| IPPM Working Group | X. Min |
| Internet-Draft | G. Mirsky |
| Intended status: Standards Track | ZTE |
| Expires: June 21, 2019 | L. Bo |
| China Telecom | |
| December 18, 2018 |
Extended OAM to Carry In-situ OAM Capabilities
draft-xiao-ippm-ioam-conf-state-02
This document describes an extension for OAM packets including MPLS LSP Ping/Traceroute [RFC8029], ICMP Ping/Traceroute for SRv6 [I-D.ali-spring-srv6-oam] and SFC Ping/Traceroute [I-D.ietf-sfc-multi-layer-oam], which can be used within an IOAM domain, allowing the IOAM encapsulating node to acquire IOAM capabilities of each IOAM transit node and/or IOAM decapsulating node easily and dynamically.
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The Data Fields for In-situ OAM (IOAM) [I-D.ietf-ippm-ioam-data] defines data fields for IOAM which records OAM information within the packet while the packet traverses a particular network domain, which is called an IOAM domain. IOAM can be used to complement OAM mechanisms based on, e.g., ICMP or other types of probe packets, and IOAM mechanisms can be leveraged where mechanisms using, e.g., ICMP do not apply or do not offer the desired results.
As specified in [I-D.ietf-ippm-ioam-data], within the IOAM-domain, the IOAM data may be updated by network nodes that the packet traverses. The device which adds an IOAM data container to the packet to capture IOAM data is called the "IOAM encapsulating node", whereas the device which removes the IOAM data container is referred to as the "IOAM decapsulating node". Nodes within the domain which are aware of IOAM data and read and/or write or process the IOAM data are called "IOAM transit nodes". Both the IOAM encapsulating node and the decapsulating node are referred to as domain edge devices, which can be hosts or network devices.
In order to add accurate IOAM data container to the packet, the IOAM encapsulating node needs to know IOAM capabilities at the IOAM transit nodes and/or the IOAM decapsulating node in a whole, e.g., how many IOAM transit nodes will add tracing data and what kinds of data fields will be added. This document describes an extension for OAM packets including MPLS LSP Ping/Traceroute [RFC8029], ICMP Ping/Traceroute for SRv6 [I-D.ali-spring-srv6-oam] and SFC Ping/Traceroute [I-D.ietf-sfc-multi-layer-oam], which can be used within an IOAM domain, allowing the IOAM encapsulating node to acquire IOAM capabilities of each IOAM transit node and/or IOAM decapsulating node easily and dynamically.
E2E: Edge to Edge
ICMP: Internet Control Message Protocol
IOAM: In-situ Operations, Administration, and Maintenance
LSP: Label Switched Path
MPLS: Multi-Protocol Label Switching
MTU: Maximum Transmission Unit
NTP: Network Time Protocol
OAM: Operations, Administration, and Maintenance
POSIX: Portable Operating System Interface
POT: Proof of Transit
PTP: Precision Time Protocol
SFC: Service Function Chain
SRv6: Segment Routing with IPv6 Data plane
TTL: Time to Live
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
IOAM Capabilities uses TLV (Type-Length-Value tuple) which have the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = IOAM Capabilities | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-IDs Length | Sub-TLVs Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. List of Namespace-IDs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. List of Sub-TLVs .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IOAM Capabilities TLV
When this TLV is present in the echo request sent by an IOAM encapsulating node, it means that the IOAM encapsulating node requests the receiving node to reply with its IOAM capabilities. If there is no IOAM capabilities to be reported by the receiving node, then this TLV SHOULD be ignored by the receiving node. List of Namespace-IDs MAY be included in this TLV of echo request, it means that the IOAM encapsulating node requests only the IOAM capabilities which matchs one of the Namespace-IDs. The Namespace-ID has the same definition as what's specified in [I-D.ietf-ippm-ioam-data].
When this TLV is present in the echo reply sent by an IOAM transit node and/or an IOAM decapsulating node, it means that IOAM function is enabled at this node and this TLV contains IOAM capabilities of the sender. List of Namespace-IDs MAY be included in this TLV of echo reply. It means that the IOAM capabilities included in this TLV match one of the Namespace-IDs. If a List of Namespace-IDs is present in the TLV of echo request, then the List of Namespace-IDs in the TLV of echo reply MUST be a subset of that one. List of Sub-TLVs which contain the IOAM capabilities SHOULD be included in this TLV of the echo reply. Note that the IOAM encapsulating node or the IOAM decapsulating node can also be an IOAM transit node.
Type is set to the value which indicates that it's an IOAM Capabilities TLV.
Length is the length of the TLV's Value field in octets, Namespace-IDs Length is the Length of the List of Namespace-IDs field in octets, Sub-TLVs Length is the length of the List of Sub-TLVs field in octets.
Value field of this TLV or any Sub-TLV is zero padded to align to a 4-octet boundary. Based on the data fields for IOAM specified in [I-D.ietf-ippm-ioam-data], four kinds of Sub-TLVs are defined in this document, and in an IOAM Capabilities TLV the same kind of Sub-TLV can appear more times than one with different Namespace-ID.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-type = Tracing Conf Data | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM-Trace-Type |F| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID | Egress_if_MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Egress_if_id (short or wide format) ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IOAM Tracing Capabilities Sub-TLV
When this sub-TLV is present in the IOAM Capabilities TLV, it means that the sending node is an IOAM transit node and IOAM tracing function is enabled at this IOAM transit node.
Sub-type is set to the value which indicates that it's an IOAM Tracing Capabilities sub-TLV.
Length is the length of the sub-TLV's Value field in octets, if Egress_if_id is in the short format which is 16 bits long, it MUST be set to 10, and if Egress_if_id is in the wide format which is 32 bits long, it MUST be set to 12.
IOAM-Trace-Type field has the same definition as what's specified in section 4.2 of [I-D.ietf-ippm-ioam-data].
F bit is specified to indicate whether the pre-allocated trace or incremental trace is enabled. F bit is set to 1 when pre-allocated trace is enabled and set to 0 when the incremental trace is enabled. The meaning and difference of pre-allocated trace and incremental trace are described in section 4.1 of [I-D.ietf-ippm-ioam-data]. If the IOAM encapsulating node receives different F bit value from different IOAM transit node, then the IOAM encapsulating node will reserve data space in the IOAM header for the IOAM transit node that set F bit to 1, and the IOAM encapsulating node won't reserve data space in the IOAM header for the IOAM transit node that set F bit to 0.
Reserved field is reserved for future use and MUST be set to zero.
Namespace-ID field has the same definition as what's specified in section 4.2 of [I-D.ietf-ippm-ioam-data].
Egress_if_MTU field has 16 bits and specifies the MTU of the egress interface out of which the sending node would forward the received echo request.
Egress_if_id field has 16 bits (in short format) or 32 bits (in wide format) and specifies the identifier of the egress interface out of which the sending node would forward the received echo request.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-type = POT Conf Data | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID | IOAM-POT-Type |P|SoR|Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IOAM Proof of Transit Capabilities Sub-TLV
When this sub-TLV is present in the IOAM Capabilities TLV, it means that the sending node is an IOAM transit node and IOAM proof of transit function is enabled at this IOAM transit node.
Sub-type is set to the value which indicates that it's an IOAM Proof of Transit Capabilities sub-TLV.
Length is the length of the sub-TLV's Value field in octets, and MUST be set to 4.
Namespace-ID field has the same definition as what's specified in section 4.3 of [I-D.ietf-ippm-ioam-data].
IOAM-POT-Type field and P bit have the same definition as what's specified in section 4.3 of [I-D.ietf-ippm-ioam-data]. If the IOAM encapsulating node receives IOAM-POT-Type and/or P bit values from an IOAM transit node that are different from its own, then the IOAM encapsulating node MAY choose to abandon the proof of transit function or to select one kind of IOAM-POT-Type and P bit, it's based on the policy applied to the IOAM encapsulating node.
SoR field has two bits which means the size of "Random" and "Cumulative" data, which are specified in section 4.3 of [I-D.ietf-ippm-ioam-data]. This document defines SoR as follow:
Reserved field is reserved for future use and MUST be set to zero.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-type = E2E Conf Data | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID | IOAM-E2E-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TSF|TSL| Reserved | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: IOAM Edge-to-Edge Capabilities Sub-TLV
When this sub-TLV is present in the IOAM Capabilities TLV, it means that the sending node is an IOAM decapsulating node and IOAM edge-to-edge function is enabled at this IOAM decapsulating node. That is to say, if the IOAM encapsulating node receives this sub-TLV, the IOAM encapsulating node can determine that the node which sends this sub-TLV is an IOAM decapsulating node.
Sub-type is set to the value which indicates that it's an IOAM Edge-to-Edge Capabilities sub-TLV.
Length is the length of the sub-TLV's Value field in octets, and MUST be set to 8.
Namespace-ID field has the same definition as what's specified in section 4.4 of [I-D.ietf-ippm-ioam-data].
IOAM-E2E-Type field has the same definition as what's specified in section 4.4 of [I-D.ietf-ippm-ioam-data].
TSF field specifies the timestamp format used by the sending node. This document defines TSF as follow:
TSL field specifies the timestamp length used by the sending node. This document defines TSL as follow:
Reserved field is reserved for future use and MUST be set to zero.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-type = End of Domain | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: IOAM End of Domain Sub-TLV
When this sub-TLV is present in the IOAM Capabilities TLV, it means that the sending node is an IOAM decapsulating node. That is to say, if the IOAM encapsulating node receives this sub-TLV, the IOAM encapsulating node can determine that the node which sends this sub-TLV is an IOAM decapsulating node. When the IOAM Edge-to-Edge Capabilities sub-TLV is present in the IOAM Capabilities TLV sent by the IOAM decapsulating node, the IOAM End-of-Domain sub-TLV doesn't need to be present in the same IOAM Capabilities TLV, otherwise the End-of-Domain sub-TLV MUST be present in the IOAM Capabilities TLV sent by the IOAM decapsulating node. Since both the IOAM Edge-to-Edge Capabilities sub-TLV and the IOAM End-of-Domain sub-TLV can be used to indicate that the sending node is an IOAM decapsulating node, it's recommended to include only the IOAM Edge-to-Edge Capabilities sub-TLV if IOAM edge-to-edge function is enabled at this IOAM decapsulating node.
Length is the length of the sub-TLV's Value field in octets, and MUST be set to 4.
Namespace-ID field has the same definition as what's specified in section 4.4 of [I-D.ietf-ippm-ioam-data].
Once the IOAM encapsulating node is triggered to acquire IOAM capabilities of each IOAM transit node and/or IOAM decapsulating node, the IOAM encapsulating node will send a batch of echo requests that include the IOAM Capabilities TLV, first with TTL equal to 1 to reach the nearest node which may be an IOAM transit node or not, then with TTL equal to 2 to reach the second nearest node which also may be an IOAM transit node or not, on the analogy of this to increase 1 to TTL every time the IOAM encapsulating node sends a new echo request, until the IOAM encapsulating node receives echo reply sent by the IOAM decapsulating node, which must contain the IOAM Capabilities TLV including the IOAM Edge-to-Edge Capabilities sub-TLV or the IOAM End-of-Domain sub-TLV.
The IOAM encapsulating node may be triggered by the device administrator, the network management, the network controller, or even the live user traffic, and the specific triggering mechanisms are outside the scope of this document.
Each IOAM transit node and/or IOAM decapsulating node that receives an echo request containing the IOAM Capabilities TLV will send an echo reply to the IOAM encapsulating node, and within the echo reply, there must be an IOAM Capabilities TLV containing one or more sub-TLVs. The IOAM Capabilities TLV contained in the echo request would be ignored by the receiving node that is unaware of IOAM.
Knowledge of the state of the IOAM domain may be considered confidential. Implementations SHOULD provide a means of filtering the addresses to which echo reply messages, MPLS LSP Ping/Traceroute, ICMP Ping/Traceroute for SRv6 or SFC Ping/Traceroute, may be sent.
This document has no IANA actions.
The authors appreciate the f2f discussion with Frank Brockners on this document.