An An IIntroduction to the World of Commercial ntroduction to the World of Commercial Peering at the National LevelPeering at the National Level

Dave McGaugh

Network Architecture, PNWGP

Quilt Peering Workshop - 10/Oct/2006

St Louis, MO

My BackgroundMy 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: Methods of Interconnect: PublicPublic

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: Methods for Interconnect: PrivatePrivate

Commonly referred to as Private Network Interconnects (PNI)

Physical point-to-point circuit is obtained between the peering networksFastE though Nx10g

Transit-free networks use this method exclusively for peering between themselves

Typically Require certain amounts of traffic exchange with minimum interconnect sizes

MotivationsMotivations

Cost SavingsDirect reduction in transit fees

PerformanceLess intermediate networks

OperationalLess intermediate NOCs

Transit-freeSee: <big> “Cost Savings”

Cost SavingsCost 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

PerformancePerformance

Intermediate networks may make poor capacity planning decisionsDirect peering networks may be able to route

around known congested paths

Intermediate networks may take suboptimal, highly latent pathsIn some cases this may be due to an

administrative decision by the intermediate

OperationalOperational

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-freeTransit-free

Some networks have an eventual goal of becoming transit-freeThis 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 ageToday, Transit-free is easier purchased than built

Non Transit-free NetworksNon 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 PoliciesPeering Policies

Types:Open: Will peer with anyone, anywhere, anytimeSelective: 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 PeeringMotivations 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 Motivations of Selective PeeringPeering

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 PeeringMotivations 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

<Insert World Domination Theory Here>

Examples of Selective or Examples of Selective or Closed Peering PoliciesClosed 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 PoliciesPublished Peering Policies

at&t http://www.att.com/peering/

Verizon Business http://www.verizonbusiness.com/uunet/peering/

RCN http://ptd.mbo.ma.rcn.net/peer-policy/

AboveNet http://www.above.net/peering/

Time Warner Telecom http://info.twtelecom.net/info.php?id=31

Establishing Peering - Self Establishing Peering - Self InitiatedInitiated

You contact target peer either via e-mail 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 Establishing Peering - Peer InitiatedInitiated

Potential peer contacts you via e-mail 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 CharacteristicsA 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 StrategyA 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?Comments / Questions?

dmcgaugh@pnw-gigapop.net