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The Session Coordinator is the underlying software engine responsible for creating, admitting, monitoring, altering and terminating sessions. A session is defined as a user running an application over the network. The Coordinator is also known as the SescoServer. There will be only a single instance of this process running on each machine in an Q-RAM-based Network.

Sesco Managed Network


Sesco Managed Network is composed of the following components:

Sesco (Session Coordinator) - It runs as global server on one node. It applies Q-RAM algorithm to maximize utility. In addition, it maintains a global resource list and provides feedback to system manager.

Lrmd (Local Resource Manager) - It runs on every node as an instance of the agent of Sesco. It does the following :

Network discovery
Resource discovery (memory, network interfaces etc.)
Proxy operations (Create/kill processes, resource reservation etc.)
Invokes RK (Resource Kernel) to enforce resource management decisions

Resource Kernel -  It is installed on each host machine. It provides mechanisms to implement virtual machine for a set of processes.

Sesco is composed of the GUI front end that will be used by both ordinary users and System Administrators. The former individuals will use Sesco to make Application Requests that are either granted and become sessions, or denied for any number of reasons. Administrators are responsible for managing Sesco itself and the underlying data files which together compose Sesco's vision of its world, from users and groups, applications and their variants and of course knowledge of all the hardware, network cards and nodes.

Session Admission in Sesco

A session admission in Sesco happens in the following way.


  1. Arq (Admission request manager) sends admission request to Sesco.
  2. Sesco determines QoS operating point of the application
  3. Sesco sends updated QoS set-point to necessary existing applications and Lrmds.
  4. Sesco sends process invocation requests to Lrmds.
  5. Sesco sends resource reservation request to Lrmds.
  6. Lrmds create processes for a new session.
  7. Lrmds report pid to Sesco.
  8. Processes register control port with Sesco.
  9. Sesco sends QoS set-point to new processes.