1. UDP Encapsulation for IP Tunneling
draft-yong-tsvwg-udp-4-ip-tunneling-01
Lucy Yong, Xiaohu Xu
* Here to present
March Orlando FL

2. Background Existing Tunneling solutions
IP Infrastructure Networks carry tunneled traffic
Transit nodes are not aware of tunneled traffic/protocols
Tunneled traffic may be IP or non-IP packets
Some tunneled layer protocols already deployed
Network overlay example: IPv6 over IPv4, GRE, etc
Network virtualization overlay: MPLS VPN, VXLAN, NVGRE, etc
Existing Tunneling solutions
IP-in-IP [RFC2003]
GRE [RFC2784]
L2TPv3 [RFC3931]

3. Background Cont. IP Networks are built on parallelized capacity
e.g. multiple 10G links bundled together as a mx10G link
equal cost multiple paths (ECMP) is available to one end
operator desire to use all the paths carrying the tunneled traffic w/ the same tunnel end point
IP Networks already support ECMP and LAG
Hashing based load distribution is the common practice
IP header and TCP/UDP header is used for ECMP load distribution
i.e. (five tuple)
packets with the same five tuple is carried on the same path, which ensures no packet re-ordering
UDP src and dst ports are used as entropy in the load distribution
The purpose…
These are real-world use cases we know of so far.
We’re hoping to gather more use cases from the folks present here in order to make this work worthwhile.
In this presentation I stay away from mash up examples so we can focus on key enabling properties individually.
The presentation is divided into four focus areas …
These focus areas are further grouped by NVO properties driven by example use cases which we’ll talk about.

4. Problem Statement
Tunneled traffic may be carried over IP network where ECMP/LAG is required
To avoid tunneled flow packets re-ordering, IP network MUST keep a tunneled flow in the same path
solution for this is to have an entropy field in packets for IP network with ECMP, in which a tunneled flow packets is assigned to the same entropy value
Solution weakness for IP network with ECMP
IP-in-IP [RFC2003] does not have a place for entropy info
GRE [RFC2784] has an entropy field but requires transit router special processing
L2TPv3 [RFC3931] has the same capability and problem as GRE

5. What is in this draft?
Specify a generic UDP encapsulation method for any tunneled layer protocol over IP networks w/ ECMP
Achieve it w/o any change in IP network transit nodes
the same LB method for both host based apps. and tunneled apps.
Have a flow entropy field in UDP header
UDP src and dst ports are commonly used as entropy in IP network
tunneled packets w/ the same entropy value carried through the same path in IP network
may map one or more tunneled flows to the same value
Have a way to identify tunneled protocol in the UDP header
needed in order to support any tunneled layer protocol
Achieve it w/o any change of tunneled layer protocols
Specify tunnel endpoint process procedures and error handling

6. UDP Encapsulation for IP Tunneling
UDP source port is used as the flow entropy field
may be set to any value by the tunnel ingress
Varying the value according to the payload flow will enable load balancing within IP networks
UDP destination port is set to indicate the tunneled layer protocol that is registered under IANA
Other UDP header fields remain the same as in [RFC768]
RECOMMEND that the UDP checksum field is set to zero.

7. UDP Header Usage in this draft
UDP port usage here is different from before
Not for demultplexing transport connection at end point
Nor identifying an upper layer service
Header does not provide transport function for upper layer application
UDP ports are to provide flow entropy and the tunneled protocol type
UDP ports have been used as entropy in IP network
The latter is necessary in order to support any tunneled layer protocol
Note: VXLAN have been implemented in this way

8. Comment from Joe Touch
Alternative ways to indicate tunneled layer protocol type A:
Use one UDP dst. port to indicate the service for underlying IP network ECMP
Use a shim header in the payload to indicate the payload protocol type that are registered under IANA
This allows an IP tunnel carrying multiple layer protocols B:
Tunnel end point always signals the tunneled protocol type ahead
This only applies when each IP tunnel carries one tunneled protocol

9. Draft Contributors
John Drake Adrian Farrel Juniper Networks Carlos Pignataro Cisco System Yiu Lee Comcast
Edward Crabbe Google, Inc. Vishwas Manral Hewlett-Packard Corp. Yangbin Fan China Telecom

10. Next Step Welcome comment and feedback on this
Determine the proper way to indicate tunneled protocol
Each option has pros and cons
Authors prefer the option described in the draft because VXLAN already implements this way
Seek WG adoption of this