Traditional RPC communication Steps for two components

1
Traditional RPC communication Steps for two
components

• Name Lookup
• Name resolution retrieval
• Component A passes message to RPC layer
• RPC layer delivers message
• Component B passes reply to RPC layer
• RPC layer deliver reply

2
Traditional RPC call method
Naming Mapping Table
1
2
4
3
RPC Delivery
5
6
3
Whats its problem?

• Works only for static components
• Static components allow safe caching at the
  endpoints
• Components are interpreted as Physical Endpoint
  (Transport layer endpoints)
• For mobile components
• Separate naming issues from location issues
• Virtualize Endpoints

4
Virtual Endpoints RPC Router
Middleware
RPC Delivery Mechanism
5
Virtual Endpoint Runtime Translation

• Application uses VE
• Send ltVEPCB, messagegt
• VE layer
• At the RPC layer only TEPCB are used
• Maps ltVEPCB, TEPCBgt
• RPC layer
• Interfaces with the transport protocol using TEP

6
Virtual Endpoints (VEP)
Virtual Endpoints
Virtual Endpoints
ltVEP,TEPgt
RPC
RPC
Transport Protocol
Transport Protocol
ltTEP, messgt
7
VEP Approach Assumptions

• There is a mapping database storing all mapping
  ltVEP,TEPgt
• When created, components get an entry created for
  themselves in the database
• Each component is responsible for keeping its
  mapping up to date
• Database is reliable and counts with an RPC
  delivery mechanisms

8
Easy Approach Steps

1. Component A sends message ltVEPCB,messagegt
2. Successful lookup handles message and mapping to
   RPC layer
3. RPC layer delivers message to TEPCB
4. Component B replies message ltVEPCA,messagegt
5. Successful lookup handles message and mapping to
   RPC layer
6. RPC layer delivers message to TEPCA

9
VEP Easy Approach
Mapping Table
4
1
2
5
RPC Delivery
6
3
10
VEP Issues

• Mapping table management
• Distribution and Organization
• Consistency protocol
• Lookup Performance
• Update and Lookup mechanisms
• Failure handling
• Recovery Failure protocol (A message can be
  delivered to a component on the move)

11
For One-to-One Patterns

• Detach location lookup from delivery
• Lookup per call is costly
• Only when necessary (configuration, failure)
• Fast lookup by caching at the endpoints
• Maintaining copy at the endpoints
• Needs a simple consistency protocol
• Producer-Consumer scheme
• Simple failure recovery protocol

12
One-to-one Communication
Naming Database
Consistency Protocol
Producer
Consumer
13
Many-to-One Patterns

• One Producer, Many Consumers
• Needs adaptable consistency protocol
• Needs adaptable failure recovery protocol
• Consumers
• Adaptable organization according to
• Number, distance, communication pattern
• Leads to adaptable protocols
• Group semantics
• Most frequent users can be leader

14
Many-to-One Communication
Naming Database
Consumers
Producer