Nathan Skrzypczak
f47122e07e
Type: improvement Change-Id: I7e821cce1feae229e1be4baeed249b9cca658135 Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
279 lines
9.6 KiB
ReStructuredText
279 lines
9.6 KiB
ReStructuredText
.. _srv6_mobile_plugin_doc:
|
||
|
||
SRv6 Mobile User Plane
|
||
======================
|
||
|
||
Introduction
|
||
------------
|
||
|
||
This plugin module can provide the stateless mobile user plane protocols
|
||
translation between GTP-U and SRv6. The plugin also provides FIB table
|
||
lookup for an IPv4/IPv6 packet encapsulated in GTP-U. These plugin
|
||
functions take advantage of SRv6 network programmability.
|
||
|
||
`SRv6 Mobile User
|
||
Plane <https://tools.ietf.org/html/draft-ietf-dmm-srv6-mobile-uplane>`__
|
||
defines the user plane protocol using SRv6 including following stateless
|
||
translation functions:
|
||
|
||
- **T.M.GTP4.D:** GTP-U over UDP/IPv4 -> SRv6
|
||
- **End.M.GTP4.E:** SRv6 -> GTP-U over UDP/IPv4
|
||
- **End.M.GTP6.D:** GTP-U over UDP/IPv6 -> SRv6
|
||
- **End.M.GTP6.E:** SRv6 -> GTP-U over UDP/IPv6
|
||
|
||
These functions benefit user plane(overlay) to be able to utilize data
|
||
plane(underlay) networks properly. And also it benefits data plane to be
|
||
able to handle user plane in routing paradigm.
|
||
|
||
In addition to the above functions, the plugin supports following
|
||
functions:
|
||
|
||
- **T.M.GTP4.DT{4|6|46}:** FIB table lookup for IPv4/IP6 encapsulated
|
||
in GTP-U over UDP/IPv4
|
||
- **End.M.GTP6.DT{4|6|46}:** FIB table lookup for IPv4/IP6 encapsulated
|
||
in GTP-U over UDP/IPv6
|
||
|
||
Noted that the prefix of function names follow naming convention of SRv6
|
||
network programming. “T” means transit function, “End” means end
|
||
function, “M” means Mobility specific function. The suffix “D” and “E”
|
||
mean that “decapsulation” and “encapsulation” respectively.
|
||
|
||
Implementation
|
||
--------------
|
||
|
||
All SRv6 mobile functions are implemented as VPP plugin modules. The
|
||
plugin modules leverage the sr_policy and sr_localsid mechanisms.
|
||
|
||
Configurations
|
||
--------------
|
||
|
||
GTP-U to SRv6
|
||
~~~~~~~~~~~~~
|
||
|
||
The GTP-U tunnel and flow identifiers of a receiving packet are mapped
|
||
to a Segment Identifier(SID) of sending SRv6 packets.
|
||
|
||
IPv4 infrastructure case
|
||
^^^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
In case that **IPv4** networks are the infrastructure of GTP-U,
|
||
T.M.GTP4.D function translates the receiving GTP-U packets to SRv6
|
||
packets.
|
||
|
||
A T.M.GTP4.D function is associated with the following mandatory
|
||
parameters:
|
||
|
||
- SID: A SRv6 SID to represents the function
|
||
- DST-PREFIX: Prefix of remote SRv6 segment. The destination address or
|
||
last SID of out packets consists of the prefix followed by dst IPv4
|
||
address, QFI and TEID of the receiving packets.
|
||
- SRC-PREFIX: Prefix for src address of sending packets. The src IPv6
|
||
address consists of the prefix followed by the src IPv4 address of
|
||
the receiving packets.
|
||
|
||
The following command instantiates a new T.M.GTP4.D function.
|
||
|
||
::
|
||
|
||
sr policy add bsid SID behavior t.m.gtp4.d DST-PREFIX v6src_prefix SRC-PREFIX [nhtype {ipv4|ipv6|non-ip}]
|
||
|
||
For example, the below command configures the SID 2001:db8::1 with
|
||
``t.m.gtp4.d`` behavior for translating receiving GTP-U over IPv4
|
||
packets to SRv6 packets with next-header type is IPv4.
|
||
|
||
::
|
||
|
||
sr policy add bsid 2001:db8::1 behavior t.m.gtp4.d D1::/32 v6src_prefix A1::/64 nhtype ipv4
|
||
|
||
It should be interesting how a SRv6 BSID works to decapsulate the
|
||
receiving GTP-U packets over IPv4 header. To utilize ``t.m.gtp4.d``
|
||
function, you need to configure some SR steering policy like:
|
||
|
||
::
|
||
|
||
sr steer l3 172.20.0.1/32 via bsid 2001:db8::1
|
||
|
||
The above steering policy with the BSID of ``t.m.gtp4.d`` would work
|
||
properly for the GTP-U packets destined to 172.20.0.1.
|
||
|
||
If you have a SID(s) list of SR policy which the configured gtp4.d
|
||
function to be applied, the SR Policy can be configured as following:
|
||
|
||
::
|
||
|
||
sr policy add bsid D1:: next A1:: next B1:: next C1::
|
||
|
||
IPv6 infrastructure case
|
||
^^^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
In case that GTP-U is deployed over **IPv6** infrastructure, you don’t
|
||
need to configure T.M.GTP4.D function and associated SR steering policy.
|
||
Instead of that, you just need to configure a localsid of End.M.GTP6.D
|
||
segment.
|
||
|
||
An End.M.GTP6.D segment is associated with the following mandatory
|
||
parameters:
|
||
|
||
- SID-PREFIX: SRv6 SID prefix to represent the function. In this
|
||
function, it should be the dst address of receiving GTP-U packets.
|
||
- DST-PREFIX: Prefix of remote SRv6 Segment. The destination address or
|
||
last SID of output packets consists of the prefix followed by QFI and
|
||
TEID of the receiving packets.
|
||
|
||
The following command instantiates a new End.M.GTP6.D function.
|
||
|
||
::
|
||
|
||
sr localsid prefix SID-PREFIX behavior end.m.gtp6.d DST-PREFIX [nhtype {ipv4|ipv6|non-ip}]
|
||
|
||
For example, the below command configures the SID prefix 2001:db8::/64
|
||
with ``end.m.gtp6.d`` behavior for translating receiving GTP-U over IPv6
|
||
packets which have IPv6 destination addresses within 2001:db8::/64 to
|
||
SRv6 packets. The dst IPv6 address of the outgoing packets consists of
|
||
D4::/64 followed by QFI and TEID.
|
||
|
||
::
|
||
|
||
sr localsid prefix 2001:db8::/64 behavior end.m.gtp6.d D4::/64
|
||
|
||
In another case, the translated packets from GTP-U over IPv6 to SRv6
|
||
will be re-translated back to GTP-U, which is so called ‘Drop-In’ mode.
|
||
|
||
In Drop-In mode, an additional IPv6 specific end segment is required,
|
||
named End.M.GTP6.D.Di. It is because that unlike ``end.m.gtp6.d``, it
|
||
needs to preserve original IPv6 dst address as the last SID in the SRH.
|
||
|
||
Regardless of that difference exists, the required configuration
|
||
parameters are same as ``end.m.gtp6.d``.
|
||
|
||
The following command instantiates a new End.M.GTP6.D.Di function.
|
||
|
||
::
|
||
|
||
sr localsid prefix 2001:db8::/64 behavior end.m.gtp6.d.di D4::/64
|
||
|
||
SRv6 to GTP-U
|
||
~~~~~~~~~~~~~
|
||
|
||
The SRv6 Mobile functions on SRv6 to GTP-U direction are End.M.GTP4.E
|
||
and End.M.GTP6.D.
|
||
|
||
In this direction with GTP-U over IPv4 infrastructure, an End.M.GTP4.E
|
||
segment is associated with the following mandatory parameters:
|
||
|
||
- SID-PREFIX: SRv6 SID prefix to represent the function.
|
||
- V4SRC-ADDR-POSITION: Integer number indicates bit position where IPv4
|
||
src address embedded.
|
||
|
||
The following command instantiates a new End.M.GTP4.E function.
|
||
|
||
::
|
||
|
||
sr localsid prefix SID-PREFIX behavior end.m.gtp4.e v4src_position V4SRC-ADDR-POSITION
|
||
|
||
For example, the below command configures the SID prefix 2001:db8::/32
|
||
with ``end.m.gtp4.e`` behavior for translating the receiving SRv6
|
||
packets to GTP-U packets encapsulated with UDP/IPv4 header. All the
|
||
GTP-U tunnel and flow identifiers are extracted from the active SID in
|
||
the receiving packets. The src IPv4 address of sending GTP-U packets is
|
||
extracted from the configured bit position in the src IPv6 address.
|
||
|
||
::
|
||
|
||
sr localsid prefix 2001:db8::/32 behavior end.m.gtp4.e v4src_position 64
|
||
|
||
In IPv6 infrastructure case, an End.M.GTP6.E segment is associated with
|
||
the following mandatory parameters:
|
||
|
||
- SID-PREFIX: SRv6 SID prefix to represent the function.
|
||
|
||
The following command instantiates a new End.M.GTP6.E function.
|
||
|
||
::
|
||
|
||
sr localsid prefix SID-PREFIX behavior end.m.gtp6.e
|
||
|
||
For example, the below command configures the SID prefix 2001:db8::/64
|
||
with ``end.m.gtp6.e`` behavior for translating the receiving SRv6
|
||
packets to GTP-U packets encapsulated with UDP/IPv6 header. While the
|
||
last SID indicates GTP-U dst IPv6 address, 32-bits GTP-U TEID and 6-bits
|
||
QFI are extracted from the active SID in the receiving packets.
|
||
|
||
::
|
||
|
||
sr localsid prefix 2001:db8::/64 behavior end.m.gtp6.e
|
||
|
||
FIB Table Lookup for Inner IPv4/IPv6 packet
|
||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||
|
||
SRv6 Mobile functions of ``t.m.gtp4.dt*`` and ``end.m.gtp6.dt*`` support
|
||
decapsulating outer IP/UDP/GTP-U headers and forwarding inner IP packet
|
||
based on specific fib table.
|
||
|
||
In case of the both outer and inner IP address families are IPv4,
|
||
``t.m.gtp4.dt4`` function supports GTP-U decapsulation and fib lookup
|
||
for inner IPv4 with an associated steering policy and the following
|
||
parameters:
|
||
|
||
- SID: A SRv6 SID to represents the function
|
||
- FIB: fib-table number for inner IPv4 packet lookup and forwarding
|
||
|
||
The following command instantiates a new T.M.GTP4.DT4 function.
|
||
|
||
::
|
||
|
||
sr policy add bsid SID behavior t.m.gtp4.dt4 fib-table FIB
|
||
|
||
For example, the below commands configure D5:: as the SID instantiates
|
||
``t.m.gtp4.dt4`` function. A steering policy for packets destine to
|
||
172.20.0.1 binds to the SID.
|
||
|
||
::
|
||
|
||
sr steer l3 172.20.0.1/32 via bsid D5::
|
||
sr policy add bsid D5:: behavior t.m.gtp4.dt4 fib-table 0
|
||
|
||
In addition, inner IPv6, or mix of IPv4 and IPv6 inner packet cases
|
||
require the function to be configured with local-fib table.
|
||
|
||
- LOCAL-FIB: fib-table number for lookup and forward GTP-U packet based
|
||
on outer IP destination address
|
||
|
||
This is inner IPv6 case specific. The reason is that GTP-U encapsulates
|
||
link local IPv6 packet for NDP (Neighbor Discovery Protocol). Outer
|
||
GTP-U header should be kept until the packets reach to the node
|
||
responsible for NDP handling. It is typically UPF(User Plane Function)
|
||
node.
|
||
|
||
The following command instantiate a new T.M.GTP4.DT6 function.
|
||
|
||
::
|
||
|
||
sr policy add bsid D5:: behavior t.m.gtp4.dt6 fib-table 0 local-fib-table LOCAL-FIB
|
||
|
||
Following example configures fib 0 for inner packet and fib 1 for outer
|
||
GTP-U packet forwarding:
|
||
|
||
::
|
||
|
||
sr policy add bsid D5:: behavior t.m.gtp4.dt6 fib-table 0 local-fib-table 1
|
||
|
||
If you need to support both IPv4 and IPv6 inner packet lookup with just
|
||
one SID, you can configure ``t.m.gtp4.dt46`` function:
|
||
|
||
::
|
||
|
||
sr policy add bsid D5:: behavior t.m.gtp4.dt46 fib-table 0 local-fib-table 1
|
||
|
||
In case of GTP-U over IPv6 case, ``end.m.gtp6.dt4``, ``end.m.gtp6.dt6``
|
||
and ``end.m.gtp6.dt46`` functions support inner IPv4, IPv6 and IPv4/IPv6
|
||
lookup and forwarding respectively. Specifying fib table for inner IP
|
||
packet forwarding is required as same as GTP-U over IPv4 case, and
|
||
local-fib table for inner IPv6 and IPv4/IPv6 cases as well.
|
||
|
||
::
|
||
|
||
sr localsid prefix D::/64 behavior end.m.gtp6.dt46 fib-table 0 local-fib-table 0
|
||
|
||
To run some demo setup please refer to: :ref:`srv6_mobile_runner_doc`
|