This document provides a set of examples to illustrate PCP operations. It is a companion document to the base PCP specification.

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 working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

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 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

1. Introduction

As a companion document to [RFC6887], this document provides examples to help understanding the PCP machinery and exchanged PCP messages in various usage contexts.

For more details about PCP protocol specification, the reader is invited to refer to [RFC6887].

Examples included in this document make use of the IPv4 and IPv6 address blocks for documentation purposes defined in [RFC5737] and [RFC3849].

2. Basic MAP Operations

The following figure illustrates the messages which are exchanged to create a mapping in a PCP-controlled device with MAP OpCode.

+------+                           +------+
| PCP  |                           | PCP  |
|Client|                           |Server|
+------+                           +------+
    |      (1) PCP MAP Request         |
    |--------------------------------->|
    |      (2) PCP MAP Response        |
    |<---------------------------------|
    |                                  |

Figure 1: Example of creating a mapping

2.1. Suggested External Port Honored by the PCP Server

This example illustrates the content of exchanged PCP messages when the PCP Client does not include any PCP Option in its request. In this example, the PCP Server assigns the suggested port number. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 2: MAP request (suggested External Port Honored by the PCP Server)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 3: MAP Response (suggested External Port Honored by the PCP Server)

2.2. IPv6-enabled PCP Client

This example illustrates the content of exchanged PCP messages when the PCP Client is assigned with an IPv6 address but the remote server controls a NAT44 device. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: 2001:db8:0:0:1::1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 4: MAP request (suggested External Port Honored by the PCP Server)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 5: MAP Response (suggested External Port Honored by the PCP Server)

2.3. Remove an Existing Mapping

This example illustrates the content of exchanged PCP messages when the PCP Client request the removal of an existing mapping.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 0 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 6: MAP request (Remove an Existing Mapping)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 0 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 7: MAP Response (Remove an Existing Mapping)

2.4. Suggested External Port Not Honored by the PCP Server

This example illustrates the content of exchanged PCP messages when the PCP Client does not include any PCP Option in its request. In this example, the PCP Server does not assign the suggested external port number. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 11000
 Suggested External Port: 11000
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 8: MAP request (Suggested External Port Not Honored by the PCP Server)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 11000
 Assigned External Port: 15200
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 9: MAP Response (Suggested External Port Not Honored by the PCP Server)

2.5. Suggested External IP Address

This example illustrates the content of exchanged PCP messages when the PCP Client does not include any PCP Option in its request. In this example, the PCP Client indicates a hinted external IP address honored by the PCP Server. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:192.0.2.1

Figure 10: MAP request (Suggested External IP Address)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 15200
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 11: MAP Response (Suggested External IP Address)

2.6. Create Mapping with Distinct External IP Addresses

Figure 12 shows a PCP Server with a pool of public IPv4 addresses (192.0.2/24) and two PCP Clients associated with different subscribers. The PCP Clients each make a port mapping request to the PCP Server which creates the mapping from its 192.0.2/24 pool.

+--------+                     +------+                   +--------+
|  PCP   |                     | PCP  |                   |  PCP   |
|Client 1|                     |Server|                   |Client 2|
+--------+                     +------+                   +--------+
    |    (1) PCP MAP Request      |                            |
    |---------------------------->|                            |
    |    (2) PCP MAP Response     |                            |       
    |<----------------------------|   (a) PCP MAP Request      |
    |                             |<---------------------------|
    |                             |   (b) PCP MAP Response     |
    |                             |--------------------------->| 
    |                             |                            |

Figure 12: Example of creating mappings with distinct external IP addresses

In this example, the PCP Clients were mapped to different public addresses as illustrated in the content of the PCP messages listed below.

The content of PCP messages exchanged between PCP Client 1 and the PCP Server is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: TCP (6)
 Internal Port: 15333
 Suggested External Port: 15333
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 13: MAP request (PCP Client 1)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: TCP (6)
 Internal Port: 15333
 Assigned External Port: 12000
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 14: MAP Response (PCP Client 1)

The content of PCP messages exchanged between PCP Client 2 and the PCP Server is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.2
MAP Request: 
 Mapping Nonce: 59869
 Protocol: UDP (17)
 Internal Port: 12000
 Suggested External Port: 12000
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 15: MAP request (PCP Client 2)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 59869
 Protocol: UDP (17)
 Internal Port: 12000
 Assigned External Port: 6000
 Assigned External IP Address: ::ffff:192.0.2.2

Figure 16: MAP Response (PCP Client 2)

2.7. Mapping Nonce Doesn't Match

This example illustrates the content of exchanged PCP messages when the PCP Client does not include any PCP Option in its request. In this example, the PCP Client indicates a distinct Mapping Nonce than the one stored by the PCP Server. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 45687
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:192.0.2.1

Figure 17: MAP request (Mapping Nonce Doesn't Match)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: NOT_AUTHORIZED (0x02)
Lifetime: 35550 sec
Epoch Time: 1300

Figure 18: MAP Response (Mapping Nonce Doesn't Match)

2.8. PREFER_FAILURE Option: Requested Port is Honored

This flow shows an example of the content of PCP messages that will be exchanged to create a mapping in a PCP-controlled device. In this example, the PCP Client indicates a requested external UDP port number and also a PREFER_FAILURE Option. In this example, we suppose the requested port can be honored by the PCP Server. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 1234
 Suggested External Port: 12536
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: PREFER_FAILURE (0x02) Option Length: 0 bytes Data: (NULL)

Figure 19: MAP request ( PREFER_FAILURE Option: Requested Port is Honored)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 36000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 1234
 Assigned External Port: 12536
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 20: MAP Response ( PREFER_FAILURE Option: Requested Port is Honored)

2.9. PREFER_FAILURE Option: Requested Port is not Honored

This flow shows an example of the content of PCP messages that will be exchanged to create a mapping in a PCP-controlled device. In this example, the PCP Client indicates a requested external UDP port number and also a PREFER_FAILURE Option. In this example, we suppose the requested port cannot be honored by the PCP Server. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 1234
 Suggested External Port: 1234
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: PREFER_FAILURE (0x02) Option Length: 0 bytes Data: (NULL)

Figure 21: MAP request (PREFER_FAILURE Option: Requested Port is not Honored)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: CANNOT_PROVIDE_EXTERNAL (0x11)
Lifetime: 1560 sec
Epoch Time: 1300

Figure 22: MAP Response (PREFER_FAILURE Option: Requested Port is not Honored)

2.10. Negative Impact of PREFER_FAILURE Option

The presence of PREFER_FAILURE option in a request may have negative impact on an application which does not require it. Figure 23 shows two examples:

With PREFER_FAILURE option: several round trips are needed for the client to retrieve the requested mapping.
Without PREFER_FAILURE option: the client retrieves a mapping without any extra delay.

    (1) PREFER_FAILURE Option        (2) No PREFER_FAILURE Option

+------+                  +------+ +------+                  +------+
| PCP  |                  |  PCP | | PCP  |                  |  PCP |
|Client|                  |Server| |Client|                  |Server|
+------+                  +------+ +------+                  +------+
 |       PCP MAP Request      |      |       PCP MAP Request      |
 |Suggested External Port=8080|      |Suggested External Port=8080|
 |       PREFER_FAILURE       |      |--------------------------->|
 |--------------------------->|      |                            |
 |      PCP MAP Response      |      |       PCP MAP Response     |
 |   CANNOT_PROVIDE_EXTERNAL  |      |Assigned External Port=6598 |
 |<---------------------------|      |<---------------------------|
 |                            |      |          TCP SYN           |
 |       PCP MAP Request      |      |--------------------------->|
 |Suggested External Port=5485|
 |       PREFER_FAILURE       |
 |--------------------------->|
 |      PCP MAP Response      |
 |   CANNOT_PROVIDE_EXTERNAL  |
 |<---------------------------|
                ....
 |       PCP MAP Request      |
 |Suggested External Port=6591|
 |       PREFER_FAILURE       |
 |--------------------------->|
 |      PCP MAP Response      |
 |   CANNOT_PROVIDE_EXTERNAL  |
 |<---------------------------|

Figure 23: Negative Impact of the mis-usage of PREFERE_FAILURE option

2.11. Existing Implicit Mapping

This example illustrates the content of exchanged PCP messages when the PCP Client requests a mapping which matches an existing implicit dynamic mapping (see Figure 24). In this example, the PCP-Controlled device assigns 10000 as external port number when translating the packet from the client having with source port set to 1234.

+------+                           +------+
| PCP  |                           | PCP  |
|Client|                           |Server|
+------+                           +------+
    |      (a) TCP SYN(src:1234)       |
    |--------------------------------->|
    |      (1) PCP MAP Request         |
    |--------------------------------->|
    |      (2) PCP MAP Response        |
    |<---------------------------------|
    |                                  |

Figure 24: Example of creating a mapping

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: TCP (0x06)
 Internal Port: 1234
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 25: MAP request (Existing Implicit Mapping)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: TCP (0x06)
 Internal Port: 1234
 Assigned External Port: 10000
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 26: MAP Response (Existing Implicit Mapping)

2.12. Shortening a Mapping Lifetime in the Presence of Client-Originated Traffic

Figure 27 shows an example illustrating the impact of requesting the deletion of a mapping in the presence of traffic originated from the client. In this example, the PCP server does not remove the requested mapping immediately; the returned lifetime is set to the remaining lifetime.

+------+                  +---------------------+
| PCP  |                  |    PCP Server       |
|Client|                  |PCP-Controlled Device|
+------+                  +---------------------+
    |                                  |
    |=========Traffic==================|===========> 
    |   PCP MAP Request (Lifetime=0)   |
    |--------------------------------->|
    |  PCP MAP Response (Lifetime=     |
    |          remaining idle-timeout) |
    |<---------------------------------|
    |<========Traffic==================|<========== 
    |                                  |

Figure 27: Shortening a Mapping Lifetime in the Presence of Client-Originated Traffic

2.13. Create a Mapping for All Incoming Traffic of a Given Protocol

This example illustrates the content of the PCP MAP request to create a mapping for all incoming traffic of a given protocol (UDP is used in this example).

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 0
 Suggested External Port: 0
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 28: MAP request (Create a mapping for all incoming traffic of a given protocol)

The PCP Server may honor the request or reject it by sending UNSUPP_PROTOCOL (0x09) error.

2.14. Create a Mapping for All Protocols

This example illustrates the content of the PCP MAP request to create a mapping for the traffic of all protocols.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: ANY (0)
 Internal Port: 0
 Suggested External Port: 0
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 29: MAP request (Create a mapping for all protocols)

The PCP Server may honor the request or reject it by sending UNSUPP_PROTOCOL (0x09) error.

2.15. Malformed Request

This flow shows an example of the content of PCP messages that will be exchanged when a malformed request is received by the PCP Server. In this example, the Protocol field is set to null.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 45698
 Protocol: ANY (0)
 Internal Port: 5698
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: PREFER_FAILURE (0x02) Option Length: 0 bytes Data: (NULL)

Figure 30: MAP request (Malformed Request)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: MALFORMED_REQUEST (0x02)
Lifetime: 0 sec
Epoch Time: 1300

Figure 31: MAP Response (Malformed Request)

2.16. Exceeded Port Quota

This flow shows an example of the content of PCP messages that will be exchanged when a per-user quota is reached. A short lifetime is returned so that the client may retry and see if the request can be honored because another state has been removed.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 45698
 Protocol: UDP (17)
 Internal Port: 8695
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: PREFER_FAILURE (0x02) Option Length: 0 bytes Data: (NULL)

Figure 32: MAP request (Exceeded Port Quota)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: USER_EX_QUOTA (10)
Lifetime: 300 sec
Epoch Time: 1300

Figure 33: MAP Response (Exceeded Port Quota)

2.17. Unsupported Protocol

This flow shows an example of the content of PCP messages that will be exchanged when the requested port is not supported by the PCP Server. In this example, SCTP is indicated as the requested protocol.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 45698
 Protocol: SCTP (132)
 Internal Port: 8695
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 34: MAP request (Unsupported Protocol)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: UNSUPP_PROTOCOL (9)
Lifetime: 0 sec
Epoch Time: 1300

Figure 35: MAP Response (Unsupported Protocol)

2.18. Unsolicited MAP Response

Suppose the client has instructed a UDP mapping for port 3938 (assigned external port is 15000 and assigned external IPv4 address is: 192.0.2.1). Upon a change of a state: e.g., change of the external IP Address, the PCP Server issues an unsolicited MAP response. The content of the MAP response sent by the PCP Server is shown below. The PCP Client is now aware of the new assigned external IP address.

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: TCP (0x06)
 Internal Port: 1234
 Assigned External Port: 10000
 Assigned External IP Address: ::ffff:192.0.2.2

Figure 36: Unsolicited MAP Response

2.19. Mapping Repair

An example of mapping repair is shown in Figure 37.

+------+                      +------+
| PCP  |                      | PCP  |
|Client|                      |Server|
+------+                      +------+
    |     (1) PCP ANNOUNCE        |
    |<----------------------------|
    |     (2) PCP MAP REQUEST     |
    |---------------------------->|
    |     (3) PCP MAP RESPONSE    |
    |<----------------------------|
    |                             |

Figure 37: Flow Example of a PING/PONG exchange: Check the availability of the PCP Server

Version: 2
R bit: Response (1)
Opcode: ANNOUNCE (0x00)
Result Code: 0
Lifetime: 0 sec
Epoch Time: 0

Figure 38: Unsolicited ANNOUNCE

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 11000
 Assigned External Port: 15200
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 39: MAP request

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 10
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 11000
 Assigned External Port: 15200
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 40: MAP Response

3. NAT Detect Example

Let us suppose a PCP-unaware NAT is located between the PCP Server and the PCP Client. An example of PCP MAP request issued by the PCP Client is shown below.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 11000
 Assigned External Port: 15200
 Assigned External IP Address: ::ffff:0.0.0.0

Figure 41: MAP request (NAT Detect)

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: ADDRESS_MISMATCH (12)
Lifetime: 0 sec
Epoch Time: 36000

Figure 42: MAP Response (NAT Detect)

4. Retrieve the External IP Address

In order to retrieve the IP address used on the external side of the PCP-controlled device, the PCP Client sends a short-lived mapping (e.g., Discard service (TCP/9 or UDP/9) or other port). The returned IP address can be displayed by any application requiring such information.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 5 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 9
 Suggested External Port: 9
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 43: MAP request

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 60 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 9
 Suggested External Port: 9
 Assigned External IP Address: ::ffff:192.0.2.1

Figure 44: MAP Response

5. THIRD_PARTY Examples

5.1. THIRD_PARTY Enabled at the Server Side

The following messages are exchanged when the THIRD_PARTY option is enabled in the PCP Server side. In this example the PCP Client creates a mapping for the host assigned with 198.51.100.2.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 16584
 Protocol: UDP (17)
 Internal Port: 8080
 Suggested External Port: 8080
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: THIRD_PARTY (0x01) Option Length: 16 bytes Data:
            ::ffff:198.51.100.2

Figure 45: MAP request with THIRD_PARTY

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 16584
 Protocol: UDP (17)
 Internal Port: 8080
 Assigned External Port: 15000
 Assigned External IP Address: ::ffff:161.105.194.14
Option Code: THIRD_PARTY (0x01) Option Length: 16 bytes Data:
            ::ffff:198.51.100.2

Figure 46: MAP Response with THIRD_PARTY

5.2. THIRD_PARTY Disabled at the Server Side

The following messages are exchanged when the THIRD_PARTY option is disabled in the PCP Server side. In this example the PCP Client tries to create a mapping for the host assigned with 198.51.100.2.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 16584
 Protocol: UDP (17)
 Internal Port: 8080
 Suggested External Port: 8080
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: THIRD_PARTY (0x01) Option Length: 16 bytes Data:
            ::ffff:198.51.100.2

Figure 47: MAP request with THIRD_PARTY

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: UNSUPP_OPTION (0x05)
Lifetime: 0 sec
Epoch Time: 1562

Figure 48: MAP Response with THIRD_PARTY

5.3. Malformed Request

In this example the PCP Client inserts a THIRD_PARTY option which include the IP address of the PCP Client.

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 16584
 Protocol: UDP (17)
 Internal Port: 8080
 Suggested External Port: 8080
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: THIRD_PARTY (0x01) Option Length: 16 bytes Data:
            ::ffff:198.51.100.1

Figure 49: MAP request with THIRD_PARTY

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: MALFORMED_REQUEST (0x03)
Lifetime: 0 sec
Epoch Time: 1562

Figure 50: MAP Response with THIRD_PARTY

6. MAP with FILTER Examples

6.1. Basic Filter Usage

This example illustrates the content of exchanged PCP messages when the PCP Client wants to receive traffic only from 192.0.2.200:5968. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: FILTER (0x03) Option Length: 20 bytes Data:
            Prefix Length: 128
            Remote Peer Port: 5968
            Remote Peer IP Address: ::ffff:192.0.2.200

Figure 51: MAP request

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1
Option Code: FILTER (0x03) Option Length: 20 bytes Data:
            Prefix Length: 128
            Remote Peer Port: 5968
            Remote Peer IP Address: ::ffff:192.0.2.200

Figure 52: MAP Response

6.2. Remove All Filters

This example illustrates the content of exchanged PCP messages when the PCP Client wants to remove all filters. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: FILTER (0x03) Option Length: 20 bytes Data:
            Prefix Length: 0
            Remote Peer Port: 0
            Remote Peer IP Address: ::ffff:0:0

Figure 53: MAP request

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
MAP Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1
Option Code: FILTER (0x03) Option Length: 20 bytes Data:
            Prefix Length: 0
            Remote Peer Port: 0
            Remote Peer IP Address: ::ffff:0:0

Figure 54: MAP Response

6.3. Change an Existing Filter

This example illustrates the content of exchanged PCP messages when the PCP Client wants to change an existing filter. In reference to Figure 1, the content of exchanged PCP messages is as follows:

Version: 2
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
Option Code: FILTER (0x03) Option Length: 20 bytes Data:
            Prefix Length: 0
            Remote Peer Port: 0
            Remote Peer IP Address: ::ffff:0:0
Option Code: FILTER (0x03) Option Length: 20 bytes Data:
            Prefix Length: 128
            Remote Peer Port: 5968
            Remote Peer IP Address: ::ffff:192.0.2.201

Figure 55: MAP request

7. Assess the Reachability of the PCP Server

In this example, the PCP Client issues a PCP ANNOUNCE request to an IP address of a PCP Server. Once received by the PCP Server, since it is configured to reply to such request, it sends back a PCP ANNOUNCE response. This procedure can be used to retrieve the Epoch time.

+------+                      +------+
| PCP  |                      | PCP  |
|Client|                      |Server|
+------+                      +------+
    |   (1) PCP ANNOUNCE REQUEST  |
    |---------------------------->|
    |   (2) PCP ANNOUNCE RESPONSE |
    |<----------------------------|
    |                             |

Figure 56: Flow Example of a PING/PONG exchange: Check the availability of the PCP Server

Version: 2
R bit: Request (0)
Opcode: ANNOUNCE (0x00)
Requested Lifetime: 0 sec
PCP Client's IP Address: ::ffff:198.51.100.1

Figure 57: ANNOUNCE Request

Version: 2
R bit: Response (1)
Opcode: ANNOUNCE (0x00)
Result Code: 0
Lifetime: 0 sec
Epoch Time: 3600

Figure 58: ANNOUNCE Response

8. PEER Operations

The following figure illustrates the messages which are exchanged when PEER OpCode is used:

+------+                           +------+
| PCP  |                           | PCP  |
|Client|                           |Server|
+------+                           +------+
    |      (1) PCP PEER Request         |
    |--------------------------------->|
    |      (2) PCP PEER Response        |
    |<---------------------------------|
    |                                  |

Figure 59: Typical Example of PEER usage

8.1. No Mapping Exists for the Internal Port Number

In reference to Figure 59, the content of exchanged PEER messages when no mapping is maintained by the PCP Server for the indicated external port number:

Version: 2
R bit: Request (0)
Opcode: PEER (0x02)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
PEER Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 60: PEER request

Version: 2
R bit: Response (1)
Opcode: PEER (0x02)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
PEER Response: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Assigned External Port: 3938
 Assigned External IP Address: ::ffff:192.0.2.1
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 61: PEER Response

8.2. A Mapping Exists for the External Port Number

In reference to Figure 59, the content of exchanged PEER messages when a mapping is maintained by the PCP Server for the indicated external port number:

Version: 2
R bit: Request (0)
Opcode: PEER (0x02)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
PEER Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 62: PEER request

Version: 2
R bit: Response (1)
Opcode: PEER (0x02)
Result Code: CANNOT_PROVIDE_EXTERNAL
Lifetime: 0 sec
Epoch Time: 36000

Figure 63: PEER Response

8.3. External IP Address Cannot be Honored

In reference to Figure 59, the content of exchanged PEER messages when the suggested external IP address does not match an existing mapping is shown below:

Version: 2
R bit: Request (0)
Opcode: PEER (0x02)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
PEER Request: 
 Mapping Nonce: 15685
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:192.0.2.5
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 64: PEER request

Version: 2
R bit: Response (1)
Opcode: PEER (0x02)
Result Code: CANNOT_PROVIDE_EXTERNAL
Lifetime: 0 sec
Epoch Time: 36000

Figure 65: PEER Response

8.4. Extend the Lifetime

In reference to Figure 66, the content of exchanged PEER messages to extend the lifetime of a mapping.

+------+                           +------+
| PCP  |                           | PCP  |
|Client|                           |Server|
+------+                           +------+
    |      (a) TCP SYN(src:3938)       |
    |--------------------------------->|
    |      (1) PCP PEER Request        |
    |--------------------------------->|
    |      (2) PCP PEER Response       |
    |<---------------------------------|
    |                                  |

Figure 66: Example of creating a mapping

Version: 2
R bit: Request (0)
Opcode: PEER (0x02)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
PEER Request: 
 Mapping Nonce: 15685
 Protocol: TCP (6)
 Internal Port: 3938
 Suggested External Port: 0
 Suggested External IP Address: ::ffff:0.0.0.0
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 67: PEER request

Version: 2
R bit: Response (1)
Opcode: PEER (0x02)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
PEER Response:
 Mapping Nonce: 15685
 Protocol: TCP (6)
 Internal Port: 3938
 Assigned External Port: 11000
 Assigned External IP Address: ::ffff:192.0.2.1
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 68: PEER Response

8.5. Learn the Lifetime of a Mapping

In reference to Figure 66, the content of exchanged PEER messages to learn the lifetime of a mapping is shown below:

Version: 2
R bit: Request (0)
Opcode: PEER (0x02)
Requested Lifetime: 5 sec
PCP Client's IP Address: ::ffff:198.51.100.1
PEER Request: 
 Mapping Nonce: 15685
 Protocol: TCP (6)
 Internal Port: 3938
 Suggested External Port: 0
 Suggested External IP Address: ::ffff:0.0.0.0
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 69: PEER request

Version: 2
R bit: Response (1)
Opcode: PEER (0x02)
Result Code: 0
Lifetime: 20000 sec
Epoch Time: 1250
PEER Response: 
 Mapping Nonce: 15685
 Protocol: TCP (6)
 Internal Port: 3938
 Assigned External Port: 11000
 Assigned External IP Address: ::ffff:192.0.2.1
 Remote Peer Port: 12456
 Remote IP Address: ::ffff:198.51.100.2

Figure 70: PEER Response

9. Version Negotiation

Suppose the PCP Client supports PCP version 1 while the PCP Server supports PCP version 2. The following exchange will be observed:

Version: 1
R bit: Request (0)
Opcode: MAP (0x01)
Requested Lifetime: 36000 sec
PCP Client's IP Address: ::ffff:198.51.100.1
MAP Request: 
 Protocol: UDP (17)
 Internal Port: 3938
 Suggested External Port: 3938
 Suggested External IP Address: ::ffff:0.0.0.0

Figure 71: MAP Request with Version 1

Version: 2
R bit: Response (1)
Opcode: MAP (0x01)
Result Code: UNSUPP_VERSION (1)
Lifetime: 0 sec
Epoch Time: 3600

Figure 72: MAP Response (Unsupported Version)

10. Security Considerations

This document does not define any protocol nor architecture. PCP security considerations are discussed in [RFC6887].

11. IANA Considerations

This document has no IANA actions.

12. Acknowledgements

Many thanks to C. Jacquenet and D. Wing for the comments.

13. Normative References

[RFC6887]	Wing, D., Cheshire, S., Boucadair, M., Penno, R. and P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 2013.
[RFC5737]	Arkko, J., Cotton, M. and L. Vegoda, "IPv4 Address Blocks Reserved for Documentation", RFC 5737, January 2010.
[RFC3849]	Huston, G., Lord, A. and P. Smith, "IPv6 Address Prefix Reserved for Documentation", RFC 3849, July 2004.

Author's Address

Mohamed Boucadair France Telecom Rennes, 35000 France EMail: mohamed.boucadair@orange.com

Abstract

Status of This Memo

Copyright Notice

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