Network Working Group A. Farrel Internet-Draft Huawei Technologies Intended status: Informational H. Endo Expires: April 18, 2011 Hitachi, Ltd. R. Winter NEC October 15, 2010 Handling MPLS-TP OAM Packets Targeted at Internal MIPs draft-farrel-mpls-tp-mip-mep-map-03 Abstract The Framework for Operations, Administration and Maintenance (OAM) within the MPLS Transport Profile (MPLS-TP) describes how Maintenance Intermediate Points (MIPs) may be situated within network nodes at the incoming and outgoing interfaces. This document describes a way of forming OAM messages so that they can be targeted at MIPs on incoming or MIPs on outgoing interfaces, forwarded correctly through the "switch fabric", and handled efficiently in node implementations where there is no distinction between the incoming and outgoing MIP. The material in this document is provided for discussion within the MPLS-TP community in the expectation that this idea or some similar mechanism will be subsumed into a more general MPLS-TP OAM document. This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network. 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 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 Farrel, et al. Expires April 18, 2011 [Page 1] Internet-Draft Internal MIP Handling October 2010 material or to cite them other than as "work in progress." This Internet-Draft will expire on April 18, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. 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. Farrel, et al. Expires April 18, 2011 [Page 2] Internet-Draft Internal MIP Handling October 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Requirements notation . . . . . . . . . . . . . . . . . . . . 5 3. Summary of the Problem Statement . . . . . . . . . . . . . . . 6 3.1. Rejected Partial Solution . . . . . . . . . . . . . . . . 9 4. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Processing of Data and Non-Local OAM . . . . . . . . . . . 13 4.2. MIP Identification . . . . . . . . . . . . . . . . . . . . 13 4.3. In-MIP Processing . . . . . . . . . . . . . . . . . . . . 14 4.4. Out-MIP Processing . . . . . . . . . . . . . . . . . . . . 14 4.5. Processing at P2MP Branch Nodes . . . . . . . . . . . . . 15 4.5.1. Out-MIP Processing . . . . . . . . . . . . . . . . . . 15 4.6. Processing When There is No Out-MIP . . . . . . . . . . . 16 5. Enhanced Proposed Solutions . . . . . . . . . . . . . . . . . 17 5.1. Incoming MIP Filtering . . . . . . . . . . . . . . . . . . 17 5.2. Outgoing MIP Label . . . . . . . . . . . . . . . . . . . . 17 6. Security Considerations . . . . . . . . . . . . . . . . . . . 19 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.1. Normative References . . . . . . . . . . . . . . . . . . . 22 9.2. Informative References . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Farrel, et al. Expires April 18, 2011 [Page 3] Internet-Draft Internal MIP Handling October 2010 1. Introduction The Framework for Operations, Administration and Maintenance (OAM) within the MPLS Transport Profile (MPLS-TP)(the MPLS-TP OAM Framework, [I-D.ietf-mpls-tp-oam-framework]) distinguishes two configurations for Maintenance Intermediate Points (MIPs) on a node. It defines per-node MIPs and per-interface MIPs, where a per-node MIP is a single MIP per node in an unspecified location within the node and per-interface MIPs are two (or more) MIPs per node on both sides of the forwarding engine. In-band OAM messages are sent using the Generic Associated Channel (G-ACh) [RFC5586]. OAM messages for the transit points of pseudowires (PWs) or Label Switched Paths (LSPs) are delivered using the expiration of the MPLS shim header time-to-live (TTL) field. OAM messages for the end points of PWs and LSPs are simply delivered as normal. OAM messages delivered to end points or transit points are distinguished from other (data) packets so that they can be processed as OAM. In LSPs, the mechanism used is the presence of the Generic Associated Channel Label (GAL) in the Label Stack Entry (LSE) under the top LSE [RFC5586]. In PWs, the mechanism used is the presence of the PW Associated Channel Header (PWACH) [RFC4385]. Given these mechanisms and the presence of multiple MIPs on a single node, these mechanisms provide no way to address one particular MIP out of the set of MIPs on the node. This document describes a way of forming OAM messages so that they can be targeted at incoming MIPs and outgoing MIPs, forwarded correctly through the "switch fabric", and handled efficiently in node implementations where there is no distinction between the incoming and outgoing MIP. The material in this document is provided for discussion within the MPLS-TP community in the expectation that this idea or some similar mechanisms will be subsumed into a more general MPLS-TP OAM document. This document is a product of a joint Internet Engineering Task Force (IETF)/International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architecture to support the capabilities and functionalities of a packet transport network. Note that the acronym "OAM" is used in conformance with [I-D.ietf-opsawg-mpls-tp-oam-def]. Farrel, et al. Expires April 18, 2011 [Page 4] Internet-Draft Internal MIP Handling October 2010 2. Requirements notation 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 [RFC2119]. Farrel, et al. Expires April 18, 2011 [Page 5] Internet-Draft Internal MIP Handling October 2010 3. Summary of the Problem Statement Figure 1 shows an abstract functional representation of an MPLS-TP node. It is decomposed as an incoming interface, a cross-connect (XC), and an outgoing interface. As per the discussion in [I-D.ietf-mpls-tp-oam-framework], MIPs may be placed in each of the functional interface components. ------------------------ | | |----- -----| | MIP | | MIP | | | ---- | | ----->-| In |->-| XC |->-| Out |->---- | i/f | ---- | i/f | |----- -----| | | ------------------------ Figure 1: Abstract Functional Representation of an MPLS-TP Node Several distinct OAM functions are required within this architectural model such as: o CV between a MEP and a MIP o traceroute over an MPLS-TP LSP and/or an MPLS-TP PW containing MIPs o OAM control at a MIP o data-plane loopback at a MIP o diagnostic tests The MIPs in these OAM functions may equally be the MIPs at the incoming or outgoing interfaces. In-band OAM messages are sent using the G-ACh [RFC5586] and ACH-TLVs [I-D.ietf-mpls-tp-ach-tlv] for MPLS-TP LSPs and MPLS-TP PWs, respectively. OAM messages for the transit points of PWs or LSPs are delivered using the expiration of the time-to-live (TTL) field in the top LSE of the MPLS packet header. OAM messages for the end points of PWs and LSPs are simply delivered as normal. OAM messages delivered to end points or transit points are distinguished from other (data) packets so that they can be processed as OAM. In LSPs, the mechanism used is the presence of the Generic Farrel, et al. Expires April 18, 2011 [Page 6] Internet-Draft Internal MIP Handling October 2010 Associated Channel Label (GAL) in the LSE under the top LSE [RFC5586]. In PWs, the mechanism used is the presence of the PW Associated Channel Header [RFC4385]. Any solution for sending OAM to the in and out MIPs must fit within these existing models of handling OAM. Additionally, many MPLS-TP nodes contain an optimization such that all queuing and the forwarding function is performed at the incoming interface. The abstract functional representation of such a node is shown in Figure 2. As shown in the figure, the outgoing interfaces are minimal and for this reason it may not be possible to include MIP functions on those interfaces. This is in particular the case for existing deployed implementations. Any solution that attempts to send OAM to the outgoing interface of an MPLS-TP node must not cause any problems when such implementations are present. ------------------ | | |------------ | | MIP | | | ---- | | ----->-| In | XC | |-->--|->--- | i/f ---- | | |------------ | | | ------------------ Figure 2: Abstract Functional Representation of an Optimized MPLS-TP Node Lastly, OAM must operate on MPLS-TP nodes that are branch points on point-to-multipoint (P2MP) trees. That means that it must be possible to target individual outgoing MIPs as well as all outgoing MIPs in the abstract functional representation shown in Figure 3, as well as to handle the optimized P2MP node as shown in Figure 4. Farrel, et al. Expires April 18, 2011 [Page 7] Internet-Draft Internal MIP Handling October 2010 -------------------------- | | | -----| | | MIP | | ->-| |->---- | | | Out | | | | i/f | | | -----| |----- | -----| | MIP | ---- | | MIP | | | | |- | | ----->-| In |->-| XC |--->-| Out |->---- | i/f | | |- | i/f | |----- ---- | -----| | | -----| | | | MIP | | | | | | ->-| Out |->---- | | i/f | | -----| -------------------------- Figure 3: Abstract Functional Representation of an MPLS-TP Node Supporting P2MP ------------------ | | | ->-|->---- | | | |------------ | | | | | | | MIP ---- | | | | | | |- | ----->-| In | XC | |--->-|->---- | i/f | | |- | | ---- | | | | | | | |------------ | | | | | | ->-|->---- | | ------------------ Figure 4: Abstract Functional Representation of an Optimized MPLS-TP Node Supporting P2MP In summary, the solution for OAM message delivery must support the Farrel, et al. Expires April 18, 2011 [Page 8] Internet-Draft Internal MIP Handling October 2010 following features: o Forwarding of OAM packets exactly as data packets. o Delivery of OAM messages to the correct MPLS-TP node. o Direction of OAM instructions to the correct MIP within an MPLS-TP node. o Packet inspection at the incoming and outgoing interfaces must be minimized. Note that although this issue appears superficially to be an implementation matter local to an individual node, the format of the message needs to be standardised so that: o An upstream MEP can correctly target the outgoing MIP of a specific MPLS-TP node. o A downstream node can correctly filter out any OAM messages that were intended for its upstream neighbor's outgoing MIP, but which were not handled there because the upstream neighbor is an optimized implementation. Note that the last bullet point describes a safety net and an implementation should avoid that this situation ever arises. 3.1. Rejected Partial Solution A reject solution is depicted in Figure 5. All data and non-local OAM is handled as normal. Local OAM is intercepted at the incoming interface and delivered to the MIP at the incoming interface. If the OAM is intended for the incoming MIP it is handled there with no issue. If the OAM is intended for the outgoing MIP it is forwarded to that MIP using some internal messaging system that is implementation-specific. Farrel, et al. Expires April 18, 2011 [Page 9] Internet-Draft Internal MIP Handling October 2010 ------------------------ | | |----- -----| local OAM ----->-| MIP |----->------| MIP | | | ---- | | data =====>=| In |=>=| XC |=>=| Out |=>==== data non-local OAM ~~~~~>~| i/f |~>~| |~>~| i/f |~>~~~~ non-local OAM |----- ---- -----| | | ------------------------ Figure 5: OAM Control Message Delivery Bypassing the Switching Fabric This solution is fully functional for the incoming MIP. It also supports control of data loopback for the outgoing MIP, and can adequately perform some OAM features such as interface identity reporting at the outgoing MIP. However, because the OAM message is not forwarded through the switch fabric, this solution cannot correctly perform OAM loopback, connectivity verification, LSP tracing, or performance measurement. Note that the local OAM message means that the OAM message which must be terminated, inspected and processed at the in or out MIP of depicted MPLS-TP node in Figure 5. Farrel, et al. Expires April 18, 2011 [Page 10] Internet-Draft Internal MIP Handling October 2010 4. Proposed Solution Figure 6 shows a proposed message format for handling the OAM messages in different cases as described in Section 3. The subsections that follow describe the processing rules for each case. Note that this proposed solution could result in a packet with a TTL=0 to be forwarded. Alternatives are discussed in Section 4.6. ------------------------ |----- -----| | MIP | ---- | MIP | ----->-| In |->-| XC |->-| Out |->---- | i/f | ---- | i/f | |----- -----| ------------------------ ----------------- ------------------- data | Label=x | TTL=n |--------------->| Label=y | TTL=n-1 | ----------------- ------------------- ----------------- ------------------- non-local | Label=x | TTL=n |--------------->| Label=y | TTL=n-1 | OAM |-----------------| |-------------------| | GAL | TTL=m | | GAL | TTL=m | |-----------------| |-------------------| | ACH Type = OAM | | ACH Type = OAM | ----------------- ------------------- ----------------- in-MIP | Label=x | TTL=1 |--- OAM |-----------------| | | GAL | TTL=m | | |-----------------| | | ACH Type = OAM | | ----------------- | <------ alternative: ----------------- in-MIP | Label=x | TTL=1 |--- OAM |-----------------| | | GAL | TTL=m | | |-----------------| | | ACH Type = OAM | | |-----------------| | | ACH TLV=in-MIP | | Farrel, et al. Expires April 18, 2011 [Page 11] Internet-Draft Internal MIP Handling October 2010 ----------------- | <------ ----------------- ----------------- out-MIP | Label=x | TTL=1 |--------------->| Label=y | TTL=0 |--- OAM |-----------------| |-----------------| | | GAL | TTL=m | | GAL | TTL=m | | |-----------------| |-----------------| | | ACH Type = OAM | | ACH Type = OAM | | |-----------------| |-----------------| | | ACH TLV=out-MIP | | ACH TLV=out-MIP | | ----------------- ----------------- | <------- ----------------- ----------------- out-MIP | Label=x | TTL=1 |--------------->| Label=y | TTL=0 |---> not |-----------------| |-----------------| supported | GAL | TTL=m | | GAL | TTL=m | |-----------------| |-----------------| | ACH Type = OAM | | ACH Type = OAM | |-----------------| |-----------------| | ACH TLV=out-MIP | | ACH TLV=out-MIP | ----------------- ----------------- Figure 6: Packet Formats for In and Out MIP OAM in the case of LSPs ------------------------ |----- -----| | MIP | ---- | MIP | ----->-| In |->-| XC |->-| Out |->---- | i/f | ---- | i/f | |----- -----| ------------------------ ----------------- ------------------- data | Label=x | TTL=n |-------------->| Label=y | TTL=n-1 | ----------------- ------------------- ------------------ ------------------- non-local | Label=x | TTL=n |------------->| Label=y | TTL=n-1 | OAM |------------------| |-------------------| | PWACH Type = OAM | | PWACH Type = OAM | ------------------ ------------------- ------------------ in-MIP | Label=x | TTL=1 |--- Farrel, et al. Expires April 18, 2011 [Page 12] Internet-Draft Internal MIP Handling October 2010 OAM |------------------| | | PWACH Type = OAM | | ------------------ | <------ alternative: ------------------ in-MIP | Label=x | TTL=1 |--- OAM |------------------| | | PWACH Type = OAM | | |------------------| | | ACH TLV=in-MIP | | ------------------ | <------ ------------------ ------------------ out-MIP | Label=x | TTL=1 |------------->| Label=y | TTL=0 |--- OAM |------------------| |------------------| | | PWACH Type = OAM | | PWACH Type = OAM | | |------------------| |------------------| | | ACH TLV=out-MIP | | ACH TLV=out-MIP | | ------------------ ------------------ | <------- ------------------ ------------------ out-MIP | Label=x | TTL=1 |------------->| Label=y | TTL=0 |---> not |------------------| |------------------| supported | PWACH Type = OAM | | PWACH Type = OAM | |------------------| |------------------| | ACH TLV=out-MIP | | ACH TLV=out-MIP | ------------------ ------------------ Figure 7: Packet Formats for In and Out MIP OAM in the case of PWs 4.1. Processing of Data and Non-Local OAM The message formats and processing rules for data and non-local OAM are not changed by this proposal. The top-of-stack label is swapped and the top-of-stack TTL is decremented. 4.2. MIP Identification [I-D.ietf-mpls-tp-identifiers] defines various identifiers to be used with MPLS-TP. Using the ACH/PWACH, the MIP identifiers as defined in [I-D.ietf-mpls-tp-identifiers] can be added as a TLV after the ACH/ PWACH. Both, in- and out-MIPs can therefore unambiguously tell Farrel, et al. Expires April 18, 2011 [Page 13] Internet-Draft Internal MIP Handling October 2010 whether an OAM packet is indeed destined to be processed by it. Various ways to address in- and out-MIPs are conceivable, such as using the TTL field in the GAL, however, the GAL is only applicable to LSPs. Furthermore, in case of a P2MP LSP one out of a number of out-MIPs might need to be uniquely addressed which a TTL field alone cannot accomplish. Therefore, in order to define a single mechanism that can be used in all MPLS-TP constructs (PWs, LSPs and P2MP scenarios) the MIP IDs as defined by [I-D.ietf-mpls-tp-identifiers] can always be consistently used. To facilitate an efficient implementation in hardware, the identifier TLV MUST be in a fixed location after the ACH/PWACH. In case, the identifier TLV is missing, the in-MIP/or per-nore MIP should process the packet. This is to ensure compatibility with in-MIP-only/ per-node-MIP-only systems. However, OAM messages which need to verify the target MIP must contain a TLV that identifies the target MIP ID as desribed in [I-D.ietf-mpls-tp-identifiers]. 4.3. In-MIP Processing The top-of-stack TTL is decremented and expires. The packet is examined further and the GAL is discovered indicating that the packet contains an ACH which needs to be further examined. In case of PWs, the S bit [RFC3032] is found to be set, and the next nibble is examined. This shows that a PWACH is present. The Channel Type field of the PWACH [RFC4385] indicates that the packet is OAM. The following ACH needs to be further examined. The ACH type indicates the type of OAM and the the MIP identifier (if present) can be found in a TLV in a fixed location following the ACH. In case the ID TLV is not present, the in-MIP (or per-node MIP) processes that OAM packet. 4.4. Out-MIP Processing OAM messages intended for the out-MIP on a node are initially intercepted as described in the previous section. That is, the TTL expires and further inspection of the packet indicates that it is OAM. The incoming interface must forward the OAM message through the switch fabric as if it was data. The packet is passed on unchanged except that the TTL has been decremented and expires. The processing at the out-MIP is comparable to the in-MIP processing. The TTL has already expired (i.e., is has been decremented to zero at the incoming interface). If the outgoing interface is capable of packet inspection, the top- level TTL is found to be zero and the Farrel, et al. Expires April 18, 2011 [Page 14] Internet-Draft Internal MIP Handling October 2010 packet is removed from the data stream. In case of LSP OAM, the GAL is discovered indicating that the packet contains an ACH which needs to be further examined. In case of PWs, the S bit [RFC3032] is found to be set, and the next nibble is examined. This shows that a PWACH is present. The Channel Type field of the PWACH [RFC4385] indicates that the packet is OAM. The following ACH needs to be further examined. The ACH type indicates the type of OAM and the MIP ID TLV (if present) MUST be in a fixed location following the ACH. Packets not intended for a given out-MIP are silently discarded. In case there is no TLV, the out-MIP should discard the packet as the in-MIP should respond in this case. A per-node MIP should respond. If the outgoing interface is not capable of packet inspection the packet will be forwarded out of the outgoing interface. See Section 4.6 for more details. 4.5. Processing at P2MP Branch Nodes At P2MP branch nodes, the OAM messages may be targeted at one or all outgoing interfaces. It should be noted that packet replication is a function of the switch fabric so that any OAM message forwarded by the incoming interface will be passed to all outgoing interfaces. The procedures operate as described before and ACH TLVs are required to limit the OAM to one or more out-MIPs. 4.5.1. Out-MIP Processing The outgoing interfaces are able to determine whether the OAM message is intended for the local out-MIP by examining a MIP identifier carried in an ACH TLV. There are two potential solutions to this problem. One could allow more than one MIP identifier to allow multiple out-MIPs on the same P2MP tree to be targeted by the same OAM message. This however complicates hardware design as the out- MIPs need to parse the TLV. Therefore, instead of having multiple TLVs in a single OAM message, in case two or more out-MIPs need to be addressed, two or more messages need to be sent, each carrying the ID TLV identifying the targeted out-MIP. A special MIP identifier number is used to indicate that all out-MIPs on the P2MP PW are targets. This identifier must include an identifier that is unique to the local node as described in [I-D.ietf-mpls-tp-identifiers]. An OAM message received at an outgoing interface for a P2MP LSP which Farrel, et al. Expires April 18, 2011 [Page 15] Internet-Draft Internal MIP Handling October 2010 does not including any ACH TLVs to identify the out-MIP, should be silently discarded. OAM messages received at outgoing interfaces that support out-MIP OAM, but that are not intended for the local MIP are silently discarded. If the outgoing interface is not capable of packet inspection the packet will be forwarded out of the outgoing interface. See Section 4.6 for more details. 4.6. Processing When There is No Out-MIP When there is no out-MIP support on an optimized node implementation there are three options. 1. The OAM message is intercepted at the incoming interface and the incoming interface is aware that it forms part of an optimized implementation that does not support an out-MIP. It can discard the received OAM message, or respond to indicate that the out-MIP is not supported. 2. The OAM message is intercepted and forwarded as described in Section 4.4. Since there is no out-MIP, the message is forwarded out of the outgoing interface to the next downstream MPLS-TP node as shown at the bottom of Figures Figure 6 and Figure 7. This means that the packet will be received at the downstream node carrying a TTL that has already expired (before it is decremented at the downstream node) indicating that the packet should be silently discarded. If the packet is examined in this case, it will reveal an ACH TLV identifying a MIP that is not local to the downstream node. This will result in the packet being dropped or a negative response being sent. 3. The OAM message is intercepted at the incoming interface and this is a per node MIP which only reacts to TTL expiry (no other inspection needs to be performed for a per node MIP). In that case it would process the OAM packet and send a reply if one is needed. For the MEP receiving the reply there might be no way of telling that this was send by the incoming MIP. Farrel, et al. Expires April 18, 2011 [Page 16] Internet-Draft Internal MIP Handling October 2010 5. Enhanced Proposed Solutions The above described mechanism has one serious disadvantage, which is that there are potential situations in which a labeled packet with a TTL of 0 could be forwarded. This is not standards conformant behavior. RFC 3032 states: "If the outgoing TTL of a labeled packet is 0, then the labeled packet MUST NOT be further forwarded; nor may the label stack be stripped off and the packet forwarded as an unlabeled packet. The packet's lifetime in the network is considered to have expired." As a consequence, there needs to be a way to achieve standard conformant behavior. The following are proposals to achieve this. 5.1. Incoming MIP Filtering In Section 4.6, one potential way of handling the case where there is no outgoing MIP is to make an incoming MIP aware of the MIP configuration for the maintenance entity it is part of via configuration. This enables the incoming MIP to make sure that no labeled packet with a TTL=0 ever leaves the node. It also enables the MIP to reply to an OAM packet which is addressed to an outgoing MIP with an error code ('No Such MIP') if desired. 5.2. Outgoing MIP Label The mechanisms described in Section 4 can be enhanced by the use of a new reserved label, the Outgoing MIP Label (OML). This label is substituted for the GAL when an OAM message intended for an outgoing MIP is processed at an incoming interface as shown in Figure 8. The advantage of this mechanism is that the outgoing interface of the local node and the incoming interface of the downstream node have something more substantial to check than just the TTL value being zero. In fact, it allows the message to be sent with TTL of one so that the rules for sending packets with zero TTL are not compromised. The disadvantage is that a further reserved label is used, potentially more to cater for the P2MP case. Note that an option is to allocate the OML as a purely local matter. That means that the implementation allocates the value of the OML from its local label space and assigns the meaning as described. This approach, however, would be risky if the packet escaped and was processed by the downstream node. Farrel, et al. Expires April 18, 2011 [Page 17] Internet-Draft Internal MIP Handling October 2010 ----------------- ----------------- out-MIP | Label=x | TTL=1 |--------------->| Label=y | TTL=1 |--- OAM |-----------------| |-----------------| | | GAL | TTL=m | | OML | TTL=n | | |-----------------| |-----------------| | | ACH TLV=out-MIP | | ACH TLV=out-MIP | | ----------------- ----------------- | <------- ----------------- ----------------- out-MIP | Label=x | TTL=1 |--------------->| Label=y | TTL=1 |---> not |-----------------| |-----------------| supported | GAL | TTL=m | | OML | TTL=n | |-----------------| |-----------------| | ACH TLV=out-MIP | | ACH TLV=out-MIP | ----------------- ----------------- Figure 8: Use of the Outgoing MIP Label Farrel, et al. Expires April 18, 2011 [Page 18] Internet-Draft Internal MIP Handling October 2010 6. Security Considerations OAM security is discussed in [I-D.ietf-mpls-tp-oam-framework] and [I-D.manral-mpls-tp-oam-security-tlv]. OAM can provide useful information for detecting and tracing security attacks. OAM can also be used to illicitly gather information or for denial of service attacks and other types of attack. Implementations therefore are required to offer security mechanisms for OAM. Deployments are strongly advised to use such mechanisms. Farrel, et al. Expires April 18, 2011 [Page 19] Internet-Draft Internal MIP Handling October 2010 7. IANA Considerations This revision of this document does not make any requests of IANA. If the solution described in Section 4 is adopted, a request will be made to IANA for the allocation of a new reserved label. Farrel, et al. Expires April 18, 2011 [Page 20] Internet-Draft Internal MIP Handling October 2010 8. Acknowledgments TBD Farrel, et al. Expires April 18, 2011 [Page 21] Internet-Draft Internal MIP Handling October 2010 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001. [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006. [RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, June 2009. 9.2. Informative References [I-D.ietf-mpls-tp-ach-tlv] Boutros, S., Bryant, S., Sivabalan, S., Swallow, G., Ward, D., and V. Manral, "Definition of ACH TLV Structure", draft-ietf-mpls-tp-ach-tlv-02 (work in progress), March 2010. [I-D.ietf-mpls-tp-identifiers] Bocci, M. and G. Swallow, "MPLS-TP Identifiers", draft-ietf-mpls-tp-identifiers-02 (work in progress), July 2010. [I-D.ietf-mpls-tp-oam-framework] Allan, D., Busi, I., Niven-Jenkins, B., Fulignoli, A., Hernandez-Valencia, E., Levrau, L., Sestito, V., Sprecher, N., Helvoort, H., Vigoureux, M., Weingarten, Y., and R. Winter, "Operations, Administration and Maintenance Framework for MPLS- based Transport Networks", draft-ietf-mpls-tp-oam-framework-09 (work in progress), October 2010. [I-D.ietf-opsawg-mpls-tp-oam-def] Andersson, L., Helvoort, H., Bonica, R., Romascanu, D., and S. Mansfield, ""The OAM Acronym Soup"", draft-ietf-opsawg-mpls-tp-oam-def-06 (work in progress), June 2010. [I-D.manral-mpls-tp-oam-security-tlv] Manral, V., "MPLS-TP General Authentication TLV for Farrel, et al. Expires April 18, 2011 [Page 22] Internet-Draft Internal MIP Handling October 2010 G-ACH", draft-manral-mpls-tp-oam-security-tlv-00 (work in progress), June 2009. Farrel, et al. Expires April 18, 2011 [Page 23] Internet-Draft Internal MIP Handling October 2010 Authors' Addresses Adrian Farrel Huawei Technologies Email: adrian.farrel@huawei.com Hideki Endo Hitachi, Ltd. Email: hideki.endo.es@hitachi.com Rolf Winter NEC Email: rolf.winter@neclab.eu Farrel, et al. Expires April 18, 2011 [Page 24]