IP Transport Network Overview - Part1

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IP Transport network Overview – part 1
© Ericsson AB 2009 | Ericsson Internal | X (X) | Date
Internet Protocol Transport Network Overview – Part 1
Introduction
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Why learn about the IP transport Network?
High level IP RAN solutions
IP Mobile Backhaul solutions
So why should you learn about the IP Transport Network?
As Mobile Operators always are looking for more cost efficient mobile network solutions there are demands on Ericsson to find the best possible solution, and one way is to use IP networks for the transport network.
In this session, which is part 1 of 2, you will get an understanding of the IP solutions Ericsson offer its customers. The on-site solutions are collected in the product portfolio ”IP RAN” and the RAN backbone network solutions are described in the product portfolio ”Mobile Backhaul”. Both these portfolios are well documented in the Ericsson Product Catalogue.
In this session, we are also looking at the delay requirements for varioius network types and the dimensioning approach that is recommended to use for the LTE L10 RAN.
Scope and objectives
Describe the IP Network solutions provided by Ericsson for LTE RAN
Describe what IPsec is and which nodes are required
Explain overall system latency and its impact
Describe how customer parameters are fed into the dimensioning model
Objectives
Scope
IP over Ethernet Backhaul
Delay vs Latency impact
The scope of this course includes:
High level IP RAN and Mobile Backhaul solutions
The IP RAN over Ethernet backhaul
The Delay vs Latency impact on different generations of mobile networks and the delay requirements in LTE
Dimensioning strategies and LTE transport dimensioning methods
After completion of this course the student shall be able to:
Describe the overall IP Network solutions provided by Ericsson for LTE RAN
Describe what IPsec is and which nodes are required to implement it
Explain overall system latency and its impact to services
Describe how customer parameters are fed into the dimensioning model for the LTE RAN Transport Network
> Pre-test
Pre-test
A pre-test will be inserted here. You do not have to take any actions on this. It is done by external vendor. The pre-test will re-use the the Quiz at the end.
> Overview
Overview
IPsec
Dimensioning for LTE RAN
In this module, we will first have a look at the IP RAN and Mobile Backhaul solutions. IP RAN means IP related equipment that is placed close to the eNodeB site, the MME or the Serving Gateway, for example security gateways, firewalls, site integration units, etcetera. Mobile Backhaul is the equipment and recommendations for the IP cloud connecting the eNodeB and the Serving Gateway and MME.
After this, we will have a brief look at IP Security, delay and latency requirements and dimensioning approaches for LTE RAN.
IP Transport Network Overview
IP RAN and Mobile Backhaul
Switch sites
IP RAN
Evolution: packet overlay
2G
3G
S-GW
MME
LTE
BSC
Evolution:seamless migration
Access, LRAN
This figure shows the IP RAN and Mobile Backhaul product portfolios that Ericsson provides. Both these portfolios can be found in the product catalogue.
IP RAN gives recommendations about for example delay, jitter, bandwith and other issues that you have to deal with in an IP backbone. IP RAN also contains suggestions on equipment to use to fulfil these requirements close to the eNodeB sites and also close to the MME/Serving Gateway sites. The types of products are covering for example Layer 2/Layer 3 switches, NTP servers, firewalls and site integration units for co-siting the LTE eNodeB’s with 2G and 3G Radio Base Stations.
Mobile Backhaul contains the products and recommendations used to describe the IP cloud that is connecting the eNodeB sites with the MME/Serving Gateway. The Mobile Backhaul contains for example MINI-LINK, various types of IP routers and switches, delay and jitter recommendations etc.
Note that it is possible to use Ethernet as transmission method between an eNodeB and the MME/Serving Gateway, but most likely some other transmission technique is used somewhere in the network. In that case, the IP packets from or to the eNodeB are just tunneled over this other transmission link.
Also note that IP RAN and Mobile Backhaul are also used to describe IP transport networks for 2G and 3G networks. Co-siting between for example a WCDMA and an LTE base could be optimized by using the same transmission like for both access technologies. Refer to the IP RAN solutions for more information.
Building blocks
So what are the building blocks all Internet protocol Radio Access Network?
The Ericsson IP portfolios provide a full interactive portfolio. In this figure you can see a number of examples, where both GSM site, WCMDA sites and LTE sites are connected to the same Transport Network.
Sharing the same transport infrastructure facilitates the reduction of the total transport capacity requirement for a specific RBS site. Although WCDMA, LTE and GSM traffic may traverse the same physical infrastructure, they may be logically separated when the requirement exists.
The products shown in the figure are first the ServiceOn, whic is a common management system for the Mobile Backhaul. It offers Centralized security and fault management thus providing an added value as an end-to-end network manager.
The second product is the MINI/LINK TN- Hybrid Node, which provides tunneling of Native Ethernet and TDM transport over the air.
The third product is EDA, which integrates xDSL, GPON and point-to-point fiber.
The fourth product, OMS1410, provides for example Ethernet, MPLS and IP switching/routing with Packet Transport standards (PBB, PBB-TE and T-MPLS) and TDM+WDM.
The SmartEdge product line, which is to be used in HRAN for Converged metro networks where service differentiation is required and it also it also takes care of traffic handling and network recillience.
IPsec – two common modes
Transport mode
The hosts use some algorithm to encrypt the IP payload field.
Drawback is that third party can monitor behavior, destination/source, times, intervals, intensity etc.
Tunnel mode
Encryption only used between SeGw. Also IP header is encrypted.
Commonly used for OaM traffic
Host
Host
IP
H
S
S
Since the traffic in LTE is only encrypted between the UE and the eNodeB, IP Security is a preferred solution to introduce security also between the eNodeB and the core network nodes MME and Serving Gateway.
IP Security, or IPsec as it is abbreviated, is not a protocol but a family of protocols and encryption algorithms used to create Virtual Private Network tunnels in IP networks.
In the figure above, two IPsec modes are shown. The Tunnel mode, shown on the right hand side, is supported in the eNodeB from LTE L11A. In this mode, both the IP header and the IP payload are encrypted, and thus a new IP address is required when sending the data. The implementation is further investigated in the next slide.
If IPsec is required prior to L11A, an external IPsec node needs to be installed next to the eNodeB. Consider the IP RAN documentation to see any recommendations.
Deployment of IPsec in LTE RAN
H_MME1
MME_1
H_MME2
MME_2
H_SGw1
SGw_1
H_SGw2
SGw_2
R
EP_RBS
IPsec_2
H_RBS_2
RBS_2
In this figure, the outer and inner hosts of the IPsec Tunnel mode are shown. The eNodeB has the inner host and the security gateway has the outer host. If the security gateway is implemented inside of the eNodeB as is the case in L11A, both the inner and the outer IP addresses are stored in the eNodeB.
On the core network side, one or several IPsec gateways need to be placed. Note that the Mul traffic, which is the traffic sent between the eNodeB and the OSS-RC, can not be protected by the eNodeB. In order to protect this traffic, an external IPsec gateway is required on each eNodeB site.
3Gpp Capacity and latency evolution
The 3GPP evolution has brought down the latency and increased the throughput significantly over the past five to ten years. With LTE, the latency is down to 10 milli seconds and the throughput reaches 150 Mega bit per second in the first release that becomes generally available.
Worth noting is that the latency in LTE is measured between the UE and the eNodeB while in WCDMA it is measured between the UE and the RNC. It is, thus, the RAN latency that is referred to when talking about latency.
Delay requirements in lte
QCI
300 ms
10 -6
Video (Buffered Streaming TCP-Based (for example www, email, ftp, p2p, file Sharing, Progressive Video, and so on)
7
7
8
8
300 ms
10 -6
Video (Buffered Streaming TCP-Based (for Example email, chat, ftp, p2p, file Sharing, Progressive video, and so on)
9
9
eusstcm (CHIS) - Same notes are on the preceding slide.
The mapping of Core Network settings to priority in the scheduler and QoS class for the Transport Network over X2 and S1 Uplink is done with the help of a so-called QCI table in the eNodeB. All values in the QCI table are in the L10 release recommended by 3GPP. At a RAB establishment, the Core Network informs the eNodeB which QCI value to use. As can be seen in this figure, each QCI value implies that a certain priority is used in the scheduler and that a certain packet delay budget is used for the service carried by the corresponding RAB.
The end-to-end voice latency limitations stated by 3GPP are as follow:
0 to 150 milliseconds is the preferred range.
at less than 30 milliseconds, the user does not notice any delay
Between 30 and 100 milliseconds, the user does not notice delay if echo cancellation is provided and no distortions exist on the link.
Between 150 to 400 milliseconds is an acceptable range but with increasing degradation.
above 400 milliseconds is unacceptable.
The Delay requirement also depends on whether the resource Type is GBR or Non-GBR. The most critical is X2 delay that imposes degradation of the interrupt time at handover. X2 refers to the one-way path from a source eNodeB to a target eNodeB via the X2 interface. X2 delay drives two backhaul requirements. The first one is the X2 Control Plane, over which round trip times up to hundreds of milliseconds can be tolerated. The second one is the X2 User Plane, over which 15 milliseconds is the theoretical minimum time for handover execution while 70-100 milliseconds is more realistic. Up to 1 second is possible, but then with significant service degradation.
Dimensioning Strategy
Bandwidth needed
for eNB
+
=
The dimensioning recommendations that Ericsson has developed for LTE are very straight forward. No co-siting examples exist yet, so dimensioning becomes a matter of first deciding the peak rate of the eNodeB and then multiply this with the overhead added by the transport network. Then, depending on how many aggregation levels there are in the backbone, aggregation gain can be obtained according to the next slide.
Dimensioning techniques
for one cell including TN overhead =
1,30*150 Mbps
Dimension for ‘Average eNodeB throughput during Busy Hour’ = 50 Mbps per eNB
A3
S-GW/
PDN GW
Dimension for ‘eNB throughput in a loaded network for a 3x1 configuration’ = 100 Mbps per eNB
Dimension for: ΣA2 × 0.8
This figure describes how the basic dimensioning is done. It can be described in five steps.
Step 1: the maximum peak rate for an eNodeB is calculated based on either what the eNodeB’s hardware can handle or how much bandwith the eNodeB can get access to based on licenses. If for example the hardware limit is 150 Mbps but the operator only has licensed features to handle 75 Mbps, the peak rate is 75 Mbps.
Step 2: The ”last mile” dimensioning is done per eNodeB. ”Last mile” means the link to the first aggregation point, which typically is a router. To derive the last mile bandwidth requirement, the peak rate for one cell is multiplied with the Transport Network overhead, which typically includes headers for Ethernet, IP, IPsec and UDP or SCTP.
Step 3: The bandwidth requirement for the link between the first two aggregation levels are calculated. Here we don’t use the peak cell rate per eNodeB as input, but the approximate ”throughput per eNodeB in a loaded network”. Each eNodeB is also considered to have three operating cells. The actual throughput per eNodeB can of course be calculated in an operators network. The figures shown in this figure are simulated.
Step 4. Calculate the bandwidth requirement for the next aggregation level, that is, between A2 and A3 in the figure. Here we use the average eNodeB throughput during Busy Hour. Busy hour is the time of the day when we expect the most traffic, so naturally this value will be on its minimum.
Step 5: If even more aggregation levels are used, there is an aggregation gain that can be applied. As shown in the figure, it could be for example 0,8.
To sum up, the operator has to provide a few input parameters to this dimensioning model. First of all, the hardware or license limitation on each RBS is used to decide the peak cell rate per eNodeB. Then, the possible use of IPsec will reflect on the Transport Network overhead used to calculate the actual transport network bandwidth on different aggregation levels. Finally, the operator also has to come up with relevant figures for traffic load in a loaded network and during busy hours. This is typically something that comes naturally once the operator has traffic in the network. Before that, either simluations or approximations have to be used.
Summary
Summary
Mobile Backhaul
Delay Requirements in LTE
LTE Transport Dimensioning Methods
- In this module, we have looked at the high level solution for the IP RAN. We first went through the two product portfolios IP RAN and Mobile Backhaul, which both are covering recommendations and suggested products in different parts of the network.
- IPsec was then covered, and we saw that to obtain security we might need external security gateways close to both the eNodeB and the OSS-RC, the MME and the Serving Gateway. Only the S1/X2 interfaces will have IPsec support in the L11 release.
- Then we looked at the delay and latency impact on the LTE RAN and that we have a QCI table in every eNodeB to map QCI table values to priority values in the scheduler. This is done in order to ensure that a certain user gets both the bandwidth and the delay associated with that particular QCI entry.
- Finally, we looked at the LTE Transport Network Dimensioning approach.
QUIZ
Quiz
How does a common IP transport backbone save money?
With IP we build one network to serve the transport needs for all standards of radio (Correct)
With IP we only save money with LTE
With IP we replace all legacy network equipment with cheaper IP based equipment
What does IP RAN refer to?
That the LTE RAN is using IP as transport bearer
The product portfolio containing recommendations and suggested products for site products in the IP area for the eNodeB, the MME and the S-GW (Correct)
The fact that the LTE services are all packet switched
What is Mobile Backhaul?
The transport network used for all mobile services
The equipment that are used to transport mobile data between an RBS and its Core nodes
The product portfolio containing recommendations and suggested products for the transport network between the RBS sites and the core networks (Correct)
Quiz
How do you dimension the last mile access to an eNodeB with the Ericsson recommended dimensioning method?
Peak allocation for one cell based on either hardware or licensing limitation multiplied with the transport network overhead factor (Correct)
Busy hour RAB establishments multiplied with average RAB bandwidth requirement multiplied with the transport network overhead factor
Average 3x1 eNodeB throughput multiplied with the transport network overhead factor
According to 3GPP, which delay causes a voice service (over for example IP) to be unacceptable?
Over 100 milliseconds
Over 200 milliseconds
Feedback FORM
More Information
Acronyms
4G four G
AH Authentication Header A H
ATM Asynchronous Transmission Mode A T M
BGP B G P
CES C E S
EDA E D A
eNodeB E node B
GBR G B R
GPS G P S
GSM G S M
IHL IP Header Length I H L
> Gå igenom och lägg till om det behövs
Acronyms
IP Internet Protocol I P
IP RAN I P ran
IPsec I P sec
IPTV Internet Protocol Tele Vision I P T V
ISAKMP Internet Security Assication and Key Management Protocol I S A K M P
L10 L ten
LRAN L ran
MME M M E
ms milli second
MTP2 Message Transfer Part Layer 2 M T P two
Mul M U L
NNI-SAAL Network Nodal Interface Signalling ATM Adaptation Layer N N I saal
NTP N T P
OSS-RC O S S R C
PBB P B B
PDH P D H
QCI Q C I
RAB rab
RBS Radio Base Station R B S
RNC Radio Network Controller R N C
RTT R T T
Acronyms
SAD Security Associated Database S A D
xDSL X D S L
SEGw Security Gateway security gateway
S-GW Serving Gateway serving gateway
SIU S I U
STN S T N
TFTP Trivial File Transfer Protocol T F T P
UDP User Datagram Protocol U D P
UE U E
VoIP Voice over Internet Protocol Voice over IP
VPN Virtual Private Network V P N
WCDMA Wideband Code Division Multiple Access W C D M A
WDM W D M

IP Transport Network Overview - Part1

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