^ Top

NANOG Meeting Presentation Abstract

Experiences with Large-scale Network Consolidation (Or, How I Spent My Summer Vacation)
Meeting: NANOG27
Date / Time: 2003-02-10 9:45am - 10:15am
Room: Anasazi Ballroom
Presenters: Speakers:
Dave Israel, Allegiance Telecom.

William Charnock, Allegiance Telecom

William Charnock has been with Allegiance Telecom for 3 1/2 years. Originally hired as the senior backbone engineer and tasked with building Allegiance\'s nationwide IP network, he is currently the Director of Data Engineering and is responsible for IP network architecture. Prior to joining Allegiance Telecom, he was the CTO of FastLane Communications, a regional ISP in the Dallas/Fort Worth metroplex.
Abstract: At the beginning of 2002, Allegiance Telecom acquired the AS2548 backbone from WorldCom. AS2548, once Digex, then Intermedia Business Internet, was at that time a nationwide OC-48 backbone running Cisco hardware. Simultaniously, Allegiance had built a brand new OC-48 nationwide backbone of their own to replace their aging DS3 IP network (AS11466.) The new network, with a Juniper core, was built independently of the old backbone, which was running a mix of vendors, but, like AS2548, was predominantly Cisco.

Historically, acquired networks have been left alone in large mergers such as this one, because merging networks is difficult. But maintaining two separate Autonomous Systems would double the maintenance workload and split the product set in two. Thus, Allegiance was faced with combining three networks, two with active traffic, into one. To make matters more complicated, it was decided that the existing policy on either network was not sufficient for the new, combined network. So a new routing policy, capable of supporting all the existing customers on the old networks, would need to be implemented as part of the merger.

Careful planning was the main requirement for success. With over 500 routers to modify, there was very little space for error. Configurations were tested in the lab, a script was written to translate from old configurations to new ones, test runs were made, and plans were probed for holes. The network was divided between 8 techs over two nights, one for AS2548, one for AS11466. On each night, the new policy would be pushed out, and the logical connections to the Juniper core activated.

While AS2548 had more routers, AS11466 was actually undergoing an ASN change, and the difference in policy was greater, so the work load was relatively even. Back-out points were defined, and staff assigned to clean up issues as they arose. Still, there were problems, mainly because of the scale of the new, combined network. A lot of tough lessons were learned, but in the end the merger was a success.
Files: youtubeExperiences with Large-scale Network Consolidation (Or, How I Spent My Summer Vacation)
pdfWilliam Charnock Presentation(PDF)
Sponsors: None.

Back to NANOG27 agenda.

NANOG27 Abstracts

  • The Spread of the Sapphire/Slammer Worm
    Speakers:
    David MooreCAIDA & UCSD CSE; .
    Vern PaxsonICIR & LBNL; .
    Stefan SavageUCSD CSE; .
    Colleen ShannonCAIDA; .
    Stuart StanifordSilicon Defense; .
    Nicholas WeaverSilicon Defense & UC Berkeley EECS; .
  • The Spread of the Sapphire/Slammer Worm
    Speakers:
    David MooreCAIDA & UCSD CSE; .
    Vern PaxsonICIR & LBNL; .
    Stefan SavageUCSD CSE; .
    Colleen ShannonCAIDA; .
    Stuart StanifordSilicon Defense; .
    Nicholas WeaverSilicon Defense & UC Berkeley EECS; .
  • The Spread of the Sapphire/Slammer Worm
    Speakers:
    David MooreCAIDA & UCSD CSE; .
    Vern PaxsonICIR & LBNL; .
    Stefan SavageUCSD CSE; .
    Colleen ShannonCAIDA; .
    Stuart StanifordSilicon Defense; .
    Nicholas WeaverSilicon Defense & UC Berkeley EECS; .
  • The Spread of the Sapphire/Slammer Worm
    Speakers:
    David MooreCAIDA & UCSD CSE; .
    Vern PaxsonICIR & LBNL; .
    Stefan SavageUCSD CSE; .
    Colleen ShannonCAIDA; .
    Stuart StanifordSilicon Defense; .
    Nicholas WeaverSilicon Defense & UC Berkeley EECS; .
  • The Spread of the Sapphire/Slammer Worm
    Speakers:
    David MooreCAIDA & UCSD CSE; .
    Vern PaxsonICIR & LBNL; .
    Stefan SavageUCSD CSE; .
    Colleen ShannonCAIDA; .
    Stuart StanifordSilicon Defense; .
    Nicholas WeaverSilicon Defense & UC Berkeley EECS; .
  • The Spread of the Sapphire/Slammer Worm
    Speakers:
    David MooreCAIDA & UCSD CSE; .
    Vern PaxsonICIR & LBNL; .
    Stefan SavageUCSD CSE; .
    Colleen ShannonCAIDA; .
    Stuart StanifordSilicon Defense; .
    Nicholas WeaverSilicon Defense & UC Berkeley EECS; .

 

^ Back to Top