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LTE QoS: SDF and EPS Bearer QoS
September 11, 2013 | By Netmanias (tech@netmanias.com)
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Page 3 of 6

 

     

Table of Contents  

1. Introduction
2. SDF and EPS Bearer
3. QoS Parameters of SDF and EPS Bearer

4. QoS Provisioning and Enforcement

5. An Example for SDF and EPS Bearer QoS

6. Closing  

 

 

3. QoS Parameters for SDF and EPS Bearer

 

In Chapter 2, we have learned that user traffic is classified by using packet filters into either SDFs or EPS bearers, and SDF QoS and EPS bearer QoS are respectively applied to the SDFs and the EPS bearers. In Chapter III, we will study QoS parameters for SDFs and for EPS bearers and explain their relationship.

 

In an LTE network, QoS parameters are defined at service level and at bearer level. SDF QoS parameters are service-level QoS parameters while EPS bearer QoS parameters are bearer-level QoS parameters. Service level and bearer level are also called as SDF level and SDF aggregate level. An SDF aggregate refers to a group of SDFs which have the same QCI (QoS Class Identifier) and ARP (Allocation and Retention Priority) values and belong to one EPS session. Both QCI and ARP are the basic QoS parameters applied to all SDFs and EPS bearers. The QCI is particularly important because it serves as a reference that indicates the performance characteristics of SDFs and EPS bearers. In addition to these two basic parameters, there are other QoS parameters, such as GBR, MBR and AMBR that specify the bandwidth (or bit rate) characteristics of SDFs and EPS bearers. SDF and EPS bearer QoS parameters are as follows:

  • SDF QoS parameters: QCI, ARP, GBR and MBR
  • EPS bearer QoS parameters: QCI, ARP, GBR, MBR, APN-AMBR and UE-AMBR

 

SDF QoS Parameters

QCI and ARP are applied to all SDFs. The QCI, in an integer from 1 to 9, indicates nine different QoS performance characteristics of each IP packet, such as resource type (GBR or Non-GBR), priority (1 ~ 9), packet delay budget (50 ms ~ 300 ms), and packet error loss rate (10-2 ~ 10-6) [2].

Maximum Bit Rate (MBR) and Guaranteed Bit Rate (GBR) are also the SDF QoS parameters, and they indicate the bandwidths (or bit rates) of SDFs. MBR specifies the maximum bit rate of an SDF. If the network traffic is not congested, user traffic travelling as SDF can be delivered at most at the specified MBR. However, GBR is the guaranteed bit rate of an SDF. This means the SDF is guaranteed with a specified GBR no matter what. So, even when the network traffic is congested, user traffic travelling as SDF is delivered at least at the guaranteed GBR.

 

There are two types of SDFs: GBR SDF and non-GBR SDF. In case of a GBR SDF, dedicated network resources are assigned according to the resource type specified by its QCI. However, in case of a non-GBR SDF, dedicated network resources are not assigned (See Table 3 for comparison between GBR and non-GBR types). A GBR SDF is assigned a GBR and an MBR, whereas a non- GBR SDF is assigned an MBR only. QoS parameters for these two SDFs are as follows:

  • GBR SDF QoS parameters: QCI, ARP, GBR (UL/DL) and MBR (UL/DL)
  • Non-GBR SDF QoS parameters: QCI, ARP and MBR (UL/DL)

A SDF that matches the packets filters of a TFT (DL TFT) is mapped to an EPS bearer in a P-GW, and delivered to a UE through its mapped EPS bearer. An aggregate of SDFs with the same QCI and ARP is mapped to one EPS bearer.

 

EPS Bearer QoS Parameters

QCI and ARP are applied to all EPS bearers. An EPS bearer is classified as a GBR bearer or a non-GBR bearer depending on the resource type specified by its QCI (See Table 3 for comparison between GBR and non-GBR types). A default bearer must be non-GBR while a dedicated bearer can be either GBR or non-GBR.

Other than QCI and ARP, there are other QoS parameters for EPS bearers: MBR and GBR indicating the bandwidth (or bit rate) of an EPS bearer, and AMBR (Aggregated Maximum Bit Rate) indicating the total bandwidth of multiple EPS bearers. MBR and GBR are the maximum and the guaranteed bandwidths of an EPS bearer respectively, and AMBR is the maximum total bandwidth of multiple EPS bearers.

 

A GBR EPS bearer is assigned a GBR and an MBR, which means dedicated network resources are allocated (i.e. a bandwidth in an amount of the specified GBR is guaranteed and a bandwidth in an amount of the specified MBR is available) to the bearer. However, a non-GBR EPS bearer is assigned an AMBR, which means dedicated network resources are not allocated to the bearer, but a maximum bandwidth to share with other non-GBR bearers is allocated. There are two types of AMBR: APN-AMBR, the maximum bandwidth that can be shared by all non-GBR bearers in a PDN, and UE-AMBR, the maximum bandwidth that can be shared in a UE. A UE can be connected to more than one PDN, in which case the total APN-AMBR of all PDNs cannot exceed the UE-AMBR. QoS parameters for the two types of EPS bearers are as follows:

  • GBR bearer QoS parameters: QCI, ARP, GBR(UL/DL) and MBR(UL/DL)
  • Non-GBR bearer QoS parameters: QCI, ARP, APN-AMBR(UL/DL) and UE-AMBR(UL/DL) 

 

SDF and EPS Bearer QoS Parameters

Figure 2 illustrates QoS parameters applied to SDFs and EPS bearers.

 

Figure 2. QoS Parameters for SDF and EPS Bearer

 

In Figure 2, the UE is connected to two PDNs. The UE has two IP addresses: IP address 1 assigned by P-GW 1 for use in PDN 1, and IP address 2 assigned by P-GW 2 for use in PDN 2. And it has one default bearer and two dedicated bearers established for each PDN. User traffic IP flows are filtered into SDFs in the P-GW by using SDF templates. There are two groups of SDFs 1~5 each received from PDN 1 and PDN 2. For these SDFs, network resources are allocated and packet forwarding is treated according to the QoS rules set in the P-GW. And the SDFs are then mapped to EPS bearers based on their specified QCI and ARP. In case of PDN 1 in the figure, SDFs 1 and 2 are mapped to the default bearer, SDFs 3 and 4 are mapped to the non-GBR dedicated bearer, and SDF 5 is mapped to the GBR dedicated bearer, all heading to the UE, their final destination. Such traffic mapped from SDF to EPS bearer is defined by using Traffic Filter Template (TFT). All the user traffic is subject to the EPS bearer QoS while being delivered through the EPS bearers.

 

All non-GBR bearers associated with a PDN are controlled by the maximum APN-AMBR they share while the ones associated with a UE are controlled by the maximum UE-AMBR they share.

 

Table 2. QoS Parameters for SDF and EPS Bearer

 

Table 3. GBR vs. Non-GBR

 
Page 3 of 6
Vassilios Stefanidis 2014-04-14 20:19:19
Hello,

I noticed a misspelling in chapter EPS Bearer QoS Parameters at p.6 of the PDF document: in the first paragraph (near the end) the MRB should be MBR.

BR
Vassilis
Netmanias 2014-04-15 17:09:13
The typo was modified. Thank you for your kind noticing.
kimfeng 2014-04-25 21:01:56
A default bearer must be non-GBR while a dedicated bearer can be either GBR or non-GBR. So, in what kind of condition, a dedicated bearer will be allocated for non-GBR service?
Netmanias 2014-04-27 12:34:08
Hi kimfeng,

3GPP defines service characteristics in terms of priority packet delay budget and packet error loss rate.
Then according to the characteristics, it maps standardized QCI values to standardized characteristics and classifies GBR type and non-GBR type services. (please see Table 6.1.7 of 3GPP TS 23.203)

Though assigning a QCI to a service depends on operators' policy, QCI 9 is typically used as a default bearer and QCIs from 5 to 8 are used as a non-GBR type dedicated bearer.
For example, a dedicated bearer with a QCI value of 5 is used for IMS signaling when operators provide VoLTE services.
vh.valluru 2018-04-07 20:46:26

QCI is 5 for IMS signaling and is default bearer with unique ip adrs .. but here dedicated bearer is mentioned?? pls correct me if iam wrong.

ramakrishna 2014-05-02 00:00:19
Good presentation thanks
sharmapeeyush840 2014-06-06 14:00:34

Hi,

 

I have a doubt about QoS per SDF. I tried reading 23.203 as mentioned in your reference. However I could not find any information which says there should be a specific MBR value associated with a SDF in case of Non-GBR SDF.  If possible kindly guide me to a particular section from where I can draw this conclusion. 

 

Regards,

Peeyush Sharma

Netmanias 2014-06-17 07:33:09

Hi Peeyush,

 

A PCC rule defines the policy control information for a service data flow.
Table 6.3 lists PCC rule information (Rule ID, SDF detection, Charging, Policy control, ..). UL/DL-maximum bitrate and UL/DL-guaranteed bitrate are being defined as (part of) Policy control information. For non-GBR SDFs, UL/DL MBR is conditional, but can be used for rate policing. 

Thank you. (and sorry for late reply due to business trip..)
 

Vimal Tewari 2014-06-23 00:58:55

First of all Thankyou for such wonderful presentations.

Based on what is written in this document and in the relevant 3GPP specifications, I have developed an understanding why a distinction needs to be maintained between EPS Bearer Flow and SDF. The 3GPP specifications define EPS Bearer as "An EPS bearer uniquely identifies traffic flows that receive a common QoS treatment between a UE and a PDN GW ". All the LTE/EPC nodes work with an EPS Bearer and one EPS Bearer can have multiple services mapped to it. A guideline for mapping the different services to different QoS classes is also provided by the specifications. However the specifications do not talk about the bit rate values for individual services and assignment of bit rate is left to the individual operators. In the absence of SDF, this notion of working only with EPS bearer can lead to 2 problems:

  1. The different nodes (UE, eNB, SGW) map user traffic to EPS Bearer and accordingly enforce the QoS rules. However these nodes do not have any understanding of the individual services that this user traffic belongs to. Two services (e.g. email and ftp) might have the same QCI characteristics but their QoS requirements can be different (they may differ in their bit rate requirement). The QCI being same, these services will be mapped to same bearer and the different nodes will enforce the combined bit rate (Bitrate (email) + Bitrate (ftp)) on this EPS Bearer. It may happen that the combined bit rate for the EPS Bearer will be achieved but individual services end up not getting the correct bit rate.
  2. The second and more critical reason is related to billing. Two services might have same QCI characteristics and even same QoS requirements, but the operator may decide to charge the two services differently. This cannot be achieved if we cannot distinguish between the different services within an EPS Bearer.

Having the notion of SDF can effectively address both the above problems. If PGW can segregate the IP flows into different Service Data Flows, it can

  1. Enforce the correct data rate on that particular SDF. So any error in achieving the correct bit rate at other nodes can be corrected at PGW.
  2. The PGW can now apply correct billing policy on the SDF and charge accordingly.

Request you to kindly confirm if this understanding is correct.

Netmanias 2014-07-16 13:03:56

Hello Vimal,

 

Thanks for sharing your understanding! We are in agreement with your comments.

Peeyoosh 2014-10-03 18:12:11

Thanks NetManias for sharing such a nice information and thanks Vimal for sharing detailed understanding, it helped me to understand the sense of SDFs.

 

Regards,

Peeyoosh S

Michael Topouzas 2014-07-01 21:08:45

Hello,

 

Very nice presentation.

Just a small typo error : Service Date Flow should be Service Data Flow 

Netmanias 2014-07-11 17:48:30

Hi Michael, 

 

We have corrected the typo. Thank you for noticing.

Shafali 2014-07-08 20:35:04

Hi,

 

Thanks for the useful information & nice presentation. Can anyone please tell the exact difference between SDF Template and TFT?

 

Thanks!!

 

Saurabh Thukral 2014-09-18 20:38:29

Please refer Table 5. Description for MBR.

It is wrongly mentioned that this QoS parameter applies for non-GBR bearers.

raghu(GESL) 2014-12-22 15:04:32

SDF(service data flow) are used to map packets  to the TFT(traffic flow template) based on 5 tuples and TFT is responsible for maping packet to the respective bearer which matches the QOS of bearer and the packet.

Is it correct?

Netmanias 2015-02-07 17:57:56

SDF template vs. TFT

 

An SDF template consists of IP packet filters, and each IP packet filter has a set of filter rules (5-tuple consisting of Source IP, Destination IP, Source Port number, Destination Port number, and Protocol ID). IP flows arriving at P-GW are identified by matching these packet filters (SDF template), one by one, and those that match the same filter rule are grouped together and classified as an SDF.

 

P-GW keeps traffic mapping information (TFT filters) that indicates which EPS bearer can support (QoS of) which SDFs, i.e. QoS the LTE network can support for UE.

 

Each SDF has a set of QoS parameters (e.g. QCI, ARP, MBR, GBR) and so does each EPS bearer (e.g. QCI, ARP, MBR, GBR, UE-AMBR, APN-AMBR). An EPS bearer has the same variety of QoS parameters that mapped SDF(s) have, except it has access system-dependent parameters as well. 
SDFs (or SDF aggregate) with the same QCI and ARP can be delivered through the same EPS bearer. If an SDF cannot be served at any of the currently available EPS bearers (e.g. if a new SDF, SDF 5 (GBR=500Kbps), arrives when SDF 3 (GBR=1Mbps) and SDF 4 (GBR=1Mbps) have already been delivered through EPS bearer 5 (GBR=2Mbps)), another EPS bearer can be created to serve the new SDF.

 

Sameer Gagneja 2015-05-28 22:16:36

Hi,

1>Please explain a bit on Protocol ID in SDF Template.

2>During downlink:how come PGW differentiate whether traffic is voice data (RTP), video streaming, voice signaling (SIP), two-way game, and Internet traffic. 

3>Like max number of EPS bearer for one UE can be 11 because of EBI bit value of 4.My question is where in your website i can have understanding of other bit values and there relative constraints.

James 2015-06-26 14:37:55

1. Protocol ID: In the IPv4 there is a field called "Protocol" to identify the next level protocol.  This is an 8 bit field (Protocol ID = 6 for TCP and 17 for UDP). In IPv6, this field is called the "Next Header" field.

 

2. PGW differentiates traffic type based on SDF filters (5-tuple based packet classification rule) and these fileters are part of PCC rule. PCC rule (SDF filters) can be provisoned by PCRF (dynamic PCC) or pre-configured on PGW (predefined PCC). Note that SDF filters are unidirectional, so detection is applied independently for downlink and uplink direction.

Probably,

- SDF filters for voice data (RTP) are provisioned by PCRF (IMS core -> PCRF -> PGW) whenever voice bearer (dedecated bearer) are established

- SDF filters for voice signalling (SIP) are predefined in PGW (TCP/UDP port = 5060 which means SIP)

- If it is not able to detect video streaming/two-way game traffic based on 5-tuple, DPI (Deep Packet Insepction) feature should be used (DPI supported PGW or external DPI box)

 

3. I cannot find any EBI value greater than 11 in this document.

Akash 2015-06-21 17:16:16

Hi ,


First of all Thank you for this wonderful presentation.


I have just 1 query,


In your example (5.1 QoS Operation in Downlink), you have written that when IP packets comes at PGW , for GBR SDF , PGW apply MBR DL policing .


My question is why not GBR DL policing ?


Thanks,

Akash


Amrendra 2015-07-14 20:09:45

Hi Netmanias,

 

Thanks a lot for wonderful explanation.

However there is one request while downloading it in pdf format, please include option to download comments too as they also contain sometimes valuable knowledge.

 

Thanks,

Amrendra

Sathish Kumar R 2015-09-10 23:19:16

Hi All,

 I am not able to understand how the SDF aggregation happens and how the sdf's mapping to EPS bearer ? My understanding in SDF aggregation is, For eg - 5.1 QoS Operation in Downlink

in that image SDF 1 and SDF 2 are GBR mapped to dedicated bearer, IS this called SDF aggregation or IP packet SDF 3 and SDF 3 marked in the image are going to SDF 3 this called SDF aggregation ? 


Thanks,
Sathish 

Sabyasachi Samal 2015-12-10 18:12:39

Hi,

Is there any document specifing the UE AMBR QOS values discussed for video calling during VoLTE?

 

Regards,

Sabyasachi

Sowmya 2016-05-16 15:11:44

For the downlink icmp packet, the icmp packet contains only the source address, destination address and protocol ID. But durinf SDF template filtering how the source port and destination port were mapped ? Please expain me in details.

vplazam 2016-06-24 12:14:25

Great document, this helps me to catch the idea that EPC/PGW is able to stablish dedicated EPS Bearer without using PCRF in the service set up. I thought before that PCRF is needed for stablishing dedicated bearer on this kind of scenarios. Many thanks

Netmanias 2016-06-27 16:04:19

We are glad you found it helpful. Stay tuned for more!

anandroni 2016-09-12 16:22:58

Hi,

 

Is the commeny by vplazam is correct ?.....we can understand atleast during Initial attach defualt bearer is setted up based on QOS parameters set by HSS....but how come a dedicated bearer can be setted up by PGW alone without PCRF ? .......For Dynamic PCC rules in the case of realm time traffic we need a PCRF provisioning PCC rules for different service data flows

 

Atleast i can guess a NON GBR dedicated bearer can be setted up without PCRF

 

please explain if i'm wrong.....

 

Best Regards

Anand R

 

Gaurav Gupta 2016-12-20 22:18:24

Hello There  

 

I had following query - What is the DL/UL Bearer mapping in EPC Network across below interface ( where it is 1:1 and where There is Only one bearer needed for UL and DL Traffic Both )  

a- UE<->eNodeB<->SGW<->PGW<->PDN 

b -How many maximum number of bearers that gets configured in EPC network for a UE in operator network .  Standards says 11 But at certain places I see at max - 3 bearer can be configured per UE ( 1 default + 2 dedicated bearer ) 

 

c- what is the service to UL/DL to bearer mapping at each Interface on   - 

 UE<->eNodeB<->SGW<->PGW<->PDN 

mostafa 2017-09-23 22:19:12

what about the reverse direction?

does the eNodeB apply TFT to the incoming IP flows from UE and genereate diffrent SDFs ,then aggregate simillar SDFs to EPS bearers?

thank you for clarification

Sebastiano Rametta 2018-04-18 22:25:35

Hello,

first of all my thanks for the wonderful pictures, explaining better than any text.

 

I suppose there is a typo error, in par EPS Bearer QoS Provisioning mentioning PDRF; supposed to be PCRF.

Thx

monisha patro 2018-09-09 11:38:32

Hi Netmanias,
In Table 5: EPS Bearer QoS Enforcement, MBR enforcements is applied for GBR Bearers only. 
So, I suppose it should be as below :

UL: Applied to only GBR bearers by UE and eNB
DL: Applied to only GBR bearers by S-GW and P-GW.
But in the above document I see it is mentioned that UL and DL should be applied to non-GBR bearers.
Correct me if i am wrong.

 

Thank you.

Sardar Sajid 2018-09-18 15:33:25

Wonderful ...

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