MultiprotocolMultiservice Servers

1
Lecture 7

• Multiprotocol/Multiservice Servers

2
Overview

• Multiprotocol Servers
• Multiprotocol Server Design
• Concept of Shared Code
• Concurrent Multiprotocol Servers
• Consolidating Servers
• Connectionless, Multiservice Server Design
• Connection-Oriented, Multiservice Server Design
• Conncurrent, Connection-Oriented, Multiservice
  Server
• Invoking Separate Programs From a Multiservice
  Server

3
Reducing the Number of Servers

• Typically a given server handles requests for one
  particular service through one particular
  protocol
• Example
• DAYTIME service runs two servers one for UDP
  request another for TCP requests
• Main disadvantage of using one server per
  protocol is replication
• Both TCP/UDP servers use the same basic algorithm
• Debugging and software management issues
• Resource depletion

4
Multiprotocol Server Design

• A multiprotocol server consists of a single
  process that uses asynchronous I/O to handle
  UDP/TCP
• Server opens two sockets (UDP/TCP)
• Uses asynchronous I/O to wait for one of the
  sockets to become ready
• TCP socket ready client requested a TCP
  connection
• UDP socket ready client requested a UDP
  connection

5
Process Structure
Server application process
server
Operating system
socket for UDP requests
socket for TCP conn requests
socket for a TCP connection
6
Concept of Shared Code
A multiprotocol server design permits the
designer to create a single procedure that
responds to requests for a given service and to
call that procedure regardless of whether
requests arrive via UDP or TCP
7
Concurrent Multiprotocol Servers

• DAYTIME server shown earlier is an iterative
  server
• Works because the server performs minimal
  computation and I/O per request
• Iterative servers may not suffice for other
  services that require more computation per
  request
• Example
• Create a separate server to handle each TCP
  request
• Create a separate server to handle each UDP
  request

8
Consolidating Servers

• Typically a computer runs one server per service
  (DAYTIME, ECHO, )
• Same advantages that apply to consolidating
  multiprotocol servers apply to consolidating
  multiserver servers
• Consolidating many services into a single server
  can drastically reduce the number of running
  processes
• Many of the small services require a trivial
  amount of computation

9
Connectionless Multiserver Server Design
Server application process
server
Operating System
master sockets (one for each service)
10
Connection-Oriented Multiserver Server Design
Server application process
master
master sockets (one for each service)
Operating System
Socket for one individual connection
11
Concurrent Connection-Oriented Multiservice Server
Server application process
master
slave1
slave2
master sockets (one for each service)
Operating System
Sockets for individual slave connections
12
Separate Programs from a Multiservice Server
fork used
Server application process
master
slave1
slave2
prog1
prog2
execve used
master sockets (one for each service)
Operating System
Sockets for individual slave connections