access networks services
TRANSCRIPT
Budapest University of Technology and Economics Department of Telecommunications and Media Informatics
Access networks – Services
BME-TMIT
Page 3
Triple Play – economical reasons
Triple Play service Architecture
Voice/data inflection point Internet > Voice
=> Best Effort (WWW)
Video inflection point Video+VoIP > Best Effort
=> Triple Play architecture
Source: Alcatel
BME-TMIT
Page 5
The network convergence
IMS
Home environment
Mobile environment
Office environment
Provider Network
One provider- everywhere
Common services
Common profile
Common billing
Beneficial for
Provider
User
BME-TMIT
Page 6
Changing Trends
● Fixed line based services are decreasing
● Mobile users are increasing despite that penetration is high
● Broadband Internet installations are increasing
Broadband
Mobile Fixed
BME-TMIT
Page 8
Video services
● IPTV – Broadcast ● SDTV ● HDTV ● Typical implementation: Multicast
● VoD – Video on Demand ● Bandwidth depends on content quality ● Typically unicast
● Other services (Time-shift, etc) – do not represent different requirements
BME-TMIT
Page 9
Video service architecture
Aggregation
STBHGW
ADSL2+
or VDSL
DSLAM
TV Source
Video ServerEdge
Router
Home network
First Mile (DSL)
Ethernet aggregation
BME-TMIT
Page 10
VoD vs. IPTV
● A VoD service requires higher bandwidth!
● IPTV broadcast, 300 channel bandwidth demand
● 300 MPEG-2 channel, 1.5Mbit each =~1Gigabit
● VoD bandwidth demand – depends on # of users
● 20000 user 10%-os peak usage =~7.5Gbps
● The IPTV is more important – priority over the VoD
● High availability => overprovisioning, protection
BME-TMIT
Page 11
Voice services - VoIP
● VoIP – cost effective
● The HGW has gateway function or IP phone is required
● Service convergence
● VoIP protocols
● IP, TCP, UDP (User Datagram Protocol)
● RTP (Real Time Protocol), RTCP (Real Time Control Protocol)
● SIP (Session Initiation Protocol), H.323 (ITU-T)
BME-TMIT
Page 12
VoIP service architecture
PSTN
Aggregation
HGW
ADSL2+
or VDSL
DSLAM
Edge
Router Soft-
switch
Home network
First Mile (DSL)
Ethernet aggregation
Coding, framing, queuing
Jitter buffer
Transport Buffering
Decoding
BME-TMIT
Page 13
Data communication- HSI
● Typical usage
● Internet access
● VPN access
● Requirements
● Best Effort
● 1.5-2 Mbps usually enough
– Except heavy p2p
BME-TMIT
Page 14
HSI service architecture
Internet
Aggregation
HGW
ADSL2+
or VDSL
DSLAM
BRASPC
PPPoE
BME-TMIT
Page 15
Triple-Play network requirements
●Video ● Low delay, low jitter, no loss
● High bandwidth
● Effective broadcast/multicast mechanism
● VoD scalability
● Below 1 sec recovery
●Voice ● Low delay and Jitter
● Low loss
● Sub-second recovery in case of failure
●HS Internet ● Guaranteed bandwidth
● Possible bursty tranfer
●Business users ● Guaranteed bandwidth
● Low packet loss ratio
● 50ms protection
●General ● Good cost/performance ratio
● Signaling support
● Network – service cooperation
● Support for resilient architecture
Budapest University of Technology and Economics Department of Telecommunications and Media Informatics
Generic service architectures
- Access network-
BME-TMIT
Page 17
Service Architecture
HSI
Voice
Video
Internet
STB
RGW
DSLAM
Video Server
Source
SoftSwitch PBX
STB
RGW Coax
DSL
?
BME-TMIT
Page 18
Ethernet in the MAN
● Large scale deployment anticipated ● MAN - Metro Ethernet
● First mile: EPON, GPON
● „Carrier grade” requirements: ● Scalability: many thousands of users
● Restoration, protection: high availability required (5x9), 50ms
● Service management (OAM)
● QoS support: SLA, guarantee
● Security
● Ethernet based services ● Standardization in progress
BME-TMIT
Page 19
Standardization
● MEF: services – from user perspective
● ITU-T: services – from network perspective, restoration and protection
● IEEE: Higher level functions: Ethernet OAM, provider bridges, EPON
● IETF: Ethernet over MPLS (Ethernet wire) és VPLS (Virtual Private LAN Service)
BME-TMIT
Page 20
Single-Edge architecture
HSI
Voice
Video
Internet
STB
RGW
DSLAM
Video Server
Source
SoftSwitch PBX
STB
RGW Coax
DSL
PPPoE
BME-TMIT
Page 21
Single Edge - 2
● Old fashioned architecture
● PPPoE tunnel to the BRAS
● Strengths
● Authentication
● Traffic containment
● Security
● Drawbacks
● Multicast is not possible
– Big disadvantage for IPTV!
BME-TMIT
Page 22
Multi-Edge architecture
HSI
Voice
Video
Internet
STB
RGW
DSLAM
Video Server
Forrás
SoftSwitch PBX
STB
RGW Coax
DSL
BRAS
BNG
BME-TMIT
Page 23
Multi-Edge architecture- 2
● Internet access still uses PPPoE
● Internet access through the BRAS
● VoIP and Video uses IPoE
● IP address by DHCP
● Service access through BNGs
● Advantages
● Multicast possibility
● Less overhead
● Lower load at the BNG
BME-TMIT
Page 24
IPoE and PPPoE
● PPPoE – Point to Point Protocol
● Authentication: user/pass, line ID
● PPP tunnel ends in the BRAS
● Connection oriented
● Not all devices support
● IPoE – DHCP
● Authentication: MAC addr, +DHCP option line ID
● „flat rate online”
● Connectionless, Multicast is possible
● All devices support
BME-TMIT
Page 25
PPPoE overhead
● PPPoE
● Two level L2 encapsulation
● 10 byte overhead for each packet
● PPPoE supports only point-to-point
● IPoE
● Fancy name for the basic IP/Ethernet encapsulation
BME-TMIT
Page 26
IPoE and PPPoE : requirements
● In both cases the authentication can be done at the DSLAM
● PPP termination is required at the DSLAM
● PPPoE
● PPPoE intermediate agent is required to add additional information to PPPoE packets
● IPoE
● DHCP option 82 for line identification
● DHCP relay agent to convert DHCP request to unicast
BME-TMIT
Definitions Auto configuration and AAA
Autoconfiguration: process of establishing a connection
AAA
Authentication
– process of determining whether someone or something is, in fact, who or what it is declared to be.
– based on identifiers and security attributes.
– part of an actual access to a network/service in the context of a SLA or contract, and often is linked with a fee (Accounting)
Authorization
– process of giving individuals access to system objects based on their identity.
Accounting
– recording, classifying, summarizing, and interpreting of events of a financial character in a significant manner
BME-TMIT
Autoconfiguration: PPP model
● Characteristics :
● PPP = Point-to-Point Protocol
● PPP session performs (between CP modem - PPP peer) – Link establishment (LCP packets)
– Authentication (optional, PAP or CHAP)
– Network-layer protocol (NCP packets : eg IPCP: CP gets its IP@)
● PPP encapsulation stays during session
● Origin of PPP for Internet Access via voice band modems (fig.)
● Continued to be used in DSL
PSTN Internet RAS Modem Modem
bank
BME-TMIT
PPPoE
● PPPoE needed when PPP transported over Ethernet: allows
– transport over shared medium
– PPP session multiplexing
● Autoconfig Procedure : - Detection of server(s):
PPPoE Active Discovery Initiation (PADI)
- Server(s) reply : PPPoE Active Discovery Offer (PADO)
- Choice of server : PPPoE Active Discovery Request (PADR)
- Server confirmation : PPPoE Active Discovery Session-confirmation (PADS)
PPP
IP
PPPoE
802.3 MAC
PPP
IP
PPPoE
802.3 MAC
RFC 2684
AAL5
ATM
PPPoE PPPoEoA
BME-TMIT
PPPoE initialisation PPPoE
Client <PADI>
Ethernet: - DA: Broadcast
- SA: User MAC@
PPPoE:
- ISP-Name
Modem
Terminator
Access Node Ethernet
Switch
PPPoE
Server in
Edge Node <PADI>
Ethernet:
- DA: Broadcast - SA: User MAC@
PPPoE:
<PADI>
Ethernet:
- S-VLAN ID
- (C-VLAN ID)
- DA: Unicast/Multicast - SA: User MAC@
PPPoE:
<PADI>
Ethernet:
- S-VLAN ID
- (C-VLAN ID)
- DA: Unicast/Multicast
- SA: User MAC@ PPPoE:
<PADO>
Ethernet: - S-VLAN ID
- (C-VLAN ID)
- DA: User MAC@
- SA: Server MAC@
PPPoE:
<PADO>
Ethernet:
- S-VLAN ID
- (C-VLAN ID)
- DA: User MAC@
- SA: Server MAC@
PPPoE:
<PADO>
Ethernet: - DA: User MAC@ - SA: Server MAC@ PPPoE:
<PADO>
Ethernet:
- DA: User MAC@ - SA: Server MAC@
PPPoE:
<PADR>
Ethernet: - DA: Server MAC@
- SA: User MAC@
<PADR>
Ethernet:
- DA: Server MAC@
- SA: User MAC@
<PADR>
Ethernet: - S-VLAN ID
- (C-VLAN ID)
- DA: Server MAC@
- SA: User MAC@
<PADR>
Ethernet: - S-VLAN ID
- (C-VLAN ID)
- DA: Server MAC@
- SA: User MAC@
<PADS> <PADS> <PADS> <PADS>
- ISP-Name
- ISP-Name
- ISP-Name
- ISP-Name - ISP-Name
- ISP-Name - ISP-Name
BME-TMIT
Autoconfiguration : DHCP model
● Characteristics : ● DHCP = Dynamic Host Configuration Protocol
● DHCP works in client/server mode
● DHCP is carried over IP, only during config phase
● DHCP session (host - server) :
– delivers host-specific config parameters
– allocates NW addresses to host ● automatic : permanent IP@
● dynamic : leased IP@ (limited time)
● manual
● Autoconfig procedure : ● Discovery of DHCP server (DHCPDISCOVER)
● Replies of server(s) (DHCPOFFER)
● Host selects server (DHCPREQUEST)
● Server acks and sets config (DHCPACK)
DHCP
IP
802.3 MAC
Config Data
IP
802.3 MAC
BME-TMIT
Page 32
Mac Forced Forwarding
● DSLAM only sends to BNG
● All other dropped
● Operation:
● PPP: sends to BRAS only
● IPoE:
– ARP request results in BNG address always
– Packets sent to other destinations dropped
● Can also be done with VLANs
BME-TMIT
Page 33
PPP intermediate agent
STB
RGW
DSLAM
DSL
BRAS RADIUS
PPPoE PPPoE+VSARADIUS+NAS port
ID
DSLAM adds to PPPoE -DSL line ID -DSLAM ID
DSLAM acts as PPPoE relay
The PPPoE relay adds PPPoE line and DSLAM ID in PPPoE VSA
The BRAS forwards the information as NAS Port ID
BME-TMIT
Page 34
DHCP option 82
STB
RGW
DSLAM
DSL
DHCP
serverRADIUS
DHCP req DHCP req + option 82RADIUS+NAS port
ID
DSLAM adds to DHCP req Option 82
A DHCP 82 option contains:
DSLAM ID, DSLAM port ID
PVC
Or any other information such phone number
BME-TMIT
Page 35
QoS
● End-to-end
● From user to Video/VoIP server
– In fact to the BNG
● Possible bottlenecks
● First mile
● Ethernet Aggregation
● Regional IP core
● The interworking between technologies is required
BME-TMIT
Page 36
QoS support
● Priority based on 802.1Q VLAN tag ● 3 bit = 8 classes
● The priority bits described in 802.1p ● VLAN priority and IP TOS are similar ● Not all switches support 8 classes
● P-bits are in VLAN header, but not associated to the ID
VLAN ID
(12 bit)
802.1p
(3 bit) CFI
(1 bit)
802.1Q VLAN TAG
P-bits
BME-TMIT
Page 37
Multicast
● Very important in case of broadcast video
● Support needed in aggregation too
● In case of PPPoE it is not possible
● Except if the PPPoE is terminated at DSLAM
● If it terminates at the BRAS, each user gets in Unicast from BRAS
● Possible with IPoE
● Support needed: IGMP snooping
● The DSLAM can be IGMP proxy
– Lower load on the multicast router
BME-TMIT
Page 38
Metro Ethernet Architecture
Metro Backbone
National IP
Network
GE
Aggregation
Switch
2 x GE
GE
GE
VOD
Server
TV Headend
3rd Party
ISP
VOD
Server VOD
Server
POP
B-RAS
Router
Internet
E.PON EFM G.PON
100BaseFX
B.PON
GE GE
GE
GE
Location Server
SIP Proxy
Server
Triple Play implementation
BME-TMIT
Page 39
Optimal network utilization
● Different solution for each service
● Video
● Multicast, low statistical multiplexing
– Possible gain since video is VBR, with many channels
● VoIP
● Call level statistical multiplexing
– Erlang formulas help in dimensioning
● HSI
● Packet level statistical multiplexing
– Multiple models exist, e.g. Guérin