local Host |----+
+-------------+
LAN Side External Side
<======UPnP IGD==============><=====PCP=====>
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Figure 3: UPnP IGD-PCP Interworking Model
In the updated model depicted in Figure 3, one or two levels of NAT
can be encountered in the data path. Indeed, in addition to the
Carrier Grade NAT, the IGD may embed a NAT function (Figure 4).
+-------------+
| IGD Control |
| Point |----+
+-------------+ | +-----+ +--------+ +------+
+---| IGD-| |Provider| |Remote|
| PCP |------| NAT |--<Internet>---| Host |
+---| IWF | | | | |
+-------------+ | +-----+ +--------+ +------+
| Local Host |----+ NAT1 NAT2
+-------------+
Figure 4: Cascaded NAT scenario
To ensure successful interworking between UPnP IGD and PCP, an
interworking function is embedded in the IGD. In the model defined
in Figure 3, all UPnP IGD server-oriented functions, a PCP Client
[I-D.ietf-pcp-base] and a UPnP IGD-PCP Interworking Function are
embedded in the IGD. In the rest of the document, IGD-PCP IWF refers
the UPnP IGD-PCP Interworking Function, which includes PCP Client
functionality.
Without the involvement of the IGD-PCP IWF, the IGD Control Point
would retrieve an external IP address and port number having a
limited scope and which cannot be used to communicate with hosts
located beyond NAT2 (i.e., assigned by the IGD and not the ones
assigned by NAT2 in Figure 4).
UPnP IGD-PCP IWF is responsible for generating a well-formed PCP
message from a received UPnP IGD message, and vice versa.
4. UPnP IGD-PCP IWF: Overview
Three tables are provided to specify the correspondence between UPnP
IGD and PCP:
(1) Section 4.1 provides the mapping between WANIPConnection State
Variables and PCP parameters;
(2) Section 4.2 focuses on the correspondence between supported
methods;
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(3) Section 4.3 lists the PCP error messages and their corresponding
IGD ones.
Note that some enhancements have been integrated in WANIPConnection
as documented in [IGD2].
4.1. UPnP IGD-PCP: State Variables
Below are listed only the UPnP IGD state variables applicable to the
IGD-PCP IWF:
ExternalIPAddress: External IP Address
Read-only variable with the value from the last PCP response or
the empty string if none was received yet. This state is stored
on a per IGD Control Point basis.
PortMappingNumberOfEntries: Managed locally by the UPnP IGD-PCP IWF.
PortMappingEnabled:
PCP does not support deactivating the dynamic NAT mapping since
the initial goal of PCP is to ease the traversal of Carrier Grade
NAT. Supporting such per-subscriber function may overload the
Carrier Grade NAT.
Only "1" is allowed: i.e., the UPnP IGD-PCP Interworking Function
MUST send back an error if a value different from 1 is signaled.
PortMappingLeaseDuration: Requested Mapping Lifetime
In IGD:1 [IGD1] the value 0 means infinite, in IGD:2 it is
remapped to the IGD maximum of 604800 seconds [IGD2]. PCP allows
for a maximum value of 4294967296 seconds.
The UPnP IGD-PCP Interworking Function simulates long and even
infinite lifetimes using renewals (see Section 5.9). The behavior
of the UPnP IGD-PCP IWF in the case of a failing renewal is
currently undefined (see Section 5.9).
IGD:1 doesn't define the behavior in the case of state loss, IGD:2
doesn't require to keep state in stable storage, i.e., to allow
the state to survive resets/reboots. The UPnP IGD-PCP
Interworking Function MUST support IGD:2 behavior.
RemoteHost: Remote Peer IP Address
Note that IGD:2 allows a domain name, which has to be resolved to
an IP address. Mapped to the Remote Peer IP Address field of
FILTER option.
ExternalPort: External Port Number
Mapped to the Suggested External Port in MAP messages.
InternalPort: Internal Port Number
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Mapped to the Internal Port field in MAP messages.
PortMappingProtocol: Protocol
Mapped to the Protocol field in MAP messages. Note that UPnP IGD
only supports TCP and UDP.
InternalClient: Internal IP Address
Note that IGD:2 allows a domain name, which has to be resolved to
an IP address. Mapped to the Internal IP Address field of
THIRD_PARTY option.
PortMappingDescription: Not supported in base PCP.
If the local PCP Client supports a PCP Option to convey the
description (e.g., [I-D.ietf-pcp-description-option]), this option
SHOULD be used to relay the mapping description.
SystemUpdateID (IGD:2 only): Managed locally by the UPnP IGD-PCP
IWF.
A_ARG_TYPE_PortListing (IGD:2 only): Managed locally by the UPnP
IGD-PCP IWF.
4.2. IGD-PCP: Methods
Both IGD:1 and IGD:2 methods applicable to the UPnP IGD-PCP
Interworking Function are listed here.
GetGenericPortMappingEntry: This request is not relayed to the PCP
Server.
IGD-PCP Interworking Function maintains a list of active mappings
instantiated in the PCP Server by internal hosts. See Section 5.7
for more information.
GetSpecificPortMappingEntry: MAP with PREFER_FAILURE Option
This request is relayed to the PCP Server by issuing a MAP request
with the PREFER_FAILURE Option. It is RECOMMENDED to use a short
lifetime (e.g., 60 seconds).
AddPortMapping: MAP
See Section 5.6.2.
AddAnyPortMapping (IGD:2 only): MAP
See Section 5.6.1.
DeletePortMapping: MAP with Requested Lifetime set to 0.
See Section 5.8.
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DeletePortMappingRange (IGD:2 only): MAP with Requested Lifetime set
to 0.
Individual requests are issued by the IGD-PCP IWF. See
Section 5.8 for more details.
GetExternalIPAddress: MAP
This can be learned from any active mapping. If there are no
active mappings, the IGD-PCP IWF MAY request a short-lived mapping
(e.g., to the Discard service (TCP/9 or UDP/9) or some other
port). However, once that mapping expires a subsequent implicit
or explicit dynamic mapping might be mapped to a different
external IP address. See section 11.6 of [I-D.ietf-pcp-base] for
more discussion.
GetListOfPortMappings: See Section 5.7 for more information.
The IGD-PCP Interworking Function maintains a list of active
mappings instantiated in the PCP Server. The IGD-PCP Interworking
Function handles this request locally.
4.3. UPnP IGD-PCP: Errors
This section lists PCP errors codes and the corresponding UPnP IGD
ones. Error codes specific to IGD:2 are tagged accordingly.
1 UNSUPP_VERSION: 501 "ActionFailed"
2 NOT_AUTHORIZED: IGD:1 718 "ConflictInMappingEntry" / IGD:2 606
"Action not authorized"
3 MALFORMED_REQUEST: 501 "ActionFailed"
4 UNSUPP_OPCODE: 501 "ActionFailed"
[I-D.ietf-pcp-base] allows the PCP server to be configured to
disable support for the MAP opcode, but the IGD-PCP IWF cannot
work in this situation.
5 UNSUPP_OPTION: 501 "ActionFailed"
This error code can be received if PREFER_FAILURE is not supported
on the PCP server. Note that PREFER_FAILURE is not mandatory to
support, but AddPortMapping() cannot be implemented without it.
6 MALFORMED_OPTION: 501 "ActionFailed"
7 NETWORK_FAILURE: 501 "ActionFailed"
8 NO_RESOURCES: IGD:1 501 "ActionFailed" / IGD:2 728
"NoPortMapsAvailable"
Cannot be distinguished from USER_EX_QUOTA.
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9 UNSUPP_PROTOCOL: 501 "ActionFailed"
10 USER_EX_QUOTA: IGD:1 501 "ActionFailed" / IGD:2 728
"NoPortMapsAvailable"
Cannot be distinguished from NO_RESOURCES.
11 CANNOT_PROVIDE_EXTERNAL: 718 "ConflictInMappingEntry" (see
Section 5.7.2) or 714 "NoSuchEntryInArray" (see Section 5.8).
12 ADDRESS_MISMATCH: 501 "ActionFailed"
13 EXCESSIVE_REMOTE_PEERS: 501 "ActionFailed"
5. Specification of the IGD-PCP IWF
This section covers the scenarios with or without NAT in the IGD.
This specification assumes the PCP Server is configured to accept the
MAP OpCode.
The IGD-PCP IWF handles the "Mapping Nonce" the same way as any PCP
Client [I-D.ietf-pcp-base].
5.1. PCP Server Discovery
The IGD-PCP IWF implements one of the discovery methods identified in
[I-D.ietf-pcp-base] (e.g., DHCP [I-D.ietf-pcp-dhcp]). The IGD-PCP
Interworking Function behaves as a PCP Client when communicating with
provisioned PCP Server(s).
If no IPv4 address / IPv6 prefix is assigned to the IGD or the IGD is
unable to determine whether it should contact an upstream PCP Server,
the IGD-PCP Interworking Function MUST NOT be invoked.
If the IGD determines that it should establish communication with an
upstream PCP server (e.g., because of DHCP configuration or having
previously been talking to a PCP server), a "501 ActionFailed" error
message is returned to the requesting IGD Control Point in case the
IGD-PCP IWF fails to establish communication with that PCP Server.
Note, the IGD-PCP IWF proceeds to PCP messages validation and
retransmission the same way as any PCP Client [I-D.ietf-pcp-base].
5.2. Control of the Firewall
In order to configure security policies to be applied to inbound and
outbound traffic, UPnP IGD can be used to control a local firewall
engine. No IGD-PCP IWF is therefore required for that purpose.
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The use of IGD-PCP IWF to control an upstream PCP-controlled firewall
is out of scope of this document.
5.3. Port Mapping Table
The IGD-PCP IWF MUST store locally all the mappings instantiated by
internal IGD Control Points in the PCP Server. All mappings SHOULD
be stored in permanent storage.
Upon receipt of a PCP MAP Response from the PCP Server, the IGD-PCP
Interworking Function MUST extract the enclosed mapping and MUST
store it in the local mapping table. The local mapping table is an
image of the mapping table as maintained by the PCP Server for a
given subscriber.
Each mapping entry stored in the local mapping table is associated
with a lifetime as discussed in [I-D.ietf-pcp-base]. Additional
considerations specific to the IGD-PCP Interworking Function are
discussed in Section 5.9.
5.4. Interworking Function Without NAT in the IGD
When no NAT is embedded in the IGD, the content of received
WANIPConnection and PCP messages is not altered by the IGD-PCP
Interworking Function (i.e., the content of WANIPConnection messages
are mapped to PCP messages (and mapped back) according to
Section 4.1).
5.5. NAT Embedded in the IGD
When NAT is embedded in the IGD, the IGD-PCP IWF updates the content
of mapping messages received from the IGD Control Point. These
messages will contain an IP address and/or port number which belong
to an internal host. The IGD-PCP IWF MUST update such messages with
the IP address and/or port number belonging to the external interface
of the IGD (i.e., after the NAT1 operation in Figure 4).
The IGD-PCP IWF intercepts all WANIPConnection messages issued by the
IGD Control Point. For each such message, the IGD-PCP IWF then
generates one or more corresponding requests (see Section 4.1,
Section 4.2 and Section 4.3) and sends them to the provisioned PCP
Server.
Each request sent by the IGD-PCP IWF to the PCP Server MUST reflect
the mapping information as enforced in the first NAT. Particularly,
the internal IP address and/or port number of the requests are
replaced with the IP address and/or port number as assigned by the
NAT of the IGD. For the reverse path, the IGD-PCP IWF intercepts PCP
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response messages and generates WANIPConnection response messages.
The content of the generated WANIPConnection response messages are
set as follows:
o The internal IP address and/or port number as initially set by the
IGD Control Point and stored in the IGD NAT are used to update the
corresponding fields in received PCP responses.
o The external IP and port number are not altered by the IGD-PCP
Interworking Function.
o The NAT mapping entry in the IGD is updated with the result of PCP
request.
The lifetime of the mappings instantiated in the IGD SHOULD be the
one assigned by the terminating PCP Server. In any case, the
lifetime MUST NOT be lower than the one assigned by the terminating
PCP Server.
5.6. Creating a Mapping
Two methods can be used to create a mapping: AddAnyPortMapping() or
AddPortMapping().
5.6.1. AddAnyPortMapping()
When a IGD Control Point issues an AddAnyPortMapping(), this request
is received by the IGD. The request is then relayed to the IGD-PCP
IWF which generates a PCP MAP request (see Section 4.1 for mapping
between WANIPConnection and PCP parameters).
If the IGD-PCP IWF fails to send the MAP request to its PCP Server,
it follows the behavior defined in Section 5.1.
Upon receipt of a PCP MAP response from the PCP Server, the
corresponding UPnP IGD method is returned to the requesting IGD
Control Point (the content of the messages follows the
recommendations listed in Section 5.5 or Section 5.4 according to the
deployed scenario). A flow example is depicted in Figure 5.
If a PCP error is received from the PCP Server, a corresponding
WANIPConnection error code (see Section 4.3) is generated by the IGD-
PCP IWF and sent to the requesting IGD Control Point. If a short
lifetime error is returned (e.g., NETWORK_FAILURE, NO_RESOURCES), the
PCP IWF MAY resend the same request to the PCP Server after 30
seconds. If a negative answer is received, the error is then relayed
to the requesting IGD Control Point.
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Discussion: Some applications (e.g., uTorrent, Vuze, eMule) wait
90 seconds or more for a response after sending an UPnP request.
If a short lifetime error occurs, resending the request may lead
to a positive response from the PCP server. IGD Control Points
are therefore not aware of transient errors.
UPnP-PCP
UPnP Control Interworking
Point Function PCP Server
| | |
|(1) AddAnyPortMapping | |
| ExternalPort=8080 | |
|--------------------->| |
| | (2) PCP MAP Request |
| |Suggested External Port=8080 |
| |---------------------------->|
| | |
| | (3) PCP MAP Response |
| | Assigned External Port=6598 |
| |<----------------------------|
|(4) AddAnyPortMapping | |
| ReservedPort=6598 | |
|<---------------------| |
Figure 5: Flow example when AddAnyPortMapping() is used
5.6.2. AddPortMapping()
A dedicated option called PREFER_FAILURE is defined in
[I-D.ietf-pcp-base] to toggle the behavior in a PCP Request message.
This option is inserted by the IGD-PCP IWF when issuing its requests
to the PCP Server only if a specific external port is requested by
the IGD Control Point.
Upon receipt of AddPortMapping() from an IGD Control Point, the IGD-
PCP IWF MUST generate a PCP MAP Request with all requested mapping
information as indicated by the IGD Control Point if no NAT is
embedded in the IGD or updated as specified in Section 5.5. In
addition, the IGD-PCP IWF MUST insert a PREFER_FAILURE Option in the
generated PCP request.
If the IGD-PCP IWF fails to send the MAP request to its PCP Server,
it follows the behavior defined in Section 5.1.
If the requested external port is not available, the PCP server will
send a CANNOT_PROVIDE_EXTERNAL error response:
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1. If a short lifetime error is returned, the IGD-PCP IWF MAY resend
the same request to the PCP Server after 30 seconds without
relaying the error to the IGD Control Point. The IGD-PCP IWF MAY
repeat this process until a positive answer is received or some
maximum retry limit is reached. When the maximum retry limit is
reached, the IGD-PCP IWF relays a negative message to the IGD
Control Point with ConflictInMappingEntry as the error code. The
maximum retry limit is implementation-specific; its default value
is 2.
2. If a long lifetime error is returned, the IGD-PCP IWF relays a
negative message to the IGD Control Point with
ConflictInMappingEntry as the error code.
The IGD Control Point may issue a new request with a different
requested external port number. This process is typically repeated
by the IGD Control Point until a positive answer is received or some
maximum retry limit is reached.
If the PCP Server is able to create or renew a mapping with the
requested external port, it sends a positive response to the IGD-PCP
IWF. Upon receipt of the response from the PCP Server, the IGD-PCP
IWF stores the returned mapping in its local mapping table, and sends
the corresponding positive answer to the requesting IGD Control
Point. This answer terminates this exchange.
Figure 6 shows an example of the flow exchange that occurs when the
PCP Server satisfies the request from the IGD-PCP IWF. Figure 7
shows the messages exchange when the requested external port is not
available.
UPnP-PCP
UPnP Control Interworking
Point Function PCP Server
| | |
| (1) AddPortMapping | |
| ExternalPort=8080 | |
|--------------------->| |
| | (2) PCP MAP request |
| |Suggested External Port=8080 |
| | PREFER_FAILURE |
| |---------------------------->|
| | |
| | (3) PCP MAP response |
| | Assigned External Port=8080 |
| |<----------------------------|
| (4) AddPortMapping | |
| ExternalPort=8080 | |
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|<---------------------| |
Figure 6: Flow Example (Positive Answer)
UPnP-PCP
UPnP Control Interworking
Point Function PCP Server
| | |
| (1) AddPortMapping | |
| ExternalPort=8080 | |
|--------------------->| |
| | (2) PCP MAP Request |
| |Suggested External Port=8080 |
| | PREFER_FAILURE |
| |---------------------------->|
| | (3) PCP MAP Response |
| | CANNOT_PROVIDE_EXTERNAL |
| |<----------------------------|
| (4) Error: | |
|ConflictInMappingEntry| |
|<---------------------| |
| (5) AddPortMapping | |
| ExternalPort=5485 | |
|--------------------->| |
| | (6) PCP MAP Request |
| |Suggested External Port=5485 |
| | PREFER_FAILURE |
| |---------------------------->|
| | (7) PCP MAP Response |
| | CANNOT_PROVIDE_EXTERNAL |
| |<----------------------------|
| (8) Error: | |
|ConflictInMappingEntry| |
|<---------------------| |
....
| (a) AddPortMapping | |
| ExternalPort=6591 | |
|--------------------->| |
| | (b) PCP MAP Request |
| |Suggested External Port=6591 |
| | PREFER_FAILURE |
| |---------------------------->|
| | (c) PCP MAP Response |
| | CANNOT_PROVIDE_EXTERNAL |
| |<----------------------------|
| (d) Error: | |
|ConflictInMappingEntry| |
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|<---------------------| |
Figure 7: Flow Example (Negative Answer)
Note: According to some experiments, some UPnP 1.0 Control Point
implementations, e.g., uTorrent, simply try the same external port
a number of times (usually 4 times) and then fail if the port is
in use. Also note that some applications use
GetSpecificPortMappingEntry() to check whether a mapping exists.
5.7. Listing One or a Set of Mappings
In order to list active mappings, a IGD Control Point may issue
GetGenericPortMappingEntry(), GetSpecificPortMappingEntry(), or
GetListOfPortMappings().
GetGenericPortMappingEntry() and GetListOfPortMappings() methods MUST
NOT be proxied to the PCP Server since a local mapping is maintained
by the IGD-PCP IWF.
Upon receipt of GetSpecificPortMappingEntry() from a IGD Control
Point, the IGD-PCP IWF MUST check first if the external port number
is used by the requesting IGD Control Point. If the external port is
already in use by the requesting IGD Control Point, the IGD-PCP IWF
MUST send back the mapping entry matching the request. If not, the
IGD-PCP IWF MUST relay to the PCP Server a MAP request, with short
lifetime (e.g., 60 seconds), including a PREFER_FAILURE Option. If
the IGD-PCP IWF fails to send the MAP request to its PCP Server, it
follows the behavior defined in Section 5.1. If the requested
external port is in use, a PCP error message will be sent by the PCP
Server to the IGD-PCP IWF indicating CANNOT_PROVIDE_EXTERNAL as the
error cause. Then, the IGD-PCP IWF relays a negative message to the
IGD Control Point. If the port is not in use, the mapping will be
created by the PCP Server and a positive response will be sent back
to the IGD-PCP IWF. Once received by the IGD-PCP IWF, it MUST relay
a negative message to the IGD Control Point indicating
NoSuchEntryInArray as the error code so that the IGD Control Point
knows the queried mapping doesn't exist.
5.8. Delete One or a Set of Mappings: DeletePortMapping() or
DeletePortMappingRange()
A IGD Control Point requests the deletion of one or a list of
mappings by issuing DeletePortMapping() or DeletePortMappingRange().
In IGD:2, we assume the IGD applies the appropriate security policies
to determine whether a Control Point has the rights to delete one or
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a set of mappings. When authorization fails, the "606 Action Not
Authorized" error code is returned to the requesting Control Point.
When DeletePortMapping() or DeletePortMappingRange() is received by
the IGD-PCP IWF, it first checks if the requested mappings to be
removed are present in the local mapping table. If no mapping
matching the request is found in the local table, an error code is
sent back to the IGD Control Point: "714 NoSuchEntryInArray" for
DeletePortMapping() or "730 PortMappingNotFound" for
DeletePortMappingRange().
Figure 8 shows an example of a IGD Control Point asking to delete a
mapping which is not instantiated in the local table of the IWF.
UPnP-PCP
UPnP Control Interworking
Point Function PCP Server
| | |
|(1) DeletePortMapping | |
|--------------------->| |
| | |
| (2) Error: | |
| NoSuchEntryInArray | |
|<---------------------| |
| | |
Figure 8: Local Delete (IGD-PCP IWF)
If a mapping matches in the local table, a PCP MAP delete request is
generated. If no NAT is enabled in the IGD, the IGD-PCP IWF uses the
input arguments as included in DeletePortMapping(). If a NAT is
enabled in the IGD, the IGD-PCP IWF instead uses the corresponding IP
address and port number as assigned by the local NAT.
If the IGD-PCP IWF fails to send the MAP request to its PCP Server,
it follows the behavior defined in Section 5.1.
When a positive answer is received from the PCP Server, the IGD-PCP
IWF updates its local mapping table (i.e., removes the corresponding
entry) and notifies the IGD Control Point about the result of the
removal operation. Once the PCP MAP delete request is received by
the PCP Server, it removes the corresponding entry. A PCP MAP
SUCCESS response is sent back if the removal of the corresponding
entry was successful; if not, a PCP Error is sent back to the IGD-PCP
IWF including the corresponding error cause (see Section 4.3).
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If DeletePortMappingRange() is used, the IGD-PCP IWF does a lookup in
its local mapping table to retrieve individual mappings instantiated
by the requesting Control Point (i.e., authorization checks) and
matching the signaled port range (i.e., the external port is within
the "StartPort" and "EndPort" arguments of DeletePortMappingRange()).
If no mapping is found, the "730 PortMappingNotFound" error code is
sent to the IGD Control Point (Figure 9). If one or more mappings
are found, the IGD-PCP IWF generates individual PCP MAP delete
requests corresponding to these mappings (see the example shown in
Figure 10).
The IGD-PCP IWF MAY send a positive answer to the requesting IGD
Control Point without waiting to receive all the answers from the PCP
Server.
UPnP-PCP
UPnP Control Interworking
Point Function PCP Server
| | |
|(1)DeletePortMappingRange() | |
| StartPort=8596 | |
| EndPort =9000 | |
| Protocol =UDP | |
|--------------------------->| |
| | |
| (2) Error: | |
| PortMappingNotFound | |
|<---------------------------| |
| | |
Figure 9: Flow example when an error encountered when processing
DeletePortMappingRange()
This example illustrates the exchanges that occur when the IWF
receives DeletePortMappingRange(). In this example, only two
mappings having the external port number in the 6000-6050 range are
maintained in the local table. The IWF issues two MAP requests to
delete these mappings.
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UPnP-PCP
UPnP Control Interworking
Point Function PCP Server
| | |
|(1)DeletePortMappingRange() | |
| StartPort=6000 | |
| EndPort =6050 | |
| Protocol =UDP | |
|--------------------------->| |
| | |
| | (2a)PCP MAP Request |
| | protocol=UDP |
| | internal-ip-address |
| | internal-port |
| | external-ip-address |
| | external-port= 6030 |
| | Requested-lifetime= 0 |
| |-------------------------->|
| | |
| | (2c)PCP MAP Request |
| | protocol=UDP |
| | internal-ip-address |
| | internal-port |
| | external-ip-address |
| | external-port= 6045 |
| | Requested-lifetime= 0 |
| |-------------------------->|
| | |
| (2b)Positive answer | |
|<---------------------------| |
| | |
Figure 10: Example of DeletePortMappingRange()
5.9. Renewing a Mapping
Because of the incompatibility of mapping lifetimes between UPnP IGD
and PCP, the IGD-PCP IWF MUST simulate long and even infinite
lifetimes. Indeed, for requests having a requested infinite
PortMappingLeaseDuration, the IGD-PCP IWF MUST set the Requested
Lifetime of the corresponding PCP request to 4294967296. If
PortMappingLeaseDuration is not infinite, the IGD-PCP IWF MUST set
the Requested Lifetime of the corresponding PCP request to the same
value as PortMappingLeaseDuration. Furthermore, the IGD-PCP
Interworking Function MUST maintain an additional timer set to the
initial requested PortMappingLeaseDuration. Upon receipt of a
positive answer from the PCP server, the IGD-PCP IWF relays the
corresponding UPnP IGD response to the requesting IGD Control Point
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with PortMappingLeaseDuration set to the same value as the one of the
initial request. Then, the IGD-PCP IWF MUST periodically renew the
constructed PCP mapping until the expiry of PortMappingLeaseDuration.
Responses received when renewing the mapping MUST NOT be relayed to
the IGD Control Point.
In case an error is encountered during mapping renewal, the IGD-PCP
Interworking Function has no means to inform the IGD Control Point.
5.10. Rapid Recovery
When the IGD-PCP IWF is co-located with the DHCP server, the state
maintained by the IGD-PCP IWF MUST be updated using the state in the
local DHCP server. Particularly, if an IP address expires or is
released by an internal host, the IGD-PCP IWF MUST delete all the
mappings bound to that internal IP address.
Upon change of the external IP address of the IGD-PCP IWF, the IGD-
PCP IWF MAY renew the mappings it maintained. This can be achieved
only if a full state table is maintained by the IGD-PCP IWF. If the
port quota is not exceeded in the PCP server, the IGD-PCP IWF will
receive a new external IP address and port numbers. The IGD-PCP IWF
has no means to notify the change of the external IP address and port
to internal IGD Control Points. Stale mappings will be maintained by
the PCP Server until their lifetime expires.
Note: If an address change occurs, protocols that are sensitive to
address changes will experience disruption (e.g., TCP).
[I-D.ietf-pcp-base] defines a procedure for the PCP Server to notify
PCP Clients about changes related to the mappings it maintains. When
an unsolicited ANNOUNCE is received, the IGD-PCP IWF makes one or
more MAP requests with the PREFER_FAILURE option to re-install its
mappings. If the PCP server cannot create the requested mappings
(signaled with the CANNOT_PROVIDE_EXTERNAL error response), the IGD-
PCP IWF has no means to notify the change of the external IP address
and port to internal IGD Control Points.
Unsolicited PCP MAP responses received from a PCP Server are handled
as any normal MAP response. If a response indicates that the
external IP address or port has changed, the IGD-PCP IWF has no means
to notify the internal IGD Control Point of this change.
Further analysis of PCP failure scenarios for the IGD-PCP
Interworking Function are discussed in [I-D.boucadair-pcp-failure].
6. IANA Considerations
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This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
7. Security Considerations
IGD:2 access control requirements and authorization levels SHOULD be
applied by default [IGD2]. When IGD:2 is used, operation on the
behalf of a third party SHOULD be allowed only if authentication and
authorization are used [IGD2]. When only IGD:1 is available,
operation on the behalf of a third party SHOULD NOT be allowed.
This document defines a procedure to create PCP mappings for third
party devices belonging to the same subscriber. Means to prevent a
malicious user from creating mappings on behalf of a third party must
be enabled as discussed in Section 13.1 of [I-D.ietf-pcp-base]. In
particular, THIRD_PARTY option MUST NOT be enabled unless the network
on which the PCP messages are to be sent is fully trusted. For
example if access control lists are installed on the PCP client, PCP
server, and the network between them, so those ACLs allow only
communications from a trusted PCP client to the PCP server.
An IGD Control Point which issues AddPortMapping(),
AddAnyPortMapping(), or GetSpecificPortMappingEntry() requests in a
shorter time frame will create a lot of mapping entries on the PCP
server. Means to avoid exhausting port resources (e.g., port quota
discussed in Section 17.2 of [I-D.ietf-pcp-base]) SHOULD be enabled.
The security considerations discussed in [I-D.ietf-pcp-base] and
[Sec_DCP] should be taken into account.
8. Acknowledgments
Authors would like to thank F. Fontaine, C. Jacquenet, X. Deng, G.
Montenegro, D. Thaler, R. Tirumaleswar, P. Selkirk, T. Lemon, V.
Gurbani, and P. Yee for their review and comments.
F. Dupont contributed to previous versions of this document. Thanks
to him for his thorough reviews and contribution.
9. References
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9.1. Normative References
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)", draft-ietf-pcp-
base-29 (work in progress), November 2012.
[IGD1] UPnP Forum, , "WANIPConnection:1 Service (http://
www.upnp.org/specs/gw/UPnP-gw-
WANIPConnection-v1-Service.pdf)", November 2001.
[IGD2] UPnP Forum, , "WANIPConnection:2 Service (http://upnp.org/
specs/gw/UPnP-gw-WANIPConnection-v2-Service.pdf)",
September 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[I-D.boucadair-pcp-failure]
Boucadair, M. and R. Penno, "Port Control Protocol (PCP)
Failure Scenarios", draft-boucadair-pcp-failure-05 (work
in progress), February 2013.
[I-D.ietf-pcp-description-option]
Boucadair, M., Penno, R., and D. Wing, "PCP Description
Option", draft-ietf-pcp-description-option-00 (work in
progress), March 2013.
[I-D.ietf-pcp-dhcp]
Boucadair, M., Penno, R., and D. Wing, "DHCP Options for
the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-07
(work in progress), March 2013.
[I-D.ietf-pcp-proxy]
Boucadair, M., Penno, R., and D. Wing, "Port Control
Protocol (PCP) Proxy Function", draft-ietf-pcp-proxy-02
(work in progress), February 2013.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
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[Sec_DCP] UPnP Forum, , "Device Protection:1", February 2011,
<(http://upnp.org/specs/gw/UPnP-gw-
DeviceProtection-v1-Service.pdf>.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Reinaldo Penno
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: repenno@cisco.com
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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