An Introduction to the World of Commercial Peering at the National Level Dave McGaugh Network Architecture, PNWGP Quilt Peering Workshop - 10/Oct/2006 St Louis, MO

My Background Up until 2002, worked at a large Tier-2 network service provider with a national IP backbone Peering coordination and engineering, participating at 11 exchange points around the country, with ~75 peers and ~225 peering sessions, with “selective peering policy” Nearly transit-free at high point, missing only two networks (AS1239 and AS3561)

Methods of Interconnect: Public Participants connect to a shared infrastructure Most commercial exchanges make use of a shared VLAN model with ability to obtain private VLANs Peering sessions are negotiated bilaterally No incremental costs to add peers New sessions can be quickly established

Methods for Interconnect: Private Commonly referred to as Private Network Interconnects (PNI) Physical point-to-point circuit is obtained between the peering networks  FastE though Nx10g Transit-free networks use this method exclusively for peering between themselves Typically Require certain amounts of traffic exchange with minimum interconnect sizes

Motivations Cost Savings  Direct reduction in transit fees Performance  Less intermediate networks Operational  Less intermediate NOCs Transit-free  See: “Cost Savings”

Cost Savings Exchange point participation or carrier meet point locations have fixed costs (can vary greatly) Every bit moved off of transit links equates to a cost savings to the peering network (assuming the fixed costs above are not above the per-megabit costs of transit) As with all fixed cost traffic drains, more traffic equals greater cost savings, i.e. per mbps costs decrease What happens when adding another peer does not move traffic off of transit links? I.e. the potential peer is already reachable via a settlement-free peering

Performance Intermediate networks may make poor capacity planning decisions  Direct peering networks may be able to route around known congested paths Intermediate networks may take suboptimal, highly latent paths  In some cases this may be due to an administrative decision by the intermediate

Operational Peering establishes a business and technical relationship between two networks During security anomalies (e.g. DOS attacks), dealing with intermediate NOCs can be painful at best, and impossible at worst Troubleshooting performance problems can be more expedient and yield better results when working directly with the other network

Transit-free Some networks have an eventual goal of becoming transit-free  This means they have established peering relationships with all other transit free networks and they can reach the entire global routing table though peering connections While this is likely an attractive notion for all peering networks, facts are that few are actively pursuing it in this day and age  Today, Transit-free is easier purchased than built

Non Transit-free Networks Large network service providers and large content networks are usually successful at “peering off” up to ~75% of their backbone traffic A well represented network (participating at multiple peering locations) can typically, quite easily peer off ~50% of their traffic

Peering Policies Types:  Open: Will peer with anyone, anywhere, anytime  Selective: Will peer when it makes sense to do so, either based on a published peering policy, review by an internal peering committee, or both  Closed: “No thanks, we have all the peers we need, we only publish a peering policy because the FCC makes us”

Motivations of Open Peering Any bit that can be offloaded is likely a cost savings Any direct peering is better than a more indirect path Peering network may not be in the business of trying to sell transit

Motivations of Selective Peering Additional peer should not appreciably increase support burden Should have diverse peering locations for load distribution and fault tolerance Additional peer should not erode traffic volumes with current, strategic peer(s) Peering connection should not worsen performance

Motivations for Closed Peering For transit free networks, by definition, adding additional peering networks on top of what they already have will not decrease transit costs Performance is not likely to be better than their Nx10Gbps connections with the pursuing peer’s transit provider Any peering is an unnecessary additional support burden

Examples of Selective or Closed Peering Policies Require Multiple peering locations across multiple geographic regions Require specific sized backbone between peering locations Require in/out traffic ratios (e.g. not to exceed 1.5:1, or 2:1) Require Asian and/or European presence Require consistent route announcements at all locations

Published Peering Policies at&t  Verizon Business  RCN  AboveNet  Time Warner Telecom 

Establishing Peering - Self Initiated You contact target peer either via or telephone You are evaluated per peer’s requirements (if any exist)  Often netflow data is used to estimate traffic volumes Peering type and location(s) are negotiated Peering contract and NDA are put in place (if req’d) Peering is established

Establishing Peering - Peer Initiated Potential peer contacts you via or telephone Potential peer is evaluated against your peering requirements (if you have any)  You may use netflow data to estimate traffic volumes if important Peering type and location(s) are negotiated Peering contract and NDA are put in place (if req’d) Peering is established

A Few Characteristics Peers do not typically prefix or AS path filter one another  Primarily due to scaling concerns  Instead use max-prefix (typically 2x normal received prefixes) While peers do not filter each other, they often still require valid IRR registrations Many require LSRR be enabled on peering routers, or maintain a publicly accessible looking glass Closest exit routing is used almost exclusively, and many strip MEDs at the border

A Few Words About Strategy Some are more or less ethical than others… Reroute traffic to more expensive paths for the potential peer Peer around the potential peer Find ways to increase traffic exchange between yourself and the potential peer

Comments / Questions?