NTP via BITS on ASR9010

[pstebner10]

Has anyone ever done this? I see that v4.3.0 has added NTP-PTP interworking and I thought that this would be possible, but the documentation is pretty scarce.

Basically, we have a GPS clock providing BITS timing via the SYNC0 port on 0/RSP0/CPU0, and we want to be able to run the ASR as a master NTP server based off of this. Any ideas?

thanks in advance,

Paul

[xthuijs]

Paul,

If you have a proper GPS TOD input then you can use the following CLI:

"ntp master ptp" is used to pick up the input source (GPS / DTI) on the master 
the CLI is to be updated to "ntp master chassis-tod-source".

xander

---

Xander Thuijs CCIE #6775

Principal Engineer ASR9000

[pstebner10]

Thank you for the reply, Xander. I am running 4.3, but the command that you listed is not available. The only command that it will take, which I believe is the correct command, is ntp master primary-reference-clock.

The problem is that I cannot get PTP to run properly using the BITS clock as a source. Here's my current config:

frequency synchronization

quality itu-t option 2 generation 2

!

clock-interface sync 0 location 0/RSP0/CPU0

port-parameters

  bits-input t1 d4 ami

!

frequency synchronization

  selection input

  priority 10

  wait-to-restore 0

  ssm disable

  quality receive exact itu-t option 2 generation 2 PRS

!

ptp

profile MASTER_PTP

  transport ipv4

  sync frequency 64

  announce timeout 2

  delay-request frequency 64

If I run show freq sync ptp I get this:

Mon Jan 21 14:45:27.099 CST

Node 0/RSP0/CPU0

==============

  PTP is unavailable.

Your help is appreciated.

thanks,

Paul

[xthuijs · Accepted solution]

Paul, ah wait, you are using the sync port, that is a BITS only for frequency.

If you want to derive the Time of Day, you need to use the 1588 ethernet port or the GPS interfaces that the RSP440 has.

Then when you pull in the TOD form the GPS, you can use that time for the system clock and at the same time declare yourself NTP master to distribute it to other clients.

In order to use PTP, you need to apply it to an interface also btw, something like this:

Global Configuration

PTP is globally enabled in the system by entering the  global configuration item.

RP/0/0/CPU0:ios#conf
RP/0/0/CPU0:ios(config)#ptp
RP/0/0/CPU0:ios(config-ptp)#commit

There are several further optional items of global  configuration that affect the system behaviourhttp://enwiki.cisco.com/PTP/Configuration/OptionalConfig.

Setting the  global enable item alone will cause PTP to run with the default clock  config:

RP/0/0/CPU0:ios(config-ptp)#do show ptp advertised-clock
Clock ID: Local Clock (123456fffe789123)
Clock properties:
  Priority1: 128, Priority2: 128, Class: 248, Accuracy: 0xfe
  Offset scaled log variance: 0xffff
  Domain: 0, Time Source: Internal, Timescale: ARB
  Current UTC offset: 24 seconds 

The default Clock ID is derived from the router's MAC  address.

Interface configuration

Configuring PTP to run as  Master

To enable  PTP on an interface, enter the PTP interface configuration item from the  interfaces config submode. By default this will cause PTP to run as a  unicast, IPv4 master.

RP/0/0/CPU0:ios#conf
RP/0/0/CPU0:ios(config)#interface GigabitEthernet 0/2/0/0 
RP/0/0/CPU0:ios(config-if)#ptp
RP/0/0/CPU0:ios(config-ptp-if)#commit

There are several further items of interface  configuration that affect the system behaviour, such as delay-request,  sync and announce message packet send rates and the transport type

Setting the  interface enable item alone will cause PTP to run on the interface with  the default configuration:

RP/0/0/CPU0:ios#show ptp interfaces gigabitEthernet 0/1/0/0
GigabitEthernet0/1/0/0 is in Master state
  PTP port number: 2049
  IPv4 transport: IPv4 address 20.0.0.2
  Linestate: Up
  Mechanism: Two-step delay-request-response
  Sync rate: every second
  Announce rate: every 2 seconds, timeout 3 intervals
  Min Delay-Request rate: every second
  CoS: 6, DSCP : 46
  Platform capabilities:
    Supported:     One-step, Ethernet, Multicast, Slave
    Not-supported: IPv6
    Max-Sync-rate: 3 per second
  0 Unicast peers

Configuring PTP to run as  Slave

In order for  PTP to run as Slave on an interface:

• The interface should be ready to run PTP

• The  interface must have foreign masters configured in its master table.
• At least one foreign master  must have a higher clock priority (or configured priority in the  interface's master table) than the local clock, and be receiving  announce messages from such a master.

When  several interfaces are configured to run as Slave, PTP determines which  interface has the best foreign master and that interface moves to Slave  state.

To add a master to an  interface's master table

RP/0/0/CPU0:ios#conf
RP/0/0/CPU0:ios(config)#interface GigabitEthernet 0/3/0/3
RP/0/0/CPU0:ios(config-if)#ptp 
RP/0/0/CPU0:ios(config-if-ptp)#master { ipv4  | ethernet  }
RP/0/0/CPU0:ios(config-if-ptp-master)#commit

From this submode you can also configure further  aspects of the foreign master, namely priority (to override the clock  properties) and multicast (whether this is a multicast master).

RP/0/0/CPU0:ios(config-if-ptp-master)#priority 24
RP/0/0/CPU0:ios(config-if-ptp-master)#multicast

You can verify  what masters are in an interface's master table by running 'show ptp  interfaces':

RP/0/0/CPU0:ios#show ptp interfaces
Thu May  6 02:54:13.907 PDT
GigabitEthernet0/1/0/0 is in Passive state
  PTP port number: 2049
  IPv4 transport: IPv4 address 20.0.0.2
  Linestate: Up
  Mechanism: Two-step delay-request-response
  Sync rate: every second
  Announce rate: every 2 seconds, timeout 3 intervals
  Min Delay-Request rate: every second
  CoS: 6, DSCP : 46
  Platform capabilities:
    Supported:     One-step, Ethernet, Multicast, Slave
    Not-supported: IPv6
    Max-Sync-rate: 3 per second
  Master table:
    MAC-address 1234.2345.3456: priority 5
    IPv4-address 20.0.0.1: priority not set
    IPv4-address 12.23.34.45: priority not set, multicast
  0 Unicast peers

xander

[pstebner10]

Xander-

Thank you for the above information.

If my GPS clock only has a BITS output I assume that I cannot achieve what I want. Does this sound correct?

thanks again,

Paul

[xthuijs · Accepted solution]

Correct Paul, the BITS just gives you freq sync (for syncE or your chan circuits)

xander

[pstebner10]

Thakns for your help, Xander.

Paul

[rakeshsekhar]

Hi Xander,

              May I know how can I configure NTP services in VPRN of ASR 9010 ?

[xthuijs]

I am sorry, I have no idea what a VPRN is? you mean a vrf?

If that is the case then the following will apply:

RP/0/RSP0/CPU0:A9K-BNG(config)#ntp ser vrf RED ipv4 1.2.3.4

xander

[rakeshsekhar]

Hi  Xander,

                                   Thanks for your reply.  I am clariying my question. I meant the NTP within a VPN service, that enables the service router to act as the NTP server to CPE devices on a vrf interface. Along with that, authentication keys can be configured on a per-vrf basis. How can we configure authentication and ntp in ASR ?? I am expecting your valid response. Can I use this command "authentication-key (NTP)"    to configure authentication for vrf ?

[manuv1984]

Hi Xander,

                      Why we need PTP because NTP can do time and frequency synchronization. I searched so many documents. But every where they have mentioned both having similar features & characterestics and having only a little difference between them. But nobody clearly mentioned the difference between them.  Could you please give the perfect difference between them or suggest any good documents for getting the knowledge. Please do the needful.

[xthuijs]

Now that is a great question and the answer is going to depend on who you ask it to... Personally I have no preference of one over the other. It is basically a comparison between Mercedes and BMW. Both are great, but the options differ a bit and there might be a slight difference in cost/performance depending on what your primary needs are. Puntting the "standard" (useless) answer aside, here some of *my* thoughts in regards to the 2 protocols:

If we're considering time sync only, then PTP is said to be more accurate due to its nature of requiring dedicated hardware support, which makes it at the same time inherently more expensive too.

Another big one is that NTP uses point to point communication and PTP uses multicast. So if your number of clients is large(r), then PTP might be lighter on network usage. Using mcast requires also the right configuration in your routers and switches in addition, that if you are not running mcast natively.

If we're looking at syncing time (of day) only, then both are really equivalent in smaller scale applications and then NTP is probably a better choice considering the well established nature it has and the accuracy it can provide by default.

When we're talking frequency sync, which is what this disucssion above was mainly focussing on, then PTP is likely a better choice as NTP is not dedicated to freq sync, and since freq sensitive applications (mobile) are in question I would tend to suggest PTP as a better option to distribute the frequency.

I saw this great overview/comparison from Symmetricom one time, so let me include that for reference:

Finally, PTP or IEEE1588 requires licenses and typhoon hardware for the asr9000 which is an additional cost and you would need to determine then if the increased accuracy and freq distribution is key to your deployment.

regards

Xander Thuijs     CCIE #6775

Principal Engineer, ASR9000

[manuv1984]

Hi Xander,

                  Ossum !!!! Thanks for your great explanation. May I know the real usage of " profile",

"priority1" and "priority2" commands in PTP configuration ? Which type of profile is used in asr 9k ? Is it

"G.8265.1 [2"(Telecom Profile).

[xthuijs]

Not a problem at all

the priority selection or profile can be used to prefer one origin over the other in case there are multiple sources to choose from.

cheers!

Xander Thuijs     CCIE #6775

Principal Engineer, ASR9000

[manuv1984]

Hi Xander,

                        May I know the relation/difference between SyncE and BITS ?? Please give me a response.