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NANOG Meeting Presentation Abstract

IPv6 and Path MTU problems in AnyCast networks
Meeting: NANOG60
Date / Time: 2014-02-12 12:00pm - 12:30pm
This item is webcast
Room: Peachtree Ballroom
Presenters: Speakers:

Hossein Lotfi, Verizon EdgeCast

Hossein Lotfi runs Performance Engineering team at Verizon EdgeCast. he spends most of his time working on ideas to make the CDN faster. Hossein has more than fourteen years of experience in various systems and network engineering roles and has a full-stack-investigation approach when dealing with complex challenges.
Abstract: The global protocol switch from IPv4 to IPv6 was a momentous occasion, and the culmination of work from around the world to address a rapidly serious problem.
But as many technology professionals quickly found out, IPv6 is still in its nascent stages; engineers are learning on-the-go IPv6 works not quite as optimally as the old system, creating communication breakdowns and affecting performance when it matters most.
In preparations for IPv6 day, EdgeCast identified it’s own IPv6 difficulties while troubleshooting content delivery problems related to one of its largest customers. During initial troubleshooting, engineers were able to narrow the problem down to clients who were accessing the images through IPv6, and relied upon 6rd Rapid Deployment tunnels to provide their access to v6 internet.
Due to the still-dominant usage of IPv4 on the Internet, reaching IPv6 servers often requires encapsulation of IPv6 packets within IPv4, also known as tunneling. As a result, such IPv6 packets can no longer make use of the most common 1500 byte packet sizes, necessitating IPv6 users to pre-negotiate smaller sizes accounting for these tunneling header overheads, or senders of packets which are too large must receive ICMPv6 PMTU indications to dynamically adjust. For CDNs with the complications of load balancing, addressing, and a variety of routing topologies, it may not always be possible for a tunnel broker to send such ICMPv6 packets to the right sender or for the sending server to receive these indications. Subsequently a flow could fail due to timeouts, fruitlessly retransmitting packets that are too large for the tunnel encapsulations.
This presentation covers IPv6 Path MTU problems due to the client connection via tunneling mechanisms, while also exploring how EdgeCast detected those problems by using RIPE Atlas probes, detailed packet flow investigation and how mechanisms were implemented to make sure they no longer cause problems.
This presentation will answer the following questions:
-What tools did we use to monitor our network prior to IPv6 Launch
-How was the original problem detected (Examples of detailed packet flow investigation will be explored)
-What was the role of load balancing and complex routing techniques in causing PMTU problems?
-What are best practices for packet transmission without fragmentation problems?
Files: pdf IPv6 and Path MTU problems in AnyCast networks(PDF)
youtube IPv6 and Path MTU problems in AnyCast networks
Sponsors: None.

Back to NANOG60 agenda.

NANOG60 Abstracts

  • Datacenter Track
    Martin Hannigan, Akamai Technologies, Inc.; Daniel Golding, Iron Mountain;
  • Datacenter Track
    Martin Hannigan, Akamai Technologies, Inc.; Daniel Golding, Iron Mountain;
  • BGP 101
    Dawit Birhanu, Cisco Systems;
  • BGP 102
    Dawit Birhanu, Cisco Systems;


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