ECE498 Introduction to Network Engineering Professor Bruce Segee Fall 2000

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.

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.

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.

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.

The Mess

Internet Growth

Why is the Internet Growing?

Common Network Problems Latency Packet loss Routing problems Too many “hops” Lack of peering (public or private)

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.

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.

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

Ping Ping is the most common way of determining if a host is “alive.” C:\WINDOWS\Desktop>ping Pinging with 32 bytes of data: A couple things can happen at this point…

Ping (cont.) Routing is wrong: Destination host unreachable. Ping statistics for : Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms

Ping (cont.) The host may be unresponsive: Request timed out. Ping statistics for : Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms

Ping (cont.) Or it may be up and responding to network requests: Reply from : bytes=32 time=181ms TTL=248 Reply from : bytes=32 time=185ms TTL=248 Reply from : bytes=32 time=660ms TTL=248 Ping statistics for : Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 181ms, Maximum = 660ms, Average = 302ms

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.

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: tracert UNIX command: traceroute

Traceroute (cont.) C:\WINDOWS\Desktop>tracert Tracing route to ns.onramp.net [ ] over a maximum of 30 hops: ms 106 ms 105 ms srv ipls.bd.ans.net [ ] ms 105 ms 110 ms core-ipls1-fe0/0/0.grid.net [ ] ms 145 ms 135 ms core-wash1-atm4/0.9.grid.net [ ] ms 150 ms 140 ms f0.iad1.verio.net [ ] ms 145 ms 150 ms p r03.mclnva01.us.bb.verio.net [ ] ms 185 ms 190 ms p1-0-2.r00.dllstx01.us.bb.verio.net [ ] ms 190 ms 190 ms ge a10.dllstx01.us.ra.verio.net [ ] ms 185 ms 190 ms fa a09.dllstx01.us.ra.verio.net [ ] ms 190 ms 185 ms tun r00.dllstx01.us.to.verio.net [ ] ms 190 ms 190 ms ns.onramp.net [ ] Trace complete.

Internettrafficreport.com This site provides a general idea about how Internet traffic flows. Higher numbers are better.

Some More Graphs

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.