Verizon BGP Community String

Verizon Business supports a user configurable routing policy by allowing customers to fine tune their routing announcements via the BGP community attribute. The following information outlines the policy and demonstrates how customers can implement the routing policy of their choice.

Verizon Business has multiple ASN within a confederation AS701. Verizon Business maintains multiple autonomous systems with each one providing continental coverage. AS701AS702 provides coverage for Europe, AS703 is for Asia and AS14551 is growing in South America. Routes Verizon Business hears from customers are advertised to all Verizon Business autonomous systems as well as Verizon Business peers.

ASN	Location / Area
701	North America
702	Europe
703	Asia
704	Multicast
705	Dial network
14551	South America

Customers now can set values which modify the BGP community attribute "Local Preference" and "AS Path Length" as well as control which route(s) should be advertised to Verizon Business peers (ISPs). These controls are customer implemented by advertising routes tagged with the appropriate BGP community attribute and when received Verizon Business will act on the BGP community value as shown below.

The attribute "LOCAL_PREF" is used to set a route as "preferred" or "least preferred" over all others. Since BGP selects the route with the highest local preference a route can be made "preferred" by setting the "LOCAL_PREF" value higher than the default value of 100. Also, any route can be made to be "least preferred" by setting the "LOCAL_PREF" value lower than the default value of 100. The "LOCAL_PREF" setting is non-transitive and affects routes only in the AS in which it is set and does not pass to external BGP peers. The table below defines the values and actions for the "LOCAL_PREF" attribute.
Customers may modify the UUNET "LOCAL_PREF" value by tagging their route announcements with ONE of the BGP communities defined below. Each route should be tagged with only one value for "LOCAL_PREF." Once Verizon Business receives this route announcement tagged with the appropriate BGP community string for modifying "LOCAL_PREF", the BGP attribute will be set accordingly. "LOCAL_PREF" is set immediately on the Verizon Business router to which the customer attaches. Please refer to the table below for the BGP community string values that Verizon Business will accept for setting "LOCAL_PREF."

BGP Community String	LocalPref Value	Description
Default	100	Default Value
70x:80	80	Set localpref 80
70x:90	90	Set localpref 90
70x:110	110	Set localpref 110
70x:120	120	Set localpref 120

ex) 701:80, 702:80, 703:80 and so on.

A case may arise where 2 or more paths exist for the same destination with the same "LOCAL_PREF" value. The next configurable option in BGP route selection process is to lengthen the AS PATH. The route with the shortest AS PATH LENGTH is preferred. The table below defines the values and actions for AS PATH LENGTH.

The AS PATH LENGTH is adjusted at the egress or Verizon Business peering points to all peers. The table below defines the community value for setting AS PATH LENGTH and the total path length announced to peers.

BGP Community String	Prepend AS	Description
70x:1	70x	Prepends 70x once on announcements to peers
70x:2	70x 70x	Prepends 70x twice on announcements to peers
70x:3	70x 70x 70x	Prepends 70x thrice on announcements to peers

ex) 701:1 = 701
701:2 = 701 701
701:3 = 701 701 701

This is accomplished by filtering routes based on a BGP community value filtering at Verizon Business's egress points.

BGP Community String	Description
70x:20	Do not send to peers, but send to customers or (701, 702, 703 and 14551)
70x:30	Do not send to continent(701, 702, 703 and 14551), but send customers and peers
70x:70	Do not send to peers or customers, but send to continent(701, 702, 703 and 14551)

Also, Verizon business provide a below BGP community string for security purpose.

BGP Community String	Description
70x:9999	Used by customers to black hole their own routes in the event of an attack. The only constraint is that the customer must be set up for multihop BGP

BGP Community String	Description
70x:20	Do not send to Peers
70x:1020	Do not send to Peers
70x:30	Do not send to continents (701,703, 14551 and etc)
70x:1030	Do not send to continents (701, 703, 14551 and etc)
70x:70	Do not send to peers or customer
70x:1070	Do not send to peers or customer

Additional BGP Community String

Summary of actions that the per-peer-community knob supports

1. Do not Announce to specified AS
2. Prepend one time
3. Prepend two times
4. Prepend three times
5. Prepend four times
6. Announce to specified AS

** The maximum recommended number of per-peer-communities that a customer should set is 20.

The per-peer BGP communities will have the following format: 64XXY:ASN

XX value Actions

1. 90: Don't send to particular AS
2. 91: Prepend 1 time to particular AS
3. 92: Prepend 2 times to particular AS
4. 93: Prepend 3 times to particular AS
5. 94: Prepend 4 times to particular AS
6. 99: send to a particular AS

Y value Actions to apply area

1. 0 Global
2. 1 North America(AS701) within VZB
3. 2 Europe(AS702) within VZB
4. 3 Asiapac(AS703) within VZB
5. 4 Latin(AS14551) within VZB

Order of operation

1. Existing "don't send to peer/AS" and regional / continental specific routes communities
2. Per-peer-communities: Continental "don't send" communities
3. Per-peer-communities: Continental "send w/o modification" communities
4. Per-peer-communities: Continental "pre-pend" communities
5. Per-peer-communities: Global "don't send" communities
6. Per-peer-communities: Global "send w/o modification" communities
7. Per-peer-communities: Global "pre-pend" communities
8. Existing "don't send" to peers, "don't send" to peers+customers communities
9. Existing continental "pre-pend" to peers communities
10. Existing global "pre-pend" to peers communities

ex) If customer send a route with communities string 701:70 and 64911:1239:

The route will pre-pend AS701 once when going to Sprint, but this route announcement won't go to any other peers/Peers or Customers

community AS1239-NA-dont-send members "^64901:1239$"; Sprint
community AS1668-NA-dont-send members "^64901:1668$"; AOL
community AS174-NA-dont-send members "^64901:174$"; COGENT
community AS209-NA-dont-send members "^64901:209$"; Qwest
community AS2914-NA-dont-send members "^64901:2914$"; NTT Ameria
community AS3356-NA-dont-send members "^64901:3356$"; Level 3
community AS3549-NA-dont-send members "^64901:3549$"; Global Crossing
community AS3561-NA-dont-send members "^64901:3561$"; Savvis
community AS6453-NA-dont-send members "^64901:6453$"; Teleglobe
community AS6461-NA-dont-send members "^64901:6461$"; AboveNet
community AS7018-NA-dont-send members "^64901:7018$"; ATT