The Session layer of the OSI model offers three different modes of communication : Simplex, half duplex, and full duplex.

A reliable Transport layer connection uses acknowledgments to make sure all data is transmitted and received reliably. A reliable connection is defined by a virtual circuit that uses acknowledgments, sequencing, and flow control, which are characteristics of the transport layer.

Routers operate at layer 3. LAN switches operate at layer 2. Ethernet hubs operate at layer 1. Word processing applications communicate to the Application layer interface, but do not operate at layer 7, so the answer would be none.

I. Inputs

• Procurement management plan


• Contract management plan


• Contract documentation


• Contract closure procedure

II. Tools and Techniques

• Procurement audits


• Records management system

III. Outputs

• Closed contracts


• Organizational process assets (updates)

I. Inputs

• Contract


• Contract management plan


• Selected sellers


• Performance reports


• Approved change requests


• Work performance information

II. Tools and Techniques

• Contract change control system


• Buyer-conducted performance review


• Inspections and audits


• Performance reporting


• Payment system


• Claims administration


• Records management system


• Information technology

III. Outputs

• Contract documentation 


• Requested changes


• Recommended corrective actions


• Organizational process assets (updates)


• Project management plan (updates)

                 - Procurement management plan

                 - Contract management plan

I. Inputs

• Organizational process assets


• Procurement management plan


• Evaluation criteria


• Procurement document package


• Proposals


• Qualified sellers list


• Project management plan

                 - Risk register

                 - Risk related contractual agreements

II. Tools and Techniques

• Weighting system


• Independent estimates


• Screening system


• Contract negotiation


• Seller rating systems


• Expert judgment


• Proposal evaluation techniques

III. Outputs

• Selected sellers


• Contract


• Contract management plan


• Resource availability


• Procurement management plan (updates)


• Requested changes

I. Inputs

• Organizational process assets


• Procurement management plan


• Procurement documents

II. Tools and Techniques

• Bidder conferences


• Advertising


• Develop qualified sellers list

III. Outputs

• Qualified sellers list


• Procurement document package


• Proposals

I. Inputs

• Procurement management plan


• Contract statement of work


• Make-or-buy decisions


• Project management plan

                 - Risk register

                 - Risk related contractual agreements

                 - Resource requirements

                 - Project schedule

                 - Activity cost estimate

                 - Cost baseline

II. Tools and Techniques

• Standard forms


• Expert judgment

III. Outputs

• Procurement documents


• Evaluation criteria


• Contract statement of work (updates)