VNF Forwarding Graph¶
VNF Forwarding Graph or VNFFG feature in Tacker is used to orchestrate and manage traffic through VNFs. In short, abstract VNFFG TOSCA definitions are rendered into Service Function Chains (SFCs) and Classifiers. The SFC makes up an ordered list of VNFs for traffic to traverse, while the classifier decides which traffic should go through them.
Similar to how VNFs are described by VNFDs, VNFFGs are described by VNF Forwarding Graph Descriptors (VNFFGD). Please see the devref guide on VNFFGD to learn more about how a VNFFGD is defined.
VNFFG can be instantiated from VNFFGD or directly from VNFFGD template by separate Tacker commands. This action will build the chain and classifier necessary to realize the VNFFG.
Prerequisites¶
VNFFG with OpenStack VIM relies on Neutron Networking-sfc to create SFC and Classifiers. Therefore it is required to install networking-sfc project in order to use Tacker VNFFG. Networking-sfc also requires at least OVS 2.5 .0, so also ensure that is installed. See the full Networking-sfc guide.
A simple example of a service chain would be one that forces all traffic from HTTP client to HTTP server to go through VNFs that was created by VNFFG.
Firstly, HTTP client and HTTP server must be launched.
net_id=$(openstack network list | grep net0 | awk '{print $2}')
openstack server create --flavor m1.tiny --image cirros-0.4.0-x86_64-disk \
--nic net-id=$net_id http_client
openstack server create --flavor m1.tiny --image cirros-0.4.0-x86_64-disk \
--nic net-id=$net_id http_server
Creating the VNFFGD¶
Once OpenStack/Devstack along with Tacker has been successfully installed, deploy a sample VNFFGD template such as the one here.
Note
A current constraint of the Forwarding Path policy match criteria is to include the network_src_port_id, such as:
policy:
type: ACL
criteria:
- name: block_tcp
classifier:
network_src_port_id: 640dfd77-c92b-45a3-b8fc-22712de480e1
destination_port_range: 80-1024
ip_proto: 6
ip_dst_prefix: 192.168.1.2/24
- name: block_udp
classifier:
network_src_port_id: 640dfd77-c92b-45a3-b8fc-22712de480eda
destination_port_range: 80-1024
ip_proto: 17
ip_dst_prefix: 192.168.2.2/24
In above example, VNFFG will have 2 flow classifier. List flow classifiers are defined in list of criteria.
You can get network_src_port_id, network_dest_port_id and destination IP address through OpenStack commands like bellow:
client_ip=$(openstack server list | grep http_client | grep -Eo '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+')
network_source_port_id=$(openstack port list | grep $client_ip | awk '{print $2}')
ip_dst=$(openstack server list | grep http_server | grep -Eo '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+')
network_dest_port_id=$(openstack port list | grep $ip_dst | awk '{print $2}')
This is required due to a limitation of Neutron networking-sfc and only applies to an OpenStack VIM.
Two “network_dst_port_id” and “ip_dst_prefix” parameters must be set when you want to create VNFFG with “symmetrical” feature. If you want to create VNFFG without “symmetrical”, you can omit “network_dst_port_id” and “ip_dst_prefix”.
Forwarding_path1:
type: tosca.nodes.nfv.FP.TackerV2
description: creates path (CP12->CP22)
properties:
id: 51
symmetrical: true
correlation: nsh
policy:
type: ACL
criteria:
- name: block_tcp
classifier:
network_src_port_id: 640dfd77-c92b-45a3-b8fc-22712de480e1
network_dst_port_id: ea206bba-7083-4364-a9f1-c0b7fdf61b6e
ip_dst_prefix: 192.168.1.2/24
destination_port_range: 80-1024
ip_proto: 6
path:
- forwarder: VNFD1
capability: CP12
sfc_encap: True
- forwarder: VNFD2
capability: CP22
sfc_encap: False
In above template, users can set symmetrical in properties of a forwarding path create symmetrical VNFFG. If this property is not set, symmetrical will be specified by –symmetrical in create VNFFG command (default value is False).
In other hand, by setting correlation in properties let users can choose SFC encapsulation between MPLS or NSH (default: MPLS). If sfc_encap is True, port pair’s correlation is set to same value with correlation to make use of correlation that SFC Encapsulation provides, otherwise port pair’s correlation is set to None to install SFC proxy SFC_PROXY. Detailed information about SFC encapsulation can be found in Networking-SFC project SFC_ENCAPSULATION
You can use the sample VNFFGD template for symmetrical feature (in port chain) such as this link.
The symmetrical argument is used to indicate if reverse traffic should also flow through the path. This creates an extra classifier to ensure return traffic flows through the chain in a reverse path, otherwise this traffic routed normally and does not enter the VNFFG.
Tacker provides the following OpenStackClient CLI to create a VNFFGD:
openstack vnf graph descriptor create --vnffgd-file <vnffgd-file> <vnffgd-name>
Creating the VNFFG¶
To create a VNFFG, you must have first created VNF instances of the same VNFD types listed in the VNFFGD. Failure to do so will result in error when trying to create a VNFFG. Note, the VNFD you define must include the same Connection Point definitions as the ones you declared in your VNFFGD.
openstack vnf descriptor create --vnfd-file tosca-vnffg-vnfd1.yaml VNFD1
openstack vnf create --vnfd-name VNFD1 VNF1
openstack vnf descriptor create --vnfd-file tosca-vnffg-vnfd2.yaml VNFD2
openstack vnf create --vnfd-name VNFD2 VNF2
Refer the ‘Getting Started’ link below on how to create a VNFD and deploy 2 VNFs: VNF1 and VNF2.
https://docs.openstack.org/tacker/latest/install/getting_started.html
Tacker provides the following OpenStackClient CLI to create VNFFG from VNFFGD:
openstack vnf graph create --vnffgd-name <vnffgd-name> --vnf-mapping <vnf-mapping> --symmetrical <vnffg-name>
or you can create directly VNFFG from vnffgd template without initiating VNFFGD.
openstack vnf graph create --vnffgd-template <vnffgd-template> --vnf-mapping <vnf-mapping> \
--symmetrical <vnffg-name>
If you use a parameterized vnffg template:
openstack vnf graph create --vnffgd-name <vnffgd-name> --param-file <param-file> --vnf-mapping <vnf-mapping> \
--symmetrical <vnffg-name>
Here,
vnffgd-name - VNFFGD to use to instantiate this VNFFG
param-file - Parameter file in Yaml.
vnf-mapping - Allows a list of logical VNFD to VNF instance mapping
symmetrical - If –symmetrical is present, symmetrical is True (default: False - The symmectical is set in template has higher priority)
VNF Mapping is used to declare which exact VNF instance to be used for each VNF in the Forwarding Path. The following command would list VNFs in Tacker and then map each VNFD defined in the VNFFGD Forwarding Path to the desired VNF instance:
openstack vnf list
+--------------------------------------+------+---------------------------+--------+--------------------------------------+--------------------------------------+
| id | name | mgmt_ip_address | status | vim_id | vnfd_id |
+--------------------------------------+------+---------------------------+--------+--------------------------------------+--------------------------------------+
| 7168062e-9fa1-4203-8cb7-f5c99ff3ee1b | VNF2 | {"VDU1": "192.168.1.5"} | ACTIVE | 0e70ec23-6f32-420a-a039-2cdb2c20c329 | ea842879-5a7a-4f29-a8b0-528b2ad3b027 |
| 91e32c20-6d1f-47a4-9ba7-08f5e5effe07 | VNF1 | {"VDU1": "192.168.1.7"} | ACTIVE | 0e70ec23-6f32-420a-a039-2cdb2c20c329 | 27795330-62a7-406d-9443-2daad76e674b |
+--------------------------------------+------+---------------------------+--------+--------------------------------------+--------------------------------------+
openstack vnf graph create --vnffgd-name myvnffgd --vnf-mapping \
VNFD1:'91e32c20-6d1f-47a4-9ba7-08f5e5effe07',VNFD2:'7168062e-9fa1-4203-8cb7-f5c99ff3ee1b' --symmetrical myvnffg
Alternatively, if no vnf-mapping is provided then Tacker VNFFG will attempt to search for VNF instances derived from the given VNFDs in the VNFFGD. If multiple VNF instances exist for a given VNFD, the VNF instance chosen to be used in the VNFFG is done at random.
Parameters for VNFFGD template¶
Similar to TOSCA VNFD template, any value of VNFFGD template can be parameterized. Once parameterized different values can be passed while instantiating the forwarding graph using the same VNFFGD template. The value of a parameterized attribute can be specified like {get_input foo} in the TOSCA VNFFGD template. The corresponding param-file in the following YAML format can be provided in the vnffg-create command,
{
foo: bar
}
VNFFG command with parameter file:
openstack vnf graph create --vnffgd-name vnffgd-param --vnf-mapping VNFD1:'91e32c20-6d1f-47a4-9ba7-08f5e5effe07',\
VNFD2:'7168062e-9fa1-4203-8cb7-f5c99ff3ee1b' --param-file vnffg-param-file.yaml myvnffg
Viewing a VNFFG¶
A VNFFG once created is instantiated as multiple sub-components. These components include the VNFFG itself, which relies on a Network Forwarding Path (NFP). The NFP is then composed of a Service Function Chain (SFC) and a Classifier. The main command to view a VNFFG is ‘openstack vnf graph show’, however there are several commands available in order to view the sub-components for a rendered VNFFG:
openstack vnf network forwarding path list
openstack vnf network forwarding path show <nfp id>
openstack vnf chain list
openstack vnf chain show <chain id>
openstack vnf classifier list
openstack vnf classifier show <classifier id>
Updating the VNFFG¶
To update an already created VNFFG template the user needs to locate the VNFFG which wants to update. To do so the following command is getting executed:
Using the below command query the list of existing VNFFG templates.
openstack vnf graph list
+--------------------+---------+--------+-------------------------------------+
| ID | Name | Status | VNFFGD ID |
+--------------------+------------------+-------------------------------------+
| f4438511-e33d-43df-| | | |
| 95d9-0199253db72e | myvnffg | ACTIVE | bd7829bf-85de-4f3b-960a-8482028bfb34|
+--------------------+---------+--------+-------------+--------+--------------+
To verify result, user can get information of port chain in networking-sfc:
$ openstack sfc port chain list --fit-width
+-----------------------+-------------------+-----------------------+-----------------------+-----------------------+----------+
| ID | Name | Port Pair Groups | Flow Classifiers | Chain Parameters | Chain ID |
+-----------------------+-------------------+-----------------------+-----------------------+-----------------------+----------+
| 60d1a3ee-8455-415e- | VNFFG1-port-chain | [u'87d7d4c2-d2d1-4a99 | [u'02fa422c-9f40-4092 | {u'symmetric': False, | 51 |
| 8ff1-e0b6b9f9f277 | | -81fb-f3d5f51dd919', | -a8b0-c04355116e5e'] | u'correlation': | |
| | | u'81213b4c-0e5e-445d- | | u'nsh'} | |
| | | add6-dea2bf55078f'] | | | |
+-----------------------+-------------------+-----------------------+-----------------------+-----------------------+----------+
After the user located the VNFFG the subsequent action is to update it. Based on the appropriate choice, update VNFFG template. Currently two choices are supported for the update of an existing VNFFG. The first choice is the use of the vnf-mapping parameter. The user needs to use a VNF which is actually derived from the VNFD which is going to be used in the vnf-mapping parameter. If the user is not sure which VNF was used for the mapping during the time of the VNFFG creation he can execute:
Execute the below command to query the VNF that was used in mapping at the time of VNFFG creation.
openstack vnf graph show myvnffg
After user determined which VNF is used and which VNF is going to be used in the update procedure he can execute:
To update the VNF mappings to VNFFG, execute the below command
openstack vnf graph set --vnf-mapping VNFD1:vnf1,VNFD2:vnf2 myvnffg
Updated vnffg: myvnffg
The second choice is the use of the vnffgd-template parameter. The aforementioned parameter provides the ability to use a vnffgd formated yaml template which contains all the elements and their parameters that Tacker is going to apply to its ecosystem.
Below there is an example usage of updating an existing VNFFG:
Assuming that the existing VNFFG in the system that we want to update is derived from the following VNFFGD template.
tosca_definitions_version: tosca_simple_profile_for_nfv_1_0_0
description: Sample VNFFG template
topology_template:
node_templates:
Forwarding_path1:
type: tosca.nodes.nfv.FP.TackerV2
description: creates path (CP1)
properties:
id: 51
symmetrical: false
policy:
type: ACL
criteria:
- name: block_udp
classifier:
destination_port_range: 80-1024
ip_proto: 17
path:
- forwarder: VNFD3
capability: CP1
groups:
VNFFG1:
type: tosca.groups.nfv.VNFFG
description: UDP to Corporate Net
properties:
vendor: tacker
version: 1.0
number_of_endpoints: 1
dependent_virtual_link: [VL1]
connection_point: [CP1]
constituent_vnfs: [VNFD3]
members: [Forwarding_path1]
By using the below VNFFGD template we can update the existing VNFFG.
tosca_definitions_version: tosca_simple_profile_for_nfv_1_0_0
description: Sample VNFFG template
topology_template:
node_templates:
Forwarding_path2:
type: tosca.nodes.nfv.FP.TackerV2
description: creates path (CP1->CP2)
properties:
id: 52
symmetrical: false
correlation: nsh
policy:
type: ACL
criteria:
- name: block_tcp
classifier:
network_src_port_id: 640dfd77-c92b-45a3-b8fc-22712de480e1
destination_port_range: 22-28
ip_proto: 6
ip_dst_prefix: 192.168.1.2/24
path:
- forwarder: VNFD1
capability: CP1
sfc_encap: True
- forwarder: VNFD2
capability: CP2
sfc_encap: False
groups:
VNFFG1:
type: tosca.groups.nfv.VNFFG
description: SSH to Corporate Net
properties:
vendor: tacker
version: 1.0
number_of_endpoints: 2
dependent_virtual_link: [VL1,VL2]
connection_point: [CP1,CP2]
constituent_vnfs: [VNFD1,VNFD2]
members: [Forwarding_path2]
The above template informs Tacker to update the current classifier,NFP and path (chain) with the ones that are described in that template. After the completion of the update procedure the new NFP will be named ‘Forwarding_path2’ with an id of ‘52’,the classifier in that NFP will be named ‘block_tcp’ and will have the corresponding match criteria and the updated chain will be consisted by two NVFs which are derived from VNFD1,VNFD2 VNFDs.
To update the existing VNFFG through the vnffgd-template parameter, execute the below command:
openstack vnf graph set --vnffgd-template myvnffgd.yaml myvnffg
Updated vnffg: myvnffg
Of course the above update VNFFG’s choices can be combined in a single command.
openstack vnf graph set --vnf-mapping VNFD1:vnf1,VNFD2:vnf2 --vnffgd-template myvnffgd.yaml myvnffg
Updated vnffg: myvnffg
Known Issues and Limitations¶
Match criteria requires ‘network_src_port_id’
Only one Forwarding Path allowed per VNFFGD
Matching on criteria with postfix ‘name’ does not work, for example ‘network_name’
NSH attributes not yet supported
n-sfc Bug: https://bugs.launchpad.net/networking-sfc/+bug/1746686
