Softwire%20Mesh%20Multicast

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Softwire Mesh Multicast

• Mingwei Xu, CERNET, China
• Yong Cui, CERNET, China
• Chris Metz, Cisco
• 70th IETF Meeting, Vancouver
• Dec. 2007

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Native IPv6 CERNET2 in China
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Review softwire mcast problem

• Why we need Softwire Multicast?
• Existing multicast applications are in IPv4
• Native IPv6 CERNET2 core supports IPv6 multicast
  protocols
• Setup/Extend IPv4 multicast tree across IPv6 core
• Forward IPv4 multicast traffic across IPv6 core

4
Review achievement after IETF69

• Multicast draft is updated
• New candidate solutions are proposed
• PIM-SSM IPv6 Transitions
• RPF-Vector-Based Address Translation

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Softwire Mesh Multicast Framework

• 11 Mapping (Internet Multicast Model)
• PIM in the Core
• PIM-SSM IPv6 Transitions
• RPF-Vector-Based Address Translation
• MPLS/mLDP in the Core
• mVPN-like
• I-IP core multicast state scales less than
  linearly with E-IP client multicast state
• AFBR routers act like PE routers supporting one
  VPN
• Techniques outlined in L3VPN Multicast docs

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Advantage of PIM-SSM

• PIM-SSM
• Single source multicast
• Address Allocation
• Makes each source independently responsible for
  resolving address collisions.
• Access Control
• This makes it much harder to "spam" an SSM
  channel than an ASM multicast group
• Handling of well-known sources
• SSM requires only source-based Forwarding trees,
  making it viable for immediate deployment

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Scenario Terminology

• E-IP The network address family of customer
  network.
• I-IP The network address family of the transit
  core.
• PE Provider edge router, which supports the
  address family of both I-IP and E-IP.
• Upstream PE The PE router located at the
  upstream of multicast data flow, which connects
  the transit core and the customer network the
  source S belongs to.
• Downstream PE The PE router located at the
  downstream of multicast data flow, which connects
  the transit core and the customer network
  containing a group member.

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Procedure on Downstream PE

• PEs receive Join/Prune message from CEs.
• Upstream PE judge whether the (S,G) tree has been
  constructed or not .
• If the multicast tree has been mapping, PE adds
  the address of CE into the management of
  multicast group membership
• Calculating the corresponding address and sending
  a Join message.

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1. Receiving a PIM Join Message
CE send join to PE1
EB1A
Join(11.1.1.2 232.0.0.1)
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2. Check existing mgroup
Join(11.1.1.2 232.0.0.1)
PE1 judge whether this tree has been constructed
or not
EB1A
Join(11.1.1.2 232.0.0.1)
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3. If the tree has already existed
PE just need to add theaddress of CE into the
management of multicast group membership
DR
EB1A
Join(11.1.1.2 232.0.0.1)
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4. Translate join message into core
Send generated Join message (S,G) and the (S,G)
by attribute field
Join(EB1A FF3x8f001) with11.1.1.2
232.0.0.1)
EB1A
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4. Join Message

• A new source encoding type
  (draft-ietf-pim-join-attributes-03)
• 0 1 2
  30 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----------
  ----------------------
  Addr Family Encoding Type Rsrvd SWR Mask
  Len ----------------------
  ---------- Source Address
  (Encoded-Source format) ------------
  --------------------FS
  Type Length Value--------------
  ---------------.....FS Type
  Length Value-----------------
  ------------.....Type
• 0, The source address of customer network
• 1, The multicast group address of customer
  network
• Value
• Source Address (Encoded-Source format)
• Group Address (Encoded-Group format)
• IPv4 addresses in the 232/8 (232.0.0.0 to
  232.255.255.255) range are currently designated
  as source-specific multicast (SSM)
• For IPv6, the address prefix FF3x/32 is
  reserved for SSM use
• When the scenario is 4over6, we choose the
  FF3X8f000/24 to be the prefix of the multicast
  address for the 232/8.

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Procedure on Upstream PE

• The upstream PE judge whether the (S,G) tree has
  been constructed or not.
• If the tree has been constructed before, the
  downstream PE keep the common state and add
  multicast members in the table
• PE sends an E-IP PIM Join message to the source S

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1. Check existing mgroup on upstream PE
Join(EB1A FF3x8f001) with11.1.1.2
232.0.0.1)
Join(11.1.1.2 232.0.0.1)
The upstream PE judge whether the (S,G) tree has
been constructedor not.
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2. Adds multicast members
Join(EB1A FF3x8f001) with11.1.1.2
232.0.0.1)
The downstream PE need to keep the common state
and add multicast members in the table
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3. Sends an E-IP PIM Join message
Join(EB1A FF3x8f001) with11.1.1.2
232.0.0.1)
Join(11.1.1.2 232.0.0.1)
sends an E-IP PIM Join/Prune message to the
source S
S
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Possible MTree in Core
Join(EB1A FF3x8f001) with11.1.1.2
232.0.0.1)
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Summary of PIM-SSM Transition

• Advantage
• IPv4 IPv6
• Support both 4over6 or 6over4
• Path optimization
• Each multicast group in customer networks has a
  corresponding I-IP PIM-SSM in the transit core
• Disadvantage
• The state information storage needed is
  proportional to the numbers of multicast trees
  passing through the routers
• Status
• I-D complete and will be submitted soon

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RPF-Vector-Based Address Translation

• PIM-SM Unicast Messages
• Register and C-RP-adv
• Use softwire unicast mechansim
• PIM-SM Multicast Messages to ALL-PIM-ROUTERS
• Register-Stop
• Use RVAT mechansim
• Hello
• Suspending
• Join/Prune
• Use RVAT mechansim
• Bootstrap
• Use softwire unicast mechansim

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JOIN(,G)DR Calculating RP for G
DR calculates RP gt 59.66.76.215
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JOIN(,G)Forwarding JOIN
59.66.74.211
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JOIN(,G)Forwarding JOIN (,G)
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JOIN(,G)Forwarding JOIN (,G)
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JOIN(,G)-- Forwarding JOIN (,G)
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JOIN(,G)JOIN (,G) Decap.
59.66.76.218
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JOIN(,G)JOIN (,G) Forwarding
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JOIN(,G)JOIN (,G) Reaching RP
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How to Fill an RPF-VECTOR
0 1
2 3 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 -------------------
---------- Addr Family Encoding
Type Rsrvd SWR Mask Len
-------------------------
----- Source Address
(Encoded-Source format)
-------------------------
---- FS Type Length
Value
-------------------------
---- FS Type Length
Value --------------------
---------
0 1
2 3 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 -------------------
---------- 2
0 0 1 1 1 120
-------------------
---------- encoded
format for ( FFFF59.66.76.215)
-------------------------
---- 1 1 0 144
eccoded format for (EA22)
-------------------------
----
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Summary for RPF-Vector-Based Address Translation

• Advantages
• Virtually the same as PIM-SM
• IPv6 multicast tree is part of the IPv4 tree
• Simple , incremental and light-weighted
• Disadvantages
• Only available in 4over6 scenario
• Status
• I-D complete and will be submitted soon

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Any new requirement?

• Unicast core?
• Some old routers in the core may not support
  multicast
• We need to forward multicast packet from one edge
  to the other by unicast encap.
• Dual-stack source
• Both IPv4 receiver and IPv6 receiver

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Multicast framework

• Main content in mcast framework
• Detail the requirement
• Restrict the problem in mesh mcast
• Leverage existing solutions
• Describe the framework for new candidate
  solutions
• Status of mcast framework
• Mainly complete as an informational draft
• Revision/comments/collaboration are welcome
• Request to be a WG document

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Multicast solutions

• 11 Mapping (mcast core)
• PIM in the Core
• RPF-Vector-Based Address Translation
• PIM-SSM IPv6 Transitions
• MPLS/mLDP in the Core
• mVPN-like (mcast core)
• Leverage L3VPN solutions
• Unicast core
• Leverage any existing solutions or propose new
  ones