Background

Application Co-existence and Integration Challenges

Partitioning of OpenFlow Resources
1. Every application must have their private flow state space (on every switch)
  1. Flow tables, group table, meter table, cookies
Ingress demultiplexing (aka “Table 0 Problem”)
1. Packets entering the switch have to be directed to the correct application pipeline
2. Applications cannot simply write ingress flow entries into table 0 without coordination
3. Need smaller granularity than OF port (e.g. VLAN, VNI, etc)? generalized interface concept
4. Co-existence of multiple applications on the same interface
5. Multi-tenancy: Several isolated service instances of the same application
Integration/Co-operation of different applications
1. Control plane: Service APIs between applications
2. Data plane: Transfer packets between the pipelines of different applications
  1. Take the use of various packet metadata into account!
3. Each application comes with its own overlay solution

Chosen approach in ODL Beryllium between SFC, GPB and Netvirt
1. Partitioning of OpenFlow Resources
  1. Design time coordination between different applications
2. Ingress demultiplexing (aka “Table 0 Problem”)
  1. All application write into table 0, but the flow entries and priorities have been agreed at design time to avoid unwanted interference
3. Integration/Co-operation of different applications
  1. Control plane: MD-SAL service APIs between applications?
  2. Data plane: Direct GOTO Table to transfer the packet from one application pipeline to another
Analysis
1. Can lead to an optimal solution for a group of specific applications
2. Design time coordination needed for every detail
3. Hard-coded dependencies between applications
4. Does not scale to many applications

Multiple applications writing into table 0 (directly or through an Ingress Manager function)
Flow conflict detection mechanisms do not allow for any overlap between flows
Overlap (or rather refinement) should be allowed using priorities to disambiguate:
1. e.g. packets on in_port with certain DMAC to application A, all the rest to application B
How can a generic Ingress Manager ensure that there is no semantic conflict between the flows if the simple non-overlap criterion is not sufficient?

Any ODL application can use these to achieve at minimum interference-free co-existence with other applications using the services
Provide support for co-operation between applications with the minimal amount of design-time coordination and hard-coded dependencies
Use APIs to move design-time coordination to run-time
1. Generic infrastructure APIs to avoid direct coupling where possible
2. Direct inter-application (client-server) APIs where necessary for stronger coupling
Factor out commonly used functions into shared services to avoid duplication & waste of resources, e.g.
1. Overlay Tunnel Manager
2. ID manager
3. MD-SAL Util

Models generic interfaces as attachment point for applications
1. Supports Hierarchy of: Port, VLAN, VXLAN Trunk, VXLAN VNI, GRE Tunnel, ...
2. Extendible to arbitrary other types of interfaces (virtual link, VPN interface, …)
3. Interface ID/tag system wide unique identifier in control/data plane.
4. Ingress interface tag stored in metadata

Handles ingress de-capsulation and de-multiplexing
1. Owns table 0 (and possibly additional tables needed for demultiplexing of interfaces)
2. Application bind to interfaces through API and register application-specific instructions/actions to be added to the interfaces ingress flow entry (e.g. write metadata, goto table)
3. Each bound service is assigned to a separate interface handle, no risk of interference on ingress traffic

South bound protocol agnostic
1. Ability to plug in different south bound renderers
2. Provides tunnel monitoring services
3. Handles egress encapsulation and output, service processing priority

Service binding data model used to bind a service on a particular interface
Service module configures following parameters
- Service-Priority
- Service-Name
- Service-Type
- Service-Info
  - (for service-type openflow-based)
  - Flow-priority
  - Instruction-list
Interface Manager maintains a Service dispatcher table to regulate pipeline dynamically between services
Listens to service-binding changes and accordingly programs the dataplane (Table 0 & Service Dispatcher)

Provide a flexible way to support multiple south bound protocols
North-bound interface/data-model is decoupled from south bound plugins
NBI Data change listeners select and interact with appropriate SBI renderers
New renderers can be added to support new Southbound interfaces/protocols/plugins
Needs to be re-concilied with Netvirt re-design proposal

Provides tunnel creation/management services
1. Can be configured to automatically create a homogenous bi-directional tunnel mesh (VxLAN/GRE/others) between agiven group of DPNs
2. API to add new nodes into an existing tunnel mesh
3. API to create uni-directional tunnels from a DPN to an external IP node (CE router) which may not be under SDN control
4. Support for tunnel level redundancy by creating a logical-group-interface, combining more than one tunnel interfaces, and allow for load-balancing or failovers in the group
API support to control monitoring of tunnel interfaces
API to get egress-actions and ingress-rules/bindService for specified uni-directional tunnel
NB Tunnel Up/Down events for services/ user-facing / analytics apps

Provides Controller driven monitoring services for
1. Point-to-point interfaces (VxLAN/GRE)
2. From an interface to destination IP Node
Consumes services from ARP, LLDP, Ping Modules
Generate Aliveness Events
Interface manager listens to Aliveness events and updates operational-state of interfaces
Consumers register for monitoring services specifying monitored interfaces and monitoring parameters
Uses –
1. Physical topology monitoring
2. monitoring of non-BFD transport tunnels
3. Service Function Monitoring

Generates and provides unique integer IDs from a pre-configured ID-Pool with configured range to requesting services
1. APIs for C/D of ID-Pool, assignment and lookups of IDs to services
Dual modes of operation
1. Consistent ID generation – consistently provide the same ID for a particular unique key String, Id-value is retained across cluster restarts, and associated with unique key (implemented)
2. Generic ID assignment, no guarantees of consistency or persistence (not implemented)
Can be used to assign IDs for and manage resources such as Openflow Tables, Groups, Meters, Service IDs
Used by Interface Manager for mapping service instances to logical tags in the data plane

Provides Java interfaces to interact with MD-SAL DS and southbound OF-plugin.
1. APIs for programming Flows & Groups
2. APIs for Data-Store Read/write
3. Generic CDN listener