T1: A Survival Guide

Trading Packets

In many cases, the ISP network engineers assigned to completing circuit turn-up are the best engineers you will have an opportunity to work with directly. (More talented engineers do exist, but they’re at work designing the ISP’s next-generation network architecture or maintaining the important peering connections in the current network.)

When the call comes, the ISP’s engineer usually starts off by discussing the configuration to make sure both of you are reading from the same sheet of music. Do not be surprised if he asks some simple questions—remember that turn-up staff deals with anybody who orders a new circuit, not just those who are fully prepared.

Both of you will bring up the link layer software on your respective routers, and it will attempt to negotiate. Assuming the link layer comes up, you should be able to send traffic out to the world. Do not be surprised if traffic does not come back at first. Many of the larger ISPs have such large networks that they must extend their routing protocol timers to much longer intervals than the defaults. It may take a few minutes to advertise and establish routes to your circuit. When the ISP engineer advises you that everything should be working, send a few ping packets—first out to destinations within the ISP’s network, then out to destinations on other ISP networks. Unless you are using Network Address Translation (NAT), initiate these connections from behind the router so the source IP addresses are in the ...