advanced/upf.rst - sdfabric-docs - Gitiles

 P4-based User Plane Function (P4-UPF)
 =====================================

 Overview
 --------

 SD-Fabric supports running a 4G/5G mobile core User Plane Function (UPF) as part
 of the switches packet processing pipeline. Like the rest of the pipeline, this
 is realized using P4 and for this reason we call this P4-UPF.

 P4-UPF is integrated with the ONF's SD-Core project. By default, SD-Core ships
 with BESS-UPF, a containerized UPF implementation, based on the Berkeley
 Software Switch (BESS).

 SD-Fabric can be used with BESS-UPF or any other UPF implementation that runs on
 servers. In this case, the fabric switches can provide routing of GTP-U packets
 to and from radio base station and servers. When P4-UPF is enabled, the same
 fabric switches perform GTP-U tunnel termination.

 .. image:: ../images/bess-p4-upf.png
     :width: 700px

 **Supported Features**

 SD-Fabric's P4-UPF implements a core set of features capable of supporting
 requirements for a broad range of enterprise use cases:

 * GTP-U tunnel encap/decap: including support for 5G extensions such as PDU
   Session Container carrying QoS Flow Information.
 * Accounting: we use switch counters to collect per-flow stats and support usage
   reporting and volume-based triggers.
 * Downlink buffering: when a user device radio goes idle (power-save mode) or
   during a handover, switches are updated to forward all downlink traffic for
   the specific device (UE) to DBUF, a K8s-managed buffering service running on
   servers. Then, when the device radio becomes ready to receive traffic,
   packets are drained from the software buffers back to the switch to be
   delivered to base stations.
 * QoS: support for enforcement of maximum bitrate (MBR), minimum guaranteed
   bitrate (GBR, via admission control), and prioritization using switch
   queues and scheduling policy.
 * Slicing: multiple logical UPFs can be instantiated on the same switch, each
   one with its own QoS model and isolation guarantees enforced at the hardware
   level using separate queues.

 **Distributed UPF**

 .. image:: ../images/upf-distributed.png
     :width: 700px

 In SD-Fabric we support different topologies to meet the requirements of
 different deployment sizes: from a single rack with just one leaf
 switch, or a paired-leaves for redundancy, to N x M leaf-spine fabric for multi-rack
 deployments. For this reason, P4-UPF is realized with a "distributed" data plane
 implementation where all leaf switches are programmed with the same UPF
 rules, such that any leaf can terminate any GTP-U tunnel. This provides several
 benefits:

 * Simplified deployment: base stations can be connected via any leaf switch.
 * Minimum latency: the UPF function is applied as soon as packets enter the
   fabric, without going through additional devices before reaching their final
   destination.
 * Fast failover: when using paired-leaves, if one switch fails, the other can
   immediately take over as it is already programmed with the same UPF state.
 * Fabric-wide slicing & QoS guarantees: packets are classified as soon as they
   hit the first leaf. We then use a custom DSCP-based marking to enforce the
   same QoS rules on all hops. In case of congestion, flows deemed high priority
   are treated as such by all switches.

 **Control Architecture and Integration with SD-Core**

 SD-Fabric's P4-UPF is integrated with the ONF SD-Core project to provide a
 high-performance 3GPP-compliant mobile core solution.

 The integration with SD-Core is achieved via an ONOS application called UP4,
 which is in charge of populating the UPF tables of the switch pipeline.

 .. image:: ../images/up4-arch.png
     :width: 600px

 The interface between the mobile core control plane and the UPF is defined by
 the 3GPP standard Packet Forwarding Control Protocol (PFCP). This is a complex
 protocol that can be difficult to understand, even though at its essence the
 rules that it installs are simple match-action rules. The implementation of such
 protocol, such as message parsing, state machines, and other bookkeeping can be
 common to many different UPF realizations. For this reason, SD-Fabric relies on
 an implementation of the PFCP protocol realized as an external microservice
 named “PFCP-Agent”, which is provided by the SD-Core project.

 The UP4 App abstracts the whole fabric as one virtual big switch with UPF
 capabilities, we call this the One-Big-UPF abstraction. Such abstraction allows
 the upper layers to be independent of the underlying physical topology.
 Communication between the PFCP Agent and the UP4 App is done via P4Runtime. This
 is the same API that ONOS uses to communicate with the actual switches. However,
 in the former case, it is used between two control planes, the mobile core, and
 the SDN controller. By doing this, the deployment can be scaled up and down,
 adding or removing racks and switches, without changing the mobile core control
 plane, which instead is provided with the illusion of controlling just one
 switch.

 The One-Big-UPF abstraction abstraction is realized with a ``virtual-upf.p4``
 program that formalizes the forwarding model described by PFCP as a series of
 match-action tables. This program doesn't run on switches, but it's used as the
 schema to define the content of the P4Runtime messages between PFCP Agent and
 the UP4 App. On switches, we use a different program, fabric.p4, which
 implements tables similar to the virtual UPF but optimized to satisfy the
 resource constraints of Tofino, as well as tables for basic bridging, IP
 routing, ECMP, and more. The UP4 App implements a P4Runtime server, like if it
 were a switch, but instead it internally takes care of translating P4Runtime
 rules from ``virtual-upf.p4`` to rules for the multiple physical switches running
 fabric.p4, based on an up-to-date global view of the topology.

 Downlink Buffering (DBUF)
 -------------------------

 TODO Carmelo: overview of DBUF

 ONOS Configuration
 ------------------

 The UPF configuration is split in two configurations, that can be provided
 independently to ONOS. Th first is used to configure the UP4 ONOS application
 and defines UPF-related information such as S1U Address, network devices
 implementing UPF etc. The second one, instead, is used to configure parameters
 related to the Downlink Buffering (DBUF) functionality.

 Here's a list of fields that you can configure via the UPF Network Configuration
 for UP4:

 * ``devices``: A list of devices IDs that implements the UPF data plane. This
   list must include all the leaf switches in the topology. The UPF state is
   replicated on all devices specified in this configuration field. The devices
   specified in this list must use a P4 pipeline implementing the UPF
   functionality. *Required*

 * ``s1uAddr``: The IP address of the S1-U interface (equivalent to N3 for 5G).
   It can be an arbitrary IP address. *Required*

 * ``uePools``: A list of subnets that are in use by the UEs. *Required*

 * ``dbufDrainAddr``: The IP address of the UPF data plane interface that the
   DBUF service will drain packets towards. *Optional*

 * ``pscEncapEnabled``: Set whether the UPF should use GTP-U extension PDU
   Session Container when doing encapsulation of downlink packets. *Optional*

 * ``defaultQfi``: The default QoS Flow Identifier to use when the PDU Session
   Container encapsulation is enabled. *Optional*

 Here is an example of netcfg JSON for UP4:

 .. code-block:: json

     {
         "apps": {
             "org.omecproject.up4": {
                 "up4": {
                   "devices": [
                     "device:leaf1",
                     "device:leaf2"
                   ],
                   "s1uAddr": "10.32.11.126",
                   "uePools": [
                     "10.240.0.0/16"
                   ],
                 "dbufDrainAddr": "10.32.11.126",
                 "pscEncapEnabled": false,
                 "defaultQfi": 0
                 }
             }
         }
     }

 The DBUF configuration block is all *optional*, we can use UP4 without the
 downlink buffering functionality. Here's a list of fields that you can
 configure:

 * ``serviceAddr``: The address DBUF service management interface in the form
   IP:port. This address is used to communicate with the DBUF service via gRPC
   (for example, to trigger the drain operation, or receive notification for
   buffered packets).

 * ``dataplaneAddr``: The address of the DBUF service data plane interface in the
   form IP:port. Packets sent to this address by the UPF will be buffered by
   DBUF. The IP address must be a routable fabric address.

 Here is an example of netcfg for DBUF:

 .. code-block:: json

     {
         "apps": {
             "org.omecproject.up4": {
                 "dbuf": {
                     "serviceAddr": "10.76.28.72:10000",
                     "dataplaneAddr": "10.32.11.3:2152"
                 }
           }
         }
     }

 SD-Core Configuration
 ---------------------

 TODO Carmelo:

 * Assuming SD-Core is already installed...
 * Instructions to install PFCP Agent for UP4
 * Reference for helm values configuration

 Should be similar to BESS install instructions (where the same helm chart
 installs both PFCP agent and BESS):
 https://docs.aetherproject.org/master/edge_deployment/bess_upf_deployment.html

 But using this helm chart (without BESS), just PFCP Agent:
 https://gerrit.opencord.org/plugins/gitiles/aether-helm-charts/+/refs/heads/master/omec/omec-upf-pfcp-agent/

 UP4 Troubleshooting
 -------------------

 ``TODO Daniele``

 Example of UP4 CLI commands to debug the state of UP4.

 DBUF
 ----


 ``TODO Carmelo`` overview


 ``TODO Hung-Wei`` deployment instructions (helm chart)
	P4-based User Plane Function (P4-UPF)
	=====================================

	Overview
	--------

	SD-Fabric supports running a 4G/5G mobile core User Plane Function (UPF) as part
	of the switches packet processing pipeline. Like the rest of the pipeline, this
	is realized using P4 and for this reason we call this P4-UPF.

	P4-UPF is integrated with the ONF's SD-Core project. By default, SD-Core ships
	with BESS-UPF, a containerized UPF implementation, based on the Berkeley
	Software Switch (BESS).

	SD-Fabric can be used with BESS-UPF or any other UPF implementation that runs on
	servers. In this case, the fabric switches can provide routing of GTP-U packets
	to and from radio base station and servers. When P4-UPF is enabled, the same
	fabric switches perform GTP-U tunnel termination.

	.. image:: ../images/bess-p4-upf.png
	:width: 700px

	Supported Features

	SD-Fabric's P4-UPF implements a core set of features capable of supporting
	requirements for a broad range of enterprise use cases:

	* GTP-U tunnel encap/decap: including support for 5G extensions such as PDU
	Session Container carrying QoS Flow Information.
	* Accounting: we use switch counters to collect per-flow stats and support usage
	reporting and volume-based triggers.
	* Downlink buffering: when a user device radio goes idle (power-save mode) or
	during a handover, switches are updated to forward all downlink traffic for
	the specific device (UE) to DBUF, a K8s-managed buffering service running on
	servers. Then, when the device radio becomes ready to receive traffic,
	packets are drained from the software buffers back to the switch to be
	delivered to base stations.
	* QoS: support for enforcement of maximum bitrate (MBR), minimum guaranteed
	bitrate (GBR, via admission control), and prioritization using switch
	queues and scheduling policy.
	* Slicing: multiple logical UPFs can be instantiated on the same switch, each
	one with its own QoS model and isolation guarantees enforced at the hardware
	level using separate queues.

	Distributed UPF

	.. image:: ../images/upf-distributed.png
	:width: 700px

	In SD-Fabric we support different topologies to meet the requirements of
	different deployment sizes: from a single rack with just one leaf
	switch, or a paired-leaves for redundancy, to N x M leaf-spine fabric for multi-rack
	deployments. For this reason, P4-UPF is realized with a "distributed" data plane
	implementation where all leaf switches are programmed with the same UPF
	rules, such that any leaf can terminate any GTP-U tunnel. This provides several
	benefits:

	* Simplified deployment: base stations can be connected via any leaf switch.
	* Minimum latency: the UPF function is applied as soon as packets enter the
	fabric, without going through additional devices before reaching their final
	destination.
	* Fast failover: when using paired-leaves, if one switch fails, the other can
	immediately take over as it is already programmed with the same UPF state.
	* Fabric-wide slicing & QoS guarantees: packets are classified as soon as they
	hit the first leaf. We then use a custom DSCP-based marking to enforce the
	same QoS rules on all hops. In case of congestion, flows deemed high priority
	are treated as such by all switches.

	Control Architecture and Integration with SD-Core

	SD-Fabric's P4-UPF is integrated with the ONF SD-Core project to provide a
	high-performance 3GPP-compliant mobile core solution.

	The integration with SD-Core is achieved via an ONOS application called UP4,
	which is in charge of populating the UPF tables of the switch pipeline.

	.. image:: ../images/up4-arch.png
	:width: 600px

	The interface between the mobile core control plane and the UPF is defined by
	the 3GPP standard Packet Forwarding Control Protocol (PFCP). This is a complex
	protocol that can be difficult to understand, even though at its essence the
	rules that it installs are simple match-action rules. The implementation of such
	protocol, such as message parsing, state machines, and other bookkeeping can be
	common to many different UPF realizations. For this reason, SD-Fabric relies on
	an implementation of the PFCP protocol realized as an external microservice
	named “PFCP-Agent”, which is provided by the SD-Core project.

	The UP4 App abstracts the whole fabric as one virtual big switch with UPF
	capabilities, we call this the One-Big-UPF abstraction. Such abstraction allows
	the upper layers to be independent of the underlying physical topology.
	Communication between the PFCP Agent and the UP4 App is done via P4Runtime. This
	is the same API that ONOS uses to communicate with the actual switches. However,
	in the former case, it is used between two control planes, the mobile core, and
	the SDN controller. By doing this, the deployment can be scaled up and down,
	adding or removing racks and switches, without changing the mobile core control
	plane, which instead is provided with the illusion of controlling just one
	switch.

	The One-Big-UPF abstraction abstraction is realized with a ``virtual-upf.p4``
	program that formalizes the forwarding model described by PFCP as a series of
	match-action tables. This program doesn't run on switches, but it's used as the
	schema to define the content of the P4Runtime messages between PFCP Agent and
	the UP4 App. On switches, we use a different program, fabric.p4, which
	implements tables similar to the virtual UPF but optimized to satisfy the
	resource constraints of Tofino, as well as tables for basic bridging, IP
	routing, ECMP, and more. The UP4 App implements a P4Runtime server, like if it
	were a switch, but instead it internally takes care of translating P4Runtime
	rules from ``virtual-upf.p4`` to rules for the multiple physical switches running
	fabric.p4, based on an up-to-date global view of the topology.

	Downlink Buffering (DBUF)
	-------------------------

	TODO Carmelo: overview of DBUF

	ONOS Configuration
	------------------

	The UPF configuration is split in two configurations, that can be provided
	independently to ONOS. Th first is used to configure the UP4 ONOS application
	and defines UPF-related information such as S1U Address, network devices
	implementing UPF etc. The second one, instead, is used to configure parameters
	related to the Downlink Buffering (DBUF) functionality.

	Here's a list of fields that you can configure via the UPF Network Configuration
	for UP4:

	* ``devices``: A list of devices IDs that implements the UPF data plane. This
	list must include all the leaf switches in the topology. The UPF state is
	replicated on all devices specified in this configuration field. The devices
	specified in this list must use a P4 pipeline implementing the UPF
	functionality. Required

	* ``s1uAddr``: The IP address of the S1-U interface (equivalent to N3 for 5G).
	It can be an arbitrary IP address. Required

	* ``uePools``: A list of subnets that are in use by the UEs. Required

	* ``dbufDrainAddr``: The IP address of the UPF data plane interface that the
	DBUF service will drain packets towards. Optional

	* ``pscEncapEnabled``: Set whether the UPF should use GTP-U extension PDU
	Session Container when doing encapsulation of downlink packets. Optional

	* ``defaultQfi``: The default QoS Flow Identifier to use when the PDU Session
	Container encapsulation is enabled. Optional

	Here is an example of netcfg JSON for UP4:

	.. code-block:: json

	{
	"apps": {
	"org.omecproject.up4": {
	"up4": {
	"devices": [
	"device:leaf1",
	"device:leaf2"
	],
	"s1uAddr": "10.32.11.126",
	"uePools": [
	"10.240.0.0/16"
	],
	"dbufDrainAddr": "10.32.11.126",
	"pscEncapEnabled": false,
	"defaultQfi": 0
	}
	}
	}
	}

	The DBUF configuration block is all optional, we can use UP4 without the
	downlink buffering functionality. Here's a list of fields that you can
	configure:

	* ``serviceAddr``: The address DBUF service management interface in the form
	IP:port. This address is used to communicate with the DBUF service via gRPC
	(for example, to trigger the drain operation, or receive notification for
	buffered packets).

	* ``dataplaneAddr``: The address of the DBUF service data plane interface in the
	form IP:port. Packets sent to this address by the UPF will be buffered by
	DBUF. The IP address must be a routable fabric address.

	Here is an example of netcfg for DBUF:

	.. code-block:: json

	{
	"apps": {
	"org.omecproject.up4": {
	"dbuf": {
	"serviceAddr": "10.76.28.72:10000",
	"dataplaneAddr": "10.32.11.3:2152"
	}
	}
	}
	}

	SD-Core Configuration
	---------------------

	TODO Carmelo:

	* Assuming SD-Core is already installed...
	* Instructions to install PFCP Agent for UP4
	* Reference for helm values configuration

	Should be similar to BESS install instructions (where the same helm chart
	installs both PFCP agent and BESS):
	https://docs.aetherproject.org/master/edge_deployment/bess_upf_deployment.html

	But using this helm chart (without BESS), just PFCP Agent:
	https://gerrit.opencord.org/plugins/gitiles/aether-helm-charts/+/refs/heads/master/omec/omec-upf-pfcp-agent/

	UP4 Troubleshooting
	-------------------

	``TODO Daniele``

	Example of UP4 CLI commands to debug the state of UP4.

	DBUF
	----


	``TODO Carmelo`` overview


	``TODO Hung-Wei`` deployment instructions (helm chart)