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Configuring LLDP-MED to send required DSCP value to a phone or device connected to the EX Switch

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Article ID: KB16318 KB Last Updated: 24 Feb 2010Version: 1.0
Summary:
This article provides a solution, and configuration steps, to allow the Link Layer Discovery Protocol - Media Endpoint Devices (LLDP-MED) on the EX Switch to send required DSCP value to a device connected to the EX Switch.


Symptoms:

Solution:
The LLDP is vendor-neutral protocol used by network devices for advertising of their identity, capabilities, and interconnections on IEEE 802 LAN network. EX switches do support LLDP as well as LLDP-MED protocol.

LLDP, which defines basic discovery capabilities, was enhanced to specifically address the voice application; this extension to LLDP is called LLDP-MED or LLDP for Media Endpoint Devices.

LLDP-MED when configured on EX switches in conjunction with VOIP, can be used to send information such as VLAN tag, DSCP value etc. to VOIP phones connected to EX switches.

LLDP-MED Sending DSCP Value of "0" (No class of service configured on EX Switch)
If the EX Switch is NOT configured with a class of service configuration and running LLDP-MED protocol. LLDP-MED protocol, by default will send DSCP value of "0" to devices (IP phones) connected to it.   The following is an example of a LLDP-MED message captured on an EX Switch interface connected to a VoIP phone. The EX Switch in this case is NOTconfigured for any kind of "class of service".

The packet capture below shows the DSCP value of 0 (which is usually best effort traffic) sent by the EX Switch to a VOIP phone connected to the EX Switch. The IP phone connected to EX Switch on receipt of such LLDP-MED message will send traffic to the switch with a DSCP value of 0.


4:27:37.538315 Out LLDP, length 278
Chassis ID TLV (1), length 7
Subtype MAC address (4): 0:1f:12:30:ff:0
Port ID TLV (2), length 4
Subtype Local (7): 269
Time to Live TLV (3), length 2: TTL 120s
System Description TLV (6), length 88
Juniper Networks, Inc. ex4200-24p , version 9.5R3.7 Build date: 2009-10-28 16:27:18 UTC
System Capabilities TLV (7), length 4
System Capabilities [Bridge, Router] (0x0014)
Enabled Capabilities [Bridge, Router] (0x0014)
Management Address TLV (8), length 24
Management Address length 5, AFI IPv4 (1): 10.85.33.115
Interface Index Interface Numbering (2): 36
OID length 12\001\003\006\001\002\001\037\001\001\001\001$
Port Description TLV (4), length 10: ge-0/0/5.0
Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
MAC/PHY configuration/status Subtype (1)
autonegotiation [supported, enabled] (0x03)
PMD autoneg capability [10BASE-T hdx, 10BASE-T fdx, 100BASE-TX hdx, 100BASE-TX fdx, Asym and Sym PAUSE for fdx, 1000BASE-{X LX SX CX} fdx, 1000BASE-T fdx] (0xa836)
MAU type Unknown (0x0000)
Organization specific TLV (127), length 7: OUI IEEE 802.3 Private (0x00120f)
Power via MDI Subtype (2)
MDI power support [PSE, enabled], power pair signal, power class class1
Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
Link aggregation Subtype (3)
aggregation status [supported], aggregation port ID 0
Organization specific TLV (127), length 6: OUI IEEE 802.3 Private (0x00120f)
Max frame size Subtype (4)
MTU size 1514
Organization specific TLV (127), length 6: OUI Ethernet bridged (0x0080c2)
0x0000: 0080 c201 0084
Organization specific TLV (127), length 16: OUI Juniper (0x009069)
0x0000: 0090 6901 4250 3032 3038 3234 3838 3039
Organization specific TLV (127), length 14: OUI Ethernet bridged (0x0080c2)
0x0000: 0080 c203 0000 0764 6566 6175 6c74
Organization specific TLV (127), length 12: OUI Ethernet bridged (0x0080c2)
0x0000: 0080 c203 0084 0576 6f69 6365
Organization specific TLV (127), length 7: OUI ANSI/TIA (0x0012bb)
LLDP-MED Capabilities Subtype (1)
Media capabilities [LLDP-MED capabilities, network policy, location identification, extended power via MDI-PD] (0x0017)
Device type [network connectivity] (0x04)
Organization specific TLV (127), length 7: OUI ANSI/TIA (0x0012bb)
Extended power-via-MDI Subtype (4)
Power type [PSE device], Power source [PSE - primary power source]
Power priority [low] (0x03), Power 3.7 Watts
Organization specific TLV (127), length 8: OUI ANSI/TIA (0x0012bb)
Network policy Subtype (2)
Application type [voice] (0x01), Flags [Tagged]
Vlan id 132, L2 priority 0, DSCP value 0
End TLV (0), length 0


To alter the DSCP value sent by LLDP-MED protocol of the EX Switch do the following:

1. Configure classifier under "class of service" (COS) on the EX Switch with required DSCP value

2. Configure VOIP under "ethernet-switching-options" to add interfaces which have VoIP phones.

EXAMPLE:

{master:1}[edit]
juniper# show class-of-service
classifiers {
   dscp test {
        import default;
        forwarding-class expedited-forwarding {
            loss-priority low code-points 101110;
            loss-priority high code-points 101111;
        }
        forwarding-class voice {
            loss-priority low code-points af21;
        }
     }
}

juniper# show ethernet-switching-options voip
interface ge-0/0/5.0 {
vlan voice;
forwarding-class expedited-forwarding;
}


class voice queue-num 6;
}
interfaces {
     ge-0/0/5 {
          unit 0 {
                classifiers {
                       dscp test;
                }
             }
       }
}
In the example above the IP phone is connected to interface ge-0/0/5. After committing the configuration the switch will advertise the DSCP value of 46 (101110) as set under classifier.

The LLDP-MED advertisement to IP phone will look like the following:

5:27:37.538315 Out LLDP, length 278
Chassis ID TLV (1), length 7
Subtype MAC address (4): 0:1f:12:30:ff:0
Port ID TLV (2), length 4
Subtype Local (7): 269
Time to Live TLV (3), length 2: TTL 120s
System Description TLV (6), length 88
Juniper Networks, Inc. ex4200-24p , version 9.5R3.7 Build date: 2009-10-28 16:27:18 UTC
System Capabilities TLV (7), length 4
System Capabilities [Bridge, Router] (0x0014)
Enabled Capabilities [Bridge, Router] (0x0014)
Management Address TLV (8), length 24
Management Address length 5, AFI IPv4 (1): 10.85.33.115
Interface Index Interface Numbering (2): 36
OID length 12\001\003\006\001\002\001\037\001\001\001\001$
Port Description TLV (4), length 10: ge-0/0/5.0
Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
MAC/PHY configuration/status Subtype (1)
autonegotiation [supported, enabled] (0x03)
PMD autoneg capability [10BASE-T hdx, 10BASE-T fdx, 100BASE-TX hdx, 100BASE-TX fdx, Asym and Sym PAUSE for fdx, 1000BASE-{X LX SX CX} fdx, 1000BASE-T fdx] (0xa836)
MAU type Unknown (0x0000)
Organization specific TLV (127), length 7: OUI IEEE 802.3 Private (0x00120f)
Power via MDI Subtype (2)
MDI power support [PSE, enabled], power pair signal, power class class1
Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
Link aggregation Subtype (3)
aggregation status [supported], aggregation port ID 0
Organization specific TLV (127), length 6: OUI IEEE 802.3 Private (0x00120f)
Max frame size Subtype (4)
MTU size 1514
Organization specific TLV (127), length 6: OUI Ethernet bridged (0x0080c2)
0x0000: 0080 c201 0084
Organization specific TLV (127), length 16: OUI Juniper (0x009069)
0x0000: 0090 6901 4250 3032 3038 3234 3838 3039
Organization specific TLV (127), length 14: OUI Ethernet bridged (0x0080c2)
0x0000: 0080 c203 0000 0764 6566 6175 6c74
Organization specific TLV (127), length 12: OUI Ethernet bridged (0x0080c2)
0x0000: 0080 c203 0084 0576 6f69 6365
Organization specific TLV (127), length 7: OUI ANSI/TIA (0x0012bb)
LLDP-MED Capabilities Subtype (1)
Media capabilities [LLDP-MED capabilities, network policy, location identification, extended power via MDI-PD] (0x0017)
Device type [network connectivity] (0x04)
Organization specific TLV (127), length 7: OUI ANSI/TIA (0x0012bb)
Extended power-via-MDI Subtype (4)
Power type [PSE device], Power source [PSE - primary power source]
Power priority [low] (0x03), Power 3.7 Watts
Organization specific TLV (127), length 8: OUI ANSI/TIA (0x0012bb)
Network policy Subtype (2)
Application type [voice] (0x01), Flags [Tagged]
Vlan id 132, L2 priority 0, DSCP value 46
End TLV (0), length 0






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