Title: Softwire%20Mesh%20Multicast
1Softwire Mesh Multicast
- Mingwei Xu, CERNET, China
- Yong Cui, CERNET, China
- Chris Metz, Cisco
- 70th IETF Meeting, Vancouver
- Dec. 2007
2Native IPv6 CERNET2 in China
3Review 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
4Review achievement after IETF69
- Multicast draft is updated
- New candidate solutions are proposed
- PIM-SSM IPv6 Transitions
- RPF-Vector-Based Address Translation
5Softwire 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
6Advantage 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
7Scenario 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.
8Procedure 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.
91. Receiving a PIM Join Message
CE send join to PE1
EB1A
Join(11.1.1.2 232.0.0.1)
102. 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)
113. 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)
124. 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
134. 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.
14Procedure 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
-
151. 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.
162. 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
173. 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
18Possible MTree in Core
Join(EB1A FF3x8f001) with11.1.1.2
232.0.0.1)
19Summary 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
20RPF-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
21JOIN(,G)DR Calculating RP for G
DR calculates RP gt 59.66.76.215
22JOIN(,G)Forwarding JOIN
59.66.74.211
23JOIN(,G)Forwarding JOIN (,G)
24JOIN(,G)Forwarding JOIN (,G)
25JOIN(,G)-- Forwarding JOIN (,G)
26JOIN(,G)JOIN (,G) Decap.
59.66.76.218
27JOIN(,G)JOIN (,G) Forwarding
28JOIN(,G)JOIN (,G) Reaching RP
29How 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)
-------------------------
----
30Summary 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
31Any 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
32Multicast 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
33Multicast 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