srv6-plugins: fixing documentation

Change-Id: I72439df585e56b3cbb7051f056fc35cddf0c864b
Signed-off-by: Francois Clad <fclad@cisco.com>

1 files changed, 93 insertions, 106 deletions

diff --git a/src/plugins/srv6-as/as_plugin_doc.md b/src/plugins/srv6-as/as_plugin_doc.md
index d8a39496a3d..7cda08b60d9 100644
--- a/src/plugins/srv6-as/as_plugin_doc.md
+++ b/src/plugins/srv6-as/as_plugin_doc.md
@@ -3,163 +3,150 @@
 ## Overview
 
 The static proxy is an SR endpoint behavior for processing SR-MPLS or SRv6
-encapsulated traffic on behalf of an SR-unaware service.  This proxy thus
-receives SR traffic that is formed of an MPLS label stack or an IPv6 header on
-top of an inner packet, which can be Ethernet, IPv4 or IPv6.
+encapsulated traffic on behalf of an SR-unaware SF. This proxy thus receives SR
+traffic that is formed of an MPLS label stack or an IPv6 header on top of an
+inner packet, which can be Ethernet, IPv4 or IPv6.
 
 A static SR proxy segment is associated with the following mandatory parameters:
 
 - INNER-TYPE: Inner packet type
-- S-ADDR: Ethernet or IP address of the service (only for inner type IPv4 and
-	IPv6)
-- IFACE-OUT: Local interface for sending traffic towards the service
-- IFACE-IN: Local interface receiving the traffic coming back from the service
-- CACHE: SR information to be attached on the traffic coming back from the
-	service
-
-A static SR proxy segment is thus defined for a specific service, inner packet
-type and cached SR information.  It is also bound to a pair of directed
-interfaces on the proxy.  These may be both directions of a single interface, or
-opposite directions of two different interfaces.  The latter is recommended in
-case the service is to be used as part of a bi-directional SR SC policy.  If the
-proxy and the service both support 802.1Q, IFACE-OUT and IFACE-IN can also
-represent sub-interfaces.
+- S-ADDR: Ethernet or IP address of the SF (only for inner type IPv4 and IPv6)
+- IFACE-OUT: Local interface for sending traffic towards the SF
+- IFACE-IN: Local interface receiving the traffic coming back from the SF
+- CACHE: SR information to be attached on the traffic coming back from the SF,
+including at least
+	* CACHE.SA: IPv6 source address (SRv6 only)
+	* CACHE.LIST: Segment list expressed as MPLS labels or IPv6 address
+
+A static SR proxy segment is thus defined for a specific SF, inner packet type
+and cached SR information. It is also bound to a pair of directed interfaces on
+the proxy. These may be both directions of a single interface, or opposite
+directions of two different interfaces. The latter is recommended in case the SF
+is to be used as part of a bi-directional SR SC policy. If the proxy and the SF
+both support 802.1Q, IFACE-OUT and IFACE-IN can also represent sub-interfaces.
 
 The first part of this behavior is triggered when the proxy node receives a
 packet whose active segment matches a segment associated with the static proxy
-behavior.  It removes the SR information from the packet then sends it on a
-specific interface towards the associated service.  This SR information
-corresponds to the full label stack for SR-MPLS or to the encapsulation IPv6
-header with any attached extension header in the case of SRv6.
+behavior. It removes the SR information from the packet then sends it on a
+specific interface towards the associated SF. This SR information corresponds to
+the full label stack for SR-MPLS or to the encapsulation IPv6 header with any
+attached extension header in the case of SRv6.
 
 The second part is an inbound policy attached to the proxy interface receiving
-the traffic returning from the service, IFACE-IN.  This policy attaches to the
+the traffic returning from the SF, IFACE-IN. This policy attaches to the
 incoming traffic the cached SR information associated with the SR proxy segment.
 If the proxy segment uses the SR-MPLS data plane, CACHE contains a stack of
-labels to be pushed on top the packets.  With the SRv6 data plane, CACHE is
+labels to be pushed on top the packets. With the SRv6 data plane, CACHE is
 defined as a source address, an active segment and an optional SRH (tag,
-segments left, segment list and metadata).  The proxy encapsulates the packets
+segments left, segment list and metadata). The proxy encapsulates the packets
 with an IPv6 header that has the source address, the active segment as
-destination address and the SRH as a routing extension header.  After the SR
+destination address and the SRH as a routing extension header. After the SR
 information has been attached, the packets are forwarded according to the active
 segment, which is represented by the top MPLS label or the IPv6 Destination
 Address.
 
 In this scenario, there are no restrictions on the operations that can be
-performed by the service on the stream of packets.  It may operate at all
-protocol layers, terminate transport layer connections, generate new packets and
-initiate transport layer connections.  This behavior may also be used to
-integrate an IPv4-only service into an SRv6 policy.  However, a static SR proxy
-segment can be used in only one service chain at a time.  As opposed to most
-other segment types, a static SR proxy segment is bound to a unique list of
-segments, which represents a directed SR SC policy.  This is due to the cached
-SR information being defined in the segment configuration.  This limitation only
-prevents multiple segment lists from using the same static SR proxy segment at
-the same time, but a single segment list can be shared by any number of traffic
-flows.  Besides, since the returning traffic from the service is re- classified
-based on the incoming interface, an interface can be used as receiving interface
-(IFACE-IN) only for a single SR proxy segment at a time.  In the case of a
-bi-directional SR SC policy, a different SR proxy segment and receiving
-interface are required for the return direction.
-
-## SRv6 pseudocode
-
-### Static proxy for inner type Ethernet - End.AS2
-
-Upon receiving an IPv6 packet destined for S, where S is an End.AS2 SID, a node
-N does:
+performed by the SF on the stream of packets. It may operate at all protocol
+layers, terminate transport layer connections, generate new packets and initiate
+transport layer connections. This behavior may also be used to integrate an
+IPv4-only SF into an SRv6 policy. However, a static SR proxy segment can be used
+in only one service chain at a time. As opposed to most other segment types, a
+static SR proxy segment is bound to a unique list of segments, which represents
+a directed SR SC policy. This is due to the cached SR information being defined
+in the segment configuration. This limitation only prevents multiple segment
+lists from using the same static SR proxy segment at the same time, but a single
+segment list can be shared by any number of traffic flows. Besides, since the
+returning traffic from the SF is re-classified based on the incoming interface,
+an interface can be used as receiving interface (IFACE-IN) only for a single SR
+proxy segment at a time. In the case of a bi-directional SR SC policy, a
+different SR proxy segment and receiving interface are required for the return
+direction.
+
+For more information, please see
+[draft-xuclad-spring-sr-service-chaining](https://datatracker.ietf.org/doc/draft-xuclad-spring-sr-service-chaining/).
+
+## CLI configuration
+
+The following command instantiates a new End.AS segment that sends the inner
+packets on interface `IFACE-OUT` towards an appliance at address `S-ADDR` and
+restores the segment list ``<S1, S2, S3>`` with a source address `SRC-ADDR` on
+the packets coming back on interface `IFACE-IN`.
 
 ```
-   1.   IF ENH == 59 THEN                                        ;; Ref1
-   2.       Remove the (outer) IPv6 header and its extension headers
-   3.       Forward the exposed frame on IFACE-OUT
-   4.   ELSE
-   5.       Drop the packet
+sr localsid address SID behavior end.ad nh S-ADDR oif IFACE-OUT iif IFACE-IN src SRC-ADDR next S1 next S2 next S3
 ```
 
-Ref1: 59 refers to "no next header" as defined by IANA allocation for Internet
-Protocol Numbers.
-
-Upon receiving on IFACE-IN an Ethernet frame with a destination address
-different than the interface address, a node N does:
+For example, the below command configures the SID `1::A1` with an End.AS
+function for sending traffic on interface `GigabitEthernet0/8/0` to the
+appliance at address `A1::`, and receiving it back on interface
+`GigabitEthernet0/9/0`.
 
 ```
-   1.   IF CACHE.SRH THEN                                        ;; Ref2
-   2.       Push CACHE.SRH on top of the existing Ethernet header
-   3.       Set NH value of the pushed SRH to 59
-   4.   Push outer IPv6 header with SA, DA and traffic class from CACHE
-   5.   Set outer payload length and flow label
-   6.   Set NH value to 43 if an SRH was added, or 59 otherwise
-   7.   Lookup outer DA in appropriate table and proceed accordingly
+sr localsid address 1::A1 behavior end.ad nh A1:: oif GigabitEthernet0/8/0 iif GigabitEthernet0/9/0 src 1:: next 2::20 next 3::30 next 4::40
 ```
 
-Ref2: CACHE.SRH represents the SRH defined in CACHE, if any, for the static SR
-proxy segment associated with IFACE-IN.
+## Pseudocode
 
-The receiving interface must be configured in promiscuous mode in order to
-accept those Ethernet frames.
+### Static proxy for inner type IPv4
 
-### Static proxy for inner type IPv4 - End.AS4
-
-Upon receiving an IPv6 packet destined for S, where S is an End.AS4 SID, a node
-N does:
+Upon receiving an IPv6 packet destined for S, where S is an IPv6 static proxy
+segment for IPv4 traffic, a node N does:
 
 ```
-   1.   IF ENH == 4 THEN                                         ;; Ref1
-   2.       Remove the (outer) IPv6 header and its extension headers
-   3.       Forward the exposed packet on IFACE-OUT towards S-ADDR
-   4.   ELSE
-   5.       Drop the packet
+IF ENH == 4 THEN                                                ;; Ref1
+    Remove the (outer) IPv6 header and its extension headers
+    Forward the exposed packet on IFACE-OUT towards S-ADDR
+ELSE
+    Drop the packet
 ```
 
-Ref1: 4 refers to IPv4 encapsulation as defined by IANA allocation for Internet
+**Ref1:** 4 refers to IPv4 encapsulation as defined by IANA allocation for Internet
 Protocol Numbers.
 
 Upon receiving a non link-local IPv4 packet on IFACE-IN, a node N does:
 
 ```
-   1.   IF CACHE.SRH THEN                                        ;; Ref2
-   2.       Push CACHE.SRH on top of the existing IPv4 header
-   3.       Set NH value of the pushed SRH to 4
-   4.   Push outer IPv6 header with SA, DA and traffic class from CACHE
-   5.   Set outer payload length and flow label
-   6.   Set NH value to 43 if an SRH was added, or 4 otherwise
-   7.   Decrement inner TTL and update checksum
-   8.   Lookup outer DA in appropriate table and proceed accordingly
+Decrement TTL and update checksum
+IF CACHE.SRH THEN                                               ;; Ref2
+    Push CACHE.SRH on top of the existing IPv4 header
+    Set NH value of the pushed SRH to 4
+Push outer IPv6 header with SA, DA and traffic class from CACHE
+Set outer payload length and flow label
+Set NH value to 43 if an SRH was added, or 4 otherwise
+Lookup outer DA in appropriate table and proceed accordingly
 ```
 
-Ref2: CACHE.SRH represents the SRH defined in CACHE, if any, for the static SR
+**Ref2:** CACHE.SRH represents the SRH defined in CACHE, if any, for the static SR
 proxy segment associated with IFACE-IN.
 
-### Static proxy for inner type IPv6 - End.AS6
+### Static proxy for inner type IPv6
 
-Upon receiving an IPv6 packet destined for S, where S is an End.AS6 SID, a node
-N does:
+Upon receiving an IPv6 packet destined for S, where S is an IPv6 static proxy
+segment for IPv6 traffic, a node N does:
 
 ```
-   1.   IF ENH == 41 THEN                                        ;; Ref1
-   2.       Remove the (outer) IPv6 header and its extension headers
-   3.       Forward the exposed packet on IFACE-OUT towards S-ADDR
-   4.   ELSE
-   5.       Drop the packet
+IF ENH == 41 THEN                                               ;; Ref1
+    Remove the (outer) IPv6 header and its extension headers
+    Forward the exposed packet on IFACE-OUT towards S-ADDR
+ELSE
+    Drop the packet
 ```
 
-Ref1: 41 refers to IPv6 encapsulation as defined by IANA allocation for Internet
+**Ref1:** 41 refers to IPv6 encapsulation as defined by IANA allocation for Internet
 Protocol Numbers.
 
 Upon receiving a non-link-local IPv6 packet on IFACE-IN, a node N does:
 
 ```
-   1.   IF CACHE.SRH THEN                                        ;; Ref2
-   2.       Push CACHE.SRH on top of the existing IPv6 header
-   3.       Set NH value of the pushed SRH to 41
-   4.   Push outer IPv6 header with SA, DA and traffic class from CACHE
-   5.   Set outer payload length and flow label
-   6.   Set NH value to 43 if an SRH was added, or 41 otherwise
-   7.   Decrement inner Hop Limit
-   8.   Lookup outer DA in appropriate table and proceed accordingly
+Decrement Hop Limit
+IF CACHE.SRH THEN                                               ;; Ref2
+    Push CACHE.SRH on top of the existing IPv6 header
+    Set NH value of the pushed SRH to 41
+Push outer IPv6 header with SA, DA and traffic class from CACHE
+Set outer payload length and flow label
+Set NH value to 43 if an SRH was added, or 41 otherwise
+Lookup outer DA in appropriate table and proceed accordingly
 ```
 
-Ref2: CACHE.SRH represents the SRH defined in CACHE, if any, for the static SR
+**Ref2:** CACHE.SRH represents the SRH defined in CACHE, if any, for the static SR
 proxy segment associated with IFACE-IN.
-