Two-Way Active Measurement Protocol (TWAMP) Light Data Model

Creating TWAMP-Light data model presents number of challenges and among them is identification of a test-session at Session-Reflector. A Session-Reflector MAY require only as little as its IP and UDP port number in received TWAMP-Test packet to spawn new test session. More so, to test processing of Class-of-Service along the same route in Equal Cost Multi-Path environment Session-Sender may run TWAMP test sessions concurrently using the same source IP address, source UDP port number, destination IP address, and destination UDP port number. Thus the only parameter that can be used to differentiate these test sessions would be DSCP value. The DSCP field may get re-marked along the path and without use of that will go undetected, but by using five-tuple instead of four-tuple as a key we can ensure that TWAMP test packets that are considered as different test sessions follow the same path even in ECMP environments.

file "ietf-twamp-light@2016-0305" module ietf-twamp-light { namespace "urn:ietf:params:xml:ns:yang:ietf-twamp-light"; //namespace need to be assigned by IANA prefix "ietf-twamp-light"; import ietf-inet-types { prefix inet; } import ietf-yang-types { prefix yang; } organization "IETF IPPM (IP Performance Metrics) Working Group"; contact "draft-mirsky-ippm-twamp-light-yang@tools.ietf.org"; description "TWAMP Light Data Model"; revision "2016-06-17" { description "01 version. RFC5357 is covered, including Appendix I and the Errata"; reference "draft-mirsky-ippm-twamp-light-yang"; } feature session-sender-light { description "This feature relates to the device functions as the TWAMP Light Session-Sender"; } feature session-reflector-light { description "This feature relates to the device functions as the TWAMP Light Session-Reflector"; } typedef enable { type boolean; description "enable"; } grouping maintenance-statistics { description "Maintenance statistics grouping"; leaf sent-packets { type uint32; description "Packets sent"; } leaf rcv-packets { type uint32; description "Packets received"; } leaf sent-packets-error { type uint32; description "Packets sent error"; } leaf rcv-packets-error { type uint32; description "Packets received error"; } leaf last-sent-seq { type uint32; description "Last sent sequence number"; } leaf last-rcv-seq { type uint32; description "Last received sequence number"; } } grouping delay-statistics { description "delay statistics grouping"; container delay { description "Packets transmitted delay"; leaf min { type yang:gauge32; units microseconds; description "Min of Packets transmitted delay"; } leaf max { type yang:gauge32; units microseconds; description "Max of Packets transmitted delay"; } leaf avg { type yang:gauge32; units microseconds; description "Avg of Packets transmitted delay"; } } container delay-variation { description "Packets transmitted delay variation"; leaf min { type uint32; units microseconds; description "Min of Packets transmitted delay variation"; } leaf max { type uint32; units microseconds; description "Max of Packets transmitted delay variation"; } leaf avg { type uint32; units microseconds; description "Avg of Packets transmitted delay variation"; } } } grouping session-light-parameters { description "Parameters common among Session-Sender and Session-Reflector"; leaf sender-ip { type inet:ip-address; mandatory true; description "Sender IP address"; } leaf sender-udp-port { type inet:port-number { range "49152..65535"; } mandatory true; description "Sender UDP port number"; } leaf reflector-ip { type inet:ip-address; mandatory true; description "Reflector IP address"; } leaf reflector-udp-port { type inet:port-number{ range "49152..65535"; } mandatory true; description "Reflector UDP port number"; } leaf dscp { type inet:dscp; default "0"; description "The DSCP value to be placed in the header of TWAMP UDP test packets generated by the Session-Sender. Whether Session-Reflector uses this value depends upon its local configuration"; } } /*Configuration Data*/ container twamp-light { description "Top level container for TWAMP-Light configuration"; container twamp-light-session-sender { if-feature session-sender-light; description "TWAMP-Light Session-Sender container"; leaf sender-light-enable { type enable; default "true"; description "Whether this network element is enabled to act as TWAMP-Light Sender"; } list test-session { key "session-id"; unique "sender-ip sender-udp-port reflector-ip" +" reflector-udp-port dscp"; description "This structure is a container of test session managed objects"; leaf session-id { type uint32; description "Session ID"; } leaf test-session-enable { type enable; default "true"; description "Whether this TWAMP Test session is enabled"; } leaf number-of-packets { type uint32; description "The overall number of UDP test packets to be transmitted by the sender for this test session"; } leaf packet-padding-size { type uint32; default 27; description "Size of the Packet Padding. Suggested to run Path MTU Discovery to avoid packet fragmentation in IPv4 and packet blackholing in IPv6"; } leaf session-authentication-mode { type enumeration { enum unauthenticated { description "Unauthenticated TWAMP-Light test session"; } enum authenticated { description "Authenticated TWAMP-Light test session"; } enum encrypted { description "Encrypted TWAMP-Light test session"; } } default unauthenticated; description "Authentication mode of the TWAMP-Light test session"; } leaf interval { type uint32; description "Time interval between transmission of two consecutive packets in the test session"; } uses session-light-parameters; } } container twamp-light-session-reflector { if-feature session-reflector-light; description "TWAMP-Light Session-Reflector container"; leaf reflector-light-enable { type enable; default "true"; description "Whether this network element is enabled to act as TWAMP-Light Reflector"; } leaf ref-wait { type uint32 { range 1..604800; } units seconds; default 900; description "REFWAIT(TWAMP test session timeout in seconds), the default value is 900"; } leaf reflector-light-mode-state { type enumeration { enum stateful { description "When the Session-Reflector Light is stateful, i.e. is aware of test session state"; } enum stateless { description "When the Session-Reflector is stateless and uses sequence number of the received TWAMP-Test packet as its own"; } } default stateless; description "The state of the mode of the TWAMP-Light Session-Reflector"; } leaf dscp-handling-mode { type enumeration { enum copy-received-value { description "Use DSCP value copied from received TWAMP test packet of the test session"; } enum use-configured-value { description "Use DSCP value configured for this test session on the Session-Reflector"; } } default copy-received-value; description "Session-Reflector handling of DSCP: - use value copied from received TWAMP-Test packet; - use value explicitly configured"; } list test-session { key "session-id"; unique "sender-ip sender-udp-port reflector-ip" +" reflector-udp-port dscp"; description "This structure is a container of test session managed objects"; leaf session-id { type uint32; description "Session ID"; } uses session-light-parameters; } } } /*Operational state data nodes*/ container twamp-light-state{ config "false"; description "Top level container for TWAMP-Light state data"; container twamp-light-session-sender-state { if-feature session-sender-light; description "Session-Sender container for state data"; list test-session-state{ key "session-id"; description "This structure is a container of test session managed objects"; leaf session-id { type uint32; description "Session ID"; } leaf sender-session-state { type enumeration { enum active { description "Test session is active"; } enum ready { description "Test session is idle"; } } description "State of the particular TWAMP-Light test session at the sender"; } container current-stats { description "This container contains the results for the current Measurement Interval in a Measurement session "; leaf start-time { type yang:date-and-time; mandatory true; description "The time that the current Measurement Interval started"; } leaf number-of-packets { type uint32; description "The overall number of UDP test packets to be transmitted by the sender for this test session"; } leaf packet-padding-size { type uint32; default 27; description "Size of the Packet Padding. Suggested to run Path MTU Discovery to avoid packet fragmentation in IPv4 and packet backholing in IPv6"; } leaf interval { type uint32; description "Time interval between transmission of two consecutive packets in the test session"; } leaf duplicate-packets { type uint32; description "Duplicate packets"; } leaf reordered-packets { type uint32; description "Reordered packets"; } leaf loss-packets { type uint32; description "Loss packets"; } uses session-light-parameters; uses maintenance-statistics; container two-way-delay{ description "two way delay result of the test session"; uses delay-statistics; } container one-way-delay-far-end{ description "one way delay far end of the test session"; uses delay-statistics; } container one-way-delay-near-end{ description "one way delay near end of the test session"; uses delay-statistics; } } list history-stats { key id; description "This container contains the results for the history Measurement Interval in a Measurement session "; leaf id { type uint32; description "The identifier for the Measurement Interval within this session"; } leaf end-time { type yang:date-and-time; mandatory true; description "The time that the Measurement Interval ended"; } leaf number-of-packets { type uint32; description "The overall number of UDP test packets to be transmitted by the sender for this test session"; } leaf packet-padding-size { type uint32; default 27; description "Size of the Packet Padding. Suggested to run Path MTU Discovery to avoid packet fragmentation in IPv4 and packet blackholing in IPv6"; } leaf interval { type uint32; description "Time interval between transmission of two consecutive packets in the test session"; } leaf duplicate-packets { type uint32; description "Duplicate packets"; } leaf reordered-packets { type uint32; description "Reordered packets"; } leaf loss-packets { type uint32; description "Loss packets"; } uses session-light-parameters; uses maintenance-statistics; container two-way-delay{ description "two way delay result of the test session"; uses delay-statistics; } container one-way-delay-far-end{ description "one way delay far end of the test session"; uses delay-statistics; } container one-way-delay-near-end{ description "one way delay near end of the test session"; uses delay-statistics; } } } } container twamp-light-session-reflector-state { if-feature session-reflector-light; description "TWAMP-Light Session-Reflector container for state data"; leaf reflector-light-admin-status { type boolean; mandatory "true"; description "Whether this network element is enabled to act as TWAMP-Light Reflector"; } list test-session-state { key "session-id"; description "This structure is a container of test session managed objects"; leaf session-id { type uint32; description "Session ID"; } uses maintenance-statistics; uses session-light-parameters; container one-way-delay { description "one way delay of the test session"; uses delay-statistics; } } } } rpc twamp-sender-start { description "start the configured sender session"; input { leaf session-id { type uint32; mandatory true; description "The session to be started"; } } } rpc twamp-sender-stop { description "stop the configured sender session"; input { leaf session-id { type uint32; mandatory true; description "The session to be stopped"; } } } }

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