Transcript MGCP Megaco H.248

MGCP
Megaco
H.248
by
Bob Young
MGCP - Megaco - H.248
"It's all one."
MGCP is a generic term, not
an IETF standard.
• RFC 2705
• RFC 2805
• and the documents that
superseded them.
RFC 2805 (MGCP)
IETF Status: "Informational"
"This memo provides
information for the Internet
community. It does not specify
an Internet standard of any
kind."
By the way, in the slides that
follow, everything in quotes is
copied straight from an IETF
RFC.
IETF = Internet Engineering Task Force
RFC = Request for Comment
RFC 2805 (MGCP)
Abstract: "This document
describes protocol
requirements for the Media
Gateway Control Protocol
between a Media Gateway
Controller and a Media
Gateway."
Megaco is currently an IETF
proposed standard.
Megaco
IETF designation: Gateway
Control Protocol Version 1
Megaco is RFC 3525
(as of Dec. 6, 2004)
RFC 3525
"The protocol presented in
this document meets the
requirements for a media
gateway control protocol as
presented in RFC 2805."
RFC 3525
"It is the result of continued
cooperation between the
IETF Megaco Working
Group and ITU-T Study
Group 16."
RFC 3525
"The present version of this
document . . . was
published by the ITU-T as
Recommendation H.248.1,
Gateway Control Protocol
Version 1."
RFC 3525
"This document replaces
RFC 3015."
Remember to always make sure
you're using the most up-to-date
version of an RFC.
Some IETF Definitions
Access gateway
"A type of gateway that provides
a User-Network Interface (UNI)
such as ISDN."
Media Gateway (MG) #1
"The media gateway converts
media provided in one type
of network to the format
required in another type of
network."
Media Gateway (MG) #2
"For example, a MG could
terminate bearer channels from
a switched circuit network (e.g.,
DS0s) and media streams from
a packet network (e.g., RTP
streams in an IP network)."
Media Gateway (MG) #3
"This gateway may be capable of
processing audio, video and
T.120 alone or in any
combination, and will be
capable of full duplex media
translations."
Media Gateway (MG) #4
"The MG may also play
audio/video messages and
perform other IVR functions, or
may perform media
conferencing."
Media Gateway Controller
(MGC):
"Controls the parts of the call
state that pertain to connection
control for media channels in a
MG."
Multipoint Control Unit (MCU):
"An entity that controls the setup
and coordination of a multi-user
conference that typically
includes processing of audio,
video and data."
Residential gateway:
"A gateway that interworks an
analogue line to a packet
network. A residential gateway
typically contains one or two
analogue lines and is located at
the customer premises."
Signaling gateway:
"This function contains the
switched circuit network (SCN)
Signaling Interface that
terminates SS7 or other
signaling links."
Trunking gateway:
"A gateway between switched
circuit network (SCN) and
packet network that typically
terminates a large number of
digital circuits."
Contexts and Terminations
Termination
"A Termination sources and/or
sinks one or more streams."
(In other words, it's where the
media stream comes from, or
where it goes).
Context
"A Context is an association
between a collection of
Terminations."
The NULL CONTEXT is
special.
"The null Context contains all
Terminations that are not
associated to any other
Termination."
Placing a call with MGCP/Megaco
MGCP/Megaco's Place In The World
(1) The Media Gateway is controlled by
the Media Gateway Controller using
MGCP/Megaco
(2) If more than one MGC is involved in
the call, inter-MGC traffic is carried via
SIP or H.323 (or similar protocols)
(3) The conversation (session) is carried
directly from MG to MG using Real-Time
Transport Protocol (RTP) (or a similar
protocol).
Note that the conversation does not need
to be routed through the controller.
Note also that the Media Gateway may be an
end device, i.e., an IP phone, OR many
"dumb" IP phones may be connected to an
Enterprise Gateway.
Terminations & Contexts
MGCP/Megaco's Place In The Network
MGCP/Megaco and GSM Cellular
MGCP/Megaco In The OSI Model
"The End"