Illustration
A second practical example covers the configuration of QoS for real-time data.
Suppose a SOHO with three computers that have Internet access mainly for e-mail purposes. Besides these three computers, one computer is a dedicated video conferencing machine running NetMeeting. All data originated from the conference computer will have the IP header TOS-byte marked with a DiffServ Expedited Forwarding DiffServ-Codepoint (DSCP).
This example will assume an upstream bandwidth of 512Kb/s and a downstream bandwidth of 4Mb/s. Because of the real-time characteristics and higher priority of the video-conferencing data, this data will be sent and received on a separate ATM PVC with appropriate Quality of Service configuration.
To achieve this, assume that the video conferencing computer has a static IP address 192.168.2.1 in a 192.168.2.0/24 subnet. The other three computers have dynamic IP addresses in a 192.168.1.0/24 subnet that are assigned by the Thomson Gateway as DHCP server.
192.168.2.254/24 PC2 192.168.1.2/24 PC3 192.168.1.3/24 8*35 UBR 8*36 UBR Internet Network 192.168.1.254/24 PC1 192.168.1.1/24 Conference 192.168.2.1/24
Configuring QoS on the Thomson Gateway
Creating ATM Qosbook Entries
As in “3.1 Example: High Priority Data via PPTP”, the first step is configuring the connections on ATM level by creating QoS profiles as Thomson Gateway QoSbook entries and adding ATM connections to the Phonebook. For the normal data, a UBR service category is configured which uses any available bandwidth. For the video conferencing data, a CBR service category is chosen (because of its real-time characteristics) with 256Kb/s guaranteed bandwidth. This example uses a somewhat shorter parameter-notation.
1 Proceed as follows to create the connection traffic descriptors (ctd):
2 Proceed as follows to create the ATM QoSbook entries:
Creating Phonebook Entries and ATM interfaces
To created the required ATM PVC connections execute the following commands:
To view the phonebook entries created execute the following command:
Proceed as follows to create two ATM interfaces, one for data and one for conference:
Configuring Classification and ToS-byte Marking
Label configuration allows enabling ToS-byte marking of all packets that match the label classification criteria.
A classification rule needs to be added to specify the classification criteria of the fromconference label.
=>:atm qosbook ctdadd name=UBR conformance=UBR peakrate=0
=>:atm qosbook ctdadd name=CBR conformance=CBR peakrate=256
=>:atm qosbook add name=My_UBR txctd=UBR rxctd=UBR
=>:atm qosbook add name=My_CBR txctd=CBR rxctd=CBR
=>:atm phonebook add name=conference addr=8*36
=>:atm phonebook add name=data addr=8*35
=>:atm phonebook list
Name Use Address conference 0 8.36 data 0 8.35
=>:atm ifadd intf=atm_conference
=>:atm ifconfig intf=atm_conference dest=conference qos=My_CBR encaps=llc retry=10 fcs=disabled ulp=ppp
=>:atm ifadd intf=atm_data
=>:atm ifconfig intf=atm_data dest=data qos=My_UBR encaps=llc retry=10 fcs=disabled ulp=ppp
Configuring QoS on the Thomson Gateway
3 Create a rule to assign the QoS label:
4 Create a rule to assign the routing label:
Creating PPPoA Interfaces
The QoS profiles are linked to the ATM connections via the protocol interface definitions, in this case PPP interfaces (because the PPP connections are terminated on the Thomson Gateway instead of relayed towards computers). The conferencing PPP interface is configured as an always-on connection (could also be a dial- on-demand) with a CBR ATM QoS profile and NAPT (network address and port translation) enabled. A classification based routing entry is created to forward all data from the conferencing machine to this PPP interface.
To create the first PPP interface proceed as follows:
The second PPP interface is configured as an always-on connection with UBR ATM QoS profile and NAPT enabled. A routing entry is created to forward all other data to this interface.
To create the second PPP interface proceed as follows:
Creating a Static NAT Entry
A static NAPT entry is created to make sure that incoming data on port 1720 (H323) is forwarded towards the video conferencing PC. This is needed to support an incoming NetMeeting call.
Execute the following command to create the NAPT entry.
Configuring LAN IP Addressing
=>:label rule add chain=qos_user_labels index=1 name=FromConference srcintf=lan srcip=192.168.2.1/32 dstip=!192.168.2.0/24 label=FromConference
=>:label rule add chain=rt_user_labels index=1 name=FromConference srcintf=lan srcip=192.168.2.1/32 dstip=!192.168.2.0/24 label=FromConference
=>:ppp ifadd intf=conference
=>:ppp rtadd intf=conference dst=0.0.0.0/0 label=FromConference metric=1
=>:ppp ifconfig intf=conference dest=atm_conference user=conference_user password=conference_pwd
=>:nat ifconfig intf=conference translation=enabled
=>:ppp ifattach intf=conference
Because of priority of label routes over destination routes the conference interface routing entry is applied before the data interface entry
=>:ppp ifadd intf=data
=>:ppp rtadd intf=data dst=0.0.0.0/0 src=0.0.0.0/0 metric 1
=>:ppp ifconfig intf=data dest=atm_data accomp=enabled user=data_user password=data_pwd
=>:nat ifconfig intf=data translation=enabled
=>:ppp ifattach intf=data
=>:nat mapadd intf=conference type=napt outside_addr=0.0.0.0 inside_addr=192.168.2.1 protocol=tcp outside_port=1720 inside_port=1720
Configuring QoS on the Thomson Gateway
Execute the following command to add the IP address.
Summary
Once this configuration has been made, the video conferencing computer can accept incoming NetMeeting calls, and the H.323 data will always be forwarded over the connection with 256Kbps guaranteed bandwidth. Important remark is that if no guaranteed bandwidth is in use (no active video conferencing), this bandwidth will be available as non-guaranteed bandwidth for data from other computers.