Tuesday, September 29, 2009

GRE Tunnels Never Down

Generic Routing Encapsulation aka GRE was originally developed by Cisco. In the recent stages, it was developed to transport packets from one network to another. As the time grows, it became a part of VPN. It is used to route non routeable packets from the IP backbones. GRE mechanism is used by various protocols to encapsulate the packet like PPTP uses GRE encapsulation for establishing tunnel and Rosen draft is fully based on GRE to provide Multicast Over VPN (MVPN) services in MPLS cloud.
GRE tunnels are completely stateless because of that, it doesn't contains the information of the remote end peer.During the creation of interface tunnel, we need to specify the valid source address or interface and destination address. Assume the remote end tunnel creation process is not in place but still the line protocol of tunnel is up which was created at one end. So it means, GRE has nothing to do with the remote destination address reachability. Due to this feature, GRE tunnel never bring down in case of remote failure or remote tunnel absence which leads lot of problems of flushing routes from the routing table. The problem was overcome by using GRE tunnel keepalives.
A decade or two decades ago, GRE was used for serving VPN to the customers. During that time, SP provide GRE connectivity among the remote sites of the customers. For complete traffic forwarding, a routeable IP address was extended from PE to CE and on the basics of that IP address a GRE tunnel was established. The main disadvantage of this model is that customers require (n*n-1)/2 tunnels for full mesh which was really a cumbersome one. This was overridden by MPLS because it provides full mesh by default.

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Wednesday, September 23, 2009

Project Management Training

Emerald Associates is a premium Oracle Primavera partner, offering complete list of certified Primavera training courses. The company is in the market since 1989 and has specialization in project management products. The products primarly focus on cost management,risk management and administration security. Now a new section of trainng has been added recently where in company will conduct trainings and train the customers according to their needs. This will lead to save cost of company in terms of project completion on time and proper resource allocation. According to the market needs company has launched three new trainings in various locations

1) Primavera training in USA
2) Primavera training in Canada
3) Primavera on-site/internal training

The courses provides the complete hands on training.

Primavera training in USA
Emerald Associates offers certified Project Risk Pertmaster training. The training s mainly targeted to Program Managers,Project Managers, Resource Managers. Risk managemnet is the leading part of any project managemnt. If the managers are not able to analyse the risk in the project then the outcomes will be weird which could not be accepted by any organisation.

Primavera training in Canada
This training mainly provides the planning and scheduling part of the project managment. This will help the managers how to start with planning phase with schedule algorithms. If the both are not consistent then create lot of problems in completion of projects.

Primavera on-site/internal training
In this type of training, users can go to emerland or ask them to come to their premises. This will save lot of cost from userend in terms of resources.
But this training is only available when the number of users are more, mainly more than 5.

The outcomes of the training are given below:-
How to create the project with activities and resources.
Scheduling of the project is mainly focussed.
Resource and Cost analysis.
Comparison between current and target cost.

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ATM - Packet and Circuit Switching

Circuit switching was the first information transform mode which was used for telephone networks. It is more efficient for transport real time services which requires quality of service qurantees in terms of delay and loss. In fact,TDM doesnot offers no delay except for switching latency and no packet losses. But on the otherhand, circuit switching was found inefficient for the transport of bursty traffic.
For bursty traffic packet switching was developed. The packet switching offers transport of bursty traffic but no quality of services. It is essentially a best effort switching technique where network will make attempt to trasfer every packet.

ATM switching is the technology which was developed by merging the concept of both packet as well as circuit switching. It has the various advantages
1. It offers quality of services like circuit switching.
2. It offers the statistical multiplexing like pacet switching.

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Monday, September 21, 2009


Customers look for the redundancy of lan and wan because of more uptime . In those scenarios , two routers deply at customer premises and two wan links from different PE are required. In this topology, I am assuming the customer is using the same service provider with redundant pops. Hot Standy Routing Protocol aka HSRP with single group is deployed for lan and static routing is being used between PE and CE. R5 is having the higher priority and working as active router and R4 is working as standby router.
Click Here to Download Full Article.

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Saturday, September 19, 2009

External LSA 5

Read more about LSAs
External LSA describes the router that are outside the OSPF domain. Type 5 LSAs are originated by ASBR and flooded throughout the entire AS. THe LSID is the external network number therefore the flooding scope and depending upon the number of the external network. The default lack of summarization can also be a major issue with external LSA. Therefore try to summarize the block of pool at ASBR to reduce the flooding problems.
Forwarding address plays a vital role in LSA5

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Friday, September 18, 2009

OSPF: Link State Advertisement (LSA) - 4

Read more about LSA1,LSA2 and LSA3

Type 4 summary LSA is generated by ABR only when ASBR exists with in the area. It identifies the ASBR and provides route to it. The LSID is set to the ASBR router id. All the traffic destined to an external AS, requires routing table knowledge of the ASBR that originates the external route.
e.g. ASBR sends type 1 router LSA with E bit known as external bit; that bit is the identity of ASBR. When ABR receives this LSA and convert it to LSA4 and flood to the backbone area subsequent ABRs regenerate a type 4 LSA and flood into their areas.

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Wednesday, September 16, 2009

OSPF: Link State Advertisement (LSA) - 3

Read About LSA1 and LSA2
ABR(Area Border Router) sends the summary LSA type 3 on by area and rest of the OSPF AS. LSID is set to the network number, the mask is also advertised. By default OSPF doesn't summaey group of contigious networks. By default type 3 lSA is advertised into the backbone area for every subnet defined in the originating area which could cause significant flooding problems consequently should configure the manula route summary at ABR. Summary lsa are flooded only in a area but regenarated by the other ABRs and flood in other areas.

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Tuesday, September 15, 2009

Fastest Encryption Algorithm

Bangalore: An Indian scientist has developed the fastest method to encrypt the hard disk of a computer. Encrypting helps in keeping the data on hard disk secure even from an attack by hackers. "From a practical point of view, the requirement is actually to achieve both speed and security. Otherwise, encryption and decryption may take so much time that software which runs on computer become unacceptably slow. And, in the current state of the art, this work provides the fastest known algorithm for disk encryption," claims Palash Sarkar, creator of this unique algorithm and Professor at the Indian Statistical Institute (ISI), Kolkata.
The new algorithm encrypts the data 30-40 percent faster than the previous ones. The results of the research will appear in October 2009 issue of the 'IEEE Transactions on Information Theory', one of the top research journals in the field of transmission, processing and utilization of information.
Source:- Silicon India

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Friday, September 11, 2009

OSPF: Link State Advertisement (LSA) - 2

Read LSA1
Type 2 LSA generates for each transit broadcast or NBMA network in area. Transit network has at least attached two directly connected routers. Multiacess like ethernet is an example of transit network. Designated Router (DR) is responsible for advertising network LSA which includes the list of directly connected routers with subnet mask list. It floods only in area and doesn't cross the Area Border Router(ABR). LSID for network LSA is the ip interface address of the DR that advertises it.

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Thursday, September 10, 2009

OSPF: Link State Advertisement (LSA) - 1

Type 1 LSA known as router lsa in OSPF. It floods all the routers in an area and states the directly connected or interfaces of the router. LSA1 includes the link ID field that identifies the network number and subnet mask. Depending on type of link id has different meanings. Each router link is defined by one of the four types.

Type 1:- Point to Point to another router.
Link ID:- It is the neighbor router id.

Type 2:- This is tcommon to transient network.
Link ID:- Link ID is the address of the DR.

Type 3:- It is connection to stub network.
Link ID:- IP network or subnet number.

Type 4:- It represents virtual link.
Link ID:- It is the neighboring router id.

With this type 1 LSA defines router as ABR or an ASBR.
A refulgent explanation of LSA1

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Wednesday, September 9, 2009

Use TOS For QOS Testing

QOS is one of the screwing topics in CCIE and in lab after QOS configuration, every classmap,policymap need to be checked. During that time, one tool helped a lot that is extended ping. In extended ping, we have TOS byte, which is used to mark the packets according to us. Lets check how to acheive this.
e.g Traffic of DSCP value 46 need to be checked with ping. First need to convert the 46 into binary then append 00 in LSB. There after get the decimal of the whole binary number and use it in extended ping when it ask for the TOS. Binary of 46 is 101110. Now append 00 so the new binary number would be 10111000. Get the decimal of number which would be 184. Use 184 in TOS and see the marking of 46 where that policy is called.

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Tuesday, September 8, 2009

Selling DHCP Services

Selling DHCP as service in service provide cloud is very benefecial. With the SP could raise the source of incomes without additional investment. Why I am talking about DHCP as service; how mpls sp could host the services per vpn basics? This is not the cost saving oppositely SP need to invest in DHCP servers as many as VPN need to be hosted. Totally wrong, SP can share the global DHCP servers among all the vrfs and ip addresses will be allocated according to the vrf. This service is nothing but need to use dhcp relay agent which will sophist this requirement.

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Monday, September 7, 2009

When and Where PHP Happens

I found a good question asked by new babie on PHP in netpro discussion. The question was, "According to PHP concept, it should happend at each and every hop."
The answer for the question is simple and straight forward. Always keep in mind one thing that PHP happens only for the destined network not for the intermediate routers. So only that router will perform the PHP which will become the second last router of destination in service provider cloud, rest all the routers will perform the swapping.

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Friday, September 4, 2009

International MPLS Conference

Good news for mpls lovers; ISOCORE is conducting international MPLS conference from 25th to 28th october,2009 at Washington DC. Register yourself as soon as possible.

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Wednesday, September 2, 2009

Forwarding L2MPLS Traffic Over MPLS Traffic Engineering

Forwarding l2mpls over traffic engineering tunnel is not a bit complex but a tricky one. This all depends over the requirement how the service provider wants to route the traffic of backhauls. In this test setup we have implemented the MPLS TE for a single customer rest of the traffic of backhaul will follow the traditional IGP path.
The two options available in pseudo wire to forward the l2mpls traffic over te tunnel.
a) preferred-path peer
b) preferred-path tunnel interface

In this test result, option a is used to route the only customer traffic. If option b is used with auto-route announce, in that case the full backhaul traffic follow the tunnel path which may create more problems.

How to use preferred-path peer option
To use this option a loopback 100 is created on R3 which is the tunnel tail-end router and is not announced in the IGP. The reason for not announcing in IGP is that because when the tunnel path will get disconnect, the traffic will fall to the normal IGP path. This could be disabled by using fallback option in preferred-path command.
On R1 a TEST pseudowire is created with preferred-path peer and a static route is imposed on R1 for with next hop as tunnel 10.

Configuration of R1
pseudowire-class TEST
encapsulation mpls
preferred-path peer

ip route Tunnel10

interface Tunnel10
ip unnumbered Loopback0
tunnel destination
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng path-option 1 explicit name R3
no routing dynamic

ip explicit-path name R3 enable

Commands Need To Be Enabled On All RSVP Participating Interfaces

mpls traffic-eng tunnels
ip rsvp bandwidth 200 200

Global Config Commands

mpls traffic-eng tunnels

Commands for OSPF
router ospf 1
mpls traffic-eng router-id Loopback0
mpls traffic-eng area 0

Test Results

Download the full test results.

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L2MPLS With Traffic Engineering

Service provider provision l2 circuits for the customers where customers need to extend the lan services to the remote offices. Provisioing of l2 circuits does in two ways; one over ip cloud and another is over mpls cloud. But sometimes customers wants to forward the jitter senstive traffic over the backbone and to fulfill the SLA service provider need to forward the l2 traffic over another path which is not best in IGP. For this traffic engineering plays a vital role with fallback mode. In the next post I will be posting how to configure MPLS TE for l2 circuits.

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