Download An Internet Service is - Connected Systems Group

Internet Architectural Fundamentals
Internet Architectural Principles
for the eBusiness Era
• Architectural Guidelines for going
forward:
–
–
–
–
A-to-A
B-to-B
Enterprise Architecture
All of the above
Rjd 06/12/2001
Internet Architectural Fundamentals
Recommending a Strategy
• Internet Architecture Principles Are Proven to Work...
– Unprecedented interoperability, scalability, and functional
extensibility
– Unprecedented economic impact: the “business case”
which changed the world
– Unstoppable combination: Collaborative Computing is
King!
• So Let’s Apply them to throughout the Entire
Architecture!
– A2A, AI, B2B, B2C, EIA, etc.
Rjd 06/12/2001
Internet Architectural Fundamentals
4 Basic Principles of Internet Architecture:
#1) The Internet Architecture is defined by a collection of
protocols which are the rules for things to talk to each other.
#2) Everything can talk to everything else.
#3) Intelligence lives at the edge of the network, not within it.
#4) Internet Service Model: functionality is provided by the
federated action (collaboration) of protocol specific services.
Rjd 06/12/2001
Internet Architectural Fundamentals
#1) The Internet Architecture is defined by a
collection of protocols:
– e.g. IP, DNS, HTTP, TCP, POP3, FTP, SNMP,
Telnet, LDAP, RIP, BGP, ...
– the protocol specifications are usually
sanctioned by the Internet Engineering Task
Force (IETF)
– World Wide Web Consortium (W3C) also
emerging as a companion source of standards
Rjd 06/12/2001
Software Service
Interface (API)
Internet Architectural Fundamentals
Software Service
Interface (API)
Network Channel
Local
Network Stack
Component
AtoB Message 1
AtoB Message 2
AtoB Msg 3
Local
Network Stack
BtoA Message 1
BtoA Message 2
Network Node A
Component
Network Node B
•The protocol defines the rules for valid types of message “on the wire” and the legal
sequence of messages.
•The Software Service Interface (SSI) defines the Application Programming Interface
(API) independently to each local network stack component.
•SSI/API relates to Protocol in N:M ways.
•In general, a specific Protocol is vastly more important than a specific SSI/API in
Network Computing Architecture. Traditional software engineering mentality not
withstanding!
Rjd 06/12/2001
Internet Architectural Fundamentals
#2) Everything can talk to everything else:
– the basic Internet Protocol (IP)
does not define a “cloud” but
rather an image of total interconnection
– inherently Peer to Peer but not physically Point
to Point
– tech note: only datagram (packet) delivery
known to the inside of the network
Rjd 06/12/2001
Internet Architectural Fundamentals
#3) Intelligence live at the edges of the
network, not within it:
SMTP Server
DNS Server
– No single point of control or failure
– Decoupling of unrelated functionality
– Simplified design of functionality,
e.g. DNS, SMTP, LDAP, SNMP, etc.
– Specific functionality controlled by
self-organizing communities
eMail Client
DNS Server
– Vast Synergy: nearly infinite number of
ways recombine functionality at the end Points!
Rjd 06/12/2001
Internet Architectural Fundamentals
#4) Internet Service Model: functionality is provided by the
federated action (collaboration) of protocol specific services:
– Each protocol specification implies the existence of a distributed computing
model (which may or may not be explicitly mentioned):
• Distributed Communication Scheme: the service protocol itself consisting of protocol
messages (logical data units) and sequence rules (“behavior”)
• Distributed Processing/Algorithm Scheme, e.g.
WWW: Navigating the “World Wide Web” as one huge hypertext document
FTP: file access & transfer rules, DNS look up, SMTP: eMail delivery, …
• Distributed Memory/Persistence Scheme, e.g.
WWW: Web page contents stored in whatever form
FTP: files, DNS:name records, SMTP: message stores, LDAP: X.500 trees, ....
• Distributed Linkage Scheme to find/relate things of interest, e.g.
WWW: the URL (an act of sheer genius!)
SMTP eMail addresses, DNS names, LDAP distinguished names, ….
– The operational result of the distributed computing model enabled by the
particular protocol is a virtual service, namely the protocol’s “Internet Service”
Rjd 06/12/2001
Internet Architectural Fundamentals
An Internet Service
• An Internet Service provides functionality which appears
to be available throughout the net provide by and to
communities of common interest.
• An Internet Service is:
– Virtual
– Well Defined
(Virtual)
Internet
Service
– Distributed
– Federated (Collaborative)
Rjd 06/12/2001
Internet Architectural Fundamentals
An Internet Service Is:
• Virtual
– An Internet Service is “virtual service” which looks like
one complete thing but in reality has many far flung
parts glued together
• Well Defined
– An Internet Service is defined by a common protocol
specification (messages and rules about exchanging
message)
– Usually promulgated through the Internet Engineering
Task Force (IETF), or more recently, the World Wide
Web Consortium (W3C)
Rjd 06/12/2001
Internet Architectural Fundamentals
An Internet Service is: (cont’d)
• Distributed
– An Internet Service protocol specification
implies (not necessarily overtly) an associated
Distributed Computing Model:
– Distributed Algorithm(s),
– Distributed Data Store(s),
– and Distributed Reference Mechanism(s)
(URI, etc.)
– An Internet Service may (C/S), or may not
(P2P), divide its participants between client and
server nodes
Rjd 06/12/2001
Internet Architectural Fundamentals
An Internet Service is: (cont’d)
• Federated (Collaborative)
– Technically
• an Internet Service is composed of many participants
• an Internet Services coexists, often beneficially, with other
Internet Services (sometimes in a layered relationship)
– Organizationally: Technical Structure follows Social Structure
• There must be an active social/technical/business community(s)
which come together around a common interest(s) in the
Internet Service
• Never, or at most rarely, is there a single enforcing point of
control over the service (protocol) specification nor over the
service operation (systems administration, etc.)
Rjd 06/12/2001
Internet Architectural Fundamentals
Internet Service Examples: IP Routing, Domain Name Service, eMail,
and the World Wide Web
Service
Protocol(s)
Distributed
Algorithm
Distributed
Data Store
Reference
Mechanism
IP connectivity
Routing Protocols:
RIP, BGP, OSPF,
etc.
Various – Open
Shortest Path First,
etc.
Routing Tables
Media Access Address,
Port Number, IP address
(recursivly)
Domain Name
Service
DNS with
hostname records,
MX (mail host)
records, etc.
Hierarchical Name
Space
DNS records
IP address, Domain
Name (recursively)
eMail (to Message
Transport Agent)
SMTP with ASCII
data which has
been extended with
MIME, HTML,
etc.
Point to Point over
TCP for stored
message exchange
Message Store
User@DNSName
World Wide Web
HTTP with HTML
data which has
been extended with
MIME, Javascript,
XML, etc.
Request/Response
of pages from one
universal WWW
hypertext document
Web Server (and
back end) contents
URL (including Service
Name, DNSName or IP
address, “file name”,
and parameters)
Rjd 06/12/2001
Internet Architectural Fundamentals
Note: even the fundamental IP connectivity of “everything to everything else” is
really a virtual service internal to the Internet called IP Routing!
IP Routing Service
Physical Network Topology:
Limited Direct Connectivity
IP Conceptual Addressing: Everything
connected to everything else
Rjd 06/12/2001
Internet Architectural Fundamentals
Further notes on the TCP as an Internet (virtual) Service:
• While IP routing is provided by the internals of the network, Transmission
Control Protocol (TCP) is the prime example of virtual service provide by
“intelligence at edge of the Network”
- IP allows packet by packet to go from anywhere to anywhere:
“datagram/connectionless” transport
- TCP provides an overlaid sequential message stream layered on top of IP:
“virtual circuit/connection oriented” transport
• By means of the TCP protocol each end node (TCP/IP procotocl stack) sorts out
packets which may arrive in jumbled order in order to maintain the illusion of a
continuous octet (byte) stream
• In its day this was radical: most contemporary network architectures in the 1970s
and 1980s were not datagram oriented, but rather virtual circuit oriented, e.g.
SNA, DECNet, X.25, ISDN, etc.
Rjd 06/12/2001
Internet Architectural Fundamentals
Architectural Observations
• Social/Business Context: most standard Internet Services provide core
functionality of interest to a large percentage of Internet users (i.e have
really large communities), e.g. DNS, HTTP, SMTP, etc.
• Most of these core Internet Services are analogous to Single Instruction
Multiple Data (SIMD) computer systems architecture
- Each server independently follows the same algorithm (SI
equivalent) with its own unique data store contents (MD equivalent)
-The algorithms and virtual data stores tend to be fairly simple
• Services may be implemented by “components” in any given node,
often they are, but they don’t have to be
• Much like “components” may be implemented by “objects”, often
are, but don’t have to be
• Services are NOT defined by APIs, programming languages, or
distributed object models, rather they are defined by protocols
Rjd 06/12/2001
Internet Architectural Fundamentals
Architecture Observations - Future Directions
• The notion of Internet “Service” is expanding from infrastructure
functionality (IP, TCP, DNS, LDAP, etc) to included support of many
application domains (B2C, B2B, engineering, finance, etc.)
• Concomitantly, Internet Architecture is expanding from SIMD like
simple protocols to more sophisticated MIMD like protocols
• Communities of interest may be smaller and more specialized, e.g.
subcultures of Boeing suppliers and customers
• A big enabler of the expanded notion of application level protocols
are new data types such as multi-media (MIME and streaming
formats) and, especially, XML
• Better ways to define and implement the behavioral aspects of a
protocol has not yet achieved the relative success of XML for the
data aspects.
Rjd 06/12/2001
Internet Architectural Fundamentals
An Example of Using Internet Services
in a Future Data Query Architecture
Rjd 06/12/2001
Internet Architectural Fundamentals
Distributed Query Services Architecture
Service
(aka "Interface")
Repository(s)
Internal Schema
Partner
OLTP/SoR(s)
&
Repository(s)
Service
Implementation
External
Service
Global & Service
Level
Security Models
Service
Implementation
(via Business
Object Schema*)
Service
Implementation
OLTP /
System of Record(s)
* e.g XML
DTD/Schema
Service
Implementation
Data Service
Data Service
Response Extract
Request Query
(via Extract Schema*) (via Query Schema*) Service
Client Application/
Service (e.g EJB)
Client User Agent
(e.g. Web Servlet)
Service Description
Description
Request
Response
Service
(e.g. WSDL)
Directory
(e.g. UDDI)
GUI (e.g
Browser)
Rjd 06/12/2001
Internet Architectural Fundamentals
Table
Instances
Relational
Schema
& Other Metadata
Service Business Object
Schema*
Data Store Model
Service Implementation:
Apply Relevant and
Permitted Business Rules to
Map, Merge, and Transform
Service Response
Response Object
Service Response Object
Schema*
Business Object Model
*e.g. All service schemas are
XML DTD/Schemas
===>
All service "object"
instances are XML
Service Request
Request Object
Service Security
Model:
Credentials &
Authorization Rules
Service Virtual BO
Data Store
"document" instances.
Service Request Object
Schema*
Anatomy of a Schema Oriented Service: Metadata Rules!
Rjd 06/12/2001