Total 16 Blogs

Created by - Orhan Ergun

What is OTT – Over the Top mean? OTT Providers

What is OTT – Over the Top and How do OTT Providers Work? Over the Top is a term used to refer to Content Providers. So, when you hear Over the Top Providers, they are Content Providers. Content can be any application, any service such as Instant messaging services (Skype, WhatsApp), streaming video services (YouTube, Netflix, Amazon Prime), voice over IP, and much other voice or video content types. This post is shared based on the information from my latest book ‘Service Provider Networks Design and Architecture First Edition‘. If you want to understand telecom (Distance communications) and Service Provider Business, I highly recommend you to purchase this book. An Over-the-Top (OTT) provider provides content over the Internet and bypasses traditional private networks Some OTT Providers distribute their content over their CDN over their private networks though (Google, YouTube, Akamai). They deliver the content over traditional ISP networks. The creation of OTT applications has created a conflict between companies that offer similar or overlapping services. The traditional ISPs and Telco have had to anticipate challenges related to third-party firms that offer OTT applications and services. For example, the conflict between a Content Provider company such as Netflix and a Cable Access Provider Company such as Comcast, which consumers still pay the cable company for having access to the Internet, but they might want to get rid of their cable TV service in favor of cheaper streaming video over the Internet. While the cable company wants to offer fast downloads, there is an inherent conflict of interest in not supporting a competitor, such as Netflix, that bypasses cable’s traditional distribution channel. The conflict between the ISPs and the OTT Providers led to the Net Neutrality discussion Net Neutrality is the principle that data should be treated equally by ISPs and without favoring or blocking particular content or websites. Those who are in favor of Net Neutrality argue that ISPs should not be able to block access to a website owned by their competitor or offer “fast lanes” to deliver data more efficiently for an additional cost. OTT services such as Skype and WhatsApp are banned in some Middle East countries by some Operators, as OTT applications take some part of their revenue. For example, in 2016, social media applications such as Snapchat, WhatsApp, and Viber were blocked by the two UAE telecoms companies, Du and Etisalat. They claimed that these services are against the country's VOIP regulations. In fact, UAE is not the only country blocking access to some OTT applications and services. Many countries in the Middle East have followed the same model. They either completely blocked access to some OTT applications or throttled them, so the voice conversation over these services became near impossible.If you liked this post and would like to see more, please let me know in the comment section below. Share your thoughts so I can continue to write similar ones.

Published - Tue, 24 May 2022

Created by - Orhan Ergun

What does PE-CE mean in MPLS?

What does PE-CE mean in the context of MPLS? What are CE, P, and PE devices in MPLS and MPLS VPN? These are foundational terms and definitions in MPLS. MPLS is one of the most commonly used encapsulation mechanisms in Service Provider networks and before studying more advanced mechanisms, this article is a must-read. In order to understand PE-CE, we need to understand first what are PE and CE in MPLS. I am explaining this topic in deep detail in our CCIE Enterprise and Self-Paced CCDE course. Let’s take a look at the below figure. Note: If you are looking for a much more detailed resource on this topic, please click here.Figure -1 MPLS network PE, P, and CE routers In Figure-1 MPLS network is shown. This can be an Enterprise or Service Provider network. MPLS is not only a service provider technology. It can provide segmentation/multi-tenancy for the enterprise environment as well. Three different types of routers are shown. CE, PE, and P routers. CE devices are located on the customer site. PE and P devices are located on the Service Provider site. If it is an Enterprise network, WAN routers can be considered PE routers, and the switches can be CE devices. PE routers don’t have to be connected to P routers. PE routers can be directly connected to each other. CE devices don’t run MPLS. PE devices run both IP and MPLS. P devices don’t run IP but only MPLS. You find the above sentence everywhere when you study MPLS. It actually means CE devices don’t switch the MPLS label to function. PE devices, when a packet arrives first lookup IP destination address and then use MPLS label to function. P devices don’t do IP lookup at all but only switch MPLS labels. Otherwise, P devices of course have IP addresses on their interfaces as well. In MPLS, the service can be Layer 2 or Layer 3. In Layer 3 MPLS VPN, IP routing is enabled between PE and CE devices. These devices have their own roles. Provider Edge and Customer Edge. The provider Edge device is attached to the customer site and the MPLS network, on the other side Customer Edge device, is at the customer site and doesn't require MPLS protocol for its function. Routing protocols in theory can be Static Routing, RIP, EIGRP, OSPF, IS-IS, and BGP. All of them are IETF standards. But in real life, most service providers only provide Static Routing and BGP as a routing protocol with the customer. PE-CE interface is only IP and not MPLS. This interface is the boundary between the MPLS network and the IP network. If Enterprise purchases MPLS VPN service, this means, the customer is receiving VPN service from the MPLS backbone service provider and the customer doesn't run MPLS with the Service Provider. MPLS is only enabled in the Service Provider network. A specific application of PE-CE as MPLS is called CSC (Carrier Supporting Carrier). But in basic MPLS Layer 3 MPLS VPN, the PE-CE link is always IP. To have a great understanding of SP Networks, you can check my newly published “Service Provider Networks Design and Perspective” Book. It covers the SP network Technologies also explains in detail a factious SP network. Click here

Published - Thu, 21 Apr 2022

Created by - Orhan Ergun

What is IRU ? Indefeasible Right of Use ?

What is IRU (a.k.a Indefeasible Right of Use)?  If you are working in the Operator, Service Provider, or Telco/Carrier networks, you probably heard this term. If you haven’t, you need to learn it. To have a great understanding of SP Networks, please check our 150 hours, detailed, CCIE SP Training Service Providers use the transport network of others. This is very common, in fact, even the biggest networks use other carriers' transport/transmission infrastructure, especially outside of their main location. For example, an operator might provide services mainly in the U.S, but want to extend its network to Europe. Instead of setup a fully-fledged telecom environment in Europe to provide a service, let’s say to Business and Residential customers, one option is to use local carrier networks in Europe. Indefeasible Right of Use (IRU) Is a permanent contractual agreement That cannot be undone, between the owners of a cable and a customer of that cable system. The cable is mostly a fiber cable as fiber can carry more data than any other type of media. Buying a fiber can be in two ways, either, Leasing or IRU (Indefeasible Rights of Use) based. Indefeasible means ‘not capable of being voided or undone. The Customer purchases the right to use a certain amount of capacity of the fiber system for a specified number of years. Customer who purchases IRU can lease the capacity to other companies. Let me give you an analogy. Think of it in this way, if you are renting an apartment, you sign a contract with the Landlord as a tenant. You cannot rent that apartment to someone else. This is similar to leasing. But if you are the landlord, you can rent it to anyone you want. This is an example of an Indefeasible Right of Use-based agreement. Let’s have a look at the differences between Leasing and IRU-based contracts in detail. There will be some technical terms, be ready. IRU vs. Leasing A Fiber IRU contracts are almost always long term such as 20 to 30 years (Cable lifetime is generally considered as 25 years) Leased fiber doesn’t have to be a long term contract The most common leased service is IPLC which is Internal Private Leased Circuits. IPLC can be a half circuit or full circuit. (I will explain the half and full circuits IPLC in a separate post) IPLC unlike IRU doesn’t dictate the buyers to pay the cost of fiber upfront, IPLC is not a prepaid service Leasing is very flexible (In terms of contract duration, speed option, etc.)  but IRU can be very cost-effective Indefeasible Right of Use based contract gives the purchaser the right to use some capacity on a telecommunications cable system, including the right to lease that capacity to someone else But is an Indefeasible right of use-based contract suitable for every company? Why people don’t buy if it has a cost advantage? Why bother with MPLS? Should smaller companies purchase an IRU-based fiber? Smaller companies that need a leased line between, say, London and New York do not buy an IRU. They lease capacity from a telecommunications company that themselves may lease a larger amount of capacity from another company (and so on), until at the end of the chain of contracts there is a company that has an IRU, or wholly owns a cable system. Buying an IRU compare to other types of circuits such as MPLS, Metro Ethernet and Internet is much more costly. Thus smaller companies generally don’t buy IRU capacity.

Published - Sun, 10 Apr 2022

Created by - Orhan Ergun

Tier 1, Tier 2 and Tier 3 Service Providers

What is tier in the first place? If you are dealing with Service Provider networks, you hear this term a lot. But how do we define Tier 1, Tier 2, and Tier 3 Service Providers?   I am explaining this topic in deep detail in my specialized “BGP Zero to Hero” course. What should be their infrastructure to be seen as Tier 1 for example? Which tier is bigger in scale? Which one is better for the customers to purchase a service from? Why do Service Providers claim that they are Tier 1 or Tier 2? Note: If you are looking for a much more detailed resource on this topic, please click here. Let’s start with the definition first. Tier 1 Service Provider  A network, which does not purchase transit service from any other network, and therefore peers with every other Tier 1 network to maintain global reachability. They are the biggest guys geographically, but not always from the number of customers' points of view. Tier 2 Service Provider A network with transit connections, customers, and some peering, but that still buys transit service from Tier 1 Providers to reach some portion of the Internet. Tier 3 Service Provider A stub network, typically without any transit customers, and without any peering relationships. They generally purchase transit Internet connection from Tier 2 Service Providers, sometimes even from the Tier 1 Providers as well (I know some non-profit organizations which have a transit connection from Tier 1) Tier 1, Tier 2, and Tier 3 Service ProvidersThe above picture shows the general idea behind Tier 1, Tier 2, and Tier 3 Service Providers' connections and relationships. Tier 2 Providers generally can be a peer with another Tier 2 and Tier 1 Service Providers only peer with other Tier 1. The logic behind is actually very simple. Tier 1 Service Providers don’t peer with Tier 2 because Tier 2 providers are potential customers of Tier 1 Service Providers. If they can be a customer and pay the money for the transit connection, why would give them peer connectivity (Peering is free, at least in theory)Unless the customer changes their path preference with communities, service providers almost always choose customer over peering links vs. transit links. They want to utilize the customer links because they pay for the transit service. Even though peering is free thus SPs don’t pay each other for the service, peering brings them some cost. (They need to have a connection to the IX and have a router and port in the IX). There are just 11 or 12 Tier 1 Service Providers in the world and some Tier 2 level Service Providers always claim that they are Tier 1. By doing it, they target to have a free peering relation with the other Tier 1 of course so they wouldn’t pay transit costs and have other Tier 2 SPs as their customers. The same thing is valid for the Tier 3 Service Providers as well. They might try to show them as Tier 2 to get free peering from the other Tier 2 Service Providers. But often the Service Providers put strict requirements for the peering so claiming may not help! Last but not least, some thoughts for my more advanced readers; if an ISP is Tier 1 for IPv4, is it also Tier for IPv6?

Published - Sun, 10 Apr 2022

Created by - Orhan Ergun

EIGRP Feasible Successor

One of the advantages of EIGRP Feasible Successor is that it speeds up the EIGRP. In fact, if there is a Feasible Successor in the EIGRP network, such network converges faster than OSPF or IS-IS. But what is EIGRP Feasible Successor and how can we find one? If there is EIGRP Feasible Successor, how does EIGRP converges faster than OSPF or ISIS? In this post, I will explain the answers to the above questions. EIGRP Feasible Successor is a backup node that can satisfy the EIGRP feasibility condition. Feasibility condition simply means that the backup router should be loop-free. Let’s examine the topology shown below (Figure-1) to understand how EIGRP finds loop-free alternate/backup node.   Figure-1 EIGRP Feasibility ConditionFrom the Router A’s point of view, Router B and Router C are the equal cost routers; as a result, both ABD and ACD path can be used in the network. What’s more, Router A installs both Router B and Router C not only in the EIGRP topology table but also in the routing table. There is no backup router in the above topology since Router A uses both Router B and Router C to reach the destination behind Router D. Let’s increase the link cost between Router C and Router D.   Figure – 2 EIGRP Feasible SuccessorThe link cost of Router C–D is 15. In order to satisfy the feasibility condition for Router A, the link cost of Router C–D should be smaller than that of Router A–B–D total cost. Since 15 < 10 + 10, Router C can be used as a backup – router by Router A – to reach Router D. Router C is installed in the EIGRP topology table of Router A.   I will explain what will happen to the route if it is installed in the EIGRP topology table, instead of the routing table. Also, let’s examine one more example so that we can understand when Router C cannot be installed in the routing table or EIGRP topology table.    Figure-3 EIGRP feasibility condition is not satisfied The link cost of Router C–D is 25. In order to satisfy the feasibility condition for Router A , the link cost of Router C –D should be smaller than that of Router A –B–D. Since 25 > 10(A–B) + 10(B–D), Router C cannot be used as a backup router – by the Router A – to reach Router D. In Figure-3, Router C is not a feasible successor (Backup Router) simply because it doesn’t satisfy the EIGRP feasibility condition. What if Router C–D link is 20? In that case, since 20 = 10(A–B) + 10(B–D), Router C cannot be used as an EIGRP Feasible Successor. The link cost of Router C–D has to be smaller than that of Router A–B–D to be Router C EIGRP FS of Router A. Now that we have learned how to find EIGRP Feasible Successor, I will explain why if there is EIGRP feasible successor, EIGRP converges faster than OSPF or ISIS. When Router C satisfies the EIGRP feasibility condition, it is installed as a backup router in the EIGRP topology table of Router A. In order to understand this concept, I will first examine how EIGRP converges if there is a failure without feasible successor. Let’s assume that in Figure-3, Router A–B link fails. Router A, since there is no feasible successor (remember that Router C didn’t satisfy the EIGRP feasibility condition), will send an EIGRP query to Router C. Router A with the EIGRP query will ask Router C whether it has an alternate route. Router C’s successor (Primary path) is Router D, which is the destination. That’s why Router C answers Router A’s query. But obviously, there is a delay in this process. Now, let’s examine what happens if Router C satisfies EIGRP feasibility condition. In Figure 2, Router C is EIGRP FS of Router A. So, let’s use that topology. If Router A–B link fails in Figure -2, Router A doesn’t send an EIGRP query to Router C anymore. Rather, Router A immediately takes all the routes from EIGRP topology table and installs them on the routing table without running EIGRP Dual algorithm. Without running EIGRP, Dual algorithm’ statement is important. This is because if there is a failure, OSPF or IS-IS can run SPF algorithm again to find a backup route. Thus, in the case of failure, EIGRP FS reduces the convergence time by avoiding running EIGRP dual algorithm again.   Conclusion:   EIGRP FS is a backup loop-free EIGRP router. EIGRP FS avoids sending EIGRP query. EIGRP FS reduces convergence time in the case of failure (Link or Node). EIGRP node doesn’t run the dual algorithm to find a backup path if there is a failure of if there is a feasible successor. That’s why arranging the link cost accurately is very important for capacity planning, fast convergence, and availability.

Published - Mon, 14 Feb 2022

Created by - Orhan Ergun

Integrated Services QoS - Hard QoS

Integrated Services QoS - Hard QoS is first QoS approach, but currently we are not using. At the end of this post, you will know what is Integrated QoS, what was the idea with it and why it is not used today.   Quality of service (QoS) is the overall performance of a telephony or computer network, particularly the performance seen by the users of the network. Two QoS approaches have been defined by standard organizations. These are: Intserv (Integrated Services) and Diffserv (Differentiated Services). Intserv QoS demands that every flow requests a bandwidth from the network and that the network would reserve the required bandwidth for the user during a conversation. Think of this as on-demand circuit switching, each flow of each user would be remembered by the network. This clearly would create a resource problem (CPU, memory , bandwidth) on the network, and thus it was never widely adopted. Not only allocation bandwidth for each and every flow on each network device in the path, but also keep tracking these flows and tearing down when the flow is terminated is very resource intensive and people thought this will not be scalable and we haven't seen deployment for it. Protocol for Integrated Services was RSVP - Resource Reservation Protocol. Although we don't see usage of RSVP for Integrated Services, it is used in MPLS , by allocation Label for the destinations. Integrated Services is known as Hard QoS because flows are assigned bandwidth, with the SoftQoS or commonly known as Diffserv - Differentiated Quality of Service, flows are not assigned a bandwidth, instead we have application classes which gets bandwidth allocation. Thus, considered as much more scalable. Diffserv doesn’t require reservation; instead flows are aggregated and placed into classes. Each and every node can be controlled by the network operator to treat differently for the aggregated flows. Diffserv is a more scalable approach compared to Intserv and today if you are using QoS, you are dealing with Diffserv - Differentiated Services QoS or another name, SoftQoS!

Published - Sat, 08 Aug 2020

Created by - Orhan Ergun

What is Urban and Rural area in networking ?

What is urban and rural area ? What is underserved area in networking ? These definitions are heavily used in networking. And all broadband network designers take always these definitions into an account while they do their design. I think knowing these definitions as a network engineer is valuable for you. In general, a rural area or countryside is a geographic area that is located outside towns and cities Whatever is not urban is considered rural area though some people uses less populate than urban but more populated than rural area as suburban area Typical urban areas have a high population and large settlements Typical rural areas have a low population density and small settlements Underserved areas where there is no good network coverage (Broadband , Voice or any other data types) Unserved areas where there is no network coverage at all For example,if mobile operator will place a cell sites in an urban area, since the population density will be too high, they consider to place more cell sites than if they place those cell sites in a rural area. FTTx planers consider to change their ODN (Optical Distribution Network) design entirely depends on they are doing FTTx deployment in urban or rural areas. In general, having a fiber access to rural areas is considered as not a good idea economically, thus in rural areas either mobile broadband or WISPs (Wireless Internet Service Provider) with unlicensed spectrum serve. This is one of the topics under ‘ Service Providers Physical Connections and Locations ‘ module of Service Provider Design Workshop. Join this workshop to learn the concepts which are not thought in any other trainings.

Published - Wed, 27 Nov 2019

Created by - Orhan Ergun

What is Optimal Routing and Suboptimal Routing in Networking

What is Optimal Routing and Suboptimal Routing in Networking? This may be seen very easy for some of you but let’s make a philosophy a little bit, means let’s design around optimal routing. Network engineers know that one of the tradeoff in network design is Optimal Routing. We want our application traffic to follow Optimal Routing right? Not exactly right. I will explain why it is not always right but let’s understand what exactly we mean with ‘ Optimal Routing’. Based on which parameter optimality we are looking for? Answer of this question is IGP Metric. From source of the traffic to the destination, between the network nodes, cumulative/total cost. It can be Layer 2 or Layer 3 protocol, we prefer shortest path. Shortest path, most of the time is calculated based on ‘Bandwidth’.  Thus, overall which path provides more bandwidth, that path is considered shortest path, thus Optimal Routing. This is not necessarily always the case, for example BGP uses shortest AS-Path length, not the bandwidth for Inter-domain routing but OSPF, IS-IS for example look at the total bandwidth for the cost calculation inside the domain/AS. Some of you might think that, other than shortest IGP cost, maybe lowest physical distance (mostly called as fiber mile distance) or cheapest monetary cost we might use for optimality purpose, you are right. You may have a valid business case for it and in fact we have technical solutions to do that. RSVP TE and Segment Routing based Traffic Engineering provides a functionality for you have different policies in the network. As we understand that Optimal Routing is mostly considered as shortest cumulative IGP cost between source and the destination network nodes, let’s talk about why we may not want to send the traffic through the path which provides optimality.    Above picture is famously called as ‘ Fish Diagram/Topology’ Reason is; it looks like a fish but for us it is important to understand that with this very basic topology, we can understand why we may need traffic engineering. If every interface between the routers has same IGP Metric, between source and the destination routers in the above topology, always top path would be chosen due to shortest cumulative/total IGP Metric. Bottom path wouldn’t be used at all if we would rely on IGP routing protocols for path selection. If we would like to utilize bottom path for some of our application traffic, we need more than IGP routing functionality. RSVP and Segment Routing provides traffic engineering capability but those are not the topics of this post. When we start doing Traffic Engineering, we are in fact accepting to do ‘ Sub Optimal Routing ‘. We send only some of our traffic over the shortest IGP cost (Remember our Optimal Routing Definition) , and intentionally we send some other traffic over longer IGP cost path which is Sub Optimal Routing path. By the way, shortest IGP cost path doesn’t have to be monetary wise cheaper one, or it may not be the lowest delay path etc. You may have satellite link with the GEO orbit, which comes with 500+ msec latency but you may have more bandwidth on that compare to other path. Let me summarize. We use Optimal Routing to define shortest IGP cost path. This path may not be Optimal path as per your policy Optimal Routing may not be desired for every of your application or service traffic Technologies such as RSVP and Segment Routing are used for Traffic Engineering which intentionally violates the Optimal Routing Path We intentionally send some of our Application traffic over Sub Optimal Routing path, but that path satisfy the constrain of the applications overlay that path There is no one correct answer for all networking requirements! If you liked this post and would like to see more, please let me know in the comment section below. Share your thoughts so I can continue to write similar ones.

Published - Wed, 27 Nov 2019

Created by - Orhan Ergun

What is last hop router and first hop router in Multicast?

What is last hop router and first hop router in Multicast? These are important  terms which are used in Multicast. In this post, I will explain the terms, differences and some detail about this term. In fact, last hop router and the first hop router can be considered as the same thing. But I will suggest a common way of use in this post and will clarify the terms in a most clear explanation.       Figure – Multicast Last Hop Router and First Hop Router The router which is connected to the Multicast receiver is called Last Hop Router. Almost all Multicast resource will explain you in this way. The router which is connected to the Multicast source is called First Hop Router. Again, almost all multicast resource would explain the term in this way. If you are dealing with Local Area Network, you might be calling Last Hop Router (Commonly called as LHR), as First Hop Router and this wouldn’t be wrong. It is all about where you are looking from. But, I would recommend you to use common definition, which is ‘Last Hop Router’ is the one which is connected to the Multicast Receiver. Multicast Receiver is connected to Layer 2 switch and runs IGMP and/or MLD to communicate with the LHR, in turns if PIM is enabled in the network, LHR’s job is to generate PIM control plane messages to create a path for multicast traffic and build a multicast routing table among the routers in the network. LHR has many functionality but this is not the scope of this post. In this post, I wanted to just highlight the term, for more Multicast posts, please click here, there are many on the website.Note: Those routing geeks will remember the last mile and the first mile in Access networks. If you are a backbone engineer, connection between user and the operator network is considered last mile, if you are access network engineer, same connection is called first mile.

Published - Wed, 27 Nov 2019