Notable Issues

munchdrabNetworking and Communications

Oct 30, 2013 (3 years and 9 months ago)

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Introduction


What are routers (Ponta)


Data Conversion (Adrian)


Routing (Albert)


Routers (Jordan)


Router Architecture (Victor)


Routers vs. Computer


What is a computer?


A general purpose machine that takes an input
translates the input under software control and gives
an output.


A router is also a computer


not a “general purpose machine”


Main purpose is to route data

Networks


Today’s networks are large masses of routers


Routers take any form of data such as email,
web
-
browser requests, and file transfers and
deliver them to the appropriate destinations.


The internet is a large network of
interconnected routers.

Routing in a nutshell


Routers work by reading the IP address of data
packets and determines the correct source and
destination for the packet.


The router can also discover the best way to get
the packet to its destination.

Routing in a nutshell (cont.)


Routers take requests from their local users and
forward those requests to the appropriate host.

Routing


Routing is the process that allows data to travel
from one host to another


Routing is responsible for the making the
Internet work.

Without Routers


Every computer would have to be connected
together


Users would need to know


the address of every website they wanted to visit


All the computers you would need to pass through
to get to the destination computer.

Accessing Websites


You enter a URL address in to your web
browser (e.g. Internet Explorer, Netscape
Navigator, etc.), e.g, http://
www.csun.edu


The browser sends a message to the router


The message notifies that you want to see the
information stored at
www.csun.edu


The process begins

Internet Explorer

Netscape

Address Conversion


DNS servers translate the alphanumeric URL,
www.csun.edu
, address to an IP address:
130.166.1.55


Packets are sent to the routers that read this
address

Routing Packets


Each router examines the packet


Determines the IP address


Matches the information against its own routing
table.


Chooses which port to route it out of

Routing Table


A two column table


First column identifies each router in the
network


Second column lists the router to which each
router should send data to

Routing Table


Router examines packet


If exact match, forwards the message


If there is no match, it runs though table again,
looking for a match


If still no match, router sends the packet out of
the default next
-
hop address

Routing Table


Router sends an ICMP() “host unreachable” or
“network unreachable” message back to sender
ultimately if no match is found.


Difficult part of router’s job is not how it routes,
but how it builds up its table

Source

Destination

Next Hop

A

A

A

A

B

B

B

C

D

E

F

G

B

B

D

B or D

C or E

C

Routing Table Example

Routing Packets

This process continues until the
request finally reaches
www.csun.edu

Routing


The routing tables have been keeping track of
the path to the destination.


The routing path is now known by the initial
router.

Routing Algorithms


Routing algorithm


complex set of rules that take into account a variety
of factors


Determines what is the best via routing
algorithm


Selects the best path between the source and
destination machine

Routing Issues

Flooding the Network



Early routers were slow


The networks they ran on were equally low
-
powered, with little bandwidth


Isolated in that they did not exchange routing
tables


As a result routers forwarded data by flooding
every path with packets

How can we solve this?


Backward learning
-
router remembers the source
addresses of all incoming packets and notes the
physical interface it came in on


Static Routing


Rely either on a human or host computer to make
these decisions


Source routing
-
end hosts place information in
every packet they place on the network

Centralized vs. Decentralized

Centralized Routing


All routing decisions are made by one central
computer or router


Typically used in host computers


All computers are connected to the central
computer

Decentralized Routing



All computer or routers in the network make
their own routing decisions


In larger networks, routing table is developed by
the network manager


In smaller networks, routing table is developed
by one individual


Most decentralized routing protocols can
automatically adapt to changes in the network
configuration



Static vs. Dynamic Routing

Static Routing



Routing decisions are made in a decentralized
manner


When new computers are added to network,
they announce their presence


Commonly used in networks that have few
routing options that seldom change

Dynamic Routing



Routing decisions are made in a decentralized
manner by individual computers


Used when there are multiple routes through a
network


Routes messages over the fastest possible route

Dynamic Routing


Distance vector dynamic
routing


Routers count the
number of hops along a
route.


Routers periodically
exchange information on
the hop count

Router A

Router B

Router C

Router D

Dynamic Routing


Link state dynamic routing


Rather than knowing a route’s distance, link state
routing tries to determine how fast each possible
route is


Routers periodically exchange this information to
other routers in the network


Preferred over distance vector protocols because
they converge quicker

Dynamic Routing
-
Drawbacks



Requires more processing by each computer or
router in the network


Transmission of routing information wastes
network capacity.

Connectionless Routing


Used when a message can fit into one single
packet


Each packet is routed independently


A router must make a decision for each packet


Used by UDP (User Datagram Protocol) to send
short control messages


Connection
-
Oriented Routing


Sets up a virtual circuit between the sender and
receiver


Packets from the same message use the same route

VC1

VC2

Router Types


Home Routers


Small Organization and Office Routers


High End Routers

Home Routers


Usually simple


Examples includes:


Linksys, Cable/DSL,
10/100 Ethernet
backbone

Features:


Voice over IP
telephone installed by
Netphone.





D
-
LINK
-
614+


22mbps “Air Plus” is twice as fast as the usual
(11
-
mbps) 802.11b connection


Utilizes Texas Instruments patented Digital Signal
Processing


Offers 256
-
bit encryption


the strongest available


Deep firewall configuration options.


Firewall features are easy to implement


Example: Can designate particular computers as
WEB servers or FTP servers which are visible to the
Internet

D
-
LINK
-
614+

Small Organization and Office
Routers


Slightly larger routers


Do little more than home router


These routers enforce rules concerning
security for the office network.








3
-
Com
-
Superstack


Provides:


Low equipment costs


Dial
-
in/dial
-
out


Frame Relay


Lease Line PPP
Connection


3
-
Com Superstack cont.


Contains:


Three stackable components


That provides multi
-
protocol remote access server


Full function WAN router technology for small
and medium sized business.


Offers secure access Authentication

3
-
Com Superstack cont.


In addition:


it can proxy or relay IP address to another
central server.


Simplifies network administration


Enhances the mobility of both remote and
local users.

High
-
End Routers


Largest routers


Handle million of packets every second


Work to configure the network efficiently


Large stand alone systems

Nortel Networks


High end routers
manufacturer


Provides large high
performance, scalable
routing devices.


Backbone Node and
Backbone
Concentrator Node

Benefits of the Nortel Networks


Enhance network performance


High Network availability


Network investment protection

IBM 2210 Nways Multiprotocol


Provides network
solutions for a range of
applications


This allows:


System administrators to build and manage
scalable Web Servers.


Superior to Domain Name Servers round robin
-
querying

Router Architecture

Router Memory


Flash


ROM


Cache


RAM


Router Memory


Flash


Location where the basic boot image is stored.


Router Memory


ROM


Initializes the processor hardware and boots the
operating system software.


Runs when the router is powered up or reset

Router Memory


Cache


Primary


Primary cache is closest to the processor core and has the
fastest access


Secondary


Secondary cache has slower access than primary cache,
but faster access than tertiary cache.


Trietary


Slowest of all cache but faster than RAM

Router Memory


RAM Random Access Memory


SDRAM


Synchronous Dynamic Random
-
Access Memory


Runs at 133MHz


DDR
-
SDRAM


Double Data Rate Synchronous Dynamic Random
-
Access Memory


Runs at 266MHz


NVRAM


nonvolatile random
-
access memory


Uses lithium batteries to maintain its contents when power is removed



Router Memory


RAM Packaging


SIMM


Single In
-
line Memory Module


DIMM


Dual In
-
line Memory Module


SODIMM


Small Outline Dual In
-
line Memory Module.

Router Ports


Ethernet


refers to the family of local
-
area network (LAN)
products covered by the IEEE 802.3 standard


10/100/1000 Mbps


ISDN


Integrated Service Digital Network


Communication protocol offered by telephone companies
that permits telephone networks to carry data, voice, and
other source traffic.

Router Ports


T3


Digital WAN carrier facility


Transmits DS
-
3
-
formatted data at 44.736

Mbps
through the telephone switching network.


OC
-
3


Operates at 155 Mbps


Provides the highest

available interface bandwidth
for packet
-
based traffic

Cisco 7200

Cisco 7200


Two models


7204VXR


7206VXR


Modules based


Modules

Cisco


7204VXR

Cisco


7206VXR

Configurable Slots

4

6

Ethernet (10BASE
-
T) Ports

32

48

Ethernet (10BASE
-
FL) Ports

20

30

Fast Ethernet (TX) Ports

4

Up to 6

Fast Ethernet (FX) Ports

4

Up to 6

EtherSwitch Port Adapters

2

2

100VG
-
AnyLAN Ports

4

Up to 6

FDDI (FDX, HDX) Ports

0

0

ATM Ports (T3, OC
-
3)

4, 4

Up to 6, 4

Packet over SONET

2

2

ATM
-
CES Port Adapters (Data, Voice,
Video), Dual
-
Wide

1

1

Token Ring (FDX, HDX) Ports

16

24

Synchronous Serial Ports

32

48

ISDN BRI Ports (U, S/T)

16, 32

24, 48

ISDN PRI, Multichannel T1/E1 Ports

32

48

Multichannel T3 Ports

Up to 4

Up to 6

HSSI Ports

Up to 8

Up to 12

Packet over T3/E3 Ports (Integrated DSU)

Up to 8

Up to 12

IBM Channel Interface Ports (ESCON and
Parallel)

6

6

VPN Acceleration Module

1

1

Cisco 7200 Processors


4 types of processor
units


NPE 225


NPE 400


NSE
-
1


NPE
-
G1

Cisco 7200 Processors


NPE 225


NSE
-
1

Cisco 7200 Processors


NPE
-
G1


NPE 400

Cisco 7200 Memory
Configuration

NPE
-
225

NSE
-
1

NPE
-
400

NPE
-
G1

Microprocessor

RM5271

262MHz

RM7000
262MHz

RM7000
350MHz

BCM1250

700MHz

Memory

SDRAM

DIMM

Max: 128

SDRAM

DIMM

Max: 256MB

SDRAM

SODIMM

Max: 512MB

SDRAM

SODIMM

Max: 512MB

Primary Cache

32K Instr.

32KB Data

16KB Instr.

16KB Data

16KB Instr.

16KB Data

16KB Instr.

16KB Data

Secondary
Cache

2MB

256KB

256KB Fixed

512KB

Tertiary Cache

2MB Fixed

4MB

Boot ROM

512KB

512KB

512KB

512KB

NVRAM

512KB

Flash Memory

16MB

16MB

16MB

16MB

THE END