Notes

This section covers discussions and some background work that went into this project.

Overview

The things covered here are:

• DHCP relay agents
• VLANS
• Trunking

VLANs

VLANs are a way to split up broadcast domains at L2. They can be statically or dynamically set, with dynamic VLANs sort of working in a similar way to DHCP.

DHCP Relay agents

Relay agents are virtual layer 3 devices residing on a switch with VLANs. In this case, they allow DHCP broadcasts to be relayed across 2 VLANs on the same switch. This is not necessary for us because the DHCP server lives beyond the ASA, and the ASA not only acts as a router between the switch and the server, but also serves to manipulate the VLAN tags (masquerades as hosts sending out DHCP requests).

Trunking

Trunking is done by making a "backbone" for all the different VLANs on a local switch to converge to. Frames from different VLANs are identified bythe means of VLAN tags, a four-byte addition to the Ethernet frame identifying which VLAN it came from. The tagging is also known as 802.1q.

Native VLANs

Normally the 4 byte addition to the Ethernet frame would cause the tagged frame to be rejected on a VLAN, and regular frames would be rejected if found in the trunk due to the lack of a tag. This is unless the "regular" frame is from a native VLAN , whose frames are intended not to have tags for devices that don't understand tagging.

A site explaining what a native vlan is: ​http://networkers-online.com/blog/2008/06/native-vlan-explained/

In our case this matters because DHCP coming from the trunk needs to assign IP addresses to both the hosts connected to the switch on different VLANs (VLAN 27) and to the switch itsself. To do this, The virtual interface to which the IP address is assigned needs to be on the trunked port(s).

some thoughts regarding th virtual switches (6/9)

• They are overlay devices that "run" on top of VLANs. VLANs need to be set up before virtual switches can be created.
• They are identified by the VLAN number of the VLAN they overlay, so one virtual switch can't encompass more than 1 VLAN.
• Conversely, they can overlay part of a VLAN. In that case, the whole VLAN takes on the virtual switch's behavior.

The last point is somewhat annoying, because the default behavior of a controllerless virtual switch is to "wait till the flow table times out." That would mean "become nonfunctional" in our case, since the virtual switches start off controller-less, and hence, flow-less. The whole switch would become a virtual brick if the trunk is specified in setvsi. This was demonstrated by overlaying a virtual switch over a single port on VLAN 27. It stopped forwarding DHCP messages all together when it used to be the only VLAN with DHCP.

Questions:

• can a virtual switch be loaded with a default flow table that would allow it to function, at least until its table times out?

SSL setup, things to know for the next day. (7/13)

using this site as reference: ​http://www.debian-administration.org/article/Creating_and_Using_a_self_signed__SSL_Certificates_in_debian

except renaming the output .pem files to what it would understand:

*ca_cert.pem - from cacert.pem *sw_cert.pem - from cert.pem *sw_key.pem - from key.pem

for the Common Name, I just used the IP address of the CA, 192.168.203.75.

because in the example on the site ca_cert.pem is named cacert.pem, I had to change "cacert" to "ca_cert" in openssl.cnf for the very last part (signing the certificate):

[ CA_default ] 
serial = $dir/serial 
database = $dir/index.txt 
new_certs_dir = $dir/newcerts 
certificate = $dir/ca_cert.pem       #change over here  
private_key = $dir/private/cakey.pem 
default_days = 365 
default_md = md5 
preserve = no 
email_in_dn = no 
nameopt = default_ca 
certopt = default_ca 
policy = policy_match 

I am not sure if changing the name of the key from ofpswitch.key.pem to sw_key.pem after making/signing the certification will affect anything.

Some lessons for the day:

• the SD card will show up as /media/disk on the PC

things to do:

• control VLAN on switch
• config control VLAN and statically assign PC to controller IP
  • VLAN not used for any legacy networking purposes for controller
• packet sniff SSL handshake

VLAN 888

arbitrary VLAN for OFP controller, since nothing probably uses that high a VLAN number. Currently only port 0/42 (formerly one of the trunk ports)

sw-sb09(config)# vlan 888
!sw-sb09(config-vlan)# name "OpenFlow control VLAN"
!sw-sb09(config-vlan)# interface gi 0/42
!sw-sb09(config-if)# sh
interface gigabitethernet 0/42
  switchport mode trunk
  switchport trunk allowed vlan 1,3,27-28
  switchport trunk native vlan 1
!
!sw-sb09(config-if)# no sw mo tru
!sw-sb09(config-if)# no switchport trunk allowed vlan 1,3,27-28
!sw-sb09(config-if)# no switchport trunk nat vlan 1            
!sw-sb09(config-if)# sh
interface gigabitethernet 0/42
  switchport mode access
!
!sw-sb09(config-if)# sw acc vlan 888
!sw-sb09(config-if)# interface vlan 888
!sw-sb09(config-if)# ip address 172.16.4.1 255.255.255.0
!sw-sb09(config-if)# save                     
sw-sb09(config-if)# 

this will probably not need a route specified for it since the controller is directly attached to the switch.

formal controller VLAN: VLAN100. (6/14)

VLAN 888 was removed since VLAN 100 is the formal controller VLAN, as decided by discussion.

sw-sb09(config-if)# sh interface gi 0/42
interface gigabitethernet 0/42
  switchport mode access
  switchport access vlan 888
!
sw-sb09(config-if)# interface gigabitethernet 0/42
sw-sb09(config-if)# no sw acc vlan 888
!sw-sb09(config-if)# switchport mod trunk
!sw-sb09(config-if)# swi trunk all vlan 1,3,27,28
!sw-sb09(config-if)# swi tru nat vlan 1
!sw-sb09(config-if)# save
sw-sb09(config-if)# no vlan 888
!sw-sb09(config)# vlan 100
!sw-sb09(config-vlan)# name "OpenFlow control VLAN" 
!sw-sb09(config-vlan)# save

Testing throughput with Iperf (7/23)

config eth0 of nodes 1-1 and 1-2, then run iperf to test the difference in bandwidth between OpenFlow and regular firmware. iperf reference: ​http://openmaniak.com/iperf.php

node1-1: 192.168.1.1/24

eth0: negotiated 1000baseT-HD flow-control
eth1: negotiated 1000baseT-HD flow-control

node1-2: 192.168.1.2/24

eth0: negotiated 1000baseT-HD flow-control
eth1: negotiated 1000baseT-HD flow-control

Server: Node1-2 Client: Node1-1
OpenFlow mode

	Transfer	Server	Client
1	278 MBytes	230 Mbits/sec	230 Mbits/sec
2	291 MBytes	243 Mbits/sec	244 Mbits/sec
3	291 MBytes	244 Mbits/sec	244 Mbits/sec
4	290 MBytes	243 Mbits/sec	244 Mbits/sec
5	284 MBytes	231 Mbits/sec	231 Mbits/sec

Normal mode

1	278 MBytes	229 Mbits/sec	230 Mbits/sec
2	291 MBytes	228 Mbits/sec	228 Mbits/sec
3	291 MBytes	228 Mbits/sec	229 Mbits/sec
4	290 MBytes	231 Mbits/sec	243 Mbits/sec
5	284 MBytes	229 Mbits/sec	230 Mbits/sec

Server: Node1-1 Client: Node1-2
OpenFlow mode

1	278 MBytes	229 Mbits/sec	230 Mbits/sec
2	291 MBytes	229 Mbits/sec	229 Mbits/sec
3	291 MBytes	232 Mbits/sec	244 Mbits/sec
4	290 MBytes	230 Mbits/sec	230 Mbits/sec
5	284 MBytes	230 Mbits/sec	230 Mbits/sec

Normal mode

1	278 MBytes	243 Mbits/sec	244 Mbits/sec
2	291 MBytes	243 Mbits/sec	242 Mbits/sec
3	291 MBytes	243 Mbits/sec	236 Mbits/sec
4	290 MBytes	243 Mbits/sec	244 Mbits/sec
5	284 MBytes	242 Mbits/sec	243 Mbits/sec

Overall, there doesn't seem to be too much difference in performance.

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