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350-801 · Question #392

SIP proxies have operations defined in RFC 3261 and supporting extensions. Though no lETF RFC completely defines how SBCs must function. SBCs evolved over the years. Which two operations demonstrate…

The correct answer is B. SlP proxies add a Via header and optionally a Record-Route header, and the rest of the headers D. SBCs are capable of interworking completely different protocols to set up, modify, and tear down. SIP proxies forward messages by adding Via and Record-Route headers as defined in RFC 3261, while Session Border Controllers (SBCs) offer advanced capabilities like interworking completely different protocols.

Voice Gateways and Session Border Controllers

Question

SIP proxies have operations defined in RFC 3261 and supporting extensions. Though no lETF RFC completely defines how SBCs must function. SBCs evolved over the years. Which two operations demonstrate the high-level differences between SBCs and SIP proxies? (Choose two.)

Options

  • AStateful proxies are context-aware and can terminate communication sessions by themselves
  • BSlP proxies add a Via header and optionally a Record-Route header, and the rest of the headers
  • CSBCs can modify headers such as To, From, Contact, and Call-D.lt can introduce new headers
  • DSBCs are capable of interworking completely different protocols to set up, modify, and tear down
  • ESIP proxies are SDP-aware and can change the SDP bodies

How the community answered

(33 responses)
  • A
    3% (1)
  • B
    88% (29)
  • C
    6% (2)
  • E
    3% (1)

Why each option

SIP proxies forward messages by adding Via and Record-Route headers as defined in RFC 3261, while Session Border Controllers (SBCs) offer advanced capabilities like interworking completely different protocols.

AStateful proxies are context-aware and can terminate communication sessions by themselves

While SBCs are stateful and can terminate media, many SIP proxies are also stateful and context-aware, making this less of a unique high-level difference.

BSlP proxies add a Via header and optionally a Record-Route header, and the rest of the headersCorrect

A standard operation for SIP proxies, as specified in RFC 3261, involves adding a 'Via' header to track the message path and potentially a 'Record-Route' header to ensure symmetric routing for subsequent requests in a dialog.

CSBCs can modify headers such as To, From, Contact, and Call-D.lt can introduce new headers

Both SBCs and some advanced SIP proxies can modify SIP headers, but extensive, policy-driven header manipulation is a common SBC feature, not a unique high-level differentiator compared to protocol interworking.

DSBCs are capable of interworking completely different protocols to set up, modify, and tear downCorrect

SBCs possess the advanced capability to perform protocol interworking, translating between entirely different signaling protocols (e.g., SIP to H.323) or different variants of the same protocol to establish, modify, and terminate calls, a feature beyond traditional SIP proxies.

ESIP proxies are SDP-aware and can change the SDP bodies

SBCs are highly SDP-aware and can manipulate SDP bodies for various functions, but some SIP proxies can also perform basic SDP awareness and modification, making this less of a distinctive high-level difference.

Concept tested: SBC vs SIP Proxy differences

Source: https://www.cisco.com/c/en/us/products/collateral/unified-communications/unified-border-element/design_guide_c07-606018.html

Topics

#SBCs#SIP Proxies#Protocol Interworking#SIP Headers

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