Foundations
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Foundations. Readings: Peterson & Davie, Chapter 1. Dave Clark. “We reject kings, presidents, and voting. We believe in rough consensus and running code.”. Admininstrivia. Website coming Friday! Assignment 1 assigned on Friday. To be discussed today TODOs: Log into lab machines

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Foundations

Foundations

  • Readings: Peterson & Davie, Chapter 1


Dave clark

Dave Clark

  • “We reject kings, presidents, and voting. We believe in rough consensus and running code.”


Admininstrivia

Admininstrivia

  • Website coming Friday!

  • Assignment 1 assigned on Friday.

    • To be discussed today

  • TODOs:

    • Log into lab machines

  • Sample Schedule

    • http://courses.washington.edu/css432/syllabi/s08.html

  • Sample FAQ

    • http://courses.washington.edu/css432/prog/prog1_faq.html


Networks

Networks

  • What is a network?


Data and links

Data and Links

  • What is a physical Network?

  • We’ll investigate these empirically, starting with the first assignment


Virtualization and overlays

Virtualization and Overlays

  • What is a virtual network?


From the text

From the Text:

  • “Think of a network as providing the means for a set of application processes that are distributed over [multiple] computers to communicate”

  • We could make every application responsible for their information exchange, but

    • Lots of redundancy and errors with this approach

  • Instead, lets distill common communication patterns

    • And offer those as services/protocols in a network stack


Perspectives

Perspectives

  • App Developer

    • What do I want?

  • Network Architect

    • Cost-effective design, reliable, QoS enabled

  • Provider

    • Account for usage, offer QoS gradients


Network styles

Network Styles

  • Links, Nodes, Clouds form network maps

  • Point-to-Point

    • Quickly becomes unmanageable

  • Multiple-Access

    • Multiplex a single bus/wire/channel across multiple hosts

    • Limitations :geographical distance limitations and number of nodes connected.

  • All styles of Networks must cope with Scalability


Switching networks

Switching Networks

  • The most common types of switched networks include:

    • Circuit-switched

      • POTS

    • Packet-switched

      • Store-and-forward


Network symbols

Network Symbols

  • Fig 1.3, p8

  • Switches, nodes (hosts), and links


Packets v s messages

Packets V.S. Messages

  • Packets refer to physical data on the wire, with a well-defined size imposed by each network

    • Or subnetwork your packet moves through

      • This could introduce packet fragmentation and rebuilding (more on that later)

  • Messages: a data payload usually exchanged at the application level

    • These messages may not fit into one packet


Networks of networks

Networks of Networks

  • Internetwork: a connection of independent networks

    • Visualize these as clouds

  • Gateway: A Node that connects two or more networks (a.k.a router)

    • Quite similar in spirit to a switch, and thus these terms are frequently blurred


Recursive networks

Recursive Networks

  • A network may be built by combining existing networks

  • This implies a recursive structure

    • Where the basis is some physical medium

  • We can recursively build larger and larger networks by connecting existing network clouds

    • Analog: Fib numbers


Network addresses

Network Addresses

  • A unique* way to identify all nodes on a network

  • Much like a cell-phone number


Effective networking

Effective Networking

  • We need to “share” links effectively

  • STDM

    • Divide time into quanta and assign the link in a RR fashion

  • FDM

    • Divide frequencies into channels, like TV

  • Limitations: Dynamic resizing of the quantum or adding new quanta/frequencies is required


Statistical multiplexing

Statistical Multiplexing

  • Or, On Demand time division multiplexing

  • Effectively uses the link

  • Could introduce starvation, so an upper bound on block-size is determined


Network architecture

Network Architecture

  • Formally, a protocol graph with protocol specifications (a standardization)

  • Multiple models have been proposed

    • OSI architecture

    • Internet (IETF) architecture

  • Architects leverage abstraction

    • This naturally introduces layers in our Network

  • Key: Start with services offered by the layer beneath you and build on top

    • Lowest layer relies on the underlying hardware

    • High level services are implemented by lower level services


Architecture v1 0

Architecture, V1.0

Application Programs

Process-To-Process Channels

Host-To-Host Connectivity

Hardware


Architecture v1 2

Architecture, V1.2

Application Programs

Application Programs

RRC

MSC

Process-To-Process Channels

Host-To-Host Connectivity

Host-To-Host Connectivity

Hardware

Hardware

A “Protocol Stack”


Interfaces

Interfaces

Peer Level

Host 1

Host 2

Application Programs

Application Programs

RRC

MSC

RRC

MSC

Host-To-Host Connectivity

Host-To-Host Connectivity

Hardware

Hardware

…1001…

Service Level Interfaces define the semantics (form & meaning) o f messages exchanged at a given level


Peer level indirect messaging

Peer-Level (Indirect) Messaging

  • Each protocol communicates “with its peer” indirectly by handing messages down the protocol stack

  • The only layer to have a non-virtualized p2p relationship is the hardware level


Open systems interconnection model

End host

End host

Application

Application

Presentation

Presentation

Session

Session

Transport

Transport

Network

Network

Network

Network

Data link

Data link

Data link

Data link

Physical

Physical

Physical

Physical

One or more nodes

within the network

Open Systems Interconnection Model


Layers

Layers

  • Physical Layer transmits bits

  • Data link layer collects bits into frames

    • NIC and drivers typically implement this

  • Network layer handles routing

    • Packet-level data

    • Note that these layers are implemented on switches in the cloud, too

  • Transport and up usually are found on the host

    • “There is less agreement about the definition of the top three layers”


Internet architecture

FTP

HTTP

NV

TFTP

Netscape, IE, Mosaic, etc.

UDP

TCP

IP

NET

NET

NET

2

1

n

Focal point for the architecture

Internet Architecture

  • Defined by Internet Engineering Task Force (IETF)

  • Hourglass Design

  • Application vs Application Protocol (FTP, HTTP)

Reliable byte-stream channel

Unreliable datagram delivery

Internet Protocol

Ethernet, FDDI, etc.

CSS 432


Ip the interconnect

IP – the Interconnect

  • The “meeting point” in our 4 layers

  • Also, the bottleneck or meeting point of various networking technologies

  • FTP over FDDI, HTTP over Ethernet

  • Transport Protocols

    • Sometimes called end to end

  • TCP – reliable, in order, slow

  • UDP – unreliable, out


Alternate view of the internet

Alternate View of the Internet

Application Layer

TCP

UDP

IP

Network


Creative

Creative?

  • We can apply the OSI model (loosely) to the IETF model

  • Note that OSI was assembled after ARPANET


Encapsulation

Encapsulation

Payload

Protocol 1 Headerr

Payload

Protocol 2 Header

Protocol 1 Header

Payload

Subnet 1 Header

Protocol 2 Header

Protocol 1 Header

Payload


Using our examples

Using Our Examples

Application Programs

RRC

MSC

Host-To-Host Connectivity

Hardware

Payload

RRP Header

Payload

HHP Header

RRP Header

Payload


Multiplexing statistical

Multiplexing (Statistical)


Network performance

Network Performance

  • RTT

  • Message Copying V.S. Passing

  • Process-per-protocol v.s. per-message

    • Context Switching v.s. Function Calls

  • Bandwidth & Latency


Client server networking

Client/Server Networking

  • We’ll be using this for the class.


Sockets

Sockets

  • Coming up!


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