Transcript PPT

Outlines
Received
due
13 March 2000
18%
Homework
Review for Midterm (1 March 2000)
 Research Paper
 Readings
[5] “Virtual Private Networks”
[6] “Internet QoS: A Big Picture”
[7] “IP Routers: New Tool for Gigabit
Networking”
[8] “Corporate-Class Internet? Don’t
Count on It!”

Bridge
Operates at OSI Layers 1 & 2
Follows MAC
 Uses MAC addresses to switch packets
 May be capable of minor protocol
conversions
 If properly placed will improve performance

 Filters
unneccesary traffic
 Improves Efficiency
 Increases average Bandwidth to each end user
 Tends to increase delay across the bridge
Router

Operates at OSI Layers 1, 2, & 3

capable of making complex routing decisions
‘peers into’ packets

Very useful on Large Networks with multiple
end-to-end paths
Switched Hub
ASK VENDOR!!!
 May be a multi-port bridge
 May route (OSI Layer 3) first packet of a
flow (OSI Layer 5), bridge (OSI Layer 2)
remainder

The Internet
VAST collection of interconnected
networks
 Key Building Block:
Routers running IPv4 (Layer 3)
 Router link speeds range from 56 Kbps to
2.5 Gbps
 Hierarchical Addressing
[email protected]

ISO OSI Seven Layer Model
Layer 7
 Layer 6
 Layer 5
 Layer 4
 Layer 3
 Layer 2
 Layer 1

Application
Presentation
Session
Transport
Network
Data Link
Physical
Netscape
Win95 (API)
Win95 (TCP)
Win95 (TCP)
Win95 (IP)
3Com NIC
3Com NIC
Internet Service Provider Backbone
Router
ISP ‘Cloud’
Trunks use StatMux & Packet Switching
11Feb00 Traceroute to WWW.CISCO.COM
3 Internal OSU routers
 2 OneNet routers
border3-okc-oc3atm.onenet.net
 4 SBC routers
edge1-fa0-0-0.okcyok.swbell.net
 2 Williams routers
williams1-oc3-gr1.dal2.dbn.net
 7 BBNPlanet routers
p1-0.lsanca1-br1.bbnplanet.net
p7-3.paloalto-nbr2.bbnplanet.net\
 2 Cisco routers

11Feb00 Traceroute to LABRATS.COM
3 Internal OSU routers
 2 OneNet routers

 OKC

7 Williams Routers
 OKC
 Dallas
 Tulsa

1 Labrat Router
Virtual Circuits
Routing decisions made once when
circuit is set up
 All packets part of info transfer follow
the same path
 Frame Relay & ATM use Virtual
Circuits


Allows switch resources (buffer space,
bandwidth) to be set aside for specific
traffic flows
Datagrams
Routing decisions are made “on the fly”
multiple times
(every time a packet hits a Router)
 Packets may follow different paths
 IP uses Datagrams


Routers get no ‘advance warning’ of
packet flows.
What works* on the Internet?
Non Real Time Data Services
EMail
Usenet
Fax
 Interactive Data Based Services
File Transfer Protocol
Telnet
World Wide Web

Excellent
Good
*Provided you’re not trying to sip
bandwidth through a straw.
What works* on the Internet?
Interactive Data Based Services
White Boarding
Application Sharing
 Non-Interactive One-Way Audio
 Interactive Two-Way Audio
 One way motion video
 Interactive motion Video

Fair
Poor
*Provided you’re not trying to sip
bandwidth through a straw.
TCP, UDP, and IP
20 year old Protocols
Designed for data
One Priority & “Best Effort” services
No QoS Guarantees
Available bandwidth depends on other
users
 TCP (Layer 4 & 5) provides reliable
transfer
 UDP (Layer 4 & 5) provides unreliable
transfer

Interactive Telephony
over the INTERNET
“... is a toy until delay and voice-quality
problems are overcome”
Network World, 19 August 1996
Interactive VOICE & VIDEO
over the INTERNET
Is not ready for Prime Time
 Delay & Quality problems not likely to be
solved under the current system...
 ...although throwing Bandwidth at the
problem will alleviate
 Has a place for the user whose main
concern is $$$$ or convenience

Thinking of moving time sensitive
traffic over the Internet?
Check back in 2-3 years when...
Priorities Enabled (IPv6 and/or DiffServ)
 Resources Guaranteed
(Resource Reservation Protocol (RSVP)
or equivalent is deployed)
 Flat rate pricing is gone

Pros of Using the Internet
Any-to-Any Connectivity
 It’s Inexpensive (save $$$$)
 Tons of valuable information available
 Excellent marketing/sales tool

Cons of Using the Internet

Any-to-Any Connectivity
puts all attached machines at risk
WARNING: SECURITY HAZARD!
Slightly higher risk of Theft of Traffic
 Tons of Worthless Information Available
 No QoS guarantees or Guaranteed Bandwidth
May have trouble rapidly moving large files
May have trouble reliably moving time
sensitive traffic

Worldwide ISP Revenues
Source:
Data Communications
Internet Performance
Probability of
dropped packets
Average Delay for
delivered packets
0%
Trunk Offered Load
100%
Backbone Engineering

Option A)
Deploy ‘best effort’ Routers
Rapidly Deploy Trunk Bandwidth
Keep Trunks Lightly Loaded
 Delays
will be small
 Dropped packets will be few
 Quality fine for Interactive Voice/Video
Backbone Engineering

Option B)
Deploy more expensive QoS enabled
Routers
Deploy fewer, more heavily loaded
Trunks
Give preferential treatment to
Voice/Video

Which is less expensive in the long run?
Connectionless vs.
Connection Oriented
Connectionless
* Packet delivery may be out of order
* Packet delivery NOT guaranteed
* Packets may be mangled
* End User’s responsibility to fix any
problems
 Connection Oriented
* Packet delivery in order
* Packet delivery usually guaranteed
