ece498 introduction to network engineering professor bruce segee fall 2000
TRANSCRIPT
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ECE498Introduction to Network Engineering
Professor Bruce SegeeFall 2000
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What is Network Engineering?
Net-eng is the profession of designing, upgrading, and implementing network systems.Net-eng is not exclusive to the data network field; telecommunication engineering (telcom-eng) is very similar to net-eng.
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Why is Net-Eng Important?
Today’s Internet infrastructure would be non-existent without network engineers. Existing infrastructure would fall into ruin over time- optimization and repair would not occur.
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What is a Network?
A network is any system of interconnected devices which communicate over a shared medium.The medium can be almost anything- a physical cable, or a wireless link.A single network can consist of multiple, smaller networks.
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What Is the Internet, then?
Well, quite honestly, it’s a big convoluted mess.The Internet consists of thousands of smaller, (not necessarily compatible) networks.The links between networks can be physical (telephone line), wireless (cell phone), satellite, etc.
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The Mess
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Internet Growth
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Why is the Internet Growing?
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Common Network Problems
LatencyPacket lossRouting problemsToo many “hops”Lack of peering (public or private)
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How Do We Fix The Problem (Instead of Patching It?)
Upgrade.Upgrade. Increase the capacity of the network interconnects.
Consolidate.Consolidate. Migrating equipment and services to a centralized location improves network efficiency, and decreases “hops.”
Decommission.Decommission. Removing legacy equipment and closing locations reduces required manpower and maintenance.
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How Do You Know When to Fix Something?
Two main factors are involved in the decision:
Does it affect customers/end-users in any way?
How much does it cost?
Unfortunately, when talking about long-term goals, it usually comes down to money.
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Something’s Broken!
If you find that something is broken,you have quite a few tools at your disposal to determine what the problem is: “Ping” “Traceroute” Network/protocol analyzers
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Ping
Ping is the most common way of determining if a host is “alive.”
C:\WINDOWS\Desktop>ping 199.1.11.2
Pinging 199.1.11.2 with 32 bytes of data:
A couple things can happen at this point…
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Ping (cont.)
Routing is wrong:
Destination host unreachable.
Destination host unreachable.
Destination host unreachable.
Destination host unreachable.
Ping statistics for 199.1.11.2:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
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Ping (cont.)
The host may be unresponsive:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 199.1.11.2:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
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Ping (cont.)
Or it may be up and responding to network requests:
Reply from 199.1.11.2: bytes=32 time=181ms TTL=248
Reply from 199.1.11.2: bytes=32 time=185ms TTL=248
Reply from 199.1.11.2: bytes=32 time=185ms TTL=248
Reply from 199.1.11.2: bytes=32 time=660ms TTL=248
Ping statistics for 199.1.11.2:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 181ms, Maximum = 660ms, Average = 302ms
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Ping (cont.)
The important aspect of ping is that the program shows if the host is responding to network requests.Minimum, Maximum, and Average round-trip times are reported. Good for diagnosing latency issues.
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Traceroute
Traceroute is one of the other staple tools of a network engineer.Traceroute allows someone to determine where a slowdown (congestion) occurs between his machine and a target host.Windows command: tracertUNIX command: traceroute
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Traceroute (cont.)
C:\WINDOWS\Desktop>tracert 199.1.11.2
Tracing route to ns.onramp.net [199.1.11.2]over a maximum of 30 hops:
1 111 ms 106 ms 105 ms srv6-2-16.ipls.bd.ans.net [207.205.227.128] 2 105 ms 105 ms 110 ms core-ipls1-fe0/0/0.grid.net [207.205.227.252] 3 140 ms 145 ms 135 ms core-wash1-atm4/0.9.grid.net [206.80.190.90] 4 149 ms 150 ms 140 ms f0.iad1.verio.net [192.41.177.196] 5 145 ms 145 ms 150 ms p1-1-0-0.r03.mclnva01.us.bb.verio.net [129.250.2.182] 6 190 ms 185 ms 190 ms p1-0-2.r00.dllstx01.us.bb.verio.net [129.250.2.209] 7 190 ms 190 ms 190 ms ge-1-0-0.a10.dllstx01.us.ra.verio.net [129.250.31.58] 8 190 ms 185 ms 190 ms fa-8-0-0.a09.dllstx01.us.ra.verio.net
[129.250.28.170] 9 185 ms 190 ms 185 ms tun6501601.r00.dllstx01.us.to.verio.net
[157.238.225.206] 10 190 ms 190 ms 190 ms ns.onramp.net [199.1.11.2]
Trace complete.
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Internettrafficreport.com
This site provides a general idea about how Internet traffic flows. Higher numbers are better.
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Some More Graphs
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What Does All of This Mean?
The Internet is a dynamic, routing nightmare where Murphy’s Law is always in effect.The ability to diagnose a problem is half the problem; Getting the right person to fix the problem is the other half.