PSTN

Nov 17 2008   7:44PM GMT

Surviving Cisco Telephony - SRST

Posted by: Troy Tate
administration, Cisco, VoIP, unified communications, IP telephony, DataCenter, PSTN, design, risk, diagnostics, vulnerability

As you may have seen in some of my previous posts the company I work for has implemented VOIP/IP telephony at some of our locations.

VOIP - IPT - QOS - COS on and on - Oh My!

CampIT Enterprise VOIP conference

VOIP virtual panel discussion

Recently we had a phone system outage at the largest of these sites. This was a site with a clustered Cisco CallManager solution. This outage lasted 4+ hours. We were definitely surprised that both members of the cluster failed at the same time and how long it took to recover. Since that time we obviously are working with our support vendor to find a better method of providing uptime to the phone system at this site. I am also looking at making sure my other sites are prepared in the event of a similar outage.

The solution for providing a backup to the CallManager cluster is called Survivable Remote System Telephony (SRST). Think of this as CallManager light. A limited number of the phones still have connectivity and can make/receive calls. I say “limited” because the SRST function is dependent on the PSTN gateway hardware. A larger gateway can support more users. The current gateway we had was a Cisco 2821 series router. This would support 96 users. A Cisco 3825 will support 175 users.

One thing I understand though is that you cannot necessarily specify which phones will get serviced by SRST. The phones are serviced on a first-come-first-served basis. This could be an issue if there are phones that should be serviced and an outage is occurring. Unneeded phones would need to be disconnected from the network to provide capacity to support the critical phones.

Hopefully this will be the last of 4+ hour outage for the phone systems at this site and none will happen at my others. The Cisco solution has been very good for my organization and so far has been very reliable with the exception reported here.

Thanks for continuing to read my blog and hope you have a great day on the technology frontier wherever that may be for you!

Oct 9 2008   3:56PM GMT

Virtual Enterprise VOIP panel discussion

Posted by: Troy Tate
administration, Networking, Cisco, Monitoring, VoIP, unified communications, IP telephony, DataCenter, IT education, WAN, LAN, PSTN, design, howto, risk, education

As you may have already read, I will not be attending the Enterprise VOIP event at CampIT Conferences in Chicago on 10/14. Well, I thought I would bring my portion of the discussion to you in this virtual panel discussion and maybe you and I both can gain some from this forum.

Some background on our environment: IP phone population - over 400, distributed at 4 sites, largest ~150, smallest 60; all Cisco

Why implement VOIP?

• greenfield site - needed a phone system and VOIP made sense for a new site install to position for future

• acquired company in process of implementing VOIP - came into a situation where an acquisition had purchased VOIP and I became owner of the implementation; had issues with chosen vendor and equipment lists; eventually came out successful but was not without its pain during implementation.

• forward looking strategy - setup the company to have regional communication hubs for IP telephony; we have VOIP in North America, Europe and Asia now; this could permit us to leverage our WAN for toll bypass provided we build other local site infrastructure to support this technology.

Our biggest challenges:

• users: they find the phones easy to use and very good features; however, there are some features like managing meet-me conference calling that they feel are too onerous so don’t take the time to use this cost-saving feature

• administrators: setting up phones is an infrequent event so it is not a real simple task to setup a new phone; moves are made easier than traditional systems; troubleshooting skills are different since voice now is carried over the data network until it reaches a PSTN gateway

Best features:

• dial another site using extensions rather than 10 digit or more dialing

• “on phone” directory - can lookup another IP phone user’s extension directly on the phone rather than finding them on a piece of paper or website somewhere

• easier conference calling than old system

• mobile-phone like features: listing missed calls; call history log

• moves are made easier; adds are a challenge since done infrequently

Desires for additional features/services:

• video

• more ringtones (must have been someone young and a heavy cell phone user)

• integration with e-mail/web

What are the risks?

• it’s challenging to implement in an “old school” infrastructure environment (flat network, no-vlans, hubs still in use, etc.) It takes lots of forethought and understanding VLAN’s, WAN links, need to update staff skills.

• The network MUST be reliable or voice will suffer. Traditional phone companies have had 100+ years to make a bulletproof network.

• Costs. It’s not cheap to implement this technology. You have to weigh the ability of the organization to support non-industry leading implementations versus choosing the best technology you can afford.

• Maintenance. Upgrading the software in the servers, gateways and phones is much riskier than upgrading a traditional PBX environment.

What are the rewards?

• It works!

• It positions the organization to take advantage of other services provided that it is not simply an IT-led project but meets business requirements.

Feel free to add comments on your own experiences, concerns. This is a great forum and keep up the good work of information sharing!