How does two different EVC communicate when using different encapsulation

In last post, ports are communicating with the same vlan encapsulation type. But how will the different encapsulation communicate with each other.

We know when we configure dot1q encapsulation on router’s port, it always remove the tag during ingress and add the tags during egress forwarding. If the router is configured with multiple sub-interfaces and every sub-interface is having different dot1q encapsulation; in that case the router always remove the vlan tags while ingress from one sub-interface and adds the tags during egress of that sub-interface. To perform this you must have router or layer 3 capable switch which could perform this. (Without Layer 3 device)

EVC architecture also works on the same mechanism, as per given configuration, both the service instances cannot communicate with each other as their encapsulation is different. One service instance is carrying 109 and other is carrying 110.  

Switch (config)# interface gigabitethernet0/10

Switch (config-if)# switchport mode trunk

Switch (config-if)# switchport trunk allowed vlan none

Switch (config-if)# service instance 101 Ethernet

Switch (config-if-srv)# encapsulation dot1q 109

Switch (config-if-srv)# bridge-domain 103

Switch (config)# interface gigabitethernet0/11

Switch (config-if)# switchport mode trunk

Switch (config-if)# switchport trunk allowed vlan none

Switch (config-if)# service instance 101 Ethernet

Switch (config-if-srv)# encapsulation dot1q 110

Switch (config-if-srv)# bridge-domain 103

Both the service instance can communicate if and only if they receive the same encapsulation type. To achieve this we must use the rewrite keyword in any of the service instance. Rewrite keyword performs the pop operation during ingress consequently vlan tag gets removed and symmetric keyword helps to perform the inverse function of adding vlans during egress.   

Switch (config)# interface gigabitethernet0/10

Switch (config-if)# switchport mode trunk

Switch (config-if)# switchport trunk allowed vlan none

Switch (config-if)# service instance 101 Ethernet

Switch (config-if-srv)# encapsulation dot1q 109

Switch (config-if-srv)# bridge-domain 103

Switch (config)# interface gigabitethernet0/11

Switch (config-if)# switchport mode trunk

Switch (config-if)# switchport trunk allowed vlan none

Switch (config-if)# service instance 101 Ethernet

Switch (config-if-srv)# encapsulation dot1q 110

Switch (config-if-srv)# rewrite ingress tag pop 1 symmetric

Switch (config-if-srv)# bridge-domain 103

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How to configure Bridge Domain For Two Different Ports

In the previous post, I have shown how to configure a single port with single service instance. But when two different ports wants to communicate, how could it be possible by using EVC?

Switch (config)# interface gigabitethernet0/10
Switch (config-if)# switchport mode trunk
Switch (config-if)# switchport trunk allowed vlan none
Switch (config-if)# service instance 101 Ethernet
Switch (config-if-srv)# encapsulation dot1q 102
Switch (config-if-srv)# bridge-domain 103
Switch (config)# interface gigabitethernet0/11
Switch (config-if)# switchport mode trunk
Switch (config-if)# switchport trunk allowed vlan none
Switch (config-if)# service instance 101 Ethernet
Switch (config-if-srv)# encapsulation dot1q 102
Switch (config-if-srv)# bridge-domain 103

Switch (config-if)# service instance 101 Ethernet
Switch (config-if-srv)# encapsulation dot1q 102
Switch (config-if-srv)# bridge-domain 103


Golden Rules while configuring multiple instances in single port:-

1. All the instances must fall under same bridge domain.
2. All the service instance should have same dot1q encapsulation, if the dot1q encapsulation is not same in that case rewrite keyword is used.

In my next port I will explain about how to make communication possible in same bridge domain with different encapsulation dot1q.


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How to configure service instance in EVC architecture?

How to configure a service instance in Cisco ME switches
Switch (config)# interface gigabitethernet0/10
Switch (config-if)# switchport mode trunk
Switch (config-if)# switchport trunk allowed vlan none
Switch (config-if)# service instance 101 Ethernet
Switch (config-if-srv)# encapsulation dot1q 102
Switch (config-if-srv)# bridge-domain 103

Remember Golden Rules While Configuring Service Instance
1.Service instance port cannot be configured as switch port.
2.Service instance port always a trunk port with no vlans allowed.
3.Bridge-domain and dot1q number could be same or different as encapsulation doesn’t affect on forwarding traffic.
4.Vlans fall under encapsulation doesn’t effect on the router vlan database as those are local to that service instance only.

Understand the configuration of service instance
“service instance 101 Ethernet” in this line 101 is the id which is local identifier of the service instance.
“encapsulation dot1q 102” matches incoming vlan under this service instance. It could be one vlan or range of vlans.
“bridge-domain 103” adding the service instance into the bridge domain number 103. 103 is the identifier which could be ranging from 1 to 8000. Number of bridge domain support depends on the license.


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Metro Ethernet EVC features

When we configure service instance on any port, that port becomes a pseudo port. The service instance defined under any port has some rules to match the incoming frames from CPE. Those rules defined the Ethernet flow points. Without the rules, service instance in itself doesn’t do anything.

Encapsulation
Encapsulation dot1q defines the matching criteria of incoming and outgoing frames. We can match single vlan, double tagged vlans, class of service (CoS), ether types and layer 2 protocols under any EFP(Service Instance).

Bridge Domain
A bridge domain is single broadcast domain which could be used to mapped two different service instances into a single one. Bridge domain is identified by the service instance number. It has nothing to do with the vlan. So the service instances in same brige domain can communicate with each other.

Split Horizon
Service instances which are in same bridge domain can communicate with each other but by adding split-horizon they cannot forward the traffic from one instance to another. This feature is used when the same vlan is used for the instances but both belong to different customers.

Rewrite
Rewrite is used to modify the vlans packets by adding or removing dot1q tag.


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What is Service Instance In Metro Ethernet?

Legacy interface gives the flexibility to create sub-interfaces which is also known as logical inteface. Every logical interface consumes one IDB which has the limitation of scalability factor of vlans in the box. But the Metro Ethernet architecture which is EVC comes up with new thing which is service instance. It gives the many more functions with addition to the legacy logical interface. Service Instance could be considered as a service which can use a single port with the combination of layer 2 and layer 3 ports. The data entering in physical ports matches the service instance rules and filters the data according to the rules. We can create different type of service instances and bind all the service instances on the single physical port which gives the flexibility to service provider in terms of scalability. The another advantage of using service instance is that one can bridge the different domains but the same functionality could not be used by the sub-interfaces.

Different Type of Service Instances:-
1. Single Dot1q tag matching
2. Double tag matching
3. Untagged or native packets matching

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Juniper Over Promises Under Delivers

No one has ever thought that competition will smash Juniper openly in market because of its false commitments. This has been seen first time in Internet history. Finally a website has been launched by CISCO which explicitly says that how CISCO(Customer Trusted Partner) is Better than Juniper not only in Data Center Networking but in each and every aspect. Below are the few facts which Juniper committed long time back to customers but still not able to deliver them:-

1. Juniper promised 100 Gigabit Ethernet on MX-series edge routing products two-and-a-half years ago. It’s still not available.
2. Juniper announced the T4000 core router in 2nd half CY2010. It’s been over a year now, where is it?
3. Juniper’s Project Falcon mobile platform: After three launches in 2009, 2010 and – again — in 2011, Juniper still has not publicly debuted the product or announced any customers of it.
4. Juniper’s Project Stratus/QFabric for the data center: Despite four announcements since February 2009, the QFabric system is still unavailable. If QFabric is finally delivered later this year, it will have taken more than two-and-a-half years to deliver. What is available does not deliver on Juniper’s “3-2-1” vision.

Read More About Stunning Facts To Select Cisco Over Juniper

Read the full story to get to know about the vendor who is over-promised and under delivered.


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Good Optical Links

Below is the list of few good links for optical power budget calculations, design and troubleshooting.

Compressed Air Cleaning Issues for Fiber-Optic Connections

Inspection and Cleaning Procedures for Fiber-Optic Connections

Calculating the Maximum Attenuation for Optical Fiber Links

Introduction to Optical Fibers, dB, Attenuation and Measurements

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