Transcript Notable Issues

Introduction
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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
Routing Table Example
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 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 lowpowered, 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 D
Router C
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
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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
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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
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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 robinquerying
Router Architecture
Router Memory
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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
Cisco
7204VXR
Modules
• Two models
– 7204VXR
– 7206VXR
• Modules based
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
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–
NPE 225
NPE 400
NSE-1
NPE-G1
Cisco 7200 Processors
• NPE 225
• NSE-1
Cisco 7200 Processors
• NPE 400
• NPE-G1
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
2MB Fixed
4MB
512KB
512KB
Tertiary Cache
Boot ROM
512KB
NVRAM
Flash Memory
512KB
512KB
16MB
16MB
16MB
16MB
THE END