How to prepare for a NOC SIP/VOIP troubleshooting position?

Morningstar79Morningstar79 Posts: 6Member ■□□□□□□□□□
Hi guys,

I just got a job for a NOC which seems to be SIP/ VoIP troubleshooting oriented. It is a great company and I really want to make a good impression but my previous experience was data oriented (CCENT certified).

I only have a vague understanding of terms like PBX or SIP and I was wondering what is the best way to prepare for the 1st day. I have a month before start day and would gladly study 5+ hours each day.

Any particular certifications that would deal with VOIP troubleshooting, or great online tutorials/books (Like Udemy or specific Youtube Video for example)

The company is a Telco and apparently they are mostly Cisco shop.

Also, for those with extensive NOC experience, what other tools or skills could come in handy? I believe they use Solarwinds, any good Solarwinds tutorials you could recommend? Anything else that will specifically help me prepare for the job?

Each and every comment is highly appreciated.

Thank you,


  • adam220891adam220891 Posts: 164Member
    We have at least one VoIP expert among us, so consider my answer fairly worthless if they show up in this thread.

    Since it's a Cisco shop, I'm going to assume they are using Cisco Unified Communications Manager (CUCM, but many people call it Call Manager). This is a full blown server environment that has many roles (like CVP, IM/P, Contact Center, Roggers, CUBEs, etc.) and even the roles themselves can be sub-divided (Publisher, Subscriber, etc.).

    Before you can even get to all that, you need to understand SIP/Skinny (SCCP) and how the phone downloads a config from the TFTP server, and how the Call Manager is really the middle man/proxy for end points to communicate with each other. I would recommend checking out one of the legacy courses on CBTNuggets for voice and also one of the newer collaboration courses (voice/video combined). You can follow along and lab yourself with GNS3 and CME (Call Manager Express, which runs on a router and is NOT the same as CUCM but can give you great insight into how to configure a device on the 'backend', setup hunt groups, dial plans, etc.). You don't even need physical phones for this. I made it work with a third party soft phone and IP Communicator, but there were some headaches. CBTNuggets will set you back $100 a month but it will be worth it. This link may also be helpful: CCNA Voice Labs in GNS3 with VTGO-PC Multilab - Intense School

    It's hard to say how deep you need to go. I haven't found a ton of resources for telephony online like I have for traditional route/switch, but they do exist. I have met telephony guys who have no idea how networking works. I would look into understanding how delay and packet loss affect call quality, understand MOS values,, how QoS can be used to prioritize voice traffic, etc. You may just be looking at a topology map of the network and responding when SLAs fall under a certain threshold. Perhaps you verify the issue yourself or just execute some pings and trace routes. Or, it could be significantly more than that.

    Chances are if they are serious enough to hire a position to monitor their voice network, that they have legitimate tools that provide the visibility needed. I worked at a place that was trying to get enough info from the CUBE and RTMT. You'll need more than that because you need to see the latency along the way and be able to simulate calls passing through the network.
  • Russell77Russell77 Posts: 161Member
    Working for a Telco you may find yourself in one of three roles or some combination of them.

    1) Trunking side. The Telco provides sip trunks to customers phone systems instead of T1,s or analog trunks. In this role you will be doing turn up and testing work. The networking skills most often needed are subnetting, Vlans, and understanding on DNS. Although the Sip protocol is generic in the industry each vendor has a flavor. Getting a Phone system to work with a SiP trunk can be difficult at times. Most phone system (pbx) vendors have interop guides on what settings are needed to work with approved vendors. Wireshark is one of the most common tools used in this role.

    2) Hosted PBX. Most telcos are providing a hosted service these days and this is a fast going area. In this role You are remotely servicing customers phone systems because the PBX is in your own servers. Again you will need some basic networking skills but on top of that you will learn telephony. I will not kid you it is a big subject and with what a system can do these days it will take a long time to get good at it. To prepare look for basic PBX administration and terminology lessons. Just to get started ELI the Computer guy has one. No sense in getting vendor specific until you know what platform you will be working on. They will give you training on the platform they are using and cisco phones are used on different platforms so do not bury yourself in learning a platform you may not be using.

    3) Supporting PBX systems sold by the company. Again this will be vendor specific. You would be remotely supporting equipment installed by a field tech and might be doing remote administration and change type work. Again basic pbx knowledge.

    If you have a job description I might be able to help further
  • shodownshodown Posts: 2,271Member
    I've done 2/3 and I actually own a business that does 2 and 3.

    The biggest skill to have is basic networking and SIP. Its seen said by pretty much everyone here. The basic networking so you can understand the path of the voice traffic and SIP because thats how the signaling is setup to make a call. Start with the networking first because SIP will be hard to understand without it. From there each telephony system has a way it processes calls and makes routing decisions. You will have to find that out for the PBX you are using.
    Currently Reading

    CUCM SRND 9x/10, UCCX SRND 10x, QOS SRND, SIP Trunking Guide, anything contact center related
  • Morningstar79Morningstar79 Posts: 6Member ■□□□□□□□□□
    Thank you to everybody who responded, these are exactly the type of answers that I was looking for. I think I will start by looking into Cisco Unified Communications Manager and check out Eli the Computer Guys Youtube videos. Then I am thinking I will sign for CBT Nuggets to learn more about the SIP.

    I am not sure what role I will have but based on the description I am fairly confident it is hosted PBX. Unfortunately they didn't ask anything about subnetting, Vlans, and understanding on DNS (to bad because I am good at that stuff) but think they did mention remotely servicing customers phone systems. The job description is not up anymore but I do remember it mentioned familiarity with SIP/ VoIP troubleshooting, MPLS network, DMVPN framework, MetaSwitch products and being CCNA certified. Those were all preferred qualifications though, the required once were just a bunch of soft skills.

    By the way, I have a general understanding of DMVPN and MPLS network but anybody know what Metaswitch products are and the best place to learn about them? Also, is Cisco's CCNA Collaboration a current certification that will most likely touch on the VOIP aspect that I am trying to get better at?

    Thank you,
  • joshuamurphy75joshuamurphy75 Senior Member Posts: 162Member ■■■□□□□□□□
    Hard to know since every telco uses different tech, but try starting by learning the SIP call ladder, and SDP (protocol used to negotiate call perimeters). You can google them, or get them straight from the RFCs for free. I recommend downloading WireShark or VoIPmonitor if they let you, and capture some working calls and non-working calls and compare them to see what failed. Sometimes it's as simple as one side not hearing the other because firewall ports are closed. It's also worth learning the SIP response codes. Don't try to learn every single one, look for the 1st digit. If the first digit was 1, something is pending, if the first digit is 2, something was successful, if it's 3 something redirected, if 4, the client failed, if 5 the server failed, if 6, both failed.

    If you are dealing with connections facing other telcos, learn what a DS0, DS1, DS3, OC12, and related are. You probably don't need to know every bit about what's going on, but learn how many calls each one can handle, what a B channel and D channel is, what AMI and B8ZS are, as well as SF and ESF are. You might also want to learn the basics of SS7. Signaling System No. 7 (SS7/C7): Protocol, Architecture, and Services (Networking Technology) by Dryburgh and Hewett is a good book for that.

    If you are dealing with connections between the main office and remote offices, you may want to learn a little about GR-303, and MGCP.

    Adtran has a lot of free courses on their website that may help with getting some of the terminology down.
  • Russell77Russell77 Posts: 161Member
    Metaswitch is the base platform this Telco is using to provide these services. It is the interface between a VOIP network and the Public service telephone network. You may or may not be working directly in the metaswitch. Hosted voip has an interface that allows you to make changes to the customers call flows. The Sip trunking would certainly be managed in the Metaswitch.

    At this point you will be way better off learning pbx terms Types of trunks, types of hunt groups, Pick up groups, Reverse transfer, It goes on and on. They may not even let you in the Meta for a long time. Happy to answer questions if you have them.
  • IsmaeljrpIsmaeljrp Posts: 480Member ■■■□□□□□□□
    Russell77, do you mean the same Telco as OP?

    Anyway. Understand basics of SIP and call flows, as well as what a Class 4 and Class 5 switch is. Apart from that, do what everyone else has mentioned.

    Metaswitch and Perimeta are actually not bad to work with, I also work with it daily and my training was purely on the job.

    Honestly, I don't enjoy VoIP.

    Ah also! pcaps pcaps pcaps... you will become a pcap working with VoIP my lord I've never dealt with a technology that required so much Wireshark usage. Even with Metaswitch SAS.
  • Morningstar79Morningstar79 Posts: 6Member ■□□□□□□□□□
    Thank you to all who responded, much appreciated and I will definitely now start working on all of the things you suggested.

    One last question though, CCNA Collaboration 210-060 CICD Certification, is that the certification that would be the most relevant to what I will probably be doing. I have enclosed the Exam objectives below:

    If so, I see CBT Nuggets being recommended a lot, I am assuming this might be a good place to start:

    Thanks again,
  • Russell77Russell77 Posts: 161Member
    Ismaeljrp, As far as the Meta switch goes I was just making a general comment.

    MorningStar79, Although the CCNA Collab would be a great cert to have It is very difficult to get without hands on experience with the Cisco call manager and associated Voice mail and Presence servers. It would most likely be overkill for a position that would be supporting a hosted platform. Hosted platforms are set up by voip engineers. The day in day out turn up, move add change, and customer side troubleshooting work is done by the Noc techs. It's all about learning how calls flow through the platform. Both calls coming in and calls going out. Just focus on basic pbx terminology and basic VOIP lessons and you will be well prepared when you walk in the door.
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