Ethernet trainingSection 1 – Why Deploy Ethernet? 1.1 Background Years ago, voice service drove the design and deployment of wide area networks throughout the world. Over the past 10 years this has changed. The desire for information across the country and across the globe has lead to a focus on next generation data networks in the wide area. Initial data deployments were at low speeds and with low reliability. Typical rates were between 9.6 kb/s and 64 kb/s running X.25. The customer, in this case, owned the data service, with the provider owning the pipe. Next generation services allowed the carrier to offer the pipe as well as the data service, offering more revenue to the carrier and more flexibility and support to the customer. The first data services were bases on the SMDS standard. Speeds were still slow, but the service was more reliable. The next step in data service is our current position. Technologies such as frame relay and ATM lead the way for customers to spread their data across the globe. Speeds are no longer limited to 64kb/s. A customer can purchase data services from 64kb/s up to 2.4Gbs and higher. Point-to-point or point-to-multi point services are available. As well as ATM and frame relay, carriers are now offering Ethernet to their customers. Why would a customer want to go to Ethernet instead of staying with their existing frame relay or ATM data services? Frame relay, a technology designed to carry data, is not widely available above a T1 (1.544Mbs). In some areas, as much as a DS3 (45Mbs) frame relay pipe can be ordered. ATM offers a wider range of speeds, T1 (1.544Mbs) to an OC-12 (622Mbs), but is not as efficient with data as frame relay. ATM was designed to carry voice, video, and data all on one pipe. This added functionality adds a lot of overhead to the data stream. Ethernet offers a range of speeds and is focused solely on data. Ethernet allows the customer to save time and money by not having to buy expensive routers to convert their LAN traffic to a WAN technology. With the wide scale carrier based deployment of Ethernet, customers will be able to buy Ethernet pipes ranging from 10 Mb/s through 1Gb/s. In the near future, the next generation of Ethernet will be available running at 10Gb/s. 1.2 Ethernet’s Capabilities The benefit of Ethernet, and its main reason to exist, is that it handles data traffic extremely well. Various technologies such as Appletalk, DECnet, TCP/IP, and IPX (Novell) are equally handled and transported by Ethernet. LAN administrators could build a network with all of these technologies running simultaneously and Ethernet could handle the task. In today’s LAN environment, there are two main types of technologies that exist with Ethernet – IPX and IP. IPX is Novell’s technology designed mainly to manage printers, servers, and access to mainframes. This technology typically resides on a LAN and does not often traverse the wide area network. It is not often that a person in Atlanta, for example, will want to print a document in their New York office. It is more likely they will print it locally and fax it, if necessary. IP (Internet Protocol) represents the bulk to the traffic that traverses Ethernet networks. This is the addressing scheme that enables the Internet and many other technologies around the globe to work together. IP is the main driver to Ethernet’s growth. Since IP was created initially to support the Internet, it is critical to understand the history of the Internet. 1.3 Internet History Today’s Internet was created in 1969 through a government-sponsored project called ARPANET (Advanced Research Projects Agency Network). The purpose of ARPANET was to test and determine the viability of packet switched networks. The first deployment of ARPANET was at four separate locations: Stanford Research Institute, the University of California at Santa Barbara, the University of California at Los Angeles, and the University of Utah. The initial tests went well and ARPANET grew. It had become obvious to the researchers that non-military as well as military personnel could benefit from a large, interconnected network. It was also clear that a more reliable set of protocols was required to handle the ever-growing network. In 1973, ARPANET added IP, TCP, UDP, and ICMP (Ping) to the list of supported protocols. This allowed traffic to be handled quickly and easily by the end stations. It also offered error correction and retransmission of lost data. In 1981, the NSF (National Science Foundation) approved funds for the Computer Science Network (CSNET). This network allowed both university and industry to share information. In 1984 ARPANET was split into two different networks – one for military and one for non-military traffic. At the same time, the NSF expanded its funding and established NSFNET. NSFNET connected six supercomputers together with high-speed lines – much faster than ARPANET. Because of this, ARPANET became obsolete, and was dismantled in the very early 1990s. In 1993 the NSF announced it would no longer provide the traditional backbone services it had it the past. It did state that it would specify several locations where users could gain access to the Internet. These sites are called NAPs (Network Access Points). The network built to replace NSFNET is referred to as the vBNS (very high speed Backbone Network Service). In 1995, NSFNET was officially turned off and vBNS took over 100% of the domestic Internet traffic (see figure below). Today. Version 2 (commonly referred to as Ethernet DIX82). Intel and Xerox (DIX. This first version of Ethernet ran at speeds up to 2. A few years later (1973). One of the first customers of Ethernet was the White House – it was used for word processing. .4 Ethernet History The University of Hawaii’s ALOHA network is considered to be the ancestor of all shared media networks. the web offers it all. Finding directions. CA applied the ALHOA network principles and created the world’s first Local Area Network (LAN). the Gang of Three) in 1980 as Ethernet. Version 2. the Internet is the maze of sites and information that we have come to use every day. Beyond that. First commercial released was by DEC. The second revision release was in 1982 as Ethernet. the name was later changed to Ethernet. or information on any topic. In 1968. Robert Metcalfe and David Boggs at Xerox Corporation in Palo Alto. 1. Norman Abramson pioneered the precepts of Ethernet by developing this packet radio networking system that ran at 4800bp/s and 9600bp/s. Initially named ALTO ALOHA. this version of Ethernet was not successfully commercialized. the weather. Version 1 (commonly referred to as Ethernet DIX80). This is the standard we know today as Ethernet.94Mbps. Ethernet and Ethernet turn-up/troubleshooting will be easily within your grasp. which used a proprietary frame format based on a preliminary specification of the IEEE 802. The model (shown below) is a series of basic building blocks. Any time two or more computers pass information. Ethernet is the technology that will allow customers access to higher speeds optimized for data. they follow the OSI model.3 specification. Each block has its own function and role in getting data from one point to another point. 2. In the late 1980s. is followed by ALL data communications.In 1980. in some form. This is the same Novell that is used today to manage printers and servers.5 Summary Next generation services such as managed IP and voice over IP. Now that the overall packet standards were finished. The following sections are focused on that goal. Section 2 . the IEEE formed its Project 802 to provide a framework for the standardization of LAN technology. 1. Since Ethernet is a mature technology. SynOptics Communications developed a mechanism for transmitting 10Mbps Ethernet signals over twisted-pair cables. It was this combination of low cost transmission medium with an agreed standard that led to the wide deployment of Ethernet.Technology Overview By understanding a few basic concepts. Novell released Novell Netware ’86 in 1983.3 specification.3. SNAP was created for the new IEEE 802. will require more bandwidth that is optimized for data. In 1983. the transmission medium needed to be agreed on. In order to resolve this incompatibility. The Ethernet-over-twisted-pair standard (10BASE-T) was approved by the IEEE in 1990 as the IEEE 802. which included IEEE 802. the IEEE approved the IEEE 802. is optimized for next generation data services. is built around a solid standard.1 OSI Model The ISO (International Standards Organization) designed the OSI (Open System Interconnect) model for data communications. and is cheap to deploy. Ethernet demand from services providers will grow tremendously over the next decade. . This model.3i standard and quickly became the preferred Ethernet media type. This made the Novell Netware proprietary format incompatible with the latest technology.2 Logical Link Control (LLC). This layer can be provided by the carrier (e. If a packet or two is missed. • Network – Layer 3 The network layer currently represents the beginning of customer traffic.g. AT&T. or fiber. frame relay) or can be provided by the customer in a point-to-point leased line environment (e. The addressing type for this layer is often a router or a computer. Connectionless applications are those that do not require all packets to get from source to destination. T1 B8ZS). the lower layers and the application meet. An example of this would be streaming audio. The physical media could be twisted pair copper.g. or any service provider offers to its customers. Connection oriented applications require all packets to get from the source to the destination. This is the layer where computers speak to each other and data is addressed for end-toend communications. This is normally what BellSouth.g. the e-mail is unreadable. If all the packets making up the e-mail don’t make it. The transport layer identifies the application that rides within the data packet and makes sure that all packets get from the source to the destination. . Examples of network layer protocols include IP and IPX • Transport – Layer 4 At this layer. There are two types of connections – connection oriented (TCP) and connectionless (UDP). There are two parts to the physical layer – the physical media and the bandwidth. The bandwidth is a combination of signal characteristics and rates (e. the computer will skip a few bars of music and keep playing. coax. This layer also specifies the connection type. HDLC or PPP). • Data Link – Layer 2 The data link is the beginning of the data and offers the basic data framing. An example of this is e-mail.LAYER 7 Application LAYER 6 Presentation LAYER 5 Session LAYER 4 Transport LAYER 3 Network LAYER 2 Data Link LAYER 1 Physical • Physical Layer – Layer 1 The physical layer represents the “pipe”. No matter how perfect the envelope or how well it is addressed. 6. it is easy to identify and solve. and Application – Layers 5. 2.g. network.3 EXAMPLES OF OSI LAYER TECHNOLOGIES The following table gives examples of technologies and what layer they reside within the OSI model. APPLICATION LAYER The application is the letter. Since the failure is total and usually very obvious. and 7 built into them. none of the data will pass across the copper. data link. the data at layers 2 and up will not properly get from the source to the destination. T1). state. these layers merge together into just the application.1. If you look at our mail model. The layers can be . If a farmer in Georgia cuts through a pair of copper. The envelope identifies one letter from another.1 OSI MODEL ANALOGY In order to better understand the five-layer model we will work with for this training (physical. being the basic data format. Presentation. In this case. a closed road or broken down mail truck means no mail delivery. Each layer builds upon the next layer – the bottom layer being the physical layer. transport. if the truck can’t carry the mail. Similarly. The more difficult problems to solve are on the marginal circuits. SMTP mail. These types of problems tend to come and go and are difficult to identify. so can a computer have multiple applications.1. and application) we offer a parallel model built around something everyone is used to – mail delivery. POP3 mail. we will combine these layers together into only layer 7 and refer to this as the application layer. the address would be the street address. Many of these marginal problems will show themselves at the higher layers. DATA LINK LAYER The data link. It is important to remember that almost any layer 3 technology can reside on any layer 2 technology which could reside on any layer 1 technology. and 7 In most data communication networks today. A house can have multiple people. The name on the envelope identifies who should read the letter NETWORK LAYER The address put on the envelope represents the network layer. When looking at problem circuits. The roads represent the copper or fiber. Aspects of Lotus Notes. It is the actual piece of information sent from one location destined for another location to be read by a specific person TRANSPORT LAYER The final part is the name that resides on the envelope. 2. city.• Session. would look like the envelope that the letter is put into. For purposes of this training class. even though the problem is at lower layers of the OSI model. some problems are easier to identify than others.2 OSI MODEL IMPORTANCE The most important portion of the OSI model is apparent when dealing with a service issue or turn-up. 2. it won’t get to the destination. if the copper that carries the customer data is bad or the T1 is mis-optioned. while the truck represents the technology (e. 6. and zip code.1. PHYSICAL LAYER The roads and trucks that carry the mail are analogous to the physical layer. and web surfing all have layers 5. The electrical specifications are based on the IEEE 802. 2. T1.1 ETHERNET 101 – PHYSICAL LAYER The physical layer for Ethernet is defined by certain electrical and bit rate specifications. SMTP. UDP. It can be run over copper for short distances. • 100BASE-X – This Ethernet standard runs at 100Mb/s. The electrical characteristics of the signal are determined by the speed at which the Ethernet runs.MODEM FROM HOME . we can move onto the technology of interest.DSL FROM OFFICE APPLICATION TRANSPORT NETWORK DATA LINK PHYSICAL HTTP (WWW) TCP IP PPP QFSK HTTP (WWW) TCP IP ATM DMT HTTP (WWW) TCP IP Frame Relay T1 Notice that the end-to-end addressing scheme (layer 3 – IP) is constant no matter how you surf the web. As the speed increases from standard to standard.25Gb/s. • 1000BASE-X/Gigabit – 1000BASE-T/Gigabit Ethernet has a speed of 1. 2. . OSI LAYER TECHNOLOGY APPLICATION TRANSPORT NETWORK DATA LINK PHYSICAL Lotus Notes. This is the same for standard TDM based services. OSI LAYER FROM HOME . 802. DMT (DSL). such as T1 (twisted pair). There are currently three standards widely deployed: • 10BASE-X – This Ethernet standard runs at 10Mb/s. and SONET (fiber). WWW. Each layer is independent of the layer above and below.2 Ethernet 101 Now that we have completed OSI model 101. This technology is most often seen running over fiber. POP3 TCP. IPX HDLC. Most new networks are built with 100BASE-X links. ATM. MAC QFSK (modem). PPP. Ethernet. The data rate is 1Gb/s. T3 (coax). Frame Relay. the cable types change (from low grade copper to higher grade copper to fiber).2. SPX IP. 100BASE-X is often seen on copper but is occasionally deployed over fiber to extend the range of the signal. T3. but the line coding used (8B/10B) creates a bit rate of 1. SONET.switched around depending on the network architecture (dial-up or DSL). if required.3 (Ethernet) Using the above table.25Gb/s.3 Ethernet standards. This standard is almost always seen running over copper. This is the most common type of Ethernet deployed within local area networks. here are three specific examples of how people can surf the web. full duplex became more critical. 100BASE-X or 1000BASEX/Gigabit. being the slowest Ethernet speed.2. as their names suggest. 100BASE-X can be seen as a full duplex or half duplex. source address. The Source address is the device that transmitted the frame and the Destination address is the device destined to receive the frame. Below is what a basic Ethernet frame looks like.Another important physical layer characteristic of Ethernet is full duplex or half duplex operation. If any of the bits change while the packet traverses the network. Because of its speed. 100BASE-X or 1000BASEX/Gigabit Ethernet. There is. This is the beginning of the basic data format for Ethernet. control information. A half duplex circuit is either speaking or listening – it is incapable of both simultaneously. This layer is referred to as the MAC layer – Media Access Control. with its high bandwidth capabilities.3. This particular type of Ethernet is what is driving the carrier based Ethernet deployment. one part of the Ethernet standard that is more prevalent for gigabit than for the 10BASE-X and 100BASE-X standard – Pause Control.The source and destination address fields. As Ethernet speeds grew and the bandwidth requirements grew with them. The device receiving the packet at the far end will see that the frame has been corrupted during transmission and will discard the frame. and the CRC. similar to a phone where a person can speak and hear at the same time. 10BASE-X Ethernet is most commonly deployed in a half duplex environment. A full duplex circuit is able to transmit and receive at the same time. 2. is almost always seen in a full duplex configuration. this is not a problem. the FCS value will no longer be correct. however. Gigabit Ethernet. . • Data Field – This field is the meat of the frame. • Frame Type – This field contains information that determines the format of the frame – either an Ethertype field for Ethernet Version II or a Length field for IEEE 802. DESTINATION ADDRESS SOURCE ADDRESS FRAME TYPE INFORMATION (DATA) F C S • Source/Destination Address Field . All of what has been discussed applies to 10BASE-X. There are four main parts to this particular frame – destination address. This is where the upper layer information is encapsulated. depending on the bandwidth requirements.2 ETHERNET 101 – DATA LINK The data link layer for Ethernet is the same for 10BASE-X. The FCS is a calculation done by the equipment generating the frame on the total bits in the frame. • FCS Field – This is the frame check sequence. are the fields in the data frame that identify the source and destination MAC addresses for the frame. causing customer traffic errors – dirty fiber connections or bad media converters (electrical-to-optical or short range optical to long range optical). this is still part of the Ethernet standard and can be seen in deployed networks. It is not responsible for quality of service. there are several danger spots that would cause the physical layer to be bad. When gigabit Ethernet was first released. That is the responsibility of higher layers of the OSI model. Although not as prevalent as a few years ago. For the purposes of our training. As with the MAC layer.2. At this layer we are looking at individual computer addresses or web site addresses. the IP layer contains source.3 If the physical layer is bad. . If a customer or a carrier element is registering bad FCS frames. all information above will be corrupted. many elements could not support long durations of full bandwidth routing. we will focus on a few of the fields below. pause control standard allowed a local element to tell the far end element to slow down until the local element caught up. It is more complicated than a MAC frame.Pause control frames allow Ethernet elements to throttle the actual throughput of the link real time. Because of this.3 ETHERNET 101 – NETWORK LAYER The network layer resides within the information field of the data link layer (2.2). Below is a picture of the IP portion of an Ethernet frame. Commonly used network layer protocols include IP (most common) and IPX (Novell). It does not keep track of numbers of packets or lost packets through the network. We will focus on IP for this section – this is the technology that almost all carriers are moving forward with to provide next generation services. If we look back to the OSI model from the previous section. there are events and issues we can see that would cause FCS errors. Almost all potential customers are standardized on IP based networks as well. a bad physical layer often causes it. Most elements could support full 10BASE-X and 100BASE-X rates. destination. and a FCS. Take a look at the OSI model for Ethernet that we have built so far… LAYERS 5/6/7 Application LAYER 4 Transport LAYER 3 Network LAYER 2 MAC LAYER 1 802. The overall role of IP is routing of the packet from the source to the destination. For an Ethernet deployment.2. 2. each ranging from 0 to 255. instead of entering in www.com. The frame check sequence is a layer 3 frame check sequence. while the response packets would be larger to accommodate the larger amounts of data.234.80 In the URL field. This server converts the web address to the IP address – you just don’t see it.43. This allows various size packets to be put into one IP frame. The overall length of the address field could range from 46 bytes to 1500 bytes. One could look like: 212.acterna. The response is often a large web page. • The Information field is the next level up on the OSI model. an Internet URL request is a short connection request.123 The mechanism that allows a user to get from a computer to an Internet site is through the IP addressing scheme built into the internet and a the local computer. We have the physical layer and the data link layer identified . a source address. The destination and source address are the final end point addresses. like Acterna’s: www. There is a difference. This includes all of the upper layer information at the Transport and Application layers. the FCS finishes off the frame. Here is how it looks: . We can now add a layer to our OSI model for Ethernet carrier based deployments.com When you enter an address in the URL field.VERSION TTL IHL IDENTIFIER TOS TOTAL LENGTH FLAGS FRAGMENT OFFSET HEADER CHECKSUM (FCS) PROTOCOL SOURCE ADDRESS DESTINATION ADDRESS INFORMATION (DATA) OPTIONS AND PADDING • Like the MAC frame.the third layer is now IP. Acterna’s IP address on the Internet is: 157. IP AND THE INTERNET IP addresses have four different value locations. you don’t enter in IP address into the URL field of your browser – you enter in a web address. the IP frame includes a and a FCS/CRC check. not the next addressable port. • The length field identifies the overall length of the information field. It is important to notice that the info field can have a wide range. However. The IP FCS allows a technician to correlate layer 2 versus layer 3 FCS issues. your computer sends that URL to a DNS sever (Domain Name Server).223. • Finally. See the insert for more information about what an IP address looks like and how it relates to the Internet.acterna. however. enter in the IP address above – you will get to the same location. The requesting packet would be small. destination address.52. For example. the OSI layers: OSI Application. 2.LAYERS 5/6/7 Application LAYER 4 Transport LAYER 3 IP LAYER 2 MAC LAYER 1 802. Example Protocol ARPA Process/ • Basic data transfer and reliability . We will break this section up into two separate sections – TCP and UDP. These numbers keep track of all of the information sent and the order in which it arrives. If any packets do not arrive. It is critical that the physical layer and MAC layer be clean for IP to properly run. Multiplexing 5. we have another layer for events to occur at. any errors at lower layers will corrupt the traffic above. Flow control 4.2. It is obvious to see that the main goal of IP is getting packets from a beginning point (source) to the end point (destination). DNS server is not operating properly). There are two main protocols that reside over IP and are common transport protocols in an IP network. users will not be able to transmit their data to the destination. Connection Management 6. 2. Reliability 3. If the addressing scheme is flawed (e.2. Presentation. the packet will not arrive at the proper destination (like mis-addressing an e-mail). the TCP layer knows which . customers will often speak in the ARPA model instead of the OSI model. These two protocols are very different in their roles and responsibilities and are important to distinguish. HTTP Application being connection oriented.g. make sure that And Session Transport TCP/UDP Host-to-Host all data gets from the beginning to the end Network IP Internet of the network.1 ETHERNET 101 – TCP – CONNECTION ORIENTED TCP has six main responsibilities. Built into the TCP Data Link MAC Network overhead information of the TCP frame are Interface Physical Ethernet sequence numbers. These protocols are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Basic data transfer 2.4. These are: 1. This is apparent from the basic IP frame format.TCP. If a user mis-addresses a packet. The chart below shows the ARPA layers vs.4 ETHERNET 101 – TRANSPORT LAYER The final layer of the OSI model prior to the actual desired data is the transport layer. As discussed earlier.3 Now that we have added the IP layer. Security THE ARPA HOST-TO-HOST MODEL When dealing with host-to-host communications. Below is a typical TCP frame: SOURCE PORT OFFSET RESERVED URG CHECKSUM DESTINATION PORT SEQUENCE NUMBER ACKNOWLEDGEMENT NUMBER ACK PSH RST SYN FIN WINDOW URGENT POINTER OPTIONS AND PADDING INFORMATION (DATA) Compared to our less featured protocols. if implemented. we can look at the frame and its parts. the requesting end point requests a connection to the receiving end point. As packets are sent from one end point to the other. TCP not only connects us to the other end point (web or e-mail). however. It is this layer that allows small blips in local area networks and wide area networks to not be noticed by the user. • Multiplexing – We are all used to running multiple applications on our PCs at one time. The window size gives each end the value of the buffer size of the far end. represents the basic CRC/FCS for the frame. the window size for each machine is passed. a few fields that are worth discussing. like our other checksum fields. There are. the TCP frame is extremely complicated and has many different fields responsible for the various tasks described above. It is this way that each end knows if it is sending to much data for the far end to handle. • Connection Management and Security – When two end points begin a conversation. • Flow Control – Along with the sequence numbers discussed above. • Checksum – This field. but it also manages which packets entering your computer are from the web or e-mail. will attempt to confirm that the requesting end has the right to access the information. and makes sure outbound packets are properly identified by the far end. Now that TCP’s responsibilities have been identified. such as MAC. Often times we are checking our e-mail and surfing one or more websites at the same time. . The receiving end point manages the connection and. there is another portion of the header that contains a value known as a window size. It is outside the scope of this training course to get into each portion of the TCP header. • Source / Destination Port – These are the address fields that identifies the application type • Sequence/Acknowledgement Number – These are the fields that keep track of the packet sequences and which packet have and have not arrived from the far end sender.packets didn’t arrive and requests those lost packets. UDP is designed with the following features: 1. connection speeds.2. CNN has many viewers with different computers.3 ETHERNET 101 – TRANSPORT SUMMARY With the solid understanding of the transport layer. the OSI model can be re-examined as a complete set of building blocks: LAYERS 5/6/7 Application LAYER 4 TCP/UDP LAYER 3 IP LAYER 2 MAC LAYER 1 802. which cannot use the information unless it arrives in the sequence in which it was sent: VoIP.2. which do not require all the data to arrive to work. When a user logs into a streaming website. UDP allows users to connect to CNN without all of the management and security that would cause the video service to fail. 2. UDP is for those applications.3 . to watch the latest news report. Connection management Based on this reduced feature set.4. CNN can’t stop transmitting video and retransmit some packets that one user did not get. we can look directly at the UDP frame and get a good understanding of how it works and why it has a reduced feature set. More importantly. CNN doesn’t want to know anything about what their users are getting real time. www. streaming video.cnn.2. Basic data transfer 2.4.2 ETHERNET 101 – UDP – CONNECTIONLESS UDP is simpler protocol than TCP.com for example. etc. SOURCE PORT LENGTH DESTINATION PORT CHECKSUM INFORMATION (DATA) Why would we use UDP? The main use for UDP is for those applications. and link qualities. A denial of service attack occurs when a hacker gets multiple computers to keep sending requests to connect.1 DEFINITIONS AND TERMS • Utilization – The utilization on a link is determined by comparing the packet rate to the overall bandwidth of a link. it is considered a “best effort” technology. and resend any data within an application. and can’t accept any legitimate requests from legitimate users. • Round Trip Delay / Latency – Round trip delay and latency are time measurements for a network. If 100 packets are sent.544Mb/s at all times. and 90 of them arrive at the far end. 100Mb/s.3. confirm. the throughput of the system is 90%. all of the users packets have the SYN bit low because the user has been granted access. Throughput. the first TCP packet they send has the SYN bit set to one (high). a denial of service attack is caused by thousands of TCP frames with the SYN bit set to one with no follow up information. DENIAL OF SERVICE ATTACKS (DOS) Over the last year we have heard reports of the Whitehouse website and Yahoo! being taken down by denial of service attacks. Depending on who is doing what at any given moment. There is no guarantee that any of the traffic will get from one side to the other. or gigabit). For example. but never actually follow up with the connection. Utilization for data can fluctuate widely throughout the day on an operational network. This tells the website to set aside bandwidth and a connection spot. • Throughput – Throughput is a measurement not unlike utilization.2. Along with our common terms and definitions. for example.3 Common Terms and Definitions There are a lot of terms that get applied to all of the technology that has been taught to this point. runs at 1. measures the number of packets sent versus the number of packets received. It is at these layers that sequence numbers along with other portions of the overhead check. 2.5 ETHERNET 101 – CONNECTIONLESS? Although Ethernet operates at specific speeds (10Mb/s.2. Ethernet does not offer similar guarantees. From there on. How does anything reliably run over Ethernet? The answer is TCP and UPD. 2. The web site is flooded with connection requests. So. then the overall utilization is 40%. Round trip delay specifically addresses the time it . a 100meg Ethernet link (100BASE-X) has an available bandwidth of 100Mb/s. we will go over some common customer complaints and what they mean. the utilization could jump from 0% to 100% and back to zero within a few moments. runs out of room. This section will explain many of these terms within the context of an Ethernet deployment. It is very much a quality of service metric. When a user connects to a website. A T1. If your packet rate is 40Mb/s. Any traffic put onto the link will get to the far end. Traditional WAN technologies are not “best effort”. however. • Payload – The payload of a packet is often viewed as layer 4 and up – effectively the application.takes for a packet to go from one point on the network to another point and back again. • VLAN – VLAN stands for Virtual Local Area Network. For frame relay. The customer’s router can often count these . A PDU is typically layer 3 and above. It is also labeled as a good packets (good FCS) or a bad packet (FCS error). but it is a little easier to manage the traffic from a network standpoint. An existing WAN technology would be DLCIs (frame relay) or VCCs (ATM). VLAN tagging actually adds a sub layer to the OSI model. packets are also counted by their size (see section 2.2. It is a lot like dividing up traffic onto major highways (VLANs) in order to get them closer to their destination.2. as it is received. Each packet. • CPE – CPE stands for Customer Premise Equipment. we learned that TCP sequences packets so that lost packets would be identified and retransmitted. Payload can also be the line between the carrier service and the customer data. o Retransmissions – Retransmissions occur when the far end does not receive all of the data it was sent. The destination is still the same (IP). Latency is the time from one point to another. is counted. Latency can be measured for a single element (router) or for an entire network path. • Frame Size – Frame size is measured from the beginning of the Ethernet packet to the end of the packet.4. It usually refers to the customer equipment or the overall customer site.5). the line is between layer 2 and 3. the maximum frame size increases to 1522 bytes. • PDU – PDU stands for Protocol Data Unit. There are several CPE terms that you need to be familiar with in order to understand the customer. A VLAN is a way to separate traffic on a LAN into different sub groups.5 VLAN LAYER 2 MAC LAYER 1 802. Occasionally. the payload line is between layers 1 and layer 2. Frame sizes range from 64 bytes to 1518 bytes. From section 2. With VLAN tagging. If VLAN tagging is added (layer 2. For a point-topoint data T1. the model looks like this: LAYERS 4 TCP/UDP LAYER 3 IP LAYER 2.3 for size ranges).3 • Frame Counts – Frame counts are just packet counts. o Trace Route – A trace route is a means for a user to trace all IP addressable devices in the network from one point to another. are based on the OSI layer that is required for the traffic to transverse the network. It is important to remember that errors in the lower layers can corrupt the higher layers. This allows a user to determine if the network will allow traffic to go from one point to another. An analogy would be when FedEX scans a package as it goes through each one of its distribution centers. The other is based on the “addressable LAN” model. this is a non-event because there are separate transmit and receive paths. One of the services is based on the “transparent LAN” model. 1 to a 0). Section 3 – Gigabit / 10BASE-X / 100BASE-X Deployment Most carriers are offering two versions of the Ethernet services to date. 3. so retransmissions can be a sign of a physical layer. data link layer. These are overly long packets (> 1518 bytes). This event is known as a collision. he can’t send traffic there.retransmissions and express them as an error condition. the packets “collide” and are unreadable. This allows the user to see all the points along the way of a packet’s journey. transparent and addressable. o Ping – Another common CPE term is a “ping”. or even the network layer. On full-duplex links. o Symbol Errors – Symbol errors represent a line coding issues at the physical layer. If a customer can’t “ping” the far end device. These are counted when one or more of the bits in a packet have been switched (e. . If two or more computers on the network broadcast at the same time. Broken NIC cards/ports often cause jabbers o Bad FCS – Bad FCS frames are those frames with an incorrect CRC/FCS value. each computer has to share the bandwidth with the rest of the computers. A ping is a packet that is sent from a source address to a destination address and back again. The user can see each point the package touched on its journey. o Collisions – On a half-duplex Ethernet link. • Ethernet Errors – There are several types of Ethernet errors that you need to be aware of in order to turn-up and troubleshoot an Ethernet service: o Runts/Undersize – These errors are generically defined as any packet less then the minimum 64 byte length and does not have a CRC/FCS value.g. o Jabbers/Oversize – A jabber is the opposite of a runt.1 – Deployment Options The two deployment options. 25Gb/s). If the electrical or optical characteristics of the signal are correct. To overcome this. An OSR looks at the Ethernet packets and routes them based on their destination MAC address. Typically. Gigabit Ethernet. The customer only has access to 60% of the total possible bandwidth. although already optical. this type of service is offered via a DWDM (Dense Wave Division Multiplexing) system. An incorrect destination MAC address causes the OSR to ignore the packet. this is more than enough.5. A media converter can receive the 850nm or 1310nm and convert it to 1550nm. or layer 3. A layer 2. the Ethernet is limited to an OC-12 worth of bandwidth.1. an STS-12 circuit only offers about 60% of the room required. If the SONET pipe available to the Ethernet is only an STS-12 (622Mb/s). Another way for transparent LANs to work is through media converters. 3. some providers are offering gigabit Ethernet encapsulated into an STS-24c or STS-48c. and have no idea if the Ethernet traffic is traveling 5 feet or 50 miles. the Ethernet signal is placed directly into the transport system. VLAN tagging allows the user to easily set up a point-to-multipoint network using a very simple addressing scheme. Whatever the card receives is transmitted over the long haul and delivered to the far end. however. The core network for a MAC based service can be a traditional core.2 ADDRESSABLE LAN (OSI LAYER 2 SERVICE) This type of offering has more flexibility but it is slightly more complicated to turn-up and troubleshoot.1. This allows 10BASE-X or 100BASE-X to travel miles. The core network for this . A final option for transparent services is using a standard ADM (Add/Drop Multiplexer). the card is Ethernet (typically gigabit). the carrier can sell the service as a point-to-multipoint service instead of just a point-to-point. This type of service is typically offered using an OSR (Optical Switched Router). converted back to the appropriate wavelength for the Ethernet service. Unlike the DWDM option. layer 2. By using addressing schemes. In OSI terms. For gigabit Ethernet (1. the tags are very easy for the carrier to read and allow for quick and efficient routing.3. can benefit from media converters. the service will pass the data. This service is ONLY point-to-point. A layer 2 service (MAC layer) is the most common available today. this requires the customer to correctly address at layer 2. A media convert takes a signal – electrical or optical – and converts it into a long haul optical signal. the customer must provide some type of addressing. such as ATM. In order for this service to operate. the signal is limited by the SONET signal structure. Instead of a SONET card being the customer interface.5 service (VLAN layer) is available with some carriers today and on the horizon for most. Transparent service requires only that the first layer of the OSI model (physical) is properly formatted in order to pass traffic. Like the DWDM based option. Also. Normally gigabit Ethernet is available at 850nm or 1310nm – both considered short haul wavelengths.1 – TRANSPARENT LAN (OSI LAYER 1 SERVICE) By “transparent” we mean that the LAN sites on either end of the service are tied together by a pipe. For 10BASE-X or 100BASE-X. the carrier takes a signal and converts it to a different type of signal. The problem. 3. however.2 Network Architecture For carriers. 10BASE-X and 100BASE-X circuit are converted to an optical signal for long haul transport. . Other Acterna products. A layer 3 service (IP layer) is not widely deployed today. typically a POS (Packet Over SONET) network. The service uses addressing schemes either at layer 2. both point-to-point services as well as point-to-multipoint services are available.5.2.2 ROUTER/OSR POINT-TO-MULTI-POINT A router or OSR (Optical Switched Router) type deployment offers carriers more flexibility and growth than a DWDM point-to-point Ethernet deployment. the pipe will not pass any of the traffic. The screen shots shown throughout this document will be using an Acterna FST-2802 Ethernet services test tool.2. When the word managed is added. layer 2. Currently. Another layer 3 type of service is generically called managed Ethernet. or layer 3. IP addressable LANs will not come to fruition. Effectively. we will discuss turn-up and troubleshooting of a basic Ethernet service. a large IP network would need to be set up in the core.service can be traditional ATM. An example of a managed Ethernet service would be a VPN. Because the service requires addressing to route the packets. without corrupted any data. Gigabit Ethernet is often converted from 850nm or 1310nm to a 1550nm signal. If either the technician or the customer misaddresses packets. Without an IP core. making the circuit look down at the physical layer. but the VPN server is owned and operated by the enterprise customer. This transformation is totally transparent to the customer. is at higher levels.1 MEDIA CONVERTER DEPLOYMENT This deployment is based on a transparent service using media converters. For the most part. such as the DA3400 and the DominoFE and DomnioGIG offer similar feature sets and could be used in place of the FST-2802. In order for a full IP addressable service to be offered. any turn-up of the service will require addressing on the test set. 3. but requires the OSR to map different VLAN tags to the appropriate ATM circuit. Section 4 – Turn-up and troubleshooting of Ethernet networks For the purposes of this section. Many enterprise networks currently utilize VPNs. such as SONET or ATM. This signal may remain as native Ethernet over fiber from end-to-end. these are the different types of equipment and architecture that will be used to deploy Ethernet. the carrier owns that portion of the service. while traversing the cloud. or it may be encapsulated in a traditional WAN service. 3. a test should be small frames have a smaller payload run for at least 15 full minutes error free. The two main units of measure are actual bit rate (megabits per second) or percent of the total available bandwidth. At high utilizations. 4. When setting up a test set to generate traffic. Smaller frames A circuit tested for a short time period (30 cause elements to work harder than seconds to just a few minutes) is not truly to be error free.1 Overview of turn-up and troubleshooting As with any service. turn-up and troubleshooting of Ethernet networks is critical to confirm that the service works prior to the hand-off. Higher speed circuits require even traffic is not corrupted is critical longer test times.1 TRAFFIC RATE – CONSTANT BANDWIDTH When setting utilization. Depending on how the carrier is offering the Ethernet service. this is the most critical portion of the service. The reason is that proven a circuit is going to be reliable. the ability to edit the payload may be a requirement for some turn-ups. Lower speeds generating traffic at the maximum circuits. generating traffic at the maximum rate is the only way to confirm that the circuit can pass the customer data at the guaranteed rate and without errors. Stating bandwidth in terms of percent of the total available bandwidth is the most common way. To confirm Ethernet services the technician will generate traffic and measure that traffic for various different parameters. such as a T1. 4. For the most part. there are several different units of measure. In order to confirm that the pipe is clean and will transport the customer’s traffic.2 Turn-up testing 4.1 TRAFFIC GENERATION An Ethernet service is a pipe offered to the customer to transport traffic from one point to another point. and less time for the element to process a frame before the next frame arrives. Therefore with the speed of the circuit. To have any sense that larger frames. have test length line rate and confirming that the requirements of 15 to 45 minutes (ANSI T1.4. the Ethernet pipe may pass 1.1. • Payload – The payload is the PDU portion of the frame. Depending on the service. the element may drop or corrupt some frames. the maximum bandwidth available to the end user may vary. This section covers those types of traffic that will need to be generated as well as the measurements to be made on that traffic. the technician must generate traffic and confirm that all of the traffic traverses the network without being corrupted. From a customer standpoint. When turning up a circuit. Because of this. The carrier and type of network will determine the The time required to fully test a circuit varies maximum throughput.2.510). • Utilization – This is the most critical setting. .25Gb/s or HOW LONG TO GENERATE TRAFFIC? less. there are three main parameters that must be specified: utilization. • Frame Size – Different frame sizes can affect elements. frame size. and traffic profile.2. this portion is irrelevant to the Ethernet service. If there are errors on the link.2 TRAFFIC RATE – RAMP Another option for generating traffic is to step up the traffic rate over time. The ramp test. confirms that the service works and will pass all of the customer’s traffic without errors.1) is also varied by the test set. 4. 10%. and bad FCS frames. The frame size (section 2. Firstly.2. not just at the maximum bandwidth being offered. When the test set is set to bursty. Customer traffic has a wide variety of frame sizes due to different applications and their different requirements. the user needs to set the time at each step (20 seconds. 4. waiting for a short time.2.The maximum bandwidth test should run error free and offer the customer proof that the circuit will pass traffic appropriately. Either the customer network or the carrier network will drop any errored of these frames A screen shot of the FST-2802 test pad offers visibility into the types of errors that are tracked. If the user sets the average at 50%. similar to the QRSS test pattern for a standard T1 BER (Bit Error Rate) test. there are a couple of extra parameters over the constant rate test.3.2 RESULTS After setting up and generating traffic. Errors include runts. etc).2. the utilization will fluctuate around the 50%. the traffic utilization is adjusted around a particular rate. To begin generating any traffic.1 INTERPRETING ERRORS When generating traffic. etc). the test set is able to emulate customer data more easily. any received errors are an indication of a problem. The easier way to accomplish this is to have the test set do it for you. By generating the different frames real time. When setting up a ramp test.2. 5 minutes. Now that you know the step size. the user must enter the step rate (2%. 1 minute. the step function will identify the rate at which the errors are being caused. 4.3 TRAFFIC RATE – BURSTY Bursty traffic is a way to simulate real customer data.1. jabbers. Any errors will be displayed . the service can be proven to be error free at all rates. much like customer traffic will.2. Setting a constant bandwidth. By stepping up the traffic at specific intervals. the test set varies the traffic in two important ways. and then restarting the test at a higher bandwidth can accomplish this. 4. 5%. like the constant rate test. the results of the test need to be analyzed to confirm that the service will or will not work per the standard.1. by design does not offer a simple way to see the information on the pipe in a monitor mode. 4. The screen shot to the left shows the link statistics that the FST-2802 collects. The FST-2802. The customer will have a similar issue when trying to monitor the WAN traffic.3 FST-2802 DETAIL INFORMATION For more information on the FST-2802. This packet has a sequence number (similar to the TCP sequence number) and a time stamp. All of the statistics captured in the screen gives the user a complete view of how the circuit is behaving. In order monitor a live circuit an optical splitter must be inserted. can generate an Acterna test packet.2. 2.2.2. there are no test points. The pause control frames are those frames that tell elements to slow down or speed up their transmission rate (section 2. This allows the FST-2802 to do real time QoS/SLA analysis including lost packet rate and round trip delay. Errors will be displayed in two different categories – Error Stats and Summary. Fiber. there are access points for analysis that do not take the customer down. as one of its packet generation options.2. This manual will give a full understanding of all of the features and set up choices for the FST-2802 4. For a more traditional customer offering. while the second three show utilization as a frame rate. .2 INTERPRETING LINK STATISTICS Whether the link has errors or is operating nominally.4 SUMMARY Proving a service is operational prior to customer traffic being placed on the circuit is critical for two reasons: 1. It is common for customers. not to let the service be taken down for an out of service troubleshooting test. especially gigabit. 4. It is EXTREMELY difficult to take down a reported marginal circuit. For Ethernet services. there are several link statistics that the technician can use to confirm that the traffic he is sending is getting properly received by the test set.2). notice the PAUSE Frames result. The summary view scans all results and picks out anything out of specification that is seen by the test unit.2. which most technicians do not have. Larger customers often have protocol analysis tools. like T1. The first three show utilization as a percent of total bandwidth. please see the FST-2802 training manual. Toward the bottom of the window. even though the service is marginal. One important error result seen in the summary portion of the picture is the lost frames result.for the user to see. The first six results are the ones that will be mainly used. The customer. for enterprise customers to use their Ethernet switches as test points. It is common. . Since the customer owns the Ethernet switches. some customers will require that the latency and packet loss / error rate be the same or better than the latency and error rate stated in the contract. By properly turning up Ethernet services. The only way to prove to the customer that his circuit meets the specified requirements is to generate known traffic and measure the latency and error rate received. however. Prior to handing off a circuit. a carrier can reduce return trips to the customer site and feel confident that their service is reliable. owns the local Ethernet switch. QOS/SLA? QoS: Quality of Service SLA: Service Level Agreement Many applications that run on a customer network are not tolerant of long delays through the network. without taking down the network. The switch has the ability to “mirror” any port to another. The cause of this delay through the network could be a LAN (customer) or a WAN (carrier) problem. the provider does not often have the ability to test from that point. therefore. Performing a test like this is often called a QoS test.