Inband OAM (iOAM)
=================
In-band OAM (iOAM) is an implementation study to record operational
information in the packet while the packet traverses a path between two
points in the network.
Overview of iOAM can be found in
`iOAM-Devnet <https://github.com/ciscodevnet/iOAM>`__ page. The
following IETF drafts detail the motivation and mechanism for recording
operational information: -
`iOAM-ietf-requirements <https://tools.ietf.org/html/draft-brockners-inband-oam-requirements-01>`__
- Describes motivation and usecases for iOAM -
`iOAM-ietf-data <https://tools.ietf.org/html/draft-brockners-inband-oam-data-01>`__
- Describes data records that can be collected using iOAM -
`iOAM-ietf-transport <https://tools.ietf.org/html/draft-brockners-inband-oam-transport-01>`__
- Lists out the transport protocols and mechanism to carry iOAM data
records -
`iOAM-ietf-proof-of-transit <https://tools.ietf.org/html/draft-brockners-proof-of-transit-01>`__
- Describes the idea of Proof of Transit (POT) and mechanisms to
operationalize the idea
Terminology
-----------
In-band OAM is expected to be deployed in a specific domain rather than
on the overall Internet. The part of the network which employs in-band
OAM is referred to as **“in-band OAM-domain”**.
In-band OAM data is added to a packet on entering the in-band OAM-domain
and is removed from the packet when exiting the domain. Within the
in-band OAM-domain, network nodes that the packet traverses may update
the in-band OAM data records.
- The node which adds in-band OAM data to the packet is called the
**“in-band OAM encapsulating node”**.
- The node which removes the in-band OAM data is referred to as the
**“in-band OAM decapsulating node”**.
- Nodes within the domain which are aware of in-band OAM data and read
and/or write or process the in-band OAM data are called **“in-band
OAM transit nodes”**.
Features supported in the current release
-----------------------------------------
VPP can function as in-band OAM encapsulating, transit and decapsulating
node. In this version of VPP in-band OAM data is transported as options
in an IPv6 hop-by-hop extension header. Hence in-band OAM can be enabled
for IPv6 traffic.
The following iOAM features are supported:
- **In-band OAM Tracing** : In-band OAM supports multiple data records
to be recorded in the packet as the packet traverses the network.
These data records offer insights into the operational behavior of
the network. The following information can be collected in the
tracing data from the nodes a packet traverses:
- Node ID
- Ingress interface ID
- Egress interface ID
- Timestamp
- Pre-configured application data
- **In-band OAM Proof of Transit (POT)**: Proof of transit iOAM data is
added to every packet for verifying that a packet traverses a
specific set of nodes. In-band OAM data is updated at every node that
is enabled with iOAM proof of transit and is used to verify whether a
packet traversed all the specified nodes. When the verifier receives
each packet, it can validate whether the packet traversed the
specified nodes.
Configuration
-------------
Configuring iOAM involves: - Selecting the packets for which iOAM data
must be inserted, updated or removed - Selection of packets for iOAM
data insertion on iOAM encapsulating node. Selection of packets is done
by 5-tuple based classification - Selection of packets for updating iOAM
data is implicitly done on the presence of iOAM options in the packet -
Selection of packets for removing the iOAM data is done on 5-tuple based
classification - The kind of data to be collected - Tracing data - Proof
of transit - Additional details for processing iOAM data to be collected
- For trace data - trace type, number of nodes to be recorded in the
trace, time stamp precision, etc. - For POT data - configuration of POT
profile required to process the POT data
The CLI for configuring iOAM is explained here followed by detailed
steps and examples to deploy iOAM on VPP as an encapsulating, transit or
decapsulating iOAM node in the subsequent sub-sections.
VPP iOAM configuration for enabling trace and POT is as follows:
::
set ioam rewrite trace-type <0x1f|0x7|0x9|0x11|0x19>
trace-elts <number of trace elements> trace-tsp <0|1|2|3>
node-id <node ID in hex> app-data <application data in hex> [pot]
A description of each of the options of the CLI follows: - trace-type :
An entry in the “Node data List” array of the trace option can have
different formats, following the needs of the a deployment. For example:
Some deployments might only be interested in recording the node
identifiers, whereas others might be interested in recording node
identifier and timestamp. The following types are currently supported: -
0x1f : Node data to include hop limit (8 bits), node ID (24 bits),
ingress and egress interface IDs (16 bits each), timestamp (32 bits),
application data (32 bits) - 0x7 : Node data to include hop limit (8
bits), node ID (24 bits), ingress and egress interface IDs (16 bits
each) - 0x9 : Node data to include hop limit (8 bits), node ID (24
bits), timestamp (32 bits) - 0x11: Node data to include hop limit (8
bits), node ID (24 bits), application data (32 bits) - 0x19: Node data
to include hop limit (8 bits), node ID (24 bits), timestamp (32 bits),
application data (32 bits) - trace-elts : Defines the length of the node
data array in the trace option. - trace-tsp : Defines the timestamp
precision to use with the enumerated value for precision as follows: - 0
: 32bits timestamp in seconds - 1 : 32bits timestamp in milliseconds - 2
: 32bits timestamp in microseconds - 3 : 32bits timestamp in nanoseconds
- node-id : Unique identifier for the node, included in the node ID
field of the node data in trace option. - app-data : The value
configured here is included as is in application data field of node data
in trace option. - pot : Enables POT option to be included in the iOAM
options.
Trace configuration
~~~~~~~~~~~~~~~~~~~
On in-band OAM encapsulating node
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- **Configure classifier and apply ACL** to select packets for iOAM
data insertion
- Example to enable iOAM data insertion for all the packets towards
IPv6 address db06::06:
vpp# classify table miss-next node ip6-lookup mask l3 ip6 dst
vpp# classify session acl-hit-next node ip6-add-hop-by-hop
table-index 0 match l3 ip6 dst db06::06
vpp# set int input acl intfc GigabitEthernet0/0/0 ip6-table 0
- **Enable tracing** : Specify node ID, maximum number of nodes for
which trace data should be recorded, type of data to be included for
recording, optionally application data to be included
- Example to enable tracing with a maximum of 4 nodes recorded and
the data to be recorded to include - hop limit, node id, ingress
and egress interface IDs, timestamp (millisecond precision),
application data (0x1234):
vpp# set ioam rewrite trace-type 0x1f trace-elts 4 trace-tsp 1
node-id 0x1 app-data 0x1234
On in-band OAM transit node
^^^^^^^^^^^^^^^^^^^^^^^^^^^
- The transit node requires trace type, timestamp precision, node ID
and optionally application data to be configured, to update its node
data in the trace option.
Example:
::
vpp# set ioam rewrite trace-type 0x1f trace-elts 4 trace-tsp 1
node-id 0x2 app-data 0x1234
On the In-band OAM decapsulating node
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- The decapsulating node similar to encapsulating node requires
**classification** of the packets to remove iOAM data from.
- Example to decapsulate iOAM data for packets towards db06::06,
configure classifier and enable it as an ACL as follows:
vpp# classify table miss-next node ip6-lookup mask l3 ip6 dst
vpp# classify session acl-hit-next node ip6-lookup table-index 0
match l3 ip6 dst db06::06 opaque-index 100
vpp# set int input acl intfc GigabitEthernet0/0/0 ip6-table 0
- Decapsulating node requires trace type, timestamp precision, node ID
and optionally application data to be configured, to update its node
data in the trace option before it is decapsulated.
Example:
::
vpp# set ioam rewrite trace-type 0x1f trace-elts 4
trace-tsp 1 node-id 0x3 app-data 0x1234
Proof of Transit configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For details on proof-of-transit, see the IETF draft
`iOAM-ietf-proof-of-transit <https://tools.ietf.org/html/draft-brockners-proof-of-transit-01>`__.
To enable Proof of Transit all the nodes that participate and hence are
verified for transit need a proof of transit profile. A script to
generate a proof of transit profile as per the mechanism described in
`iOAM-ietf-proof-of-transit <https://tools.ietf.org/html/draft-brockners-proof-of-transit-01>`__
will be available at
`iOAM-Devnet <https://github.com/ciscodevnet/iOAM>`__.
The Proof of transit mechanism implemented here is based on Shamir’s
Secret Sharing algorithm. The overall algorithm uses two polynomials
POLY-1 and POLY-2. The degree of polynomials depends on number of nodes
to be verified for transit. POLY-1 is secret and constant. Each node
gets a point on POLY-1 at setup-time and keeps it secret. POLY-2 is
public, random and per packet. Each node is assigned a point on POLY-1
and POLY-2 with the same x index. Each node derives its point on POLY-2
each time a packet arrives at it. A node then contributes its points on
POLY-1 and POLY-2 to construct POLY-3 (POLY-3 = POLY-1 + POLY-2) using
lagrange extrapolation and forwards it towards the verifier by updating
POT data in the packet. The verifier constructs POLY-3 from the
accumulated value from all the nodes and its own points on POLY-1 and
POLY-2 and verifies whether POLY-3 = POLY-1 + POLY-2. Only the verifier
knows POLY-1. The solution leverages finite field arithmetic in a field
of size “prime number” for reasons explained in description of Shamir’s
secret sharing algorithm.
| Here is an explanation of POT profile list and profile configuration
CLI to realize the above mechanism. It is best to use the script
provided at `iOAM-Devnet <https://github.com/ciscodevnet/iOAM>`__ to
generate this configuration. - **Create POT profile** : set pot
profile name id [0-1]
| [validator-key 0xu64] prime-number 0xu64 secret_share 0xu64
| lpc 0xu64 polynomial2 0xu64 bits-in-random [0-64]
| - name : Profile list name. - id : Profile id, it can be 0 or 1. A
maximum of two profiles can be configured per profile list. -
validator-key : Secret key configured only on the
verifier/decapsulating node used to compare and verify proof of
transit. - prime-number : Prime number for finite field arithmetic as
required by the proof of transit mechanism. - secret_share : Unique
point for each node on the secret polynomial POLY-1. - lpc : Lagrange
Polynomial Constant(LPC) calculated per node based on its point (x
value used for evaluating the points on the polynomial) on the
polynomial used in lagrange extrapolation for reconstructing
polynomial (POLY-3). - polynomial2 : Is the pre-evaluated value of the
point on 2nd polynomial(POLY-2). This is unique for each node. It is
pre-evaluated for all the coefficients of POLY-2 except for the
constant part of the polynomial that changes per packet and is
received as part of the POT data in the packet. - bits-in-random : To
control the size of the random number to be generated. This number has
to match the other numbers generated and used in the profile as per
the algorithm.
- **Set a configured profile as active/in-use** :
set pot profile-active name ID [0-1]
- name : Name of the profile list to be used for computing POT data
per packet.
- ID : Identifier of the profile within the list to be used.
.. _on-in-band-oam-encapsulating-node-1:
On In-band OAM encapsulating node
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Configure the classifier and apply ACL to select packets for iOAM
data insertion.
- Example to enable iOAM data insertion for all the packet towards
IPv6 address db06::06 -
vpp# classify table miss-next node ip6-lookup mask l3 ip6 dst
vpp# classify session acl-hit-next node ip6-add-hop-by-hop
table-index 0 match l3 ip6 dst db06::06
vpp# set int input acl intfc GigabitEthernet0/0/0 ip6-table 0
- Configure the proof of transit profile list with profiles. Each
profile list referred to by a name can contain 2 profiles, only one
is in use for updating proof of transit data at any time.
- Example profile list example with a profile generated from the
script to verify transit through 3 nodes is:
vpp# set pot profile name example id 0 prime-number
0x7fff0000fa884685 secret_share 0x6c22eff0f45ec56d lpc
0x7fff0000fa884682 polynomial2 0xffb543d4a9c bits-in-random 63
- Enable one of the profiles from the configured profile list as active
so that is will be used for calculating proof of transit
Example enable profile ID 0 from profile list example configured above:
::
vpp# set pot profile-active name example ID 0
- Enable POT option to be inserted
vpp# set ioam rewrite pot
.. _on-in-band-oam-transit-node-1:
On in-band OAM transit node
^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Configure the proof of transit profile list with profiles for transit
node. Example:
vpp# set pot profile name example id 0 prime-number
0x7fff0000fa884685 secret_share 0x564cdbdec4eb625d lpc 0x1
polynomial2 0x23f3a227186a bits-in-random 63
On in-band OAM decapsulating node / verifier
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- The decapsulating node, similar to the encapsulating node requires
classification of the packets to remove iOAM data from.
- Example to decapsulate iOAM data for packets towards db06::06
configure classifier and enable it as an ACL as follows:
vpp# classify table miss-next node ip6-lookup mask l3 ip6 dst
vpp# classify session acl-hit-next node ip6-lookup table-index 0
match l3 ip6 dst db06::06 opaque-index 100
vpp# set int input acl intfc GigabitEthernet0/0/0 ip6-table 0
- To update and verify the proof of transit, POT profile list should be
configured.
- Example POT profile list configured as follows:
vpp# set pot profile name example id 0 validate-key
0x7fff0000fa88465d prime-number 0x7fff0000fa884685 secret_share
0x7a08fbfc5b93116d lpc 0x3 polynomial2 0x3ff738597ce bits-in-random
63
Operational data
----------------
Following CLIs are available to check iOAM operation: - To check iOAM
configuration that are effective use “show ioam summary”
Example:
::
vpp# show ioam summary
REWRITE FLOW CONFIGS - Not configured
HOP BY HOP OPTIONS - TRACE CONFIG -
Trace Type : 0x1f (31)
Trace timestamp precision : 1 (Milliseconds)
Num of trace nodes : 4
Node-id : 0x2 (2)
App Data : 0x1234 (4660)
POT OPTION - 1 (Enabled)
Try 'show ioam pot and show pot profile' for more information
- To find statistics about packets for which iOAM options were added
(encapsulating node) and removed (decapsulating node) execute *show
errors*
Example on encapsulating node:
::
vpp# show error
Count Node Reason
1208804706 ip6-inacl input ACL hits
1208804706 ip6-add-hop-by-hop Pkts w/ added ip6 hop-by-hop options
Example on decapsulating node:
::
vpp# show error
Count Node Reason
69508569 ip6-inacl input ACL hits
69508569 ip6-pop-hop-by-hop Pkts w/ removed ip6 hop-by-hop options
- To check the POT profiles use “show pot profile”
Example:
::
vpp# show pot profile
Profile list in use : example
POT Profile at index: 0
ID : 0
Validator : False (0)
Secret share : 0x564cdbdec4eb625d (6218586935324795485)
Prime number : 0x7fff0000fa884685 (9223090566081300101)
2nd polynomial(eval) : 0x23f3a227186a (39529304496234)
LPC : 0x1 (1)
Bit mask : 0x7fffffffffffffff (9223372036854775807)
Profile index in use: 0
Pkts passed : 0x36 (54)
- To get statistics of POT for packets use “show ioam pot”
Example at encapsulating or transit node:
::
vpp# show ioam pot
Pkts with ip6 hop-by-hop POT options - 54
Pkts with ip6 hop-by-hop POT options but no profile set - 0
Pkts with POT in Policy - 0
Pkts with POT out of Policy - 0
Example at decapsulating/verification node:
::
vpp# show ioam pot
Pkts with ip6 hop-by-hop POT options - 54
Pkts with ip6 hop-by-hop POT options but no profile set - 0
Pkts with POT in Policy - 54
Pkts with POT out of Policy - 0
- Tracing - enable trace of IPv6 packets to view the data inserted and
collected.
Example when the nodes are receiving data over a DPDK interface: Enable
tracing using “trace add dpdk-input 20” and execute “show trace” to view
the iOAM data collected:
::
vpp# trace add dpdk-input 20
vpp# show trace
------------------- Start of thread 0 vpp_main -------------------
Packet 1
00:00:19:294697: dpdk-input
GigabitEthernetb/0/0 rx queue 0
buffer 0x10e6b: current data 0, length 214, free-list 0, totlen-nifb 0, trace 0x0
PKT MBUF: port 0, nb_segs 1, pkt_len 214
buf_len 2176, data_len 214, ol_flags 0x0, data_off 128, phys_addr 0xe9a35a00
packet_type 0x0
IP6: 00:50:56:9c:df:72 -> 00:50:56:9c:be:55
IP6_HOP_BY_HOP_OPTIONS: db05::2 -> db06::6
tos 0x00, flow label 0x0, hop limit 63, payload length 160
00:00:19:294737: ethernet-input
IP6: 00:50:56:9c:df:72 -> 00:50:56:9c:be:55
00:00:19:294753: ip6-input
IP6_HOP_BY_HOP_OPTIONS: db05::2 -> db06::6
tos 0x00, flow label 0x0, hop limit 63, payload length 160
00:00:19:294757: ip6-lookup
fib 0 adj-idx 15 : indirect via db05::2 flow hash: 0x00000000
IP6_HOP_BY_HOP_OPTIONS: db05::2 -> db06::6
tos 0x00, flow label 0x0, hop limit 63, payload length 160
00:00:19:294802: ip6-hop-by-hop
IP6_HOP_BY_HOP: next index 5 len 96 traced 96 Trace Type 0x1f , 1 elts left
[0] ttl 0x0 node ID 0x0 ingress 0x0 egress 0x0 ts 0x0
app 0x0
[1] ttl 0x3e node ID 0x3 ingress 0x1 egress 0x2 ts 0xb68c2213
app 0x1234
[2] ttl 0x3f node ID 0x2 ingress 0x1 egress 0x2 ts 0xb68c2204
app 0x1234
[3] ttl 0x40 node ID 0x1 ingress 0x5 egress 0x6 ts 0xb68c2200
app 0x1234
POT opt present
random = 0x577a916946071950, Cumulative = 0x10b46e78a35a392d, Index = 0x0
00:00:19:294810: ip6-rewrite
tx_sw_if_index 1 adj-idx 14 : GigabitEthernetb/0/0
IP6: 00:50:56:9c:be:55 -> 00:50:56:9c:df:72 flow hash: 0x00000000
IP6: 00:50:56:9c:be:55 -> 00:50:56:9c:df:72
IP6_HOP_BY_HOP_OPTIONS: db05::2 -> db06::6
tos 0x00, flow label 0x0, hop limit 62, payload length 160
00:00:19:294814: GigabitEthernetb/0/0-output
GigabitEthernetb/0/0
IP6: 00:50:56:9c:be:55 -> 00:50:56:9c:df:72
IP6_HOP_BY_HOP_OPTIONS: db05::2 -> db06::6
tos 0x00, flow label 0x0, hop limit 62, payload length 160
00:00:19:294820: GigabitEthernetb/0/0-tx
GigabitEthernetb/0/0 tx queue 0
buffer 0x10e6b: current data 0, length 214, free-list 0, totlen-nifb 0, trace 0x0
IP6: 00:50:56:9c:be:55 -> 00:50:56:9c:df:72
IP6_HOP_BY_HOP_OPTIONS: db05::2 -> db06::6
tos 0x00, flow label 0x0, hop limit 62, payload length 160
