BGPv4 SAFI-Specific Attribute draft-kapoor-nalawade-idr-bgp-ssa-00.txt

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BGPv4 SAFI-Specific Attributedraft-kapoor-nalawad
e-idr-bgp-ssa-00.txt

• Ruchi Kapoor ruchi_at_cisco.com
• Gargi Nalawade gargi_at_cisco.com
• Chandrashekhar Appanna achandra_at_cisco.com

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Problem description

• Tunnel configuration O(N2)
• Need a dynamic mechanism of exchanging Tunnel
  endpoint information, inter and intra-AS
• For a BGP-learnt route, Tunnel endpoint has
  one-to-one correspondence with the BGP next hop
• Traffic to that destination can be
  Tunnel-switched or IP-switched

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The Solution

• A New SAFI to advertise the Tunnel endpoint
  information
• A New attribute to encode TLVs of Tunnel
  Encapsulation Capabilities

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BGPv4 SAFI-Specific Attributedraft-kapoor-nalawad
e-idr-bgp-ssa-00.txt

• Ruchi Kapoor ruchi_at_cisco.com
• Gargi Nalawade gargi_at_cisco.com
• Chandrashekhar Appanna achandra_at_cisco.com

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The SAFI-Specific Attribute (SSA)

• Today the Tunnel application needs a BGP
  Attribute that can encode a set of TLVs and
  sub-TLVs inside it
• The need for a simple and flexible encoding for
  carrying a TLV-set exists
• The SAFI-Specific Attribute gives the ability to
  encode such TLV-sets on an as-needed basis.

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The SSA Encoding

• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6
  7 8 9 0 1 2 3 4 5
• ---------------------
  -----------
• 110?UNUSED Type TBD Length (2
  Octets)
• -----------------------
  ---------
• 
  
• Attribute Value
  
• 
  
• -----------------------
  ---------

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The SSA Value field

• The Value field contains a set of one or more
  TLVs of the following form
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
  3 4 5 6 7 8 9 0 1
• -----------------------
  ---------
• T Type Length
  
• -----------------------
  ---------
• Value
  
• -----------------------
  ---------
• The Value will contain a set of Fixed fields
• May contain optional Sub-TLVs after the fixed
  Value

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The TLV Type-codes

• A SAFI that wants to use this attribute will have
  to specify the Type-codes it recognizes
• The Type of the TLV will be a global space
  irrespective of what SAFI or application defines
  it

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Operational details

• The attribute defined as Optional Transitive
• No Capability defined for this attribute
• For new SAFIs that want to use this, presence of
  the SAFI indicates understanding of the attribute
• Forward compatibility
• Experimental Typecode space
• Open for suggestion on a better name

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The Tunnel SAFIdraft-nalawade-kapoor-tunnel-safi-
00.txt

• Gargi Nalawade gargi_at_cisco.com
• Ruchi Kapoor ruchi_at_cisco.com
• Dan Tappan tappan_at_cisco.com

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The Tunnel SAFI

• The Tunnel endpoint address will be the NLRI in
  this SAFI
• The Tunnel Encapsulation Capabilities will be
  carried in the BGPv4 SAFI-Specific Attribute in
  the form of a set of one or more TLVs

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The Tunnel SAFI NLRI

• The NLRI for the IPv4 Tunnel SAFI will be a
  2-octet Reserved field followed by the IPv4
  address of the Tunnel endpoint
• The Reserved field to contain a 2-octet
  Identifier that identifies
• a Tunnel and
• a set of Prefixes that want to use the Tunnel

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The Tunnel SAFI NLRI (contd.)

• The NLRI containing the Tunnel endpoint address,
  expected to do the binding between a set of BGP
  routes in other SAFIs and the Tunnel
  Encapsulation information carried by this SAFI
• The 2-octet Identifier could be carried as
• Part of the Nexthop using MP Nexthop
• Part of the SNPA in the Nexthop
• Part of a community

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TLV Type-code definitions

• This SAFI defines the following Typecodes for the
  Tunnel Encapsulation Capabilities
• Type 1 L2TPv3 Tunnel information
• Type 2 mGRE Tunnel information
• Type 3 IPSec Tunnel information
• Type 4 MPLS Tunnel information

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L2TPv3 Tunnel TLV

• The L2TPv3 Tunnel TLV looks as follows
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
• ----------------
• Type 0x01
• ----------------
• Length (2 octets)
• ----------------
• Preference (2 octets)
• ----------------
• S Flags Cookie Length
• ----------------
• Session ID (4 Octets)
• ----------------
• Cookie (Variable)
• ----------------

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L2TPv3 Tunnel TLV (contd.)

• The fixed fields defined in the TLV can be
  followed by one or more sub-TLVs of the form
• 0 1
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
• ----------------
• Sub-Type Length
• ----------------
• Value (Variable)
• ----------------

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mGRE Tunnel TLV

• The mGRE Tunnel TLV looks as follows
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
• ----------------
• Type 0x02
• ----------------
• Length (2 octets)
• ----------------
• Preference (2 octets)
• ----------------
• SK Flags
• --------
• mGRE Key (4 Octets)
• ----------------

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mGRE Tunnel TLV (contd)

• The Fixed fields in the mGRE Tunnel TLV may also
  be followed by a set of one or more sub-TLVs

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Capability

• A BGP Speaker must advertise the MP_EXT
  Capability with this AFI-SAFI pair, in order to
  speak this SAFI
• Use of this SAFI implies understanding of the SSA
  Attribute and at least one Tunnel Encapsulation
  TLV as specified by this SAFI

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Conclusion

• A New SAFI to provide
• isolation of Tunnel information from other
  existing SAFIs
• optimum amount of information advertised
• The NLRI encoding help conserves address-space
  when using multiple Tunnels
• A New Attribute
• That can carry a set of TLVs
• Flexible and adaptive to future extensions