Symptoms and Diagnoses for Common Bring-Your-Own-Bandwidth Challenges
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This document provides symptoms, diagnoses, questions to ask, and solutions for common bring-your-own-bandwidth challenges including registration issues, one-way audio, calls dropping at specific intervals, choppy audio, packet loss, echo latency, WAN outages, issues obtaining an IP address, and DNS resolution errors. It describes how to determine if the issue is on the LAN or WAN and whether contacting the internet service provider may be needed to resolve connectivity, firewall, or router configuration problems. The document provides guidance on steps to isolate and troubleshoot common voice over IP connection problems.
Symptoms and Diagnoses for Common Bring-Your-Own-Bandwidth Challenges
- 1. Symptoms and Diagnoses for Common Bring-Your- Own- Bandwidth Challenges (Template) Symptoms Diagnosis Ask the Right Questions Solutionor Instructions Registration issues Choppy audio FlappingInterface Link flap means that an Ethernet interface is continuously changing from an up to down state. Are you havinginternet connectivity issues? Is the registration error visually displayed on the phone (URL callingis disabled or a dash through the phone icon) or is it audible? “The firststep is to determine where the ‘link flap’is occurring. If it is occurringon the LAN, determine the connectivity issues thatareoccurringon your network. If this is happeningon your WAN interface, open a ticket with the internet service provider (ISP) for intermittent connectivity issues.” One-way audio Registration issues SIP ALG SIP ALG is an application on a firewall or router that re- writes the SIP packet headers by changing the phone’s private IP address to the WAN IP address and random UDP port. Once this occurs, the router will often stop sending the media or SIP signaling to the correct endpoint. Does the timer on the phone continue after there is no audio? Which party has lost the audio (callingparty, called party or both)? “Do you own and have access to the router? Check to see if SIP ALG is enabled on your router. We recommend that you disableitand reboot the network applianceto resolve your intermittent one-way audio issues thatyou are experiencing. If it is an ISP-managed router, open a ticket with the ISP to have SIP ALG disabled in the modem or router. Pleasere-test once this change has been applied and report any issues goingforward with call examples.”
- 2. Symptoms Diagnosis Ask the Right Questions Solutionor Instructions Calls drop atspecific intervals,usually atthe 10-minute mark UDP session timer UDP Session Timer is a setting on firewalls and routers that determine how longto keep a session alive. The server sends a “SIP UPDATE” message after 10 minutes to ensure the call is still active.If the UDP session is closed by the router before the 10- minute mark, the phone will not respond to the update messages and the call is terminated by the proxy server. Does the call drop and the timer on the phone display stop a few seconds after the call duration surpassesthe 10 minute mark? “Do you own and have access to the router? If so,expand the threshold in the router. If it is an ISP-managed router, open a ticket with the ISP to extend the UDP session timer in the modem or router.” Choppy audio Calls drop atvarying intervals Possibleregistration issues Packet Loss Packet Loss occurs when a packet fails to reach its intended destination (In this caseour proxy and/or media server). How much available bandwidth do the phones have? Is QoS implemented on your network? “If this occurs,your IT person will need to determine where the packet loss is occurring (LAN or WAN). If itis happeningon the WAN interface, open a ticket with the ISP and provideping test and traceroute results for the ticket. If it is occurringon the LAN, your IT person will need to isolatethe causeof the packet loss between the phone and local gateway.” Echo Latency Latency is the amount of time ittakes for a packet to reach its destination. Excessivelatency occurs when there is network congestion that causes voicepackets to be delivered at or beyond 150 milliseconds. How much available bandwidth do the phones have? Is QoS implemented on your network? “In this case,your IT person will need to determine the sourceof the latency (LAN or WAN). If it is happeningon the WAN, open a ticket with the ISP to have them investigatewhere the latency is occurringwithin their network.”
- 3. Symptoms Diagnosis Ask the Right Questions Solutionor Instructions Registration issue: URL callingis disabled (all phones on the same network). No dial tone WAN outage WAN link is hard down Is your internet connection down? Are the phones on the same connection? “Have your IT person open a ticket with your ISP to resolve the WAN outage.” Registration issue: Network Link is down displayed on phone. (See below) Registration The phone cannotobtain an IP address from the DHCP server. Does the phone have an IP address? “In this case,you will need to determine why the phone is not obtainingan IP address. The causemay be a physical layer link,a port speed mismatch between 10/100 ETH ports on phones negotiating with a gigabit switch,or CDP/LLDP being enabled on the LAN.” Registration issue: Broadsoftaudibleerror when placingan outbound call: “This device is not registered to placecalls on the network, pleasecontact your administrator”. DNS The phone is unableto resolvethe prioritized SRV record for the proxy server in the allotted time to live. It then fails over from the primary SBC to the secondary and back again before the initial registration expires. Is the registration error you are experiencingaudibleor visually displayed on the phone? Does rebooting the phone temporarily resolve the registration error? “Your IT person will need to determine why the phone is not ableto resolvethe proxy address within the allotted time required to prevent it from failingover. Pleaseverify with your IT person what is being used for DNS resolution and update the resolver if possible. Werecommend Google, Open DNS, etc.”