Routing Info

• BGP customer communities
• BGP IPv4 peer filter policy
• BGP IPv6 peer filter policy
• Verio Routing Registry (VRR)
• Route Dampening

Community	Local-pref	Description
Verio BGP customers may choose to affect our local preference on their routes by marking their routes with the following communities:
(default)	120	customer
2914:490	120	customer default
2914:480	110	customer backup
2914:470	100	peer
2914:460	98	peer backup
2914:450	96	customer fallback
Verio BGP customers may choose to prepend to all Verio peers with the following communities:
2914:429		do not advertise to any peer
2914:423		prepends o/b to peer 3x
2914:422		prepends o/b to peer 2x
2914:421		prepends o/b to peer 1x
Verio BGP customers may choose to prepend to all other Verio BGP customers with the following communities:
2914:413		prepends o/b to customer 3x
2914:412		prepends o/b to customer 2x
2914:411		prepends o/b to customer 1x
Verio BGP customers may choose to prepend to selected tier 1 peers with the following communities, where nnn is the tier 1 peer's ASN.
65500:nnn		do not announce to tier 1 peer
65501:nnn		prepend o/b to tier 1 peer 1x
65502:nnn		prepend o/b to tier 1 peer 2x
65503:nnn		prepend o/b to tier 1 peer 3x

Note:2914 is the ASN prepended in all cases.

Verio sends routes to customers marked with the following communities.

Community	Interpretation
2914:410	Verio and customer routes
2914:420	Peer routes
2914:20--	North American country origins
2914:2000	US
2914:22--	European country origins
2914:2201	uk
2914:2202	de
2914:2203	nl
2914:2204	fr
2914:2205	es (Spain)
2914:24--	Asian country origins
2914:2401	jp
2914:2402	au
2914:2403	hk
2914:2404	tw
2914:2405	kr
2914:2406	sg
2914:2407	my
2914:3---	world region origins
2914:3000	North America
2914:3200	Europe
2914:3400	Asia

BGP IPv4 peer filter policy The following is Verio's filtering policy with its peers:

inbound:

• Verio accepts only those prefixes of length /24 and shorter from traditional class A, B, and C space.
• Verio uses max-prefix filters at most public exchanges. The max-prefix filter is set to 110% of the greater of the following values:
  • number of prefixes announced in the last 24 hours
  • number of prefixes registered in the routing registries under the peer's as-set if this number is less than 5000.

outbound:

• Verio will accept any properly registered prefix from our customers but will announce only /24 and shorter prefixes to our peers.
• All Verio's announcements are registered in one of the routing registries and included under as-set AS-VERIO.

Verio reserves the right to modify this policy without prior notice.

BGP IPv6 peer filter policy

inbound:

• Verio accepts /19 through /32, and /35 from 2001::/16 (global unicast allocations)
• Verio accepts /19 through /32 from 2003::/16 (RIPE allocations)
• Verio accepts /24 from 3ffe::/18, /32 from 3ffe:4000::/18, and /28 from 3ffe:8000::/20 (6bone allocations; until 6/6/2006 per rfc3701)
• Verio accepts 2002::/16 (6to4 prefix)

outbound:

• Verio will announce /48 and shorter prefixes to our peers.

Verio reserves the right to modify this policy without prior notice.

Verio Routing Registry

altdb apnic arcstar bell enterzone gt host level3 radb rgnet ripe savvis sinet

Route Dampening

Route dampening is a BGP feature designed to minimize the propagation of flapping routes across an internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable, then available, then unavailable, and so on.

The Route Dampening Process:

The route dampening feature minimizes the flapping problem as follows.

Suppose a route in network A flaps. A route that is flapping receives a penalty of 1000 for each flap and moves it to "history" state. When the route flaps so often that the penalty exceeds a configurable suppress limit, the router stops advertising the route, regardless of how many times it flaps. Thus, the route is dampened.

The accumulated penalty is decremented by the half-life time. When the accumulated penalty is less than the reuse limit, the dampening information for the route is removed and the route is advertised again.

Verio sets different dampening parameters for different sizes of address blocks across the network.

a) For /24 and longer prefixes: max=min outage 60 minutes half-life = 30 Maximum suppress limit = 60 Reuse limit = 820 Suppress limit = 3000

b) for /22 and /23 prefixes: max outage 45 minutes but potential for less because of shorter half life value - minimum of 30 minutes outage Half-life = 15 Maximum suppress limit = 45 Reuse limit = 750 Suppress limit = 3000

c) all else prefixes: max outage 30 minutes min outage 10 minutes Half-life = 10 Maximum suppress limit = 30 Reuse limit = 1500 Suppress limit = 3000

Understanding Route Dampening Terms:

The following terms are used when describing route dampening:

• Flap - A route is available, then unavailable, or vice versa.

• History state - After a route flaps once, it is assigned a penalty and put into "history state," meaning the router does not have the best path, based on historical information.

• Penalty - Each time a route flaps, the router configured for route dampening in another AS assigns the route a penalty of 1000. Penalties are cumulative. The penalty for the route is stored in the BGP routing table until the penalty exceeds the suppress limit. At that point, the route state changes from "history" to "damp."

• Damp state - In this state, the route has flapped so often that the router will not advertise this route to BGP neighbors.

• Suppress limit - A route is suppressed when its penalty exceeds this limit. The default value is 2000.

• Half-life - Once the route has been assigned a penalty, the penalty is decreased by half after the half-life period (which is 15 minutes by default). The process of reducing the penalty happens every 5 seconds.

• Reuse limit - As the penalty for a flapping route decreases and falls below this reuse limit, the route is unsuppressed. That is, the route is added back to the BGP table and once again used for forwarding. The default reuse limit is 750. The process of unsuppressing routes occurs at 10-second increments. Every 10 seconds, the router finds out which routes are now unsuppressed and advertises them to the world.

• Maximum suppress limit - This value is the maximum amount of time a route can be suppressed. The default value is 4 times the half-life.

The routes external to an AS learned via IBGP are not dampened. This policy prevent the IBGP peers from having a higher penalty for routes external to the AS.