Internet DRAFT - draft-nalawade-idr-mdt-safi
draft-nalawade-idr-mdt-safi
Network Working Group Gargi Nalawade
Internet Draft Arjun Sreekantiah
Expires: April 2006 Cisco Systems
MDT SAFI
draft-nalawade-idr-mdt-safi-03.txt
1. Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
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2. Copyright Notice
Copyright (C) The Internet Society (2005). All Rights Reserved.
3. Abstract
There is a need for transporting Multicast Tunnel attributes within
and across Autonomous Systems. This draft defines a new Address-
Family that can be used to do the distribution.
4. Introduction
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Internet Draft draft-nalawade-idr-mdt-safi-03.txt July 2005
Two end-points of a Multicast Tunnel need to know the end-point
information and its binding to a network address and the Multicast
Tunnel used for the respective VRF at the remote PE. Normally, Tunnel
endpoint addresses can be statically configured. But in case of a
large network with large number of VPNs where there may be a need for
a large number of endpoints and a large number of VRFs, the amount of
information that needs to be exchanged and maintained between PEs for
Multicast Tunnels for VPNs, is quite large. It therefore needs a
mechanism that can maintain and support Multicast Tunnel based VPNs
in a flexible, scalable manner. Also, in inter-AS and inter- provider
scenarios, this mechanism needs to be supported across autonomous
systems and provider domains.
5. The MDT SAFI
A new Subsequent-Address Family called the MDT SAFI is being defined.
The NLRI for this SAFI, will contain the address of the nexthop which
will be used by the multicast source PE to send the PIM Join for the
default MDT address to.
The NLRI format is 8-byte-RD:IPv4-address followed by the MDT group
address. i.e. The MP_REACH attribute for this SAFI will contain one
or more tuples of the following form :
+------------------------------+
| |
| RD:IPv4-address (12 octets) |
| |
+-------------------------------+
| MDT Group-address (4 octets) |
+-------------------------------+
where :
Route-Distinguisher : is the RD of the VRF to which this MDT
attribute belongs.
MDT Group Address : is the Group-address of the MDT-Group that a VRF
is associated to. This can be variable length. But for
IPV4 addresses - this will be 4 octets.
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6. The Connector Attribute
An Optional Transitive Connector attribute [BGP-CONN] will be used to
transport the address of the originating PE router unchanged to the
remote PE router which is participating in the same MVPN.
The format of this attribute is a 2-octet Type field followed by the
Value. Type 1 of this attribute defines that this is an IPv4 unicast
nexthop set by the PE which advertises the CE-learnt prefixes to its
peers.
The attribute contains one or more tuples of the form :
+------------------------------+
| |
| Type (2 octets) |
+------------------------------+
| |
| Value (Variable) |
| |
+------------------------------+
where :
Type : is the Type of the data contained in this TLV.
Value : is a variable length field as defined by the Type.
When the Type is 1, the value will contain the IPv4 address of the PE
sourcing the CE-learnt VPNv4 prefixes. This would be the same address
this PE uses to set itself as the nexthop. This attribute will
accompany the VPNv4 prefix advertisement.
7. Capability Advertisement
A BGP speaker that wishes to exchange the MDT SAFI, MUST use the
MP_EXT Capability Code as defined in [BGP-MP], to advertise the
corresponding (AFI, SAFI) pair.
A BGP speaker MAY participate in the distribution of MDT information.
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8. Operation
A BGP Speaker that receives the Capability for the MDT SAFI, MAY
advertise the MDT SAFI prefixes to that peer. The prefixes in the MDT
SAFI are populated by the PEs that advertise their CE-learnt
prefixes.
9. Applicability Statement
Multicast Tunnels are built between Provider Edge (PE) routers to
allow multicast communication between different site's of a VPN. The
MT tunnel has a destination MDT group address that is unique to the
VPN. All routers that act as PE's and are configured for a specific
VPN join the VPN MDT multicast group in the backbone of the provider
network to be able to receive each others packets. Each router is
also a sender to the MDT group. In PIM SSM mode, the following
procedure is followed.
A Multicast tunnel is setup between the PEs in one or more VPN-
Providers networks. Over the Multicast tunnel we create PIM
neighbor's. The IP address of the PIM neighbor that is seen over the
Multicast tunnel depends on the configured address of the Tunnel
endpoint. This can either be an unnumbered address from a different
interface or a configured address on the Tunnel itself. The PE router
that does an RPF check on a VPN source can find which Tunnel the
source is on, but may not know what PIM neighbor to target on that
tunnel. Therefore we need a way to connect the BGP VPNv4 prefix to
the PIM neighbor on the tunnel to allow the RPF check to succeed.
Suppose we want to join to a source that is behind another VPN site.
We do an RPF lookup on the source address in the VPNv4 unicast table
on this PE. The RPF lookup will return a connected next-hop and
interface to use to reach the source. The returned next-hop may not
be the neighbor on the Multicast tunnel. This can be due to the
next-hop being rewritten by BGP Route Reflectors (RR) or crossing
AS's. Therefore we don't know which PIM neighbor to target as
upstream neighbor in the PIM join.
defines a new attribute called the BGP Connector attribute. This We
propose sending the Originating PE's IP address through the BGP
Connector Attribute. It will be sent as the value field when the BGP
Connector attribute contains Type 1. This is the Multicast Tunnel's
IP address which is used to establish the PIM neighbor relationship
on the Multicast tunnel. This attribute is attached to all the BGP
VPNv4 prefixes used for reaching to multicast sources in the
Customer's network. The PE router that was able to successfully RPF
on a BGP VPNv4 prefix will use the IP address learned from the
connected attribute to find the PIM neighbor on the Multicast tunnel.
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10. Security Considerations
This extension to BGP does not change the underlying security issues.
11. Acknowledgements
The authors would like to thank IJsbrand Wijnands for his contr-
ibution towards the Connector Attribute needed for the IPv4-MDT SAFI.
The authors would also like to thank Shyam Suri, Ruchi Kapoor, Shyam
Suri, Yiqun Cai, Dan Tappan, Jennifer Li, Yi Chou, Arjen Boers for
their comments and contributions. We would also like to thank Bhavani
Parise for his review and comments.
12. Normative References
[BGP-4] Rekhter, Y. and T. Li (editors), "A Border Gateway Protocol
4 (BGP-4)", Internet Draft draft-ietf-idr-bgp4-26.txt, April 2005.
[BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with
BGP-4", draft-ietf-idr-rfc2842bis-02.txt, April 2002.
[BGP-SSA] Kapoor R., Nalawade G., “BGPv4 SAFI-Specific Attribute”,
draft-nalawade-kapoor-bgp-ssa-00.txt, January 2006.
[MULTI-BGP] Bates et al, Multiprotocol Extensions for BGP-4, draft-
ietf-idr-rfc2858bis-02.txt, work in progress.
[BGP-CONN] Nalawade Gargi, Kapoor Ruchi "BGPv4 Connector Attribute",
OCT-05, <draft-nalawade-bgp-connector-00.txt>, work in progress.
13. Author's Addresses
Gargi Nalawade
170 Tasman Drive
San Jose, CA, 95134
E-mail: gargi@cisco.com
Arjun Sreekantiah
170 Tasman Drive
San Jose, CA, 95134
E-mail: asreekan@cisco.com
14. Intellectual Property Statement
Cisco Systems may seek patent or other intellectual property
protection for some of all of the technologies disclosed in this
document. If any standards arising from this document are or become
protected by one or more patents assigned to Cisco Systems, Cisco
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intends to disclose those patents and license them on reasonable
and non-discriminatory terms.
15. Full Copyright Statement
Copyright (C) The Internet Society (2005). All Rights Reserved.
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
16. Expiration Date
This memo is filed as <draft-nalawade-idr-mdt-safi-03.txt>, and
expires April, 2006.
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