1. Softwire Mesh Solution Framework
Jianping Wu,
Yong Cui,
Chris Metz,
IETF Softwires WG Meeting, Dallas
March 2006

2. Contents High-Level One Slide Terminology Problem to Solve
Requirements
Solution Framework
Consensus from Hong Kong Interim Meeting
Next Steps

3. High-level One Slide AF/SAF Island Network 2 Single AF Transit Network
AF/SAF Reachability,
softwire tunnel info
Single AF Transit
Network
AF/SAF Island
Network 2
AFBR #2
AF/SAF Island
Network 1
AFBR #1
AF/SAF Island
Network 3
AFBR #3
softwire
Tunnel the packets of one or more address families (AF/SAF) across a single inter-AF transit network
AF/SAF(s) can be IPv4, IPv6, VPNv4, VPNv6, etc. and originate/terminate in AF/SAF Island Networks
single AF transit network is IPv4 or IPv6
tunnels between edge routers (AFBR) are called Softwires and use existing encaps (e.g. GRE, L2TPv3, etc.)
use routing protocol (e.g. MP-BGP) between edge routers (AFBRs) to announce softwire tunnel type/encaps/prefs and AF/SAF reachability thru the softwire tunnel

4. Terminology (1) Address Family (AF) – IPv4 or IPv6
Subsequent Address Family (SAF) – additional info about AF (e.g. unicast, multicast, VPN, etc.)
Address Family Border Router (AFBR) – dual stack router that connects two address families
peers with other AFBRs and downstream CPE routers
distributes and stores AF/SAF prefixes in VRF and/or global tables
establishes and maintains softwire tunnels with other AFBRs
performs encap/decap function on softwire tunnel headers

5. Terminology (2)
Softwire (SW) – pt-pt (or mpt-pt) tunnel established between two or more SW end-points (AFBR)
Softwire Transport Header (STH AF) – address family of the outermost IP header of the packet flowing on the softwire
Softwire Payload Header (SPF AF) – address family of the IP packet encapsulated and transported across the softwire

6. Terminology (3)
AF(i) Island
Network
Single AF(j) Transit
Network
AFBR(I,j)
AF(i) Island
Network
AFBR(I,j)
AF(I,j) Island
Network
AFBR(I,j)
AF(i) Island
Network
AFBR(I,j)
AF(j) Island
Network
AF Island Network – single or multi-AF network that is single- or multi-homed to dual-stack AFBR nodes
Single AF Transit Network – single AF transit network providing routing/forwarding between AFBR nodes

7. Basic Problem to Solve
Single AF(j) Transit
Network
AF(i) Island
Network 2
AFBR(I,j) #2
AF(i) Island
Network 1
AFBR(I,j) #1
AF(i) Island
Network 3
AFBR(I,j) #3
Support inter-AF(i) connectivity across a single AF(j) transit network
e.g. IPv4-over-IPv6

8. So what is needed here? AF(i) Island Network 1 Single AF(j) Transit
AFBR(I,j) #1
Single AF(j) Transit
Network
AF(i) Island
Network 2
AFBR(I,j) #2
AF(i) Island
Network N
AFBR(I,j) #N
Softwire tunnel discovery
so that egress AFBR #2 can tell AFBRs (#1,…,#N) the tunnel types/encaps/prefs it can support
Multi-AF/SAF Reachability
so that egress AFBR #2 can tell AFBRs (#1,…, #N) what AF/SAF prefixes are reachable through it
Way to associate AF/SAF reachability to the softwire
so ingress AFBRs (#1,…,#N) will know which softwire to use when forwarding packets to AF/SAF prefixes reachable through AFBR #2
Softwire Tunnel Encaps
so packets sourced from the AF(i) island network can be transparently forwarded across single AF transit network

9. Other Requirements to Consider (1)
Scalability
AFBR peering: O(# of peering AFBR + # of CPE routers)
AFBR routes: O(global Internet + # AF/SAF island prefixes)
AF/SAF Reachability
not limited to VPN AF/SAF combinations (e.g. AF=x, SAF=128)
must support tunneling of any AF/SAF combination (like IPv4-over-IPv6)
Softwire Encaps
must support different encaps
possible for AFBR to support more than one encap type (e.g. GRE, IPsec) and express a preference for one
different AF/SAF prefixes may use different encaps
Multicast
support native AF/SAF multicast routing/forwarding across single AF transit network

10. Other Requirements to Consider (2)
Use existing protocols where possible
e.g. re-use the hub-spoke encap
Time-to-market
consider what is already deployed and working

11. Solution Framework (1) Basic Idea
Leverage and reuse existing protocols where appropriate
MP-BGP can carry multiple AF/SAFs
multiple tunnel encaps already exist (e.g. L2TPv3, IPv4-in-IPv6)
lots of code, experience and deployments supporting large scale VPN AF/SAF reachability across transit networks (e.g. MPLS, IP)
Extend MP-BGP to
enable egress AFBR(s) to advertise their softwire tunnel capabilties, encapsulation parameters and preferences to participating ingress AFBR nodes … thus forming the softwire mesh
connect AF/SAF reachability to a softwire

12. Solution Framework (2)

13. Solution Framework (3) Notes
General AF(i)-over-AF(j) solution
must support any AF/SAF combination like IPv4-over-IPv6
Leverage existing tunnel signaling machinery where appropriate

14. Solution Framework (4) MP-BGP Notes
Comes with scalability (e.g. route reflectors), interoperable multi-AF/SAF reachability deployments (RFC4364) and policy controls (e.g. no-export)
Softwire tunnel extensions:
AFBR express softwire support using BGP capabilities
egress AFBR announces softwire tunnel types, encap parameters and preferences
associate AF/SAF reachability with softwire and be as efficient as possible
Tunnel SAFI is one possibility … Tunnel Encapsulation Attribute defines tunnel type/encap/preference and is carried by MP-BGP

15. Softwire Encapsulation Possibilities (over IPv4 Transit)
IPv6/IPv4
IPv6/VPN label/IPv4 -
UDP/IP
IPv6/UDP/IPv4
GRE
IPv6/GRE/IPv4
IPv6/VPN Label/GRE/IPv4
IPsec
IPv6/IPsec/IPv4
MPLS
if IPv4 transit is MPLS-enabled then MPLS label may be pushed on top or replace outer IPv4 header
L2TPv3
IPv6/L2TPv3/IPv4
IPv6/VPN label/L2TPv3/IPv4
IPv6/L2TPv3/IPsec/IPv4
IPv6/VPN label/L2TPv3/IPsec/IPv4
IPv6/L2TPv3/UDP/IPv4

16. Softwire Encapsulation Possibilities (over IPv6 Transit)
IPv6 only
IPv4/IPv6
IPv4/VPN label/IPv6
UDP/IP only
IPv4/UDP/IPv6
GRE
IPv4/GRE/IPv6
IPv4/VPN Label/GRE/IPv6
IPsec
IPv4/IPsec/IPv6
MPLS
if IPv6 transit is MPLS-enabled then MPLS label may be pushed on top or replace outer IPv6 header
L2TPv3
IPv4/L2TPv3/IPv6
IPv4/VPN label/L2TPv3/IPv6
IPv4/L2TPv3/IPsec/IPv6
IPv4/VPN label/L2TPv3/IPsec/IPv6
IPv4/L2TPv3/UDP/IPv6

17. Consensus Actions from Honk Kong Interim meeting
Agreed to merge two efforts
draft-wu-softwire-4over6-00 & C. Metz BGP Tunnel SAFI+ presentation
Softwire Mesh Framework
AFBRs use MP-BGP to announce softwire tunnel types/encaps/prefs, AF/SAF reachability and softwire tunnel to use
establish baseline set of IP(x)-over-IP(y) encaps
Present Softwire Mesh Framework in Dallas – DONE 
Commence effort on Softwire Mesh Framework draft after Dallas IETF
build on Tunnel SAFI notion in Softwires WG with review from various related WG (i.e. L2VPN, L3VPN, IDR, Security, etc.)

18. Next Steps Softwire Mesh Framework Draft
Supporting MP-BGP softwire tunnel drafts
Tunnel SAFI idea
support for IPsec control/encap
Tie in to the Multicast efforts
e.g. draft-ietf-softwires-4over6vpn.txt

19. References http://tools.ietf.org/wg/softwire/
draft-wu-softwire-4over6-00.txt
draft-nalawade-kapoor-tunnel-safi-04.txt
Wu, J., et al., “The Transition to IPv6 Part I: 4over6 for the China Education and Research Network”, IEEE Internet Computing, Summer 2006